Air Conditioning - Goodman m#PBG048075-1 heat blower trouble
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T IN TEXAS
12-24-07, 07:21 PM
Got a goodman m#PBG048075-1 on heat blower comes on 30 sec after burner lites . Heat exchanger never gets a chance to got hot have replaced control board and still no luck.Anybody got any ideas.
Thanks
Thanks
pflor
12-24-07, 08:55 PM
I'm not sure I understand you fully.
It is normal for a blower to take a few seconds after the burners light-up before itself kicks ON...of course after the blower is ON the furnace should remain lit until the thermostat says "NO MAS".
Is the problem perhaps that the fire starts and a few seconds later ceases? If so, you seem to have a problem with the board being told that the flame is not present (though it is)...which causes an inmediate safety shut-down.
This would NOT be a board problem but rather a "flame sensing" problem or a "defective igniter".
So please ellaborate a bit more about the problem.
It is normal for a blower to take a few seconds after the burners light-up before itself kicks ON...of course after the blower is ON the furnace should remain lit until the thermostat says "NO MAS".
Is the problem perhaps that the fire starts and a few seconds later ceases? If so, you seem to have a problem with the board being told that the flame is not present (though it is)...which causes an inmediate safety shut-down.
This would NOT be a board problem but rather a "flame sensing" problem or a "defective igniter".
So please ellaborate a bit more about the problem.
T IN TEXAS
12-25-07, 10:21 AM
Unit has good strong flame stays on induction motor running fine also, Blower starts in 30 seconds heat exchanger does not get to heat up enough you get cool maybe warm air at best. Most units Ive see have a limit switch to start fan we it reaches operating temp this one does not guess its built into control board I guess.
pflor
12-25-07, 12:41 PM
When it comes to switching the fan ON and OFF, there are 4 different way to doing so. Different manufacturers have their preferences and add controls that will cycle the fan accordingly.
The limit switch you're talking about is really 2-switches in one (i.e., Honeywell L4064), it is both a high-limit and a fan-cycling switch; it is very common in older units and is a Temperature-ON/Temeperature-OFF switch.
Other type of control (typically an electronic board) cycle the fan "not" on temperature but rather on a factory-set time delay. This is what is known as a Fan-ON/Fan-OFF strategy. Such appears to be the case with your Goodman furnace.
Why is your air only lukewarm? I can foresee four possible reasons: (1) the fan speed is set too high, (2) your supply-air system [trunk and branches] is not insulated and runs trhough an unconditioned space, (3) you may be expecting too much from gas heat, and (4) your house is too drafty
How to fix any of these?
(1) Find out from the nameplate which is the manufacturer's recommended temperature rise [techs call this the "split"]. If it is too low, the fan speed is high, disconnect and choose a lower speed
(2) Insulate supply trunk and branches. I did this in my house years ago and got to see how the temp of the air coming off the registers rose from 90 to 120F [I'm not kidding!, and I live in NJ]
(3) Oil heat allows for supply air temperatures in excess of 130F. With gas heat you're lucky if you get 125F
(4) Add weatherstripping (and/or infiltration stoppers) to windows and doors
Hope this helps.
PF
The limit switch you're talking about is really 2-switches in one (i.e., Honeywell L4064), it is both a high-limit and a fan-cycling switch; it is very common in older units and is a Temperature-ON/Temeperature-OFF switch.
Other type of control (typically an electronic board) cycle the fan "not" on temperature but rather on a factory-set time delay. This is what is known as a Fan-ON/Fan-OFF strategy. Such appears to be the case with your Goodman furnace.
Why is your air only lukewarm? I can foresee four possible reasons: (1) the fan speed is set too high, (2) your supply-air system [trunk and branches] is not insulated and runs trhough an unconditioned space, (3) you may be expecting too much from gas heat, and (4) your house is too drafty
How to fix any of these?
(1) Find out from the nameplate which is the manufacturer's recommended temperature rise [techs call this the "split"]. If it is too low, the fan speed is high, disconnect and choose a lower speed
(2) Insulate supply trunk and branches. I did this in my house years ago and got to see how the temp of the air coming off the registers rose from 90 to 120F [I'm not kidding!, and I live in NJ]
(3) Oil heat allows for supply air temperatures in excess of 130F. With gas heat you're lucky if you get 125F
(4) Add weatherstripping (and/or infiltration stoppers) to windows and doors
Hope this helps.
PF