Installation - Piping
4
Temperature & Pressure (T&P) Relief Valve
To reduce risk of excessive pressures and tem-
peratures in the water heater, install tempera-
ture and pressure protective equipment
required by local codes, but no less than a com-
bination temperature and pressure relief valve
certified by a nationally recognized testing lab-
oratory that maintains periodic inspection of
production of listed equipment or materials, as
meeting the requirements for Relief Valves and
Automatic Gas Shutoff Devices for Hot Water
Supply Systems, ANSI Z21.22. This valve must
be marked with a maximum working pressure
of the water heater.
•
Every SMART water heater must be protected
with a T&P relief valve.
•
Determine T&P relief valve size by the follow-
ing specifications, unless they conflict with
local codes:
- SMART 30/40/50: 3/4”NPT with an AGA
Rating of 100,000 BTU/hr and a maximum
pressure rating of 150 psig. (Watts 100XL-
8 or equivalent).
- SMART 60/80/100/120: 3/4”NPT with an
AGA Rating of 200,000 BTU/hr and a maxi-
mum pressure rating of 150 psig. (Watts
40XL-8 or equivalent).
For proper operation of the T&P and to pre-
vent the T&P from activating due to boiler
water temperature, use a T&P relief valve
with extended element. We recommended
an 8” minimum length to ensure element
senses domestic water.
Standard Installation
•
Install T&P relief valve in the
Auxiliary
con-
nection located behind the air vent on the top of
the water heater (Figure 1 page 8).
or
•
Install the T&P relief valve in the run (straight
through leg) of a tee located at the domestic hot
water outlet when using the
Auxiliary
connec-
tion for a recirculation return (Figure 2 page 8).
Commonwealth of Massachusetts Installation
Follow this procedure for jurisdictions requiring a
vacuum breaker to be installed on the domestic
cold water inlet.
•
Install the T&P in the run (straight through leg)
of a tee located at the domestic hot water out-
let. Use a long element T&P relief valve (Fig.
3B page 9).
T&P Relief Valve Discharge Piping
T&P relief valve discharge piping must be:
- made of material serviceable for tempera-
tures of 250ºF or greater.
- directed so that hot water flows away from
all persons.
- directed to a suitable place for disposal.
- installed so as to allow complete draining
of the T&P relief valve and discharge line.
T&P relief valve discharge piping
must not
be:
- excessively long. Using more than 2
elbows or 15 feet of piping can reduce dis-
charge capacity.
- directly connected to a drain. Terminate
discharge piping within 6” from drain.
Refer to local codes.
- plugged, reduced or restricted.
- subject to freezing.
CAUTION
NOTICE
