Furnace Problems

[bruceb58]

Re: Furnace Problems

Usually, the only fuse in a furnace is a small fuse for the control board and that board is usually powered by 24VAC.

 

[jlinder]

Re: Furnace Problems

Bruceb58,

You may be right about the fuse for the 24v supply, but it gets a little weird here. The fuse is after the switch and protects a 24v transformer (assume it is a 24v transformer). This transformer is mounted on a quad box that is mounted to the switch box on the outside of the furnace.

Odd thing is this transformer is not connected to anything. The primary is wired up but no wires on the secondary. I wonder if it is a leftover from when this furnace replaced the original furnace??

 

[bruceb58]

Re: Furnace Problems

That is odd but the furnace's circuit card has to get 24VAC from somewhere so maybe there is another transformer. Is the fuse on the circuit card or just near that one transformer you mentioned. Is there another fuse mounted on your circuit card?

 

[j_martin]

Re: Furnace Problems

That is odd but the furnace's circuit card has to get 24VAC from somewhere so maybe there is another transformer. Is the fuse on the circuit card or just near that one transformer you mentioned. Is there another fuse mounted on your circuit card?

Probably a wire, and maybe a rewire by someone who didn't know the rules and practices of household wiring. For instance automotive wiring usually has a black ground. House wiring, the white wire is neutral, bonded to ground at the entrance. I've seen many basements and additions wired backwards.

In the old days, a furnace had a 24V gas valve, you supplied the power. the transformer was often mounted on a box outside the furnace. Maybe this one is just a vestige of an old install.

I'd wire the switch and fuse properly, completely ignoring the way it's wired now. Any self help wiring guide will give you the connections. (Richter's Wiring Simplified, for instance)

 

[jlinder]

Re: Furnace Problems

Pretty sure the furnace now has an internal transformer now. Think I saw a fuse also on the internal wiring diagram.

Color codes are all correct. I just have a hot lead (black) from the switched side of the switch to the primary of the transformer (other primary wire goes to neutral). It is just the screw terminals on the secondary of the transformer that are not connected to anything.

Suspect it is a hold over from the original furnace where the transformer was external and you put a fuse on it.

I will probably go and remove the transformer that is unused and change the switch/fuse plate to just a switch to keep anyone in the future from thinking the fuse does anything.

 

[jlinder]

Re: Furnace Problems

OK, new board came in and installed. Inducer motor now comes on but same problem plus it now blows the fuse protecting the 24v transformer after about a minute. Air conditioning works fine, heat is the problem. (Left alone for a day since it was hot here - in October!)

Thermostat acting funny so I replaced it (had been hard to set for year or so but worked fine). Same problem.

Down to the circuit board that controls the inducer motor. It has a full wave rectifier on the 24v supply that powers a relay. Probably best to just replace the board (already see some burn marks on the relay contacts.

Problem is finding the board, so I turn to the forum members again for help. Numbers on the board are HH84AA007 or 990-490 or 87-50-01. Anyone have a lead?

 

[PiratePast40]

Re: Furnace Problems

Old trick I was taught a long time ago was if you had to touch a wire that could be hot (like rewiring a switch or ceiling lamp) do a quick slap of the wire with the tips of your fingers from the back of your hand. That way if there was power on it for some reason your muscles could not latch onto the wire and the slap would make the contact very short.

I remember that question from oral boards. The electrician on the board would ask if doing what you just mentioned is acceptable. A yes answer would result in immediate failure and loss of qualifications.

I'm assuming that you're kidding or it's prefaced with: "here, hold my beer and watch this"!

 

[jlinder]

Re: Furnace Problems

It was not suggested as a test to replace meters and other safeguards. It was just one of those last ditch "I've already shut everything off and metered it, but I still have some doubt" things. You are right, I would never do this to a circuit I had not checked with test gear.

I used to work on occasion at AM broadcast transmitter sites. With those frequencies you can get voltages on anything, even plumbing, and meters may not read it. Called circulating currents.

For example I remember a story from someone I used to work with. He was at a customers transmitter site (worked for the manufacturer of the transmitter) and went to use the facilities. As he was standing there and began relieving himself the last thing he heard was "Nooooooo....". Then the stream hit the bowl and the world turned blue.

RF went from the bowl right up the stream to the last part of your body you ever want to apply voltage to.

Decided to be extra careful after hearing that.

 

[dolluper]

Re: Furnace Problems

I'm thinking your inducer motor has shorted....but if your want more parts first search on ebay link here
http://cgi.ebay.ca/ws/eBayISAPI.dll...11839&_sacat=See-All-Categories&_fvi=1&_rdc=1

 

[jlinder]

Re: Furnace Problems

Pretty sure it is not the motor. The motor spins and is 120v so any problems with it would not affect the 24v supply fuse.

Thanks for the link. Trying to buy the board but they only accept PayPal it seems and I do not have a PayPal account.

