Spirax Sarco RediHeat RH-90 User manual

1
RediHeat
INSTALLATION AND MAINTENANCE INSTRUCTIONS
IM-12-002-US March 2018
Table Of Contents Page
I. Installation 4
2. RediHeat Start-Up Procedure 4
2.1 Initial start-up 4
2.2 RH-30/60 temperature stabilization adjustment table 5
2.3 RH-90/120 temperature stabilization adjustment table 6
2.4 Rediheat with recirculation system start-up 7
3. Maintenance 7
3.1 Blending valve disassembly 7
3.2 Blending valve re-assembly 7
3.3 Heat exchanger inspection disassembly 8
3.4 Heat exchanger re-assembly 8
4. Troubleshooting 9
5. Recirculation Systems 10
6. Ordering Spare Parts 11

2
Safety Information
Safe operation of these products can only be guaranteed if
they are properly installed, commissioned, usedand maintained
by qualied personnel (see Section 1.11) in compliance with
the operating instructions. General installation and safety
instructions for pipeline and plant construction, as well as the
proper use of tools and safety equipment must also be complied
with.
1.1 Intended use
Referring to the Installation and Maintenance Instructions,
name-plate and Technical Information Sheet, check that the
product is suitable for the intended use / application.
i) The products have been specically designed for use on
steam, air or water/condensate. The products’ use on other
uids may be possible but, if this is contemplated, Spirax
Sarco should be contacted to conrm the suitability of the
product for the application being considered.
ii) Check material suitability, pressure and temperature and
their maximum and minimum values. If the maximum
operating limits of the product are lower than those of the
system in which it is being tted, or if malfunction of the
product could result in a dangerous overpressure or
overtemperature occurrence, ensure a safety device is
included in the system to prevent such over-limit situations.
iii) Determine the correct installation situation and direction
of uid ow.
i v ) S p i r a x S a r c o p r o d u c t s a r e n o t i n t e n d e d t o w i t h s t a n d e x t e r n a l
stresses that may be induced by any system to which they
are tted. It is the responsibility of the installer to consider
these stresses and take adequate precautions to minimise
them.
v) Remove protection covers from all connections and
protective lm from all name-plates, where appropriate,
before installation on steam or other high temperature
applications.
1.2 Access
Ensure safe access and if necessary a safe working platform
(suitably guarded) before attempting to work on the product.
Arrange suitable lifting gear if required.
1.3 Lighting
Ensure adequate lighting, particularly where detailed or intricate
work is required.
1.4 Hazardous liquids or gases in the pipeline
Consider what is in the pipeline or what may have been in the
p i p e l i n e a t s o m e p r e v i o u s t i m e . C o n s i d e r :  a m m a b l e m a t e r i a l s ,
substances hazardous to health, extremes of temperature.
1.5 Hazardous environment around the product
Consider: explosion risk areas, lack of oxygen (e.g. tanks, pits),
dangerous gases, extremes of temperature, hot surfaces, re
hazard (e.g. during welding), excessive noise, moving
machinery.
1.6 The system
Consider the effect on the complete system of the work
proposed. Will any proposed action (e.g. closing isolation
valves, electrical isolation) put any other part of the system or
any personnel at risk?
Dangers might include isolation of vents or protective devices
or the rendering ineffective of controls or alarms. Ensure
isolation valves are turned on and off in a gradual way to avoid
system shocks.
1.7 Pressure systems
Ensure that any pressure is isolated and safely vented to
atmospheric pressure. Consider double isolation (double block
and bleed) and the locking or labelling of closed valves. Do not
assume that the system has depressurised even when the
pressure gauge indicates zero.
1.8 Temperature
Allow time for temperature to normalise after isolation to avoid
danger of burns.
1.9 Tools and consumables
Before starting work ensure that you have suitable tools and / or
consumables available. Use only genuine Spirax Sarco
replacement parts.
1.10 Protective clothing
Consider whether you and / or others in the vicinity require any
protective clothing to protect against the hazards of, for example,
chemicals, high / low temperature, radiation, noise, falling
objects, and dangers to eyes and face.
1.11 Permits to work
All work must be carried out or be supervised by a suitably
competent person. Installation and operating personnel should
be trained in the correct use of the product according to the
Installation and Maintenance Instructions.
