HELP! Killed HVAC Installing Thermostat

[pgray007]

I was installing a new thermo (Aprilaire 8870) and accidentally shorted the Blue (Common) and Red RH wires. The Aprilaire diagram is backwards from the actual thermo for some reason, but I should have looked more closely. Of course we are leaving on vacation tomorrow so no heat in the house would be a very, very bad thing.

I got a spark when I shorted C and RH and now there is no life at the new thermo. I assume I blew a fuse or tripped a breaker and am not sure where to look for it. The air handler is in the crawl space so if there are other places to start I'd rather avoid playing in the dark under the house.

Thanks for any suggestions!

 

[brotsten]

I was installing a new thermo (Aprilaire 8870) and accidentally shorted the Blue (Common) and Red RH wires. The Aprilaire diagram is backwards from the actual thermo for some reason, but I should have looked more closely. Of course we are leaving on vacation tomorrow so no heat in the house would be a very, very bad thing.

I got a spark when I shorted C and RH and now there is no life at the new thermo. I assume I blew a fuse or tripped a breaker and am not sure where to look for it. The air handler is in the crawl space so if there are other places to start I'd rather avoid playing in the dark under the house.

Thanks for any suggestions!

My Trane has a small circuit breaker in the air handler.

Brian

 

[bingl]

My furnace has a fuse/circuit board where the tstat wires come into it. Others have done the same short circuiting when installing their 8870s. So I knew to unplug my furnace before my own 8870 install even though it was kind of a hassle climbing in/out of the attic multiple times.

Wish you the best.

 

[BraveSirRobbin]

Do you have a multimeter? Is so see if 24 VAC exists at the wires.

 

[IVB]

Heh, i did almost the same thing but when moving wires.

In my case, I had the furnace manual. The installer had left it on my furnace, I believe a leave-behind is required. In that, it was seriously easy to find the fuses, and they even use a standard automotive fuse. Took me all of 5mins to drive to the local kragen auto shop, pick up one (well, twenty. they don't sell just one), slap it back in, I was back in business.

It is depressing that I know the answer to so many "help - i screwed up!" posts, and from personal experience at that.

 

[pgray007]

Well I checked out the furnace in the attic (easier to get to than the one in the crawl space) and there does not appear to be any fuse or breaker that I could locate. The Trane manual online is oh-so-helpful and says to call a "licensed installer." Unfortunately I ended up doing just that and will likely end up paying someone to show me where the painfully obvious fuse is located.

The guy I talked to on the phone did mention some units have no fuse so they just blow their transformer (nice feature!) so we'll see!

 

[BraveSirRobbin]

The guy I talked to on the phone did mention some units have no fuse so they just blow their transformer (nice feature!) so we'll see!

If that is the case and since you are paying him the big bucks anyway, maybe have him install an in-line fuse (they sell them at Rat Shack).

 

[brotsten]

The guy I talked to on the phone did mention some units have no fuse so they just blow their transformer (nice feature!) so we'll see!

When the service guy opened my air handler last week, I could see the breaker. It was odd, it was hanging off a pigtail of wires about 4 inches long. If I hadn't been watching and pestering him, I doubt I would have realized it was a breaker.

Just so you know....

Brian

 

[ctwilliams]

The guy I talked to on the phone did mention some units have no fuse so they just blow their transformer (nice feature!) so we'll see!

When the service guy opened my air handler last week, I could see the breaker. It was odd, it was hanging off a pigtail of wires about 4 inches long. If I hadn't been watching and pestering him, I doubt I would have realized it was a breaker.

Just so you know....

Brian

I have a trane unit (btw, I did the same thing when installing my 8870...blew the fuse) and it is on a little pigtail as well. It uses the blade style automotive fuses...

CT