VST VRC-80 User manual

REVOLUTION CONDENSING
COMBI-BOILERS
Installation
Manual
Keep this manual near this boiler for future reference
whenever maintance or service is required.
Model
VRC-80 VRC-100
VRC-120 VRC-140
For Your Safety
WARNING: If the information in these instructions are not followed exactly, a re or explosion may result
causing property damage, personal injury or death.
- Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this or any other appliance.
 WHAT TO DO IF YOU SMELL GAS
• Do not try to light any appliance.
• Do not touch any electrical switch; do not use any phone in your building.
• Immediately call your gas supplier from a neighbor’s phone. Follow the gas supplier’s instructions.
• If you cannot reach your gas supplier, call the fire department.
This boiler must be installed in accordance with local codes. In the absence of local codes, it must be installed in compliance
with The Federal Manufactured Home Construction and Safety Stand Title 24 CRF, part 3280 or CAN/CSA Z240 MH series,
mobile home. In the absence of such standard, The Standard for mobile Homes (ANSI/NFPA No. 601B-1977).
The installation must conform with local codes or, in the absence of local codes, the National Fuel Gas Code, AN-
SIZ223.1/NFPA 54 and/or CSA B149.1, Natural Gas and Propane Installation Code.
Improper installation, adjustment, alteration, service or maintenance can cause property damage, personal injury (exposure
to hazardous materials)* or loss of life. Refer to the user's information manual provided with this boiler. Installation and service
must be performed by a qualified installer, service agency or the gas supplier (who must read and follow the supplied instruc-
tions before installing, servicing, or removing this boiler. This boiler contains materials that have been identified as carcino-
genic, or possibly carcinogenic, to humans).
WARNING

2Installation Manual
Safety Information
The following safety symbols are used in this manual for user's safety. Read this manual carefully and follow all instructions to avoid property
damage, fire, explosion, personal injury, or death.
Warning
Caution
Indicates an imminently hazardous situation which, if not avoided, will result in severe injury or death.
Indicates a potentially hazardous situation which, if not avoided, will result in injury or death.
Indicates a potentially hazardous situation which, if not avoided, could result in property damage.
Danger
If you smell gas:
•Do not try to light any appliance.
•Do not touch any electrical switches or use landline phones.
•From a neighbor’s phone, call your gas provider and follow their instructions.
•If you cannot reach your gas provider, call the fire department.
Do not use or store flammable products, such as gasoline, solvents, or adhesives in the same room or area as the boiler.
•Vapors from flammable liquids can explode and/or catch fire causing death or severe burns.
•Keep flammable products far away from the boiler and store them in approved containers. Keep the containers tightly closed and out of the
reach of children.
•The boiler has a main burner flame that can come on at any time and will ignite flammable vapors.
•Vapors cannot be seen and are heavier than air. They can travel long distances along the ground and can be carried from other rooms to the
boiler’s main burner flame by air current.
Avoid using hot water over 125F.
•Water temperature over 125°F can cause severe burns or death from scalding.
•If it is necessary to set the water temperature above 125°F (52°C), consider installing a thermostatically-controlled mixing valve.
Contact a licensed plumber or your local plumbing authority for more information.
•Children, the disabled and the elderly are at highest risk of being scalded.
•Test water before bathing or showering.
Temperature Time to Produce Serious Burn Temperature Time to Produce Serious Burn
120 °F (48 °C) More than 5 minutes 140 °F (60 °C) Less than 5 seconds
125 °F (51 °C) 1.5 to 2 minutes 145 °F (62 °C) Less than 3 seconds
130 °F (54 °C) Approx. 30 seconds 150 °F (65 °C) Approx. 1.5 seconds
135 °F (57 °C) Approx. 10 seconds 155 °F (68 °C) Approx. 1 second
Danger