Where a formal ‘permit to work’ system is in force it must be
c o m p l i e d w i t h . W h e r e t h e r e i s n o s u c h s y s t e m , i t i s r e c o m m e n d e d
that a responsible person should know what work is going on
and, where necessary, arrange to have an assistant whose
primary responsibility is safety.
Post ‘warning notices’ if necessary.
1.12 Handling
Manual handling of large and/or heavy products may present
a risk of injury. Lifting, pushing, pulling, carrying or supporting
a load by bodily force can cause injury particularly to the back.
You are advised to assess the risks taking into account the
task, the individual, the load and the working environment and
use the appropriate handling method depending on the
circumstances of the work being done.

3
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1.13 Residual hazards
I n n o r m a l u s e t h e e x t e r n a l s u r f a c e o f t h e p r o d u c t
may be very hot. If used at the maximum
permitted operating conditions the surface
temperature of some products may reach
temperatures in excess of 300°C (572°F).
Many products are not self-draining. Take due
care when dismantling or removing the product
from an installation (refer to 'Maintenance
instructions').
1.14 Freezing
Provision must be made to protect products
which are not self-draining against frost
damage in environments where they may be
exposed to temperatures below freezing point.
1.15 Disposal
Unless otherwise stated in the Installation
and Maintenance Instructions, this product
is recyclable and no ecological hazard is
anticipated with its disposal providing due
care is taken.
1.16 Returning products
Customers and stockists are reminded that
under EC Health, Safety and Environment Law,
when returning products to Spirax Sarco they
must provide information on any hazards and
theprecautionstobetaken due tocontamination
residues or mechanical damage which may
present a health, safety or environmental risk.
This information must be provided in writing
including Health and Safety data sheets relating
to any substances identied as hazardous or
potentially hazardous.
1.17 Working safely with cast iron
products on steam
Cast iron products are commonly found on
steam and condensate systems. If installed
correctly using good steam engineering
practices, it is perfectly safe. However, because
of its mechanical properties, it is less forgiving
compared to other materials such as SG iron or
carbon steel. The following are the good
engineering practices required to prevent
waterhammer and ensure safe working
conditions on a steam system.
Cast Iron is a brittle
material. If the product
is dropped during
installation and there
is any risk of damage
the product should
not be used unless it
is fully inspected and
pressure tested by the
manufacturer.
Safe Handling
Steam Trap set Trap set Trap set
Steam
Gradient 1:100
Gradient 1:100
30 - 50 metre intervals
Condensate Condensate
Condensate
Prevention of water hammer
Steam trapping on steam mains:
Steam Mains - Do's and Dont's:
Steam 4
7
7
7
7
4
4
4
Prevention of tensile stressing
Pipe misalignment:
Installing products or re-assembling after maintenance:
Do not over tighten.
Use correct torque gures.
1
1
4 2
3
8
2
6
3
7
Flange bolts should be gradually tightened across
diameters to ensure even load and alignment.
7
4
5
4

4
Section 1
Installation
1. Heater may be wall or floor stand mounted or can be
suspended from the ceiling. Approximately 3’ clearance
from the floor is required to allow room for steam and
condensate connections and the hot water outlet.
2. For optimal heater performance, the steam trap should
discharge to 0 psig, below the level of the trap. If lift of
condensate is required or the trap must discharge to a
back pressure, an automatic pump trap (APT) should
be fitted for correct operation. Contact Spirax Sarco for
details.
3. Install a pressure relief valve set at 75 PSIG (for RH-30
& RH-60) or 50 PSIG (for RH-90 & RH-120) in the steam
inlet pipe downstream of the pressure reducing valve
if steam pressure to the heat exchanger can exceed
these limits.
Note: The Heliflow®heat exchanger can be supplied
with a steel shell to accommodate higher design
pressures if required.
4. The heater incorporates an integral pressure relief valve
(located on side of the RediHeat valve) to relieve excess
water pressure caused by thermal expansion.
5. Install the temperature gauge provided in the hot water
outlet piping.
6. Install the pressure gauge and pigtail fitting on the
steam supply line, either directly on the heat exchanger
or in close proximity.
7. Standard operating steam pressure to the exchanger is
15 PSIG or less. The pressure reducing valve should be
set at 15 PSIG if furnished.
8. The water pressure must exceed the steam pressure by
15 PSI at all times for proper operation.
9. Check tightness of all connections.
10. See typical installation drawings in Section 7. It is also
advisable to install a drain/test valve close to the heater.
