LAARS EDN Series - Installation, Operation and Maintenance Instructions - Manual (Page 36)

Page 36 LAARS Heating Systems Company
Gas valve regulation problems can also cause
delayed ignitions. See “Gas valve calibration”.
Incorrect gas orifice – Check orifice size.
A defective burner can cause a delayed ignition
during operation or at shutdown. If the gas supply
pressure is proper the gas valve is functioning properly
and the gas orifice is correct, the burner should be
inspected. To inspect it, remove the blower. The burner
is retained by the blower and it will drop out of the
bottom of the chamber when the blower is removed.
There should be no distortion or perforations in
the burner other than the punched holes. Replace if
indicated.
11.2 Short Cycling
Possible causes
a. Reduced system flow - EDP
b. Thermostatic union (EDP) or anti-condensing
valve not opening (EBP).
c. T-T wires cross connected (jumped) – improper
installation - EBP or EDP/EDN
d. Leakage of flue products into the combustion
air stream – Direct Vent Installations only, see
Section 9.2.3, Resolving Lockouts.
11.3 Noisy Operation
There are two principal sources of noisy
operation:
a. Combustion - high pitched noise - whistle or
hoot.
b. Boiling (kettling) - lower frequency noise which
varies with temperature - moan.
Many times it is difficult to determine the source
of the noise or if it is combustion related or boiling
related. Combustion noises always have the same
frequency; however, their volume may change from
the time that the burner first fires to the time that
it shuts off. A boiling noise is identified by rapidly
raising or lowering the system water pressure while
the noise is present. A change in the pitch or intensity
of the noise indicates a boiling problem.
Combustion noise occurs at any boiler discharge
temperature and is heard the loudest at the flue outlet
(especially on units that are sidewall vented). There
are two basic causes for the noise, rich mixture (high
CO
2
or low O
2
) or cross contamination. The mixture
is determined by measuring the percent O
2
or CO
2
in
the flue products. O
2
readings lower than 4½ % or CO
2
readings higher than 9¼ % (natural gas) and 10.8%
(LP) will often cause combustion related noise. The
rich mixture could be caused by the mis-calibration of
the gas valve (offset adjustment) or by the gas orifice
size. To eliminate the noise; first, check the gas valve
calibration. If it is correct, install a smaller gas orifice
so that the O
2
will rise above 4½% or the CO
2
will
drop to 8½% (natural) or 9½% (LP).
The CO
2
& O
2
readings may be influenced by
cross contamination. Suspect cross contamination if
the noise returns when the front panel is replaced.
Boiling (kettling) may occur at boiler discharge
temperatures from 170°F to 210°F. The temperature
at which it starts will vary from one installation to
another. The primary cause of the problem is poor heat
transfer on the inside of the boiler coil. This may be
caused by foaming due to excessive concentration of
antifreeze in the system or by scaling from the boiler
water due to hardness of make up water.
Plumbing antifreezes should never be used in a
boiler system. Only boiler antifreezes, with effective
antifoamants, are appropriate for the ENDURANCE
boilers.
NOTE: The concentration of appropriate antifreeze
should be always be kept as low as possible to
minimize its effect on heat transfer and efficiency.
The method for eliminating the boiling noise
is the same regardless of the cause. However, if
antifreeze in the system is suspected of being the
cause, the concentration (<35%) and type should be
investigated.
Moisture
Although it is not a primary cause of lockouts,
moisture in the combustion chamber may cause
lockouts by weakening the flame signal to the boiler
control. It should be suspected if the boiler temperature
does not rise above 160°F during long periods of
operation. This condition can be caused by a defective
thermostat in the thermostatic union of EDN or EDP
boilers (or the omission of the thermostatic union at
installation) or failure of the anticondensing valve in
the EBP (combi) boilers. Moisture can also get into the
combustion chamber through an incorrectly pitched or
incorrectly installed flue pipe (pitched back toward the
boiler without a condensate trap). The flue assembly
of EBP, EDN and EDP boilers installed as Direct Vent
boilers should always pitch down from the boiler.
11.4 Insufficient Hot Water (EBP only)
Possible cause:
a. No flow restrictor (supplied with unit - field
installed)
b. Water flow switch failure
c. Mixing valve setting or failure
d. Domestic hot water (DHW) heat exchanger
contamination
The most common cause for insufficient hot
water complaints results from failure to install a flow
restrictor. The absence of a flow restrictor allows
water to pass through the heat exchanger at a greater
rate than the boiler output is capable of heating to the
desired temperature.