Furnace 不工作, 急! 请教高人

[hitony]

Thank you very much! Can I disconect the red, blue and black wire of the limit switch to see if the furnace works or not? I think the limit switch was damaged when I turn on the furnace for few hours without turnning on the fan. Am I right?

 

[Timothy's]

You don't need to turn on the fan. The fan usually has two setting. ON and auto. If you are not at ON then is auto.

For ON the fan would run 24/7

For auto fan only run when it fires. I don't think you damaged furnace by not put fan on. It was just in auto.

I think if you disconnect the limit switch . The furnace should not work. Try to jump the red and blue wire. If it works then it is the limit switch.

 

[zipped]

according to your schematic, please check the thermostat connected to the gas valve. If the temperature does not rise to a burning level, the gas valve will be shut off by itself. The thermostat does that as well. This is also a common failure.

Please take a close-up pic of the fan/limit switch and also the gas valve assy. Please also include the burner section so that I can tell you where the thermostat is.

 

[hitony]

To Timothy's:

do you mean connecting the red and blue wire of the limit switch? Thanks

 

[iiWii]

according to your schematic, please check the thermostat connected to the gas valve. If the temperature does not rise to a burning level, the gas valve will be shut off by itself. The thermostat does that as well. This is also a common failure.

Please take a close-up pic of the fan/limit switch and also the gas valve assy. Please also include the burner section so that I can tell you where the thermostat is.

You are absolutely correct! check the thermostat first. mostly poor contact.

 

[hitony]

thank you all for your help!

the fan has it's own switch, I set for Auto, here are some pics, thank you all for your help!

 

[hitony]

我再看了一下电路图, 觉得好像不是Fan limit的问题, 因为 24v一直有,如果有问题, 变压器就会断电, 没有24v的输出, 现在有24v供电, 起码它能控制气体阀门打开一会, 点燃大火后再被Fan limit控制,切断110v供电,24v没有了,气体阀门关闭熄灭大火, 火苗Pilot不熄灭. 我也觉得是气体阀门控制器的可能性高些. 因为现在大火不能被点燃. 不知对否?

 

[iiWii]

To be very clear about the problem, please let us know yes or no folr the following:

1/ Pilot will lit and stable by itself?

2/ Burner fires but will shut itself out shortly?

 

[sip]

我再看了一下电路图, 觉得好像不是Fan limit的问题, 因为 24v一直有,如果有问题, 变压器就会断电, 没有24v的输出, 现在有24v供电, 起码它能控制气体阀门打开一会, 点燃大火后再被Fan limit控制,切断110v供电,24v没有了,气体阀门关闭熄灭大火, 火苗Pilot不熄灭. 我也觉得是气体阀门控制器的可能性高些. 因为现在大火不能被点燃. 不知对否?

和我原来的情况很相似，Furnace 刚点燃一会儿（大约３０秒）就自动熄灭。原因是电线老化，接触不良。风扇一动以后振动使电源断掉。因此就不工作了。再次建议把所有线头都检查一下，看有没有接触不好的。主要查１１０Ｖ到２４Ｖ变压器周围的电线。如果可能，重新拔插一下。

 

[hitony]

To iiwii:
1) yes, Pilot always lights and stable by itself.
2)No, Burner never fires after it had problem.
3) I set fan in auto position, but the fan is always on .

Thanks

 

[ccc]

To iiwii:
1) yes, Pilot always lights and stable by itself.
2)No, Burner never fires after it had problem.
3) I set fan in auto position, but the fan is always on .

Thanks

Module/ignition control problem.

 

[iiWii]

To iiwii:
1) yes, Pilot always lights and stable by itself.
2)No, Burner never fires after it had problem.
3) I set fan in auto position, but the fan is always on .

Thanks

Here what you will need to do,

Check if the connections to the Gas Valve are good or not.
1/ Thermostat from your upstair,
2/ the 24V supply,

If 24V presence and Thermostat calls for heat, you will need a new gas valve and has to be installed by lic tech. This is a law. Simple way to check is the short the thermostat wire, the gas valve should be activated. If not, the valve is no good.

If there's no 24V, follow the diagram, check if the 110V connections to the transformer and the continunity of the fan/limit swtich (red/blue arrows in the schematic picture).

 

[iiWii]

schematics

 

[hitony]

iiwii, Thanks a lot, I will check it again right now.

 

[bbb52]

Fan/Limit must have problem if...

谢谢楼上的答复!

上个月我请人清洗了furnace, 然后开Furnace后忘记开送风电机约一小时, 后打开送风电机,furnace正常工作了2天, 然后就不工作了.
Furnace的后挡盖子原来是盖好的,为了拍照才打开. 火苗一直都有,另附上多图, 望有用.
电压测量: RH--W. 26V, RH--Y 26V, RH--G 26V 全是交流电压.RH=RC.

电路图里那个继电气体阀门控制器 都有26v的交流电.
电阻: 室内温度小于设定温度时. RH---W 之间导通, 反之 不通. Y--RH 电阻一直变.
请问, 那个FAN/LIMIT CONTROL 是如何工作的? 我认为温度调节器正常, 不知对否?

Furnace should work like this:
When the furnace is ready: power on, all valve set to on position, door closed and ...
The thermostat call for heat.
Furnace start ignition process.
flame sensor sense flame (pilot ormain).
No flame, gas valve off.
Has flame, once temperature reach fan temperature setting, fan start automatically.
if fan no come or air flow could not take all heat (dirty filter or blocked ductworks) , temperature reach high limit setting, high limit switch open, shut off gas valve, fan switch should be on.

I don't really understand "然后开Furnace后忘记开送风电机约一小时", 后打开送风电机", If the fan would not start automatically and let the high limit shut off the furnace without wiring problem, the fan/limit switch must have problem.


You have to hire some technician to troubleshoot the problem.