This valve can be used to assist in initial temperature
adjustment of the unit.
Section 2
RediHeat Start-Up Procedure
2.1 Initial Start-up
1. Check all joints for tightness. If a recirculation system
will be used, initial temperature adjustment of the
RediHeat should be performed with the circulating
pump turned “off.” After the RediHeat is set at the
correct temperature, the circulator may be operated.
2. Turn on the cold water supply. Set flow at approximately
50% of the heater capacity. (Maximum water pressure
150 PSIG.)
3. Loosen the compression fitting on the sensing line at
the upper diaphragm cover. Permit water to flow until
free of any air. Retighten fitting.
4. A steam side vent valve should be installed on either
of the vent connections located on top of the heat
exchanger casing. Then slowly turn on the steam supply
to the heat exchanger. Adjust the pressure regulator (if
equipped) so steam pressure to the exchanger is 15
PSIG.
Note: Carefully vent any trapped air using the vent
valve.
5. By loosening the setscrew and locking ring, the desired
outlet temperature can be calibrated by sliding the
control rod from left to right (hotter to colder).
6. The valve also features a temperature stabilizer which
will fine-tune the proportion of hot and cold water
through all rated flows. The stabilization adjustment is
performed by rotating the control rod from vertical to
30 degrees. To rotate the control rod, insert a nail or
similar object into the hole drilled in the rod. Then rotate
to the approximate position as indicated in Table 1 or
1A.
Vary the flow to simulate high and low usage and note
any variations in temperature based on flow rate.
If the outlet temperature increases with increased flow,
rotation should be decreased (toward 0 degrees, the
12:00 o’clock position).
If the outlet temperature decreases with increased
flow, the rotation of the stabilizer should be increased
(toward 30 degrees, the 2:00 o’clock position).
Correct adjustment will yield stable temperature
output throughout the heater’s flow capacities. Once
the correct adjustments have been made, tighten the
locking ring and set screw.
7. The RediHeat water heater should now be adjusted and
operating. No further adjustments are required, unless
there is a large fluctuation in the inlet water temperature.
In climates with large seasonal temperature changes, a
felt tip marker may be used to mark the summer and
winter control rod positions.
Note: Every 3°F change in supply water temperature
will yield approximately a 1°F change in the outlet water
temperature.
8. Tighten all casing bolts on the heat exchanger after 2 to
3 hours of operation and check after 24 hours.
Thermal expansion:
Short
distance Fixing point
Axial movement
Axial movement
Guides
Guides
Guides
Guides
Limit rods
Limit rods
Fixing point
Medium
distance
Small
lateral
movement
Small
lateral
movement
Large
lateral
movement
Large
lateral
movement

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Table 1
Temperature Stabilization Adjustment Table
(Approximate setting in degrees of rotation - see illustration below)
* Steam pressure measured at heat exchanger inlet
Inlet
water
temp
Set
Point
(ºF)
RH-30 RH-60
40ºF
* 2 psig 5 psig 10 psig 15 psig 2 psig 5 psig 10 psig 15 psig
120 25 24 23 22 15 14 13 12
140 30 30 30 30 30 28 25 20
150 30 30 30 30 30 30 27 25
160 - - - 30 30 30 30 30
180 - - - 30 30 30 30 30
60ºF
120 22 21 20 19 12 11 10 9
140 25 24 23 22 15 14 13 12
150 28 27 27 26 23 21 18 16
160 - - - 30 30 28 25 20
180 - - - 30 30 30 30 30
0˚ 30˚
Hole through Control Rod
– insert pin and rotate for
stabilization adjustment
Control Rod – Slides left to
right for base temperature
settiing
Blending Valve

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Table 1A
Temperature Stabilization Adjustment Table
(Approximate setting in degrees of rotation - see illustration below)
* Steam pressure measured at heat exchanger inlet
Inlet
water
temp
Set
Point
(ºF)
RH-90 RH-120
40ºF
* 2 psig 5 psig 10 psig 15 psig 2 psig 5 psig 10 psig 15 psig
120 25 24 23 22 15 14 13 12
140 27 27 25 24 22 22 23 20
150 30 30 30 30 27 27 27 25
160 30 30 30 30 30 30 30 30
180 30 30 30 30 30 30 30 30
60ºF
120 22 21 20 19 12 11 10 9
140 25 24 23 22 15 14 13 12
150 28 27 27 26 23 21 18 16
160 30 30 30 30 30 28 25 20
180 30 30 30 30 30 30 30 30
0˚ 30˚
Hole through Control Rod
– insert pin and rotate for
stabilization adjustment
Control Rod – Slides left to
right for base temperature
settiing
Blending Valve

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2.2 Start-up Procedure for RediHeat Water
Heaters with Recirculation Systems
The following procedure should be used when starting the
RediHeat fitted with a forced recirculation loop system.
