LAARS Mighty Therm HH (Sizes 2000-5000) - Installation, Operation and Maintenance Instructions - Manual (Page 14)

LAARS Heating Systems
Page 14
4. Boiler is pounding, Knocking or emitting steam
from relief valves.
Possible Cause What To Do
A. Low or no water flow. A.This condition is usually caused
by lack of adequate water flow
through boiler.
Check the following:
1. Is the heater wired into the
pump circuit so that the boiler
cannot fire unless the pump is
running?
2. Check to see that all valves
in system are open to be sure
that water can circulate through
the boiler and the system.
3. If the system has automatic
water valves (2-way or 3-way)
that can cut off the water flow
through the boiler check to see
that they are equipped with
end-switches which shut the
boiler down when the water
flow through the boiler is
reduced by 70% from full flow.
Also be sure that manual
bypasses are provided around
two-way zone valves where
necessary in order to assure
15% of full flow through the
boiler at all times.
4. Examine pump for clogged
impeller
5. Water flow through the
system may be impeded by air
locks at high points. Residual
oil in system tends to collect at
high points and clog automatic
air vents. Be sure that all high
points are adequately vented.
B. Low or no system pressure B.Check for inoperative water
makeup valve or pump. Also
clean strainer in pressure
reducing valve which furnishes
makeup water. Look for closed
valve in makeup water line or a
leak in the system.
C. Clogged “Y” strainer. C.Remove strainer element and
clean screen.
D. Debris from system piping is D.Remove header covers.
blocking tubes. Examine all tubes and
waterways. Use new gaskets
when reassembling.
Clean out tubes.
E. Scale has formed in tubes. E.This is always caused by the
inflow of raw water into the
system. Check for leak in
system, especially at pump
packing. Check for water-
logged expansion tank. This
condition will cause water to
discharge through the relief
valve every time the boiler fires
and permits raw water to enter
the system every time it cools
down. Drain expansion tank.
5. Pressure relief valves leaking intermittently or
steadily.
Possible Cause What To Do
A. Static pressure in system A.Calculate height of water in
exceeds setting of relief valve. system above boiler. Install
new valve with psi setting
25% above required static
system working pressure.
Do not exceed 160 psi.
B. Expansion tank is B.Drain expansion tank, then
waterlogged. reopen it to the system. Look
for leaks in expansion tank or
fittings. Calculate required
volume of expansion tank in
relation to system to
determine that tank is
adequate.
C. Valve between system and C.Open valve so that pressure
expansion tank is closed. in system will be open to tank.
6. Soot in flueways or in tubes, or noxious fumes
indicative of bad combustion.
Possible Cause What To Do
A. Combustion air supply to A. Check air supply opening.
heater room is inadequate. Look for debris in screen or
louvre which covers
combustion air opening, or for
material blocking the opening.
B. Stack or vent is blocked or B. Look for blocked stack and
restrictive. excessive number of elbows in
stack or excessive length of
horizontal runs.
C. Severe down draft is C. Check for (1) proper vent cap
causing spillage of flue on stack; (2) adequate height
products into room. of stack above roof; (3)
equipment exhausting air from
inside of building; and (4)
setting on the barometric
damper if applicable and
(5) proper installation of draft
diverter.
D. Gas pressure to burners is D. Check gas pressure with
excessive. manometer, and adjust with
heater firing at full rate.
E. Boiler not fitted for the fuel E. See nameplate for correct
being supplied fuel.
F. Boiler installed at high F. Installations at altitudes in
altitude without proper excess of 2000 ft. above sea
derating. level are subject to jurisdiction
of the local inspection
authorities.
G.Water entering boiler is G.Add balancing valves if
105°F needed to raise entering
temperature.