
Heater Model T & P valve location T & P valve installs into: Watts Model or Equivalent*
WH-30 hot water outlet 3/4”NPT Tee 100 XL-8 3/4”Male inlet
WH-40†hot water outlet 3/4”NPT Tee 100 XL-8 3/4”Male inlet
WH-60†hot water outlet 1” NPT Tee with bushing 100 XL-8 3/4” Male inlet
WH-80†dedicated port3/4”Male x Female nipple 40 XL-8 3/4”Male inlet
*T & P valve must have 8” long temperature probe.
†Also applies to double wall coil models WH-40 D, WH-60 D and WH-80 D.
Temperature and pressure relief valve specifications
3
INSTALLATION REQUIREMENTS
The installation of this indirect-fired storage water heater must
conform to the following:
1. Local, state, provincial, and national codes, laws, regulations
and ordinances.
2. National Electrical Code (NEC).
3. National Plumbing Code (NPC).
4. Building Officials and Code Administrators International
(BOCA).
In any case where instructions in this manual conflict with the
above, let those codes take precedence.
The location of this indirect-fired storage water heater should be
made in consideration of the following:
1. Install indoors where not subjected to freezing temperatures or
physical damage.
2. Install as close to boiler as practical, to minimize piping con-
nections pressure drop and heat loss.
3. For system service convenience, do not install too close to the
boiler or other objects.
4. Install near a floor drain if possible, to prevent possible proper-
ty damage due to relief valve discharge or equipment leakage.
A drain pan is most suitable for protecting the surrounding
area.
The boiler used to supply hot water to the heater must meet these
requirements:
1. In some jurisdictions the boiler’s operating pressure must be
limited to 30 psig by a safety relief valve.
2. The boiler’s input rating must be within the heater’s recom-
mended sizing guide specifications. Too low an input rating
may cause excessive condensation in the boiler. Too high an
input rating may cause a boiler short cycling condition. Either
of these conditions could be detrimental to the life and perfor-
mance of the system.
PIPING REQUIREMENTS
TEMPERATURE AND PRESSURE RELIEF VALVE
1. Use only the Watts model or equivalent specified in the chart
below. The rating of each valve meets the absorption capaci-
ty of only the model of heater for which it is specified.
2. Must be installed in the run of a tee located in domestic hot
water outlet in heater, unless a dedicated installation port is
provided. No shutoff valves are permitted to be piped between
the relief valve and the heater tank, nor on the T & P discharge
line. (See Fig. 4)
3. Must be positioned to discharge downward, with the dis-
charge line within 6” of the floor line and directed towards a
drain or drain pan, if possible. The discharge line must not be
excessively long or reduced in size, be subject to freezing, or
be directly connected to a drain.
BOILER PIPING CONNECTIONS
1. General piping recommendations (See Fig. 4)
a) Install unions and shutoff valves for servicing conve-
nience.
b) Use 1” nominal minimum piping size and keep number
of elbows and overall piping length to a minimum to
insure the proper water flow rate to the heater coil.
c) Pipe the supply from the boiler into the coil inlet con-
nection, located at the top of the coil.
d) Pipe the return to the boiler from the coil outlet con-
nection, located at the bottom of the coil. Install a tee
with a drain at the coil connection, with a shutoff valve,
to aid in manual air purging.
2. Circulator zoning recommendations (See Fig. 2)
a) The preferred location of the circulator pumps for each
zone is on the boiler supply, with the expansion tank
between the boiler and the circulators.
b) A flow check valve must be installed on each zone,
preferably at the outlet side of each circulator pump, to
prevent water flow to other zones when they are not
demanding flow.
3. Zone valve zoning recommendations (See Fig. 3)
a) The preferred location of the circulator pump is on the
boiler supply, with the expansion tank between the
boiler and the circulator.
b) Use zone valves with low pressure drop specifications,
particularly on the water heater zone. A 1” zone valve
is recommended.
Figure 2. Typical piping for circulator zoning
Figure 3. Typical piping for zone valve zoning