This procedure will be applicable in systems with either a
fixed thermostatic element diverting valve, or the adjustable
thermostat diverting valve.
Note: Before starting up a RediHeat incorporating
a recirculation system, carefully read: SECTION 5 -
RECIRCULATION SYSTEMS. This section covers how the
recirculation system should be correctly piped up.
1. With the circulating pump “off”, set the RediHeat water
outlet temperature as described in 5 & 6 of section 2.1
Initial start-up.
2. Check that the temperature indicator has been placed
in the correct position to measure the temperature in
the return line to the users. Now start the circulating
pump. With all faucets “off”, observe the temperature
of the recirculated water.
3. Typically the diverting valve is set 10ºF below the
normal set temperature of the RediHeat. Because
diverting valves are less accurate than the water heater,
temperature variations up to 10ºF may be experienced
in the loop temperature.
4. If an adjustable diverting valve has been fitted, the
recirculated temperature should be adjusted with all
faucets “off”, after the piping system has had time to
stabilize.
Section 3
Maintenance
3.1 Blending Valve Disassembly
Refer to Section 4 of this manual for troubleshooting.
Disassembly of the blending valve need only be undertaken
if problems in performance or instability of temperature is
linked to the blending valve. Be sure all work is performed
in a clean environment to prevent the introduction of foreign
matter into the valve mechanism. Part numbers below refer
to the cross sectional drawings found on pages 31 and 32
in Section 7 Drawings, of this manual.
Procedure
1. Close all steam and water supply lines.
2. Disconnect the sensing tube (46) from the lower valve
body (42 or 43) and diaphragm cover (5). (Note position
of notch in cover relative to the valve body.)
3. Disconnect Victaulic couplings at all valve connections
and remove the valve.
4. Loosen and remove casing bolts (14) and lift off the
diaphragm cover.
5. Hold the upper stem (1) by placing wrench on flats.
Remove jam nuts (7) taking care not to turn the stem.
Remove shouldered washer (8) and O-ring (9) along
with diaphragm (13), diaphragm plate (11), spring (10)
and guide washer (16).
6. Inspect diaphragm for any cracks or tears.
7. Remove retaining clip (19) from the temperature control
rod (18). Unscrew the locking ring (21) and remove
cover plate (22).
8. Compress the circlip (23) and remove from adjusting
sleeve (27). Remove temperature control rod (18) and
adjustor key cylinder (25).
9. Caution: Do not permit valve plug to drop from lower
valve body. Hold valve stem (1) from above.
10. Unscrew retaining screw (35), remove spring (36), and
spacer washers (37 & 38).
11. Remove the valve plug assembly through lower
housing.
12. Remove socket head cap screws (12) and lift off lower
diaphragm case (5) Remove O-ring (15) taking care not
to damage groove.
13. Unscrew cap screws (49) and remove lower valve body
(42 or 43).
14. Push black teflon coated temperature-adjusting sleeve
(27) out of upper valve body (17).
15. Remove main valve stem (1).
Notes:
a) Inspect all parts for wear or damage. Replace all
gaskets and O-rings.
b) Clean, flush and dry with clean cloth.
c) See parts list for recommended overhaul parts. Gaskets
and O-rings should be replaced during any repair
procedure.
3.2 Blending Valve Re-assembly
Procedure
1. Install the temperature adjusting sleeve (27) into the
upper valve body (17).
2. Assemble upper valve body (17) to lower valve body (42
or 43) and secure cap screws. Note the cold water inlet
will be on same side as the control rod opening.
3. Insert main valve stem (1) into bottom of temperature
adjusting sleeve (27) and push until the collar washer
seats against upper valve body.
4. Insert valve assembly into adjusting sleeve (27) and
push until it is fully seated.