3
Safety Information
Warning
•Do not store combustibles, such as papers or laundry, near the boiler or venting system.
Failure to do so may result in fire or explosion.
•Do not store or use gasoline or other flammable liquids near this boiler.
Failure to do so may result in fire or explosion.
•Do not store or use compressed gases, such as hair sprays or spray paints, near the boiler or venting system, including the vent
termination.
Failure to do so may result in fire or explosion.
•Do not remove the front cover unless the power to the boiler is turned off or disconnected.
Failure to do so may result in electric shock.
•Do not touch the internal components of the boiler or the power cord with wet hands.
Failure to do so may result in electric shock.
•Do not operate the boiler with the front cover opened.
Failure to do so may result in fire or carbon monoxide (CO) poisoning, which may result in property damage, personal injury, or death.
•Do not operate the boiler without proper venting.
Failure to do so may result in fire or carbon monoxide (CO) poisoning, which may result in property damage, personal injury, or death.
•Shut off the gas supply if the boiler is damaged.
Have your installer or plumber show you the location of the gas shut off valve and demonstrate how to close the valve. If the boiler is
damaged as a result of overheating, fire, flood, or any other reason, close the manual shut off valve and do not operate the boiler again until
it has been inspected by a qualified technician.
•Should overheating occur or if the gas supply fails to shut off, turn off the manual gas shut off valve.
Caution
•Do not use the boiler for anything other than its intended purpose, as described in this manual.
Failure to do so may result in property damage, personal injury, or death.
•Do not turn on the boiler unless the water and gas supplies are fully opened.
Failure to do so may damage the boiler.
•Do not use unapproved replacement or accessory parts.
Failure to do so may result in improper or dangerous operation and will void the manufacturer's warranty.
•When servicing the controls, label all wires prior to disconnecting them.
Failure to do so may result in wiring errors.
•Do not place anything in or around the vent terminals that could obstruct the air flow in or out of the boiler.
Failure to do so may result in fire or carbon monoxide (CO) poisoning, which may result in property damage, personal injury, or death.
•Do not attempt to repair or replace any part of the boiler, unless it is specifically recommended in this manual.
For all other service, contact an authorized technician or licensed professional. Improper adjustments, alterations, service, or maintenance
may lead to property damage, personal injury, or death and will void your warranty.
•Do not operate the boiler if you suspect something might be wrong with it.
Doing so may result in product damage or personal injury.
•Do not allow children to operate or have access to the boiler.
Doing so may result in product damage or personal injury.
•Do not use this appliance if any part has been immersed in water.
Immediately call a qualified service technician to inspect the appliance and replace any part of the control system and/or any gas control
which has been immersed in water.
•This boiler has been approved for use in the USA and Canada only.
Using the boiler in any other country will void the manufacturer's warranty.

4Installation Manual
Important Note for the State of Massachusetts
NOTICE BEFORE INSTALLATION
This appliance must be installed by a licensed plumber or gas fitter in accordance with the Massachusetts Plumbing and Fuel Gas Code 248 CMR
Sections 4.00 and 5.00.
IMPORTANT: In the State of Massachusetts (248 CMR 4.00 & 5.00)
For all side wall horizontally vented gas fueled equipment installed in every dwelling, building or structure used in whole or in part for residential
purposes, including those owned or operated by the Commonwealth and where the side wall exhaust vent termination is less than seven (7) feet
above finished grade in the area of the venting, including but not limited to decks and porches, the following requirements shall be satisfied.
1. INSTALLATION OF CARBON MONOXIDE DETECTORS. At the time of installation of the side wall horizontal vented gas fueled equipment,
the installing plumber or gasfitter shall observe that a hard wired carbon monoxide detector with an alarm and battery backup is installed
on the floor level where the gas equipment is to be installed. In addition, the installing plumber or gasfitter shall observe that a battery
operated or hard wired carbon monoxide detector with an alarm is installed on each additional level of the dwelling, building or structure
served by the side wall horizontal vented gas fueled equipment. It shall be the responsibility of the property owner to secure the services of
qualified licensed professionals for the installation of hard wired carbon monoxide detectors
a. In the event that the side wall horizontally vented gas fueled equipment is installed in a crawl space or an attic, the hard wired carbon
monoxide detector with alarm and battery backup may be installed on the next adjacent floor level.
b. In the event that the requirements of this subdivision cannot be met at the time of completion of installation, the owner shall have a
period of thirty (30) days to comply with the above requirements; provided, however, that during said thirty (30) day period, a battery
operated carbon monoxide detector with an alarm shall be installed.
2. APPROVED CARBON MONOXIDE DETECTORS. Each carbon monoxide detector as required in accordance with the above provisions shall
comply with NFPA 720 and be ANSI/UL 2034 listed and IAS certified.
3. SIGNAGE. A metal or plastic identification plate shall be permanently mounted to the exterior of the building at a minimum height of eight
(8) feet above grade directly in line with the exhaust vent terminal for the horizontally vented gas fueled heating appliance or equipment.
The sign shall read, in print size no less than onehalf (1/2) inch in size,“GAS VENT DIRECTLY BELOW. KEEP CLEAR OF ALL OBSTRUCTIONS”.
4. INSPECTION. The state or local gas inspector of the side wall horizontally vented gas fueled equipment shall not approve the installation
unless, upon inspection, the inspector observes carbon monoxide detectors and signage installed in accordance with the provisions of 248
CMR 5.08(2)(a)1 through 4.

