Electronic thermostat Issues

[beorning]

Just bought a new Honeywell programmable thermostat to replace the old one that kept on malfunctioning. I had assumed that installation would be fairly simple. I was wrong...

The wire designations don't match up between the two at all. Honeywell presents several alternative diagrams in case they don't match up, but those don't seem to jive either.

Here's the set up, as well as I can depict it here:


Old "perfect temp" thermo - The letter "o" represents a terminal

o - RS2 ( blk wire)
o - W1 (White)
o - RS1 ( Orange wire)
o - Y1 (Yellow)
o - RS+V (Brown)
o - G (Green)
o - R (Bridged to terminal below)
o - 24v (Red)
o - 24v(c) - ( Blue wire)



New thermo - with conventional and heat pump designations in parenthesis ( I'm pretty sure we don't have a heat pump)

o-C (C)
o - W2(aux)
o-G (G)
o - Y2 (E)
o-Y (Y)
o- no designation(L)
o-W (O/B)
o-RC (RC)
o- R (R) <~ the bottom two terminals are bridged


anyone want to take a crack at sorting out my gibberish?

Thanks in advance

[beorning]

Well the old thermo has completely crapped out and we have no heat. 10 pm and 4º outside. Hopefully the joint won't freeze before morning...

[wilderness1989]

Try touching the 24V red wire to the orange or brown wire to see if the furnace will start if so you can cycle the furnace by hand to keep warm until you can figure things out. It's worth a try if all else fails try the 24V to the black wire. That's what I'd do anyway. And 1st make sure the circuit breaker/fuse to the furnace if not tripped.

[beorning]

Breaker isn't tripped, I checked the fuse on the furnace and it's good, but touching wires in any of the suggested combinations produced no results. We've got the dryer rigged up to vent indoors in the winter, So I'm running that now. It'll keep the pipes from freezing at any rate. I'll love my electric bill this month, I'm sure.

Looks like I'll be on the phone with my friendly neighborhood HVAC guy in the morning. That's the last time I believe the "installs in minutes" advertisement on the outside of anything I'm not intimately familiar with.

[ninny]

Do you have a "split" system?", by this I mean do you have an A/C condensing unit outside and a furnace inside, or do you have a "packaged" unit, this being a single unit, usually sitting outside, that contains both your heating and cooling unit???

The designations on the new t-stat are:

C terminal is usually a common for your 24Volt control circuit can be any color wire, usually brown or blue.
Y terminal is for the "cooling" circuit, usually a yellow wire connects here...
R&RC terminals are the "hot" side of your 24Volt control circuit, usually a red wire is attached here...
W terminal is your "heating" circuit, usually a white wire is attached here...
G terminal is your "fan" circuit" usually a green wire is attached here.
W2 or "aux" terminal is for auxilliary heat circuit, mostly used in heat pump applications...
Y2 terminal is probably also for a heat pump application, my guess would be to energize the reversing valve...
L terminal is probably used for controlling dampers or other auxilliary equipment...

Keep in mind that I'm doing a lot of guessing here. These are the color code/letter designations that we use down here in So. Texas. Yours may be completely different.
I'm not completely familiar with your t-stat either and the different manufacturers do a lot of changing on their letter designations...
It would help if you could tell us if you have elect. or gas heat, a packaged or split system, a heat pump or a standard heat/cool system...

My guess would be that the letter designations on the old t-stat, G Y R W, terminals are the same on both t-stats so the color wire that was on those terminals on the old t-stat will go back to the same letter designation on the new t-stat...

You did make a diagram of what wire/color went on what letter in the old t-stat didn't you???

You are learning the joy of having a programmable t-stat. I'm gonna make a strong suggestion here, keep the booklet you get with the new t-stat where you can find it because sooner or later you're gonna have to re-program the t-stat and if you loose the book, you're in deep do-do. The instructions on how to program are on the cover of the new t-stat but they are a little difficult to understand. The booklet usually does a better job of explaining how to program...
If you lose power to your house/t-stat and the battery back-up in the t-stat is dead/gone, you're going to have to re-program...

Don't know if this is any help and I may be just confusing you more thoroughly but a little more info on your system would have been a little more helpful..
If you still have doubts call an A/C person to help you, my suggestion would be someone that is familiar with your system if that is possible...

Good luck...

[beorning]

It's a split system. A/C unit is outside, furnace is in.

It's natural gas. Not a heat pump.

I did make a diagram of the wiring for the old T-stat. Hooked it back up exactly when I couldn't make any sense of the new stats terminals, and it failed to function. It's been off and on for about a month though, so I wasn't too surprised. Couldn't have happened at a better time though...

I did hook the new stat up with the obvious matches ( green to green, etc.)
But couldn't figure out the Black, orange, and brown wires to save my life. No dice on functionality, any way I swung it.

Hopefully, the Hvac guy will get here soon and sort it out.

I keep the books for everything. I was overjoyed to find a drawer full of appliance manuals when we bought this place. Unfortunately, there wasn't one for the T-stat. Incidentally, there are no programming instructions anywhere on the Honeywell unit. Though it did come with a nifty little cd that has next to no useful information on it at all.

[ninny]

If this is as newer system, you may have blown a fuse on the 24Volt controls when you installed the new t-stat. New systems have a fuse that looks like the type used in automobiles, although some use a really weird looking glass fuse also...