5. On lower end of valve stem install spacer (2), washer
(37), bearing washer (38), spring (36), and tighten
retaining screw (35).
6. Install O-ring (15) in groove on upper valve body and

8
install lower diaphragm case (5) securing it with cap
screws (14) tightening in a sequential manner (note
location of notch in relation to valve body).
7. Install adjustor key cylinder (25) on the pin located on
the valve shaft. Replace O-ring on temperature control
rod (18) and insert so adjustor key is centered in slot
and notch on control rod fits with groove pin in adjusting
sleeve (27). Install circlip (23) and locking ring (21).
8. Install, in order, the control valve spring (10), spring
guide washer (16), diaphragm plate (11), diaphragm
(13), O-ring (9), shouldered washer (8), and jam nuts (7),
on main valve stem. Position diaphragm over holes and
notch on lower case prior to tightening the jam nuts.
9. Install upper cover (6) and be sure notches in lower
cover, diaphragm and upper cover line up. Install bolts
and tighten sequentially.
10. Install valve on frame.
11. Install sensing tube (46) and Victaulic fittings. Check all
fittings for tightness.
12. Refer to start-up procedures for temperature
adjustment.
3.3 Heat Exchanger Inspection Disassembly
The heat exchanger coil is readily accessible for inspection
and cleaning without disturbing the steam or water piping.
Procedure
1. Remove plug to drain the casing.
2. Remove all base plate nuts (93 or 94).
3. Lift off the casing (80 or 81), being careful not to damage
the gasket (84 or 85).
4. If a leak in the tubing is suspected, water pressure can
be turned on. Any leaks should be easily seen with the
unit still in place.
To Clean the Coil
Depending on local water conditions, scale deposits from
hard water can form inside the heat exchanger coil. The
coil can be cleaned in place using an acid pump cleaning
system employing the following procedure:
1. Remove the two cast bronze elbow manifolds from
the heat exchanger by disassembling the four Victaulic
couplings.
2. Attach the 3/8” nipple supplied with the acid cleaning
system adaptor kit to one of the adaptors.
3. Insert this adaptor into the heater connection closest to
the center of the exchanger.
Note: the 3/8” nipple must extend up into the exchanger.
4. Secure the adaptor with one of the Victaulic couplings
removed in Step 1.
5. Connect the other adaptor to the remaining exchanger
connection with a Victaulic coupling.
6. Connect the acid hoses, pump and reservoir.
7. For proper cleaning, the acid must be pumped through
the exchanger in the direction shown in Fig 1 below.
The 3/8” nipple avoids gas pockets in the top of the
exchanger coil and must be on the outlet connection of
the cleaning system.
3/8” nipple must
be on return line
to acid reservoir Heat Exchanger
Outlet
adaptor
3/8” or 1/2”
Globe Valve
Acid reservoir:
Oakite #32 or
similar acid
Intlet
adaptor
3/8” pipe
connections
Acid pump:
Jabasco,
Little Giant,
Calgon
or similar
Furnished
by customer
8. After cleaning is complete, the coil should be flushed
with water before reconnecting the manifolds.
Note: For acid preparation, cleaning and safety
procedures, refer to the instructions supplied by the
acid manufacturer.
If Removal of the Coil is Necessary
1. Disconnect water piping and remove the manifold nuts
and lock rings.
2. Lift off the coil assembly (78 or 79), being careful not to
damage the manifold gaskets.
3.4 Re-assembly
Procedure
1. Replace manifold and baseplate gaskets.
2. Check that the tabs on the manifold lock rings fit into
the base plate slots. These keep the manifold-coil
assembly from turning when tightening the manifold
nuts.
3. Be sure the bottoms of the manifolds are seated in
pockets located inside the casing.
4. Install and tighten manifold nuts.
5. Install casing and tighten bolts sequentially.
6. Check nuts for tightness after an hour or two and again
after 24 hours of operation.
FIG. 1

9
Section 4
Troubleshooting
Observations regarding any problems should be recorded.
1. Does the problem present itself during no flow, low
flow, or high flow conditions, etc?
2. High temperature or low temperature? Note the
RediHeat is designed to prevent high temperature
failures, however, recirculation system failures may
lead to overtemperature situations during low flow
conditions.
