1) You have determined that the furnace has power. That's good.
2) Turn the thermostat down below the temperature of the house... Have an assistant stand by the thermostat and now go to the furnace. When you are there have them turn the thermostat up.
Does anything at all happen?
Of so...describe what it is doing and post back.
If *absolutely* nothing happens, then a wire on the thermostat could be broken.
If you hear a click and gas starts to flow, but nothing ignites, then it shuts down...then the igniter is bad.
Hi, Then there is no reason blower would run. Just jumper W and C at the furnace after taping down the cover interlock switch. If furnace works go to 'stat and do the ssame. If furnace does not start then can assue wire is broken or loose some where.
He already determined that the blower came on. Now, we need to determine why. That is why I asked for him to get the t-stat set up to all off, then have the cover replaced. If the blower turns back on something is making an improper contact, one of the relays is stuck, or the HTR relay is not functional (bad coil). That is if he is correct when he stated that he had a nominal control voltage. 27vac, I believe.
Be careful asking him to play with the access door switch. That switch has
120V going to it. Sometimes they are not finger proof. :-)
May be different in your part of the world and I'm not sure what that code actually says. But every furnace I've ever seen there has been at least one emergency switch with a red plate. Sometimes it's in the basement stairwell, with the furnace in the basement.
Yes, you can jumper from the red to the white on the right side, the R and WH terminals.
If you hadn't put it back together, you could have just connected the red and white together there.
IIRC, I took it off months ago, when it was something like 95 degrees outside, but all I could do was stare at the setup as I didn't understand how to troubleshoot.
But, not having A/C in 95 degree weather is nothing like not having heat in 32 degree weather; so, it's more important to figure it out now than in the summer.
I'm ok, by the way; but the wife and kids don't like the cold.
The stove and hot water heater are burning fine, and the propane tank is nearly full; and the valve is in the "on" position; so, I can pretty much assume I have gas.
Some units will use a cord plugged into a receptacle. Usually this is only for control voltage, but in his case the control power supply also powers the blower. He might have a disconnect that he has not noticed. Usually this is required, but if in eyesight of the panel I don't think it is in this case.
Check for 24VAC between SEC1 and SEC 2. If there is no 24VAC, check the transformer solder joints on the circuit board
Leave one lead on SEC2 and check for 24VAC on the red wire terminal. If you have 24VAC the interlocks are OK. If not, trace back until the open interlock is found
With the stat calling for heat, check for 24VAC at the W terminal. If you have 24VAC, the stat heat circuit is good. You should hear the gas valve click and the igniter spark.
If you look at the schematic for 394JA you will see the blower motor relay is normally closed. If the furnace is powered up and there is not 24VAC at the R terminal, the blower motor will run right away and not shut off, which is what you said it's doing (note the jumper between R and GH)
The California-specific PDF that I was sent says what you say, in that a switch must be within sight of the furnace; but it also allows for the door switch serving double duty as that shutoff.
Literally, that PDF says: "a disconnecting means must be located within sight of, and readily accessible to, the furnace. The blower door switch may be acceptable in some areas as a disconnecting means".
So, from that, I must assume the blower door switch is *my* disconnecting means. I'll snap a photo of the electrical wires tomorrow (in the daylight) to show you what mine looks like.
I read the entire PDF, from front to back. Here's a summary of what I gleaned about the furnace operation:
Summary:
Red wire is 24VAC hot.
Thermostat "calls for heat" by connecting Red to White.
Thermostat "calls for fan" by connecting Red to Green.
Details: Thermostat "calls for heating" by connecting Red to White.
Power then goes from the Transformer -> Fusible Link -> Limit Switch -> Vent Safety Shut-off Switch -> pilot (both "pick" & "hold" gas valves) such that pilot gas flows, where it ignites.
~60 seconds after pilot, safety pilot switches its contacts and energizes the main valve portion of the gas valve, where, about 10 seconds later, the main gas valve opens, and the main gas is ignited by the pilot flame.
~75 seconds after the pilot lights, the fan control board activates the fan on low speed (it uses the low speed for heating purposes).
When the thermostat "is satisfied", the connection between R & W is broken. Gas is immediately stopped to both the pilot and main burners. The blower continues for about 100 seconds.
If the furnace overheats, the Limit Switch opens. If the furnace overheats in the vestibule, the Fusible Link opens. If the furnace overheats in the vents, the Vent Safety Switch opens.
I see the fusible link on the red wire here:
formatting link
I'm guessing this is the limit switch:
formatting link
But, I can't seem to find the "Vent Safety Switch".
The electrical code in the US demands that the furnace have a permanent connection to the power source...no plugs allowed. But when I asked the electrical inspector if I could put a plug on it so I could run it from a generator, he said, "no problem". The electrical code is very strict...except when it isn't.
Hi, I already mentioned about that too. Maybe he can read but can't comprehend? Getting zapped will make him call for pro help. It is hard to get killed by 120V AC unless one's feet are bare and wet. If he is afraid, some one has to be nearby to watch, ready to throw the breaker in case he is getting zapped. Desire to learn is good thing but one has to have some basic knowledge first. He can enroll at community college to take electricity 101 or some thing like that. Oh, no, then he'll be more dangerous knowing little bit......
Nope. Now the blower doesn't go on at all when I hold down the furnace door switch. I did hear some snapping at one point, but then it went away. It was like a sharp click click click...
So I opened the blower door (to interrupt the power) and gently tapped on everything, especially the solenoids; and I wiggled all the wires. I found one that seemed loose; and now it's back on tightly...
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.