5
Important Note for the State of Massachusetts
Table of Contents
Safety Information .................................... 2
Important Note for the State of
Massachusetts ........................................... 4
General Information.................................. 6
Included Items ................................................................... 6
Optional Accessories........................................................ 6
Specifications...................................................................... 7
Rating Plate ......................................................................... 8
Dimensions.......................................................................... 9
Components .....................................................................10
Installing the Boiler ................................. 12
Installer Qualifications...................................................12
Compliance Requirements ..........................................12
Location..............................................................................12
Installing the System Piping................... 15
Installing a Space Heating System............................15
Installing a Domestic Hot Water(DHW) System ...17
Connection the Condensate Drain...........................20
System Filling....................................................................21
Test the Water System ...................................................22
Example of System Applications ...............................22
Connecting the Gas Supply .................... 25
Gas Pipe Sizing Tables....................................................25
Gas Piping..........................................................................26
Inlet Gas Pressure............................................................27
Installing a Vent ....................................... 29
Vent Type............................................................................29
Vent Pipe Materials.........................................................33
Vent Length.......................................................................33
Connecting the Vent Clip .............................................34
Vent Termination.............................................................34
Setting the DIP Switches......................... 37
Connecting the Power Supply ................ 38
Installation Checklist............................... 39
Operating the Boiler................................ 42
Turning the Boiler On or Off........................................42
Setting the Space Heating Temperature ................42
Setting the DHW(Domestic Hot Water)
Temperature......................................................................43
Viewing Basic Information...........................................43
Setting the Heat Load for The Outdoor Reset
Control Mode....................................................................47
Appendix.................................................. 49
Gas Conversion ................................................................49
Wiring Diagram........................................ 53
Component Assembly Diagrams and
Parts Lists ................................................. 54
Case Parts (VRC)...............................................................54
Flue Parts (VRC)................................................................56
Water Parts (VRC Model)...............................................59
Outdoor Temperature Sensor
Installation .............................................. 61
Outdoor Temperature Sensor (Optional)................61
Outdoor Reset Control (Available with Optional
Outdoor Temperature Sensor)....................................61

6Installation Manual
General Information
Included Items
The following items are included with the boiler. Check each of the
following items before installation.
Wall mounting bracket Tapping screws & anchors
Installation and
User manual
Quick installation manual
Vent clip Gas conversion kit
Spare parts Pressure Relief Valve
2" Vent termination cap &
Wall flange
Notice
If there is a missing item, please contact Technical Support at 1-800-761-
0053.
Optional Accessories
The following optional accessories are not included with the boiler,
but may be necessary for the installation. Check the need for any of
the following optional accessories before installation.
Cascade communication
cable
Plumb easy valve set
Outdoor temperature sensor Pipe Cover

7
General Information
Specifications
The following table shows the specifications for the boiler. Additional specifications about water, gas, electric, and air supplies (venting) appear
in each installation section.
MODEL VRC-80 VRC-100 VRC-120 VRC-140
Heat Capacity
(Input)
Space Heating 19,900–80,000 BTU/H 19,900–100,000 BTU/H 19,900–120,000 BTU/H 19,900–140,000 BTU/H
Domestic Hot Water 19,900–155,000 BTU/H 19,900–180,000 BTU/H 19,900–199,000 BTU/H 19,900–199,000 BTU/H
Flow Rate (DHW)
45°F (25°C) Temp Rise 6.0GPM(23LPM) 6.9GPM(26LPM) 7.7GPM(29LPM) 7.7GPM(29LPM)
67°F (37°C) Temp Rise 4.0GPM(15LPM) 4.7GPM(18LPM) 5.2GPM(20LPM) 5.2GPM(20LPM)
AFUE Natural Gas (propane) 95.0%(95.0%) 95.0%(95.0%) 95.0%(95.0%) 95.0%(95.0%)
Dimensions (W x D x H) 18.1“ x 27.6” x 11.6“ (460 mm x 700 mm x 295 mm)
Installation Type Indoor wall-hung
Venting Type Forced draft direct vent
Ignition Electronic ignition
Water Pressure(Hydronic/DHW) 12~30psi/15~150 psi
Supply Pressure
Natural Gas 3.5" – 10.5" WC
Propane 8" – 13" WC
Minimum Flow Rate (DHW) 0.5GPM(2.0LPM)
Temperature
Range
Space Heating 82°F – 180°F(27°C – 82°C)
DHW 86°F – 140°F(31°C – 60°C)
Connection Sizes
Space heating
Supply/Return 1" NPT
Cold water Inlet 3/4" NPT
Hot Water Outlet 3/4" NPT
Gas Inlet 3/4" NPT
Power Supply Main Supply 120V AC, 60 Hz / use less than 5 AMP
Materials
Primary Heat Exchanger
Stainless steel
Secondary Heat Exchanger
Venting
Exhaust/Intake 2" or 3" PVC, CPVC, Polypropylene
2" or 3" Special gas vent type BH (Class II, A/B/C)
Length
2" 60ft(18.3m)
3" 150ft(45.7m)
Vent Clearances 0" to combustibles
Safety Devices Flame rod, APS, Over heat preventer, Low water cut off switch
Exhaust temperature high limit sensor, Power surge fuse

