A
G-TRAC2
IOM-25
39 of 42
Mar 99 R7
9.
Usually changing the pilot assembly will not have much of an affect on the pilot signal if both assemblies are in good
condition and installed correctly.
10.
Ensure the pilot assembly gasket is tightly installed to stop air leakage into the pilot area.
11.
Standard
(round)
burner only. If the burner plate is not centered in the hole, it may allow too much of a gap over the
top of the burner, thus increased airflow through the larger opening may roll onto the pilot box. Place a spacer under
the burner plate to raise it into a centered position.
12.
Due to the low capacities of some small units with standard
(round)
burners only, there may be too much air entering
into the pilot air tube. It may be necessary to reduce this air quantity by placing a screw through the side of the
combustion blower outlet in a manner that the screw also passes through the metal tube that the rubber hose
connects to. This normally only occurs on units with an input of less then 300,000 BTUH.
Some units have a screw
mounted capacitor; ensure the screw does not obstruct the pilot tube’s air path.
13.
If a BMS signal is applied, caution should be taken about removing the transformer grounds that may interfere with the
BMS signal. It is possible that you may have disconnected the ignition control or ignition transformer ground.
14.
Water and ice have been located in the pilot gas lines, in the pilot air tube, in the pilot box, and in the pilot gas orifice.
Ensure these areas are free of moisture, locate the source and correct it.
15.
Snow, ice, or water on the ignition control(s) can stop a pilot from igniting or proving. These devices and their
associated parts must be kept clean and dry.
Regulator Gas Pressure Responses
On some indoor units the vent orifice fitting on the RV appliance regulator is to be vented to atmosphere. The field installed
vent line should be sized adequately, especially on longer runs. If there is more than one regulator connected to a common
run, which includes the main regulator and the line, is not adequately sized, changes in pressure on the RV diaphragms are
applied to all regulators. This includes the main regulator so an erratic inlet pressure will result and cause improper
combustion and also burner pulsating problems.
Some DJ unit manifolds have RV appliance regulators with a vent-limiting orifice, usually a brass orifice marked ‘12A06’.
Ensure that this tiny orifice is free of dirt or debris. A plugged orifice will impede regulators opening flow and cause
improper air/fuel mixtures.
Pilot Sensing Problems
Check the condition of the pilot assembly. Check for damaged or dirty ceramics, damaged gasket, and pilot set up. Ensure
the pilot tube is free of debris and blockages. Note that there is an orifice where the pilot gas line is connected to the pilot
air tube. This orifice is sized to the BTU and altitude requirements of the burner. It must be free of dirt and burrs to operate
properly. If there are problems lighting or proving the pilot that do not appear to be related to the ignition/flame
supervision device then carefully clean and inspect this orifice from both the gas tube and air tube side. If a burr exists,
remove it. Pilot pressure is 3 – 5” WC.
Smell from Flue
(Products of Combustion)
Smells are usually created by improper combustion set up. This can be due to a low inlet gas pressure, or just a bad
combustion set up. Note the comments below about combustion set up.
Water and Ice from Combustion
These heat exchangers are very efficient. Water is one of the major products of combustion and as such must be
controlled. The units are equipped with a drain. It is however best to allow water to leave the unit in the flue gases in vapor
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