3. Unsteady temperature?
4. Is the unit new or what is length of service?
5. What is the local water hardness?
6. Is the problem repeatable, sporadic?
The first step in resolving a problem with a RediHeat water
heater system should be to determine the source of the
problem:
• The recirculation system
• The RediHeat blending valve
• The RediHeat heat exchanger
1. Check the position of the water outlet temperature
gauge. Has it been installed according to the
recommended Piping & Instrumentation Diagram?
The gauge should be downstream relative to the point
where the recirculated water returns to the unit.
2. For facilities with recirculation systems, the circulating
pump should be turned off to start the troubleshooting
analysis.
Water Temperature Is Too High
1. Has inlet water temperature changed since the valve
temperature setting was adjusted?
2. Is the RediHeat temperature adjustment set correctly?
3. Has steam pressure changed since the RediHeat
temperature was adjusted?
4. If fitted with a recirculation system, turn the circulating
pump off. If the problem is eliminated, the trouble is
with the recirculation system.
5. For a new installation with a recirculation loop, check
the setting of the thermostatic valve. The thermostatic
element setting should be approximately 10°F below
the normal operating temperature of the RediHeat. For
example, if 120°F is the desired loop temperature, the
thermostatic element should be set for 110°F.
6. If the problem developed in an existing system, the
thermostatic element should be replaced.
See Section 5 “Recirculation Systems” for thermostatic
diverting valve piping instructions. Because this valve is
used in a non-typical manner, it is important to install the
valve as recommended in this manual.
Water Temperature Is Too Low
1. Is the problem in the RediHeat valve or the RediHeat
heat exchanger? The easiest method to answer this
question is to check the temperature of the pipe which
runs from the heat exchanger to the blending valve. At
low flows and when the unit is idle, this pipe should
be at a temperature about 200°F. At higher flow rates,
check the surface temperature of the pipe which
should remain above 150°F. If this pipe goes cold when
water demand increases, the problem lies in the heat
exchanger. Otherwise, the source of the problem is in
the RediHeat blending valve.
Heat Exchanger Is Source of Problem
1. Has air been vented from the shell side of the heat
exchanger?
2. Is steam supply at constant pressure? During high
demand?
3. Is the condensate drain trap functioning correctly?
4. Is the coil fouled due to hard water?
RediHeat Blending Valve Is Source of Problem
1. Is temperature adjustment correct?
2. Disassemble valve - is the plug stuck in the open
position?
3. Is the seal plate assembly and gasket in need of repair?
Restricted Water Flow
1. Is the valve diaphragm ruptured?
2. Is the sensing tube plugged?
3. Are there any restrictions in the water piping?

10
Section 5
Recirculation Systems
A problem many hot water systems encounter is the
delayed supply of hot water to fixtures that are a substantial
distance from the heater. During idle periods, heat loss in
the piping system will result in cool water at the tap until hot
water produced from the heater is able to reach that point.
Delays in providing hot water at the tap can result in user
dissatisfaction.
The compactness of the RediHeat permits installation close
to the point of use in many cases. However, in systems with
long pipe runs, conditions may exist where the supply of hot
water at the faucet will be delayed.
To provide instantaneous hot water on demand in systems
with long pipe runs, various methods can be utilized. The
appropriate system will be influenced by site conditions,
plan requirements, and user preference.
The following describes several systems and their interaction
with the RediHeat instantaneous heater:
A. Heat Tape Systems
Many building systems avoid the costly pipe runs of
conventional loop or return systems. Instead, electrical
resistance heat is applied to the pipe in tape form to replace
heat lost from the system. This method can be very effective
and the RediHeat will function perfectly with this type of
system. Heat tape installed up to the hot water outlet of the
control valve will assure maximum performance.
B. Bleed System
This system consists of a single line distribution pipe with a
thermostatically operated bleed valve. A temperature switch
is set to open the bleed valve if the line temperature falls
below the system set point. Upon opening, water in the line
is dumped to drain until heated water from the RediHeat
fills the line and signals the valve to close. This cycle will
continue to hold the water temperature within set limits.
This system eliminates the costs of return piping and
circulation pumps, however the cost of water consumption
may prove too high for many installations.
C. Forced Recirculation Loop - Diverting Valve with
Fixed Thermostat:
Most systems incorporate a circulating pump to maintain
constant flow in a forced recirculation loop. The RediHeat
is used to maintain loop temperatures as well as supply
demand requirements. The system includes a self contained
3-way thermostatic type diverting valve to direct the
recirculated water flow as required. The diverting valves
normally are provided with fixed thermostatic elements.
