Wierd electric furnace problem

[welling service]

I went on a no heat service call in a mobile home with electric furnace. I found one of the 60A DP breakers on the heater gone bad and replaced it. Everything worked worked fine for a day and they call me backed complaining that it wasn't heating as good as it had been. Went back and found one of the sequencers gone bad. When replacing the sequencer my son placed the fan wire on the line side of the sequencer by mistake so the fan did not shut down but ran continuously. He found the problem and corrected it and put the furnace back in operation. We turned the stat down and observed that the fan cycled off. As he was putting the panels back in place we noticed what sounded like one of the sequencers closing and energizing one of the elements. The 5kw strip would cycle on and off with no call for heat. Checked for 24V on the sequencer and found none. We pulled the wire from the sequencer feeding the element and still observed a 20A draw on the other side. Needless to say we were amazed at this point. Pulled the element out and found the element grounded to the frame at about mid point of the element. What we were hearing was the high limit cycling off and on. Exactly half of the element was heating up through the grounded portion of the coil. You would think that the element would have just burned out at the contact point with the frame. First time I have ever seen this.

[Frederick_Tech]

I have had this happen to me in the past also. As long as the high limit is shutting down the heat strip before it gets hot enough to melt the wire itself it will continue to cycle. If the customer ran the fan continuously it would have stayed on and over heated the house. Actually had this happen in a new home in the summer. Heat strip has grounded and the A/C was running. Needless to say the house would not cool and the system just ran and ran....

[beenthere]

Somewhat common occurrence. It can also causes the blower to run very slow during the off cycle depending which element it is.

[54regcab]

Good thing the limit and squencer were on opposite legs of the heat strip !

[SuperTech2010]

yes yes and yes to all....seen it happen on A/C calls also...when the element goes to ground you are completing the circuit 110v, that is. so the element will glow with no fan causing the limit to open....dont waste your time restringing the element. get a new set and start over

[uniservice]

Usually caused by dirty filters, blower wheel, too many registers closed. Lets the element get too hot and then they sag enough to ground out. Restring kits are OK, but most of the later model Colemans and Intertherms I hit are Oval shaped elements, and only available as complete replacement elements. Kinda pricey too. I have a lot of older Colemans and Wesco furnaces, that I restring. The most important thing is to prestretch the element before trying to install it, being careful not to overstretch it. It needs to be uniform, in the gap between coil loops, or it's going to overheat and fail again.

[toocoolforschool]

Usually caused by dirty filters, blower wheel, too many registers closed. Lets the element get too hot and then they sag enough to ground out. Restring kits are OK, but most of the later model Colemans and Intertherms I hit are Oval shaped elements, and only available as complete replacement elements. Kinda pricey too. I have a lot of older Colemans and Wesco furnaces, that I restring. The most important thing is to prestretch the element before trying to install it, being careful not to overstretch it. It needs to be uniform, in the gap between coil loops, or it's going to overheat and fail again.

This is a prctice that is going by the way side, kudos to you I have tried to restring but ends up being a disaster.
Beleive it or not I tried to restring Lenny Kravitzs' old Amana unit to no avail and the parts were obsolete, needless to say lesson learned on my part.

[uniservice]

I live in an area that is 75% electric furnaces. Most of em are 60s and 70s vintage. If I didn't use restring kits, I'd be selling a lot of furnaces. Unfortunately most of my customers are on limited incomes, and even paying for elements and sequencers is very difficult for a lot of them. Glad I'm still able to keep them in heat. My counterparts in service are always recommending replacement. Probably that's why I'm still doing service on furnaces after retiring 3 years ago,,,,,,,,,,,,,

[54regcab]

I live in an area that is 75% electric furnaces. Most of em are 60s and 70s vintage. If I didn't use restring kits, I'd be selling a lot of furnaces. Unfortunately most of my customers are on limited incomes, and even paying for elements and sequencers is very difficult for a lot of them. Glad I'm still able to keep them in heat. My counterparts in service are always recommending replacement. Probably that's why I'm still doing service on furnaces after retiring 3 years ago,,,,,,,,,,,,,

Maybe show them how much they wil save in utility costs by going to a heat pump instead of heat strips?

[uniservice]

There have been a few heat pump rebate programs here in the past 15 years. Quite a few people did add on heat pumps to their existing electric furnaces. Now the rebate programs available from the local PUD is focusing on mini-splits. Unfortunately because of the ocean environment, a ten year old heat pump is usually corroded out and or rusted out.

[SuperTech2010]

There have been a few heat pump rebate programs here in the past 15 years. Quite a few people did add on heat pumps to their existing electric furnaces. Now the rebate programs available from the local PUD is focusing on mini-splits. Unfortunately because of the ocean environment, a ten year old heat pump is usually corroded out and or rusted out.

you can order salt resistant heatpumps, just for areas like yours.....i never have...but i know they do make them. anyone else know bout these "treated" units?

[uniservice]

Yeah, it gives about an extra year here. Changed an OD coil on a Trane a few years back, that all the bottle brush fins were laying in the bottom of the unit. It was two years old.This is a perfect environment for heat pumps except for the salt air. Temperatures and humidity is ideal. Besides, in comparison to the rest of the country, our power rates are pretty cheap.

[54regcab]

Does it not rot out air conditioners at the same rate as heat pumps?

[Snapperhead]

Somewhat common occurrence. It can also causes the blower to run very slow during the off cycle depending which element it is.

isnt electricity fun sometimes .....

[54regcab]

isnt electricity fun sometimes .....

Backfeeding of voltage and other oddities seem to occur in the field more often that I'd like to see.

[beenthere]

isnt electricity fun sometimes .....

LOL, it keeps service interesting.

[uniservice]

Not more than a handful of A/Cs on the whole Peninsula. Not needed. Not more than 10 days a year when the temperature hit 70+. When it gets hot inland, it gets foggy and cool here. Normal high temps are in the 60s.

[54regcab]

Not more than a handful of A/Cs on the whole Peninsula. Not needed. Not more than 10 days a year when the temperature hit 70+. When it gets hot inland, it gets foggy and cool here. Normal high temps are in the 60s.

Where do you live?

[welling service]

I would think that in heat mode the heat pump is going to condensate causing more corrosion faster.

[SuperTech2010]

Yeah, it gives about an extra year here. Changed an OD coil on a Trane a few years back, that all the bottle brush fins were laying in the bottom of the unit. It was two years old.This is a perfect environment for heat pumps except for the salt air. Temperatures and humidity is ideal. Besides, in comparison to the rest of the country, our power rates are pretty cheap.

wow