Engineered air DG series Technical Information PDF herunterladen (Seite 39)

A G-TRAC2 MANUAL

General Manual Revised: 03/15/99

Page

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 diaphrams 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 form. Combustion that is set at maximum efficiency will produce excess moisture. Often it is

desirable to have 1% to 2% higher excess oxygen readings then those normally listed to assist in keeping the flue

gases drier. Also note that extended chimneys can contribute to condensation problems (especially if they are not

insulated or at least double walled). Water in the heat exchanger can lead to premature failure due to thermal

stress or freezing. Another source of excess condensation is when a unit designed with capacity to heat 100%

outside air is operating with very little outside air, therefore operating at a low fire or cycling. This allows the cool

flue gases from low fire to cool and condense in the chimney.

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