LAARS NeoTherm NTV (Sizes 399-850 MBTU/h) - Service Manual - Manual (Page 64)

54
Service Manual - NeoTherm 500
If the system pressure exceeds the relief valve setting,
the pressure relief valve is designed to open and release
the excess pressure and water. Note - This type of valve
is designed to relieve a limited number of times during
its life cycle, so it is not a good idea to “test” the valve by
tripping the small metal handle on top. Sometimes when
this type of valve is opened, it will not re-seat correctly,
causing a slow leak. If this happens, and the valve can-
not be cleared, it must be replaced.
Tools and equipment required:
* Plumber’s torch, solder, and flux
• Two pipe wrenches
• Pipe dope or Teflon® tape
Procedure:
1. Turn off power to the system. Use the main discon-
nect switch mounted above the front panel.
2. Isolate the boiler from the system. To relieve the
pressure, open the boiler drain to the right of the
heat exchanger.
Fig. B35-1 - Pressure relief valve (typical)
Note -
Normally a drain pipe
would run from here to
within 6” of the floor.
3. The pressure relief valve is mounted on a pipe that extends up a few inches
above the top panel of the NT unit.
4. Disassemble and remove the drain pipe.
5. Unscrew the valve from the vertical pipe using the two pipe wrenches.
6. The replacement valve must be the correct size and capacity to match the size
of the NT unit. Check the old valve for two important numbers:
• The capacity of the old valve, listed in BTU
• The relief pressure of the old valve, listed in p.s.i.
These numbers will be marked on the body of the valve. Check for this before
you get a replacement. The replacement valve must have ratings for both BTU
and psi which are the same as or higher than the ratings on the old valve
7. Wrap a piece of Teflon® tape around the threads on the end of the vertical pipe.
Install the new valve using the two pipe wrenches.
8. Reassemble the drain pipe.
WARNING! Always re-install the drain pipe. If the pressure relief valve were
to open without the drain pipe in place, the boiling water could shoot out, caus-
ing personal injury or property damage. Most plumbing codes call for the drain
pipe to extend straight down to a point about 6” above the floor. Check your
local code.
B35
Removing and Replacing the Pressure Relief Valve