Tip & How-To about Heating & Cooling

Heater check out list for heater failures

Almost all furnaces built after 1978 have intermittant type pilots.
Ca banned them requiring electronic spark or hot surface ignitors, followed by induced draft motors, pressure switches or centrifigal switches that "prove" a induced draft exists, allowing the pilot sequence to commence.
electronic spark type units have a high voltage low amperage spark that is AC. Fire rectifies electricity that passes through it meaning AC becomes DC ! Fire is a terrible conducter however as a result , the DC signal is only milliamps/volts signal strength. the DC prescence is proof a flame exists for pilot, and safe to commence to mainburners.

As long as pressure switches stay closed, safeties and limits stay closed
and the DC signal to the ignition module is not broken, the furnace will run.

The normal sequence of operation is upon a call for heat from the thermostat a 24 volt signal is sent to W white (heat circuit) at the low voltage terminal board on furnace.
from there depending on unit and age the heat circuit may include a circuit board, but it still has the typical limits and safetys reqired for operation
its just not using electromechanical relays to control fan and induced draft motor etc.

for the induced draft to begin ,all limits, safetys in heat circuit must be closed.

induced draft begins and a proving switch, either pressure or centrifigal close allowung the pilot to begin, a spark or hot surface ignitor is energized and a pilot flame established,modern types use flame rectification to prove a flame, older Carrier, Payne,types have a 3 wire switch in the piloyt assembly that is a bi metal that expands and contracts clicking open and shut, allowing pilot or main burners, depending if cold or hot.

pressure switches are attached with tubing to the induced draft wheel housing and sense pressure differential and close upon induced draft running, the orifices that the tube attaches to on induced draft housing often plugs or is restricted causing pressure switch to fail to close, or waver on open and close , open , close, .

if you can run the fan in the on postion , you have both high and low voltage to the furnace.

if you dont have fan control check power, breaker , fuses.

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Rheem Furnace


do you have a standing pilot or electronic ignition furnace........you could have a problem with a safety switch, bad electrical connections, electrical short, circuit board issue, hot surface igniter issue....etc...........need to know the type of furnace

Dec 05, 2013 | Heating & Cooling

1 Answer

how do you light the furnace of a goodman ez 1625


We have not lit pilot lights ourselves since 1978 when they outlawed standing pilots in Ca for furnaces. We have electronic ignitions of spark oror hot surface ignition, neither of which can be manually lit.
Do you get any fan action if you flip the fan on from auto?if so, you have power and 24v control power too, I would start there.

Oct 31, 2012 | Goodman Heating & Cooling

1 Answer

Lighting pilot on Ruud 80 plus furnace?


Hi, There is no pilot and the flame is lit by a hot surface ignitor... The hot surface ignitors go bad frequently...you probably need to replace that...

Here is a tip that will help you try to figure out why your furnace is notworking.

BasicFurnace or Heating System Troubleshooting

heatman101

May 14, 2011 | Ruud Heating & Cooling

1 Answer

why heater coils glow?


It sounds like you're describing one of two things. The hot surface ignitor in a gas-fired furnace, or the resistive heat strips in an electric furnace.

The hot surface ignitor in a gas-fired furnace lights the burners. This ignitor in modern furnaces serves the same purpose as the standing pilot flame did in older furnaces. It provides the required heat to ignite the gas at the burners. Without an ignition source, a gas-fired furnace cannot provide heat. When the ignitor is activated it will glow bright orange or yellow.

The resistive heat strips in an electric furnace actually provide the heat to a home or building. When the furnace turns on, the heat strips are activated and usually glow orange when they reach peak temperature. In almost all cases, the heat strips are not easily seen or accessed without removing covers or panels inside the furnace.

Feb 28, 2011 | Heating & Cooling

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