8Installation Manual
Rating Plate
Danger
The gas type and electricity voltage must match the rating plate. Using a different gas type and electricity voltage will cause the boiler
to malfunction.
Before the installation, check the rating plate located on the side of the boiler to ensure that the boiler matches the gas type, gas pressure, water
pressure, and electrical supply available in the installation location. If the boiler does not match each of these ratings, do not install the boiler.
If the gas conversion is required, the included gas conversion kit must be used.
-
۰.

9
General Information
Dimensions
Description Diameter
ASpace heating Return 1" NPT
BCold water inlet 3/4" NPT
CCondensate Outlet 1/2" NPT
DHot water Outlet 3/4" NPT
ESpace heating Supply 1" NPT
FGas Inlet 3/4" NPT
GExhaust Vent 2"
HAir inlet 2"
27.56" (700 mm)
31.87" (809.5 mm)
2.80"
(71.1 mm) 0.36" (9.2 mm)
18.11" (460 mm)
5.57"
(141.5 mm)
5.26"
(133.5 mm)
11.61" (295 mm)
G
H
4.0"
(101.6 mm)
3.6"
(91.4 mm)
2.7"
(68.6 mm)
1.6" (40.6 mm)6.1"
(154.9 mm)
2.8"
(71.1 mm)
3.4"
(86.4 mm)
4.7" (119.4 mm)
2.2"
(55.9 mm)
8.0" (203.2 mm)
A B C D E F 1.8"
(45.7 mm)

10 Installation Manual
Components
Flue connector Air intake connector
Gas connector
Gas valve
3-way valve
Pressure sensor
Space heating supply
Gas inlet
Hot water outlet
Burner hood
Heat Exchanger Cover
Pump
Air vent
Condensate drain
Space heating return
Cold water inlet
Exhaust temperature
sensor

11
General Information
Ignition transformer
PCB assembly
Front panel
Secondary heat
exchanger
Primary heat
exchanger
Flow sensor
Air Pressure Sensor
TDR damper
Water Pressure Sensor
Turbo fan assembly