Models with adjustable elements are also available (see
section D).
Water flow in the system is governed by the temperature
of the recirculating loop. When the loop is at the desired
temperature, the flow of recirculated water by-passes the
RediHeat. As the temperature in the loop decreases due
to heat loss through the piping, the thermostatic element
responds and causes a portion of the water to be diverted
through the RediHeat. Typical recirculated flow rate is
10% of the RediHeat capacity, however more accurate
calculation methods should be used in complex systems.
Installation of the diverting valve is as shown. If you have
any questions regarding installation, contact Spirax Sarco.
Incorrect installation can lead to serious overheating of the
water, resulting in dangerous temperatures.
D. Forced Recirculation Loop (Diverting valve with
adjustable thermostat):
In addition to the fixed thermostatic element diverting valve,
Spirax Sarco offers as an option an adjustable diverting
valve. The adjustable diverting valve can be used to provide
additional flexibility in the temperature of the hot water when
the system is in the recirculation mode. The valve supplied is
a Lawler Thermostatic Water Controller or equal. As Spirax
Sarco uses the valve in a non-typical manner, do not follow
the standard installation instructions supplied by the valve
manufacturer. The following should be used as a guide for
installation of this system.
Connect the Lawler port labeled “outlet” to the recirculating
loop return line. This is the flow into the valve from the
circulating pump, indicated as “A” below.
Connect the port labeled “H” (hot water inlet) to the cold
water supply line feeding the RediHeat. This port will open
when the recirculation loop water has cooled, and sends a
portion back to the RediHeat for reheating.
Connect the port labeled “C” (cold water inlet) to the hot
water supply line feeding the recirculation loop. This port
is open when the recirculation loop water is at the desired
set point and allows the recirculating water to by-pass the
RediHeat.
Installation of the diverting valve is as shown. If you have
any questions regarding installation, contact Spirax Sarco.
Incorrect installation can lead to serious overheating of the
water, resulting in dangerous temperatures.
Diverting Valve
(Fixed Thermostat)
*
RediHeat Cold Water
Supply
Hot
Water To
Users
Diverting Valve
(Fixed Thermostat)
*
RediHeat Cold Water
Supply
Hot
Water To
Users
* A Thermal expansion tank may be required when the cold
water inlets include check valves.
* A Thermal expansion tank may be required when the cold
water inlets include check valves.

11
The following procedure should be used when starting the
RediHeat fitted with a forced recirculation loop system.
This procedure will be applicable in systems with either a
fixed thermostatic element diverting valve, or the adjustable
thermostat diverting valve.
1. With the circulating pump “off”, set the RediHeat water
outlet temperature as described in Section 2 – RediHeat
Start-up Procedure.
2. Check that the temperature indicator has been placed
in the correct position to measure the temperature in
the return line to the users. Now start the circulating
pump. With all faucets “off”, observe the temperature
of the recirculated water.
3. Typically the diverting valve is set 10ºF below the
normal set temperature of the RediHeat. Because
diverting valves are less accurate than the water heater,
temperature variations up to 10ºF may be experienced
in the loop temperature.
4. If an adjustable diverting valve has been fitted, the
recirculated temperature should be adjusted with all
faucets “off”, after the piping system has had time to
stabilize.
Section 6
Ordering Spare Parts
When ordering spare parts, please address your
communication to:
Spirax Sarco, Inc
1150 Northpoint Blvd.
Blythewood, South Carolina, 29016
Telephone: [phone]
Fax: [phone]
E-Mail: [email protected]
Website: spiraxsarco.com/global/us
IMPORTANT
The following information should be given in order to iden-
tify thespare parts required:
• Serial number of unit (stamped on nameplate)
• Name or description of part required
Spirax Sarco presents the information in this manual as
good engineering practice. We cannot be held responsible
for any damage to equipment that may result from mal-
operation nor for any personal injuries should they occur
during normal or abnormal operation.

12
SPIRAX SARCO, INC. • 1150 NORTHPOINT BLVD. • BLYTHEWOOD, SC 29016
PHONE [phone] • FAX [phone]
www.spiraxsarco.com/global/us
Spirax Sarco Applications Engineering Department
Toll Free at:
1-800-883-4411