 

[dolluper]

Re: Furnace Problems

Heres a fast check to do Set T stat to heat and temp so cold it won't call for heat...take furance door off check transformer line A for power going to heat blower relay if there is transformer has problem or wires{24 volts} if no power perfect ....clamp door switch you should now have 24 volts going on Line A to heating blower relay and thru it to low speed side of blower motor if not wiring or blower motor relay bad

 

[dolluper]

Re: Furnace Problems

You say the T Stat was working funky so you replaced the T stat ???? wiring 4SURE is correct at trans and T stat you checked ??.....Did you try the fast test if so what was the result "SeQuence" is howto troubleshoot by metering...unles intermedite problem....usually if tstat wired wrong it blows fuses in furnace

 

[jlinder]

Re: Furnace Problems

Sorry for the long delay. Out for work and could not get back to the furnace until now.

Dolluper - The thermostat had been acting funny for a number of years in that it was hard to set the temp. Had to work the up and down buttons to try to get it to move. Lived with it since I did not make changes often, but with this work I just got tired of it so I replaced it.

I am losing patience with this problem, but I think I am closer now.

When I call for heat it looks like everything works right. Inducer fan now starts, pilot lights, and the time delay relay waits for about 40 seconds before it applies 24vac to the main gas valve.

If the valve is connected this is when the 24v transformer fuse blows. If I disconnect the valve (lead 1 on the valve) there is 24v on the lead and the fuse does not blow.

I believe the lightening strike damaged the solenoid and this is blowing the fuses.

Thoughts anyone? How often does this happen? How hard & expensive is it to replace it?

Furnace & valve have the following numbers:

Furnace: model 58SSL095-CC
Valve: Model 36E93 and has a number on it EF32CB197A

Book for the furnace says the valve is a White Rogers 36E.

I think it is this one, but not sure: http://www.patriot-supply.com/products/showitem.cfm/WHITE_RODGERS_36E93_304

Thanks in advance for everyone who has been helping with this.

 

[dolluper]

Re: Furnace Problems

low speed wire on blower motor not burn't or cap burn't on blower motor NOT talking about inducer motor.....The blower motor

 

[Eric 3.7LX Alpha 1]

Re: Furnace Problems

Sorry for the long delay. Out for work and could not get back to the furnace until now.

Dolluper - The thermostat had been acting funny for a number of years in that it was hard to set the temp. Had to work the up and down buttons to try to get it to move. Lived with it since I did not make changes often, but with this work I just got tired of it so I replaced it.

I am losing patience with this problem, but I think I am closer now.

When I call for heat it looks like everything works right. Inducer fan now starts, pilot lights, and the time delay relay waits for about 40 seconds before it applies 24vac to the main gas valve.

If the valve is connected this is when the 24v transformer fuse blows. If I disconnect the valve (lead 1 on the valve) there is 24v on the lead and the fuse does not blow.

I believe the lightening strike damaged the solenoid and this is blowing the fuses.

Thoughts anyone? How often does this happen? How hard & expensive is it to replace it?

Furnace & valve have the following numbers:

Furnace: model 58SSL095-CC
Valve: Model 36E93 and has a number on it EF32CB197A

Book for the furnace says the valve is a White Rogers 36E.

I think it is this one, but not sure: http://www.patriot-supply.com/products/showitem.cfm/WHITE_RODGERS_36E93_304

Thanks in advance for everyone who has been helping with this.

Just to confirm what you are saying, there IS power to the gas valve, but if the gas valve is connected to the wiring, it will pop the inline fuse to the transformer?

Sounds like a bad gas valve from that information.

 

[jlinder]

Re: Furnace Problems

Measured the resistance of the valve coil. Looks like i is under 1 ohm (probably a dead short - just can't get good enough of a connection on my $10 meter ). Should draw about 0.5 Amp at 24v which comes to about 50 ohms. Seems like it is bad to me.

Tried buying one locally but the only guy with one (and only 5 min from house) would not sell retail - only to a company. I did find one at a good price here:
http://www.pexsupply.com/White-Rodg...-Delay-Slow-Open-W-Pressure-Switch-14618000-p

Anyone have experience with them?

I have to wait until Monday to order. In the meantime a couple of electric heaters seem to be keeping the house comfortable until I get the part.

 

[jlinder]

Re: Furnace Problems

OK - valve came, installed, all working again. Thanks to everyone who helped.

 

[jaykb2006]

Re: Furnace Problems

Just a word of advice. Not sure if you are using natural gas or LP gas but make sure if its lp gas you have converted the valve to work with lp. ( LP spring). and have set the correct wc pressure.

 

[jlinder]

Re: Furnace Problems

Thanks. It is natural gas. I checked the install instructions with the valve and it did have the LP mod kit with the spring, but that did not apply here.

 

[j_martin]

Re: Furnace Problems

Now that you have this electronic wonder running again, perhaps you should consider a surge protector (wired in) for it.