12 Installation Manual
Installing the Boiler
Installer Qualifications
A licensed professional must install and inspect the appliance. A
licensed professional is a person who is licensed for the following:
•Connecting gas lines, water lines, valves, electricity
•Vent installation through walls and roofs
•Applicable of local, state, and national codes
Compliance Requirements
•National electrical code.
•National fuel gas code, ANSI Z223.1/NFPA 54 and/or CSA B149.1,
natural gas and propane installation codes.
•Local, state, provincial, and national codes, laws, regulations,
and ordinances.
•Standard for Controls and Safety Devices for Automatically Fired
Boilers, ANSI/ASME CSD-1, when required.
•For Canada only: B149.1 installation Code, CSA C22.1 Canadian
Electricity supply enters the building.
Location
For installation :
This appliance provides for separation of the combustion system
from the indoor atmosphere of the manufactured (mobile) home by
an installation method.
This appliance shall be installed only in a space closed from the
atmosphere within the manufactured (mobile) home.
The doors or access panels serving the space in which the appliance
is located shall communicate only to the outdoors.
in the manufactured homes This appliance shall not be installed in a
recreational vehicle.
When considering a location for installation, the installer, must
ensure the following:
•Access to utilities
•Humidity and contact with water
•Water quality
•Drainage
•Venting and ventilation
•Proximity to fixtures and appliances
•Clearances
•Clean, debris and chemical-free combustion air
•High elevation Installations
Access to utilities
•Electricity – Close to where the electrical supply enters the building
•Water – Close to where the domestic water supply enters the
building
•Gas – Close to where the gas supply enters the building
Humidity and contact with water
Avoid places with excessive humidity. The boiler has electric gas
ignition components. If water gets inside the boiler, the ignition system
can be damaged. The boiler must be installed in such a way as to
ensure that the gas ignition system components are protected from
water (dripping, spraying, rain, etc.) during operation and service.
Drainage
A significant amount of condensate is produced during the boiler
operation. Install the boiler near a suitable drain and where damage
from a possible leak will be minimal. Installing the boiler without a
drain will void the warranty. For more information about condensate
drainage, refer to "Connection the Condensate Drain" on page 20.
The Boiler must be located in an area where leakage of the unit or
connections will not result in damage to the area adjacent to the
appliance or to lower floors of the structure. When such locations
cannot be found, installation of an adequately-draining drain pan
under the boiler is highly recommended. When installing the drain pan,
ensure that the installation does not restrict combustion air flow.
Venting and ventilation
Consider venting restrictions caused by windows, doors, air intakes,
gas meters, foliage and other buildings, and select a location that
requires minimal venting.
When considering an adequate venting and ventilation, ensure the
following:
•Maintain a minimum clearance of 4 feet (1.2 meters) from
heating and cooling vents.
•Maintain proper clearances from any openings in the building.
•Install the boiler with a minimum clearance of 12 inches
(300 mm) above an exterior grade or as required by local codes.
•Install the exhaust vent in an area that is free from obstructions
and does not allow the exhaust to accumulate.
•Do not enclose the vent termination.
•Do not install the boiler where moisture from the exhaust may
discolor or damage walls.
•Do not install the boiler in bathrooms, bedrooms, or any other
occupied rooms that is normally kept closed or that is not
adequately ventilated.
For more information about venting, refer to "Installing a Vent" on
page 29.

13
Installing the Boiler
Clearances
The boiler should be installed in an area that allows for service and
maintenance access to utility connections, piping, filters, and traps.
Ensure the following clearances are maintained:
Side
Side
Front
Back
Top
Bottom
Clearance From Wall Mounting
Top 12 inches (305 mm) min.
Back 0.6 inches (15 mm) min.
Front 6 inches (152 mm) min.
Sides 3 inches (76 mm) min.
Bottom 12 inches (300 mm) min.
Caution
Do not install the boiler on carpeting.
Clean, debris and chemical-free combustion
air
•Do not install the boiler in areas where dust and debris may
accumulate or where combustion air can be contaminated.
•Do not install the boiler in areas with greasy fumes or heavy
amounts of steam, if necessary, take measures to prevent
fumes and steam from entering the boiler.
•Chemicals that are corrosive in nature should not be stored
or used near the boiler.
Position
Caution
Do not mount the boiler to dry wall that has not been
reinforced.
The boiler can be mounted to the wall. For easy installation, use
the mounting bracket to mount the boiler to standard wall studs.
If the strength of the wall is insufficient and or if the framing is
non-standard or uneven, reinforce the area before installation.
Avoid installation in unstable locations as the boiler will make some
operational noises while it is running.
Notice
Consider vent length and surrounding circumstances when mounting
the boiler.

14 Installation Manual
Mounting to the wall
To mount the boiler to the wall:
1Check that the wall is level and can support the weight of the
boiler.
2Affix the mounting bracket securely to the wall.
3Align the grooves on the back of the boiler with the tongues
on the mounting bracket and hang the boiler from the
bracket.
Warning
•The boiler is heavy. Always lift the unit with assistance. Be
careful not to drop the boiler while lifting or handling it to
avoid bodily injury or damage to the unit.
•Do not rest the bolier on the bottom end after removing it
from the shipping carton. Doing so may result in excessive
pressure on protruding pipes and cause product damage.
If you must put the boiler down, lay it on its back or put it
inside the protective shipping base.

