Page 32 | LAARS HEATING SYSTEMS |
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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.
10B. Short Cycling
Possible causes
a.Reduced system flow - EDP
b.Thermostatic union (EDP) or
c.
d.Leakage of flue products into the combustion air stream – Direct Vent Installations only, see Section
10C. 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 CO2 or low O2) or cross contamination. The mixture is determined by measuring the percent O2 or CO2 in the flue products. O2 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 O2 will rise above 4½% or the CO2 will drop to 8½% (natural) or 9½% (LP).
The CO2 & O2 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.
10D. 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.
Failure of the water flow switch to operate during a hot water draw prevents boiler water from