Do you have a volt meter that you can check to make sure you have 24 Volts??
Also check your 110 Volts to the furnace...

Make sure you don't have the lower door open to the furnace as it has a safety switch that kills the controls...

If you have 110 Volts to the furnace (take a lamp or some other moveable appliance and plug it into the outlet by the furnace to check for 110 volts) you should be able to make a jumper wire and connect between the red terminal and the green terminal on the t-stat and see if your fan comes on... If the fan comes on you have both 24Volts and 110 Volts. If the fan doesn't come on, you may have blown the fuse, will need to find it... When/if you make the red/green connection, give the fan a few seconds to come on as some of the newer models are on a time delay...

I have no idea what the other wires (black, orange and brown) are for. Usually the brown would be a common on the 24Volt circuit but again I'm stressing the color codes we use down here may not be applicable where you are...
The black/orange wires could possibly be for vent dampers or something like that, just don't know.

Take a look in the furnace where the low voltage wiring connections are made and see where the black/orange/brown wires connect to if that's possible...

Honeywell usually prints a programming schedule on an inside cover of the t-stat because so many people do lose the booklets. Odd that yours doesn't, just keep the booklet handy...

Once again good luck...

[beorning]

Thanks for all the advice.

There's power to the furnace, I found the fuse last night and checked that. It is odd, Has a weird spring device inside, but it looks intact.

I don't have a volt meter. Need to get one.

One of the biggest sources of confusion is that the wires in the furnace don't match the thermostat wires at all. I couldn't find a brown, orange or black wire in the furnace that matched the gauge of the thermostat wiring. The guy who owned the place before us seemed to like to wade into anything DYI with little regard to code or safety. The spiderweb of romex in the basement before we moved in clued me into it and the last few years have been all about discovering his "ingenuity". It wouldn't shock me if he installed the furnace himself.


After this little experience, I'm thinking about reading up on HVAC or maybe tracking down a course at one of the tech schools. It's funny how you never know how little you know about something until you're forced to be in it up to your eyeballs.

The new honeywell stat doesn't have a cover. It's an RTH7500 model.

[ninny]

Sorry I couldn't be more help.

Just a suggestion, go to WMart and buy a cheap volt/ohm meter. I think you can get them for around $10 now and they're really useful. Just be careful around electricity if you're not used to working with it...

Sounds like the do-it-yourselfer that had your house before you did a bang up job...

Don't waste your time with the A/C school, unless you use the info on a daily basis, in a couple of months you will have forgotten all you learned and the little that you would learn would probably cause you more trouble than good...
Best let someone that knows what they're doing if you run into a problem that you can't handle...
I fix problems all the time that some homeowner was gonna save some money on and do it themselves...
Generally have to fix what they screwed up and then have to fix the original problem...Ends up costing twice as much...

Again... Good luck, hope it's not too bad...

[beorning]

Well, The HVAC guy just left. I'm both relieved that the problem wasn't critical, and wanting to kick myself for missing the obvious. The black brown and orange wires were not connected to anything. The pro speculated that there used to be a heat pump installed, and they didn't change the thermostat when they upgraded the system.

My problem? a little tiny automotive type blade fuse that I failed to notice. Must have blown it when I was farting around with the thermostat change out. I cut the power before I yanked all the wires on the old thermo. One of those light bulb moments, but it must have come too late.

I'm usually pretty cautious about doing anything that I'm not familiar with. Not cautious enough this time.

Ah, well. The bill was only $120, and he did clean my flame sensor for me...

Thanks for the help. Much appreciated.

[ninny]

I told you to check for an automotive type fuse in post #7, would've saved you $120.

Never assume a fuse is good because it "looks good." Need to check them with a meter.

If I were you I'd go to a store and get a couple of extra fuses and put them in the furnace somewhere. Chances are you'll never need them but they're not that expensive and it would be good insurance. Be sure and get the same size (amperage rating) fuse as what's in the furnace.
Did you see where the fuse was that the repairman replaced??
If you should have a problem again, you can put a new fuse in and might correct the problem.

Good luck...

[beorning]

I told you to check for an automotive type fuse in post #7, would've saved you $120.

At 8:33 am this morning (the time that you posted post #7) the HVAC dude had allready been called and was on his way. At that point I had pretty much decided to hang it up and let someone who knew what they were doing handle it. It would be bad form to have turned the guy away at the door, and I still would have had to pay the $75 service visit charge for nothing.

If I were you I'd go to a store and get a couple of extra fuses and put them in the furnace somewhere. Chances are you'll never need them but they're not that expensive and it would be good insurance. Be sure and get the same size (amperage rating) fuse as what's in the furnace.

I've got a couple of boxes of them in the garage. Made this morning all the more humiliating.

Did you see where the fuse was that the repairman replaced??

Yep, right underneath a bundle of wires that were zip tied in just the right place so that I would have had to go digging to notice it. The repairman actually cut the tie to get to the fuse. This was about the only part of the process that didn't drive the moron dagger in a little deeper.

Mistakes are made to be learned from. I've certainly done a good deal of that since 10pm last night.

[ninny]

If you have to replace the fuse again, be sure to use the correct size, usually a 3 amp on a gas furnace. Don't go bigger or you could cause a fire...