15
Installing the System Piping
Installing the System Piping
Before connecting the pipes to the boiler, clean all systems to
remove sediment, flux, solder, scale, debris, or other impurities that
may be harmful to the boiler system. It is important to maintain the
inside of the pipes free of debris, copper dust, sand, and dirt while
installing the heating system.
When installing the VST boiler and keeping the existing pipes, all
pipes including the radiator should be cleaned.
Warning
If you fail to remove the above-mentioned contaminants
from the heating system, your warranty will be void, the heat
exchange will break down faster than normal, and property
damage may occur as a result.
Installing a Space Heating System
The primary heat exchanger and secondary heat exchanger of
VST VRC boiler are designed optimally to obtain high thermal
efficiency. The primary heat exchanger is configured in the finned
tube method and the secondary heat exchanger is configured
in the plate to plate method, maximizing the heating surface
area to achieve high thermal efficiency. In order to allow the heat
exchanger to operate effectively over time without trouble, it is
important to follow the rules and guidelines mentioned in this
section.
Caution
If you fail to follow the guidelines provided in this section, your
warranty will be void and property damage, fire, serious injury,
or death may occur as a result.
Guidelines for a Space Heating System
Read the guidelines below for installing the boiler heating system
safely and properly.
Freeze protection for the space heating system
•Freeze protection products may be used to prevent the
space heating system from becoming frozen. A specially
manufactured glycol is necessary for preventing a new or
existing piping system from becoming frozen. This glycol should
include inhibitors not harmful to metallic system components.
•Before using freeze protection products, it is necessary
to check if the amount of glycol use in the space heating
water is appropriate and if the inhibitor level in such glycol
is appropriate. VST recommends against exceeding a 35%
concentration of glycol.
•If freeze protection products are used, the system should be
tested at least once a year.
•When using the freeze protection products, allowance should
be made for expansion of the glycol solution.
•Freeze damage is not covered by the warranty.
Warning
For a system requiring freeze protection, use only inhibited
propylene glycol, specially formulated for hydronic heating
systems; use of other types of antifreeze may be harmful to the
system and will void the warranty.
System Pressure
•VST VRC boiler is intended solely for use in a pressurized closed
loop heating system operating with 7-30psi water pressure
at the boiler outlet. To obtain the minimum system design
pressure, comply with the piping diagram in this section.
•The space heating system of VST VRC boiler is not approved to
operate as an“open system”, and thus cannot be used for direct
potable water heating or to process heating of any kind.
Air Elimination
This boiler can be installed only in a pressurized closed-loop heating
system free of air and other impurities.
Install a proper-sized air-purging device at a proper position to
eliminate air from the entire heating system.

16 Installation Manual
Essential Elements in a Space Heating System
Low Water Cut Off(LWCO) Device
Internal LWCO
The VST VRC boiler is equipped with a factory-installed, pressure-
sensing type low water cutoff (LWCO) device. The minimum
operating pressure of this device is 7.1psig.
Refer to local codes to determine if a LWCO device is required
for your system and ensure that the built-in device meets the
requirements.
External LWCO
Install LWCO if it is required by local code.
The following figure shows an example of general LWCO
installation.
External LWCO
Space heating
return
Space heating
supply
LWCO installed outside should be installed at least 6 inches
(150mm) or more away from the end of the heat exchanger.
Backflow Preventer
When filling the device with water, install a backflow preventer if it is
required by local code.
Expansion Tank
The expansion tank should be installed in the system pipes in order
to prevent excessive pressure in the heating pipes.
When installing the expansion tank, follow the guidelines below.
•If the air separator is located on the suction side of the system
circulator, connect the air separator to the expansion tank.
•VST VRC boiler has a connection (water fill connection) for
additional water. Therefore, in most cases, an additional water
fill connection is not necessary.
•If an additional water fill connection is necessary for special
use, install the water fill connection at the same location as the
expansion tank’s connection to the system.
•When replacing the expansion tank, refer to the literature of the
expansion tank manufacturer for selecting the proper size.
•When installing the diaphragm expansion tank, always install
an automatic air vent at the top of the air separator in order to
remove residual air in the system.
Isolation Valves and Unions
•This boiler system requires a full port ball valve. If a full port ball
valve is not used, water may flow at a limited flow rate through
the boiler.
•It is recommended to use unions for the serviceability of the
device.
Pressure Relief Valve
This boiler comes with an ASME-approved pressure relief valve to
install space heating. To complete the installation of the boiler, you
must install an approved 3/4", maximum 30 PSI (for space heating).
Warning
Improper installation of the pressure relief valve may result
in property damage, personal injury, or death. Follow all
instructions and guidelines when installing the pressure relief
valve. Only a licensed professional should install the valve.
Caution
Install the pressure relief valve as close to the boiler as possible.
No other valve should be installed between the pressure relief
valve and boiler.
Pressure relief valve
Space heating return Space heating supply

