Air Conditioning - Ac transformer question

I have a rheem ac system from 1989 no problems with it only issue was with thermostat i have a ct8775 digital round thermostat thermostat works fine only problem is it was reading wrong inside temperature it was saying that it was 5 degrees warmer in house then it really was but then at times it reads fine thermostat is on inside wall and not near windows. for curiosity called honeywell and they say that it is normal and will correct itself because it reads temperature 2 ways ambient and something else i forget. But for curiosity he told me to check the voltage at thermostat he said to check voltage been red and green which i did and it said it was 32 volts he said it should only be between 24 and 28 volts. Then he said that the extra voltage may be throwing off temperature. Today i checked the voltage again and it said 36 volts do i have a problem or was he wrong?

check all this at the furnace transformer......whats the primary voltage into the TR or in fact the furnace voltage.if it is anything but 115V you may have to retap the primary for the reading you get on the furnace power.if the TR has muliti colored wires coming out of it you have a multi primary TR........this all depends on whats at the furnace power.if it is 115V intot the furnace you need to get a new TR to get that secondary down into the 24V-27V range....like stated that 32V+ could be throwing it off on the readings.

Yes, it should be 24-28 VAC, and too high can cause all sorts of erratic behavior. When I used to do HVAC testing and a step-down current donut failed it induced all sorts of problems in our thermocouples and thermistors.

The red and green are the correct wires to follow back to the furnace/AC. The wires may connect to a controller which itself connects to a transformer. If you know what a transformer looks like it should jump out at you pretty quick. I bet you'll find it is bad, or as sminker says your input is not 115V. Check both sides to verify.

24VAC transformers are a dime a dozen, so if its that, this will be a cheap fix.

Ok guys just went up to the attic and went to air handler to check transformer.

I've got the transformer it is an

Essex 291-421106-10701
46-20478-01
Pri 208V 50/60HZ Red-Blu
240V 50/60 HZ Red-Blk
Sec 24V 40 VA Yel- Yel

i check the output of the transformer it was putting out like 38 volts and when i went up there i it was making a very loud humming sound. i assumed it is bad so i ripped the thing out.

Coming out of the transformer on one side was a Black Red and Blue wire and on the other side was two yellows one of the yellows was going to a blue wire on the blower relay which is also pigtailed with the wires going to the thermostat i believe or might be condensor wires the other yellow was going to another red wire either going to condensor wire. The red and black wires were going to the terminal power block and the blue i don't think was going to anything at least i hope.

Will any 240 volt pri and 24 volt secondary work? will it need two yellow 24 volt wires or can it only have one? will this transformer be easy to find? Would a 120v 24 volt thermostat work? any pointers you can give me is greatly appreciated. i am fairly knowledgeable with electrical so i think i can handle it thanks

Your original hookup on your primary was probably 208 red-blue if you disconnect the blue wire and hook that same wire up the black you will get your secondary voltage down in range. Also you may want to check your line voltage you may have a transformer on your incoming electrical service that is feeding too high of voltage. This happens all the time you may notice that you burn up a lot of light bulbs or other unexpected electrical failures.

i just went back up there to go look at the wiring i have the 240 volt wiring figured out i think but the 24 volt wiring is confusing me. i just wanted to find out if i have this correct because what happened is i went to turn around and all the 24 volt wiring pulled out from the wire nuts. the way i remember the wiring being is

Green wire from thermostat going to blue wire from white rodgers blower relay

White wire from thermostat going to other blue wire from blower relay if i belive that one of the 24 volt wires from transformer also hooked up to this.

I have a Red and White from Compressor remaining and a Red wire from thermostat remaining where do these wires go do i pigtail the two reds togather and does the other 24 volt wire go there? Any help is greatly appreciated

Thanks for the response mike The blue from the transformer wasn't wired to anything it they used the black and the red wire which means it was already wired for 240

If it is already wired for 240 then you need to check your incoming voltage if it is over 255 call your utility company.

I just checked incoming voltage and it is about 255 max 257 so what does this mean? if possible can you give me a hand and tell me if the wiring is correct?

You need to call your utility company if your voltage is that high during the day in the middle of the night when most activity stops there is no telling how high it will get.

OK I called power company they are going to come check out why i have high voltage. I already bought new transformer so i am going to install it the one that was in there i cut all the wires on it when i took it out. I already hooked up the 240 power to the transformer i used the orange and white. On the 24 volt wires i checked and am getting 32 volts. I just need a hand with the 24 volt wiring there is a blue and a yellow coming out from the transformer. I read somewhere that it is a good idea to put in an in line fuse 5 amp so i don't burn up transformer. I put it on the blue coming out from transformer and i hooked the in line fuse to the blue wire from the white rodgers blower relay and also pigtailed with that is the yellow from the thermostat that is how i believe it was before Next the yellow coming out from the transformer i pigtailed with the red from condensor and red from thermostat. I don't know what to do with the white from condensor so i didn't hook it up yet. Just for curiosity i wanted to see if the air handler would come on so i put the thermostat on and once i did that the inline fuse i installed blew right away what did i do wrong?

OK guys getting somewhere i got it working somewhat i took the blue wire and hooked it up to the red thermostat wire and then i took the red condensor wire and hooked it up to the blue fan relay wire along with the green thermostat wire and problem is now system comes on but condensor is coming on when i put the thermostat in fan mode what do i have to do?
Please any help is greatly appreciated?

I wish I could draw in this format but you have a wiring diagram somewhere on your system and it can tell you better than I can write how to wire up the transformer. one wire on your transformer secondary needs to go to the common side of your control voltage circuit, the other wire needs to go to the power side, sometimes you can run this wire directly to the thermostat R terminal but if you can look at your wiring diagram it will tell you exactly where it needs to be hooked up.

Can someone please explain the wiring to me the best they can There is no diagram when i put the thermostat in fan mode the air handler and condensor come on fine but once i put it in regular cooling mode nothing comes on and i blow the inline fuse to the transformer i installed. What did i do wrong i just need to know which wires go togather there are 2 blue wires coming out of the white rodgers fan relay THanks

All right I can try to give you a for instance but I am telling you there is probably a wiring diagram somewhere on that unit that will explain better than this. You will have 2 line voltage wires coming into the primary side of your transformer (judging from your posts you have this right) then on the secondary side you will have 2 wires coming out, if there is a pc board they will probably plug into this. If not they will go out into the control circuitry. One wire will ultimately go to a red wire that goes to the R terminal on your thermostat, through the switches in the thermostat to each load (load examples not limited to, fan control, condensor section and heating circuitry) The wire to the fan controls will come from the G terminal on your thermostat. Since it sounded like you only had 2 control wires going to your condensor I will have to assume you have straight cooling with electric heat so the Y wire from your thermostat should go directly to your outdoor unit with another wire from the outdoor unit going back to the transformer on the opposite wire that is going to R on your thermostat. The wire that is hooked up to the W terminal on your stat should go to the heating section of your air handler. I saw a couple of posts back where you were confused about the 2 wires going to your outdoor unit so I am guessing this is where your problem is and why you blow a fuse when you call for cooling. disconnect these 2 wires put a new fuse in turn the unit on and call for cooling and if you do not blow a fuse you will know there it is! Then follow what I have written and you should be fine, good luck.