HS Tarm 2000, Installation And Operation Manual

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T
ROUBLESHOOTING (continued)
PAGE 54
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BOILER OVERHEATING (continued)
Following the recommendations in this manual will minimize the possibility of overheating.
However, even the most experienced person may occasionally overheat his boiler. To cope
with this problem, the boiler is equipped with two safety devices-- the Overheat Circuit and the
Pressure Relief Valve. The Overheat Circuit is wired to circulate excess boiler heat to the house
when the boiler reaches a preset temperature of 210
°
F. This control turns on the circulator or
opens the mixing valve for the largest heating zone. Generally, the overheated boiler can be
cooled within 10 minutes.
If the overheating condition is more severe, the temperature will continue to rise. At about 250
°
F, the pressure in the boiler will have reached 30 psi; and the pressure relief valve will open,
discharging steam. For your information, all Tarm EXCEL boilers are pressure tested to 60 psi
at the factory.
NOTE: TO PREVENT THE POSSIBILITY OF SERIOUS BURNS OR PROPERTY
DAMAGE FROM THIS STEAM, THE DISCHARGE TUBE FROM THE RELEASE
VALVE MUST BE PIPED TO A POINT 6” FROM THE FLOOR OR TO A DRAIN!
The reason that steam rather than water is discharged is due to the fact that water under
pressure can reach temperatures above 212
°
F without boiling (as in a boiler), but, when
released to the atmosphere by the relief valve, water turns immediately to steam if it is over
212
°
F.
Should overheating occur, or the gas supply fail to shut off, do not turn off or disconnect the
electrical supply to the circulator. Instead, shut off the gas supply at a location external to
the burner.
TO COOL A SEVERELY OVERHEATED BOILER (relief valve discharging, or temperature rising
over 230
°
F) follow these steps:
1. Be sure the loading door and ash door are tightly closed.
2. Be sure the by-pass is in the closed position.
3. Open all hot water faucets in the house if the boiler has a domestic hot water coil.
4. Turn all thermostats up to their highest setting.
5. Open windows as necessary to keep the house cool.
When the boiler has cooled to normal operating temperature, resume normal operation.
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