17
Installing the System Piping
When installing the pressure relief valve, follow the guidelines
below.
•The discharge capacity of the valve should be greater than or
equal to the maximum pressure rating of the space heating
system in the boiler.
•The maximum Btu/h rating of the pressure relief valve should
be greater than or equal to the maximum input Btu/h rating of
the boiler.
•If the pressure relief valve operates, discharging domestic hot
water, domestic hot water may scatter or splash onto other
equipment around. Connect the pressure relief valve to the
outlet pipe.
•When installing the discharge piping line, do not install a
coupling whose internal diameter decreases or has other
restrictions.
If the pressure relief valve discharges hot water periodically, thermal
expansion may occur due to an expansion tank problem or small
expansion tank size. Do not plug the pressure relief valve.
Space Heating Piping
When connecting the space heating system, follow these
guidelines.
•Tighten the connection valves carefully in order to avoid
damage.
•After installing the boiler, check if the space heating water flows
smoothly and if there is a water leak. Inform the boiler owner
of the fact that the strainer should be cleaned periodically to
maintain the smooth flow of space heating water. (The strainer
is located on the side of the space heating return.)
Installing a Domestic Hot
Water(DHW) System
VST VRC boiler can supply domestic hot water continuously
when the flow rate is detected by the flow switch. This is the most
appropriate way to minimize standby losses and improve the
combustion efficiency.
Guidelines for a DHW System
VST VRC boiler is designed to use space heating and domestic hot
water.
This boiler is equipped with the flow switch, and when
approximately 0.5GPM or more water flows, the flow switch will
sense such water flow. The boiler will then switch to the DHW mode
immediately regardless of the space heating system's status.
Read and follow the guidelines stated below for the safety and
proper installation of DHW system.
Scald Hazard
The hotter the water, the higher the risk of burns. If the DHW
temperature is set too high, there is a risk of burns from domestic
hot water. Make sure to follow the usage guidelines in the user
manual.

18 Installation Manual
About the DHW Quality
If the quality of water cannot meet the EPA standard, appropriate
boiler maintenance is required. Any damage resulting from bad
quality of water voids the warranty. The following table shows the
permitted maximum contaminant levels based on the EPA National
Secondary Drinking Water Regulations (40 CFR Part 143.3).
Contaminant Maximum Allowable Level
Total Hardness 200 mg/l (12 grains/gallon)
Aluminum 0.05 – 0.2 mg/l
Chloride 250 mg/l
Copper 1.0 mg/l
Iron 0.3 mg/l
Manganese 0.05 mg/l
pH 6.5 – 8.5
Sulfate 250 mg/l
Total Dissolved Solids (TDS) 500 mg/l
Zinc 5 mg/l
VST is not responsible for the blockage of the domestic system due
to the accumulation of foreign matters or scaling.
The installer or the user should take appropriate measures in order
to avoid any problem related to the quality of water.
Freeze Protection
VST recommends insulating the DHW pipes. The pipes can be
covered using heat-insulating materials. Freeze damage voids the
warranty.
Essential Elements in a DHW System
DHW Heat Exchanger
The DHW heat exchanger installed on the VRC boiler is designed to
withstand a significant amount of water pressure.
Drain and Isolation Valves
Install drain and isolation valves on the inlet and outlet of the DHW
heat exchanger, so it can be flushed free of possible build-up caused
by dirt or hard water.
DHW Filter
VST VRC boiler has a filter on its cold water inlet nipple. Clean the
filter periodically to prevent the interruption of water flow by
foreign matters.
If such foreign substances adhere to the flow switch, the boiler may
malfunction.

19
Installing the System Piping
Pressure Relief Valve for DHW
To complete the installation of the DHW system, you must install
the approved ¾”, maximum 150psi pressure relief valve on the hot
water outlet.
Warning
Improper installation of the pressure relief valve may result
in property damage, personal injury, or death. Follow all
instructions and guidelines when installing the pressure relief
valve. Only a licensed professional should install the valve.
The DHW pressure relief valve is not provided together with the
product. However, it is necessary to install such a valve.
Caution
Install the pressure relief valve as close to the boiler as possible.
No valve should be installed between the pressure relief valve
and the boiler.
When installing the pressure relief valve, follow the guidelines
below.
•The discharge capacity of the valve should be greater than or
equal to the maximum pressure rating of the DHW system in the
boiler.
•The maximum Btu/h rating of the pressure relief valve should
be greater than or equal to the maximum input Btu/h rating of
the boiler.
•If the pressure relief valve operates, discharging domestic hot
water, domestic hot water may scatter or splash onto other
equipment around. Connect the pressure relief valve to the
outlet pipe.
•When installing the discharge piping line, do not install a
coupling whose internal diameter decreases or has other
restrictions.
If the pressure relief valve discharges hot water periodically, it
may be caused by thermal expansion of the closed water system.
Contact the water supplier or a local plumbing inspector in order to
such a problem. Do not plug the pressure relief valve.
DHW System Piping
Caution
In order to meet the requirements of ASME or CRN, an
additional high temperature limitation device may be
necessary. Refer to the requirements of the local code for
whether this device is necessary or not.
Cold water supply
DHW supply
When installing the DHW system, follow the guidelines below.
•Only use permitted pipes, valves and other parts such as a
solder for the potable water system.
•Tighten the connection valves carefully in order to avoid
damage.
•VST recommends the use of unions and manual shut-off valves
for the cold water inlet and DHW outlet.
•Keep the hot water piping system as short as possible, to deliver
hot water to the fixtures more quickly.
•When installing a mixing valve on the DHW piping, ensure that
the cold water pressure does not exceed the hot water pressure.
•To conserve water and energy, insulate the DHW supply and
DHW recirculation lines (if applicable). Do not cover the drains
or pressure relief valves.
•After installing the boiler, clean the cold water inlet filter. Then,
check if domestic water flows properly and check for water
leaks. Inform boiler owner that the filter should be cleaned
periodically to ensure that domestic hot water flows smoothly.

20 Installation Manual
Connection the Condensate Drain
Caution
•All condensate must drain and be disposed of according to
local codes.
•Do not cap or plug the integrated condensate line. If
prevented from draining, condensate can damage the
boiler.
•The condensate line must have a negative slope to drain
properly.
•Do not run drain outdoors. Freezing of condensate can
cause property damage.
•Do not connect the condensate drain line directly to the
rain sewer.
•Do not connect the condensate drain line with an air
conditioning evaporator coil drain.
•Use only corrosion resistant materials for the condensate
drain lines such as PVC pipe or plastic hose.
•The end of the condensate drain pipe should be open to the
atmosphere. The end should not be under water or other
substances.
The VRC boiler creates condensation when it operates. This
condensation has an acidic pH of 3-5. Follow all local codes and
regulations when disposing of condensate from the boiler.
We recommend draining the condensate into a laundry tub,
as the alkali in laundry detergent will neutralize the acid in the
condensate. However, other suitable waste drain locations may be
used according to local codes.
Before connecting the condensate drain, choose one of the
following disposal options:
External drain
Direct to an
external drain
To a drain via
a neutralizer To a laundry
tub
To a laundry tub via a
condensate pump
(a) From the boiler directly into an external drain.
(b) From the boiler, through a neutralizing agent, and then into an
external drain.
Notice
•If you choose this option, the neutralizing agent must be replaced
periodically. Depletion of the neutralizing agent will vary, based on
the usage rate of the boiler. During the first year of operation, the
neutralizer should be checked every few months for depletion and
replaced as needed.
(c) From the boiler into a condensate pump, and then into a
laundry tub.
Notice
A pump can be used when there is a long distance between the boiler
and the laundry tub or when the bottom of the boiler is lower than the
top of the laundry tub.
(d) From the boiler into a laundry tub.
Notice
The bottom of the boiler must be higher than the top of the laundry tub
to use this option.
The condensate line must have a negative slope to drain properly.
To connect the condensate drain:
1Connect a drain line to the boiler.
Notice
Use only corrosion-resistant material for the drain line, such as PVC or
CPVC. Do not reduce the size of this ftting or the drain line to less than
1/2".
NPT 1/2 in.
2Place the free end of the drain line into an appropriate drain.
Notice
•If you are using a condensate pump, ensure that the pump allows for
up to 2 GPH of drainage for each boiler in the system.
•If you are not using a condensate pump, ensure that the drain line is
pitched downward at a minimum slope of 1/4" per foot.