# 1991 Intertherm/Nordyne furnace with added AC split system



## Bluejean (Sep 7, 2017)

Here are photos of the actual parts of the system in whole


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## Wilbits (Mar 11, 2017)

This is kinda confusing. The company that installed it can't get the AC to work?


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## user_12345a (Nov 23, 2014)

That air handler is very old.

Not sure why you're getting the outdoor suction replaced. You're pretty much dealing with clowns if they replace the outdoor unit because it doesn't turn on without identifying what's wrong.

Yah, if it's not working, call them back -> you shouldn't have to fix this yourself.

Really, re-using an old coil is a mistake. So is going with R22 - it's being phased out and repairs will be very costly.

The old coil can leak.

It's the wrong size for the new unit because the efficiency standards have changed.

The coil has a restrictor (call a metering device) that has to match the spec of the new unit -> some contractors may not change it, leading to really poor performance.

The operating pressure of the new unit is different so your old coil's metering device won't allow enough refrigerant to flow into the coil.

All in all, you should request that they make it work and also request that the coil and metering device are changed to match the new outdoor unit.

A new coil may not fit into that air handler, necessitating replacement.


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## Bluejean (Sep 7, 2017)

Wilbits said:


> This is kinda confusing. The company that installed it can't get the AC to work?


Nope. Said they needed the wiring diagram. I know that having three different techs out has probably caused some issues because of each one not knowing what the other did. When the outside unit was replaced it all worked for a few hours, but something went wrong, I believe he tried to wire it all up on one transformer which could not hold the load. This is the reason I have asked if the outdoor unit has been wired properly to the transformer within the unit. Here is a photo of it. All the wiring has been reverted back to the way it was designed to be per the schematics on the individual parts. I just don't have anything to compare the outside unit too.


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## Bluejean (Sep 7, 2017)

user_12345a said:


> That air handler is very old.


Yes, it is very old. So old that the company does not have any of the information (installation instructions, wiring diagrams, or manuals) for any of the parts.

I have followed all of the wiring per the schematics on each individual part but do not have anything to compare the outdoor unit to. I installed the new transformer to the condenser but want to be sure it is wired properly.

The furnace runs in one transformer and the AC in its own.


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## user_12345a (Nov 23, 2014)

presumably it worked before and was wired right.

the wiring shouldn't be different with a new condenser.

it sounds like in trying to run it off of one transformer, it was overloaded and failed or the fuse on the low voltage circuit blew.

The transformer in the air handler was probably for heat only, not having a high enough volt-amp rating for a/c.

If this is the case, the next step would be to rectify that and re-wire the low voltage circuits so cooling runs off of the fan centre's transformer again.

This is impossible to deal with over the net and you need a competent technician to straighten this all out.

If you have the funds, the best option at this point may be to put in a matching air handler and coil with the transformer and relays for cooling built in.

You aren't dealing with the highest quality people at least based on your posts. 

Matching a new 13 seer unit to a very old coil in itself is a horrible idea.

Now they can't get it to run? residential control circuits aren't overly complex.

The brand is a chinese one -> nothing necessarily wrong with the unit itself but rather that the contractor is more interested in cutting costs than anything else.

What prompted the replacement in the first place?


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## Wilbits (Mar 11, 2017)

user is right, these guys are pathetic. Wiring diagram should be on the inside of the cover. A good tech could figure that out without a diagram. Who installed the transformer in the condensing unit?


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## Bluejean (Sep 7, 2017)

user_12345a said:


> presumably it worked before and was wired right.
> 
> the wiring shouldn't be different with a new condenser.
> 
> ...


When the new condenser was added a transformer was not put in and yes it was all wired to one transformer which I also assume overloaded and stopped working. 

I have corrected all of the wiring per the diagrams but have nothing to compare the outdoor unit wiring to in order to make sure the transformer has been wired in properly.

Not sure why the outdoor unit was replaced other than a tech telling me I needed to. This all started when an unnamed person in my household decided to put in a new thermostat. I believe the jumper was left in and the two circuits were crossed causing the transforms to blow as well as the relay.

I got a new relay as well. Prior to switching all of the wiring back to the diagrams the blower would kick on when calling for heat but not cooling. The HVAC could not get 24 from the condenser to the airhandler but he also did not have a transformer in there.
The blower relay box says the system has been wired for a two transformer system. I told them that over the phone when I called them back to say it wasn't working. The replays was that must be the problem so I am going to need your wiring diagram. The only thing I have is what is on the units individual pieces.


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## Wilbits (Mar 11, 2017)

The condensing unit does not need a transformer. I would remove the transformer and see what size it is, should say something like 40 VA. Let us know.

Did you check the fuse on the inside transformer?


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## Bluejean (Sep 7, 2017)

Wilbits said:


> user is right, these guys are pathetic. Wiring diagram should be on the inside of the cover. A good tech could figure that out without a diagram. Who installed the transformer in the condensing unit?


I did. I don't know if it's correct. I figured someone could tell me by looking at the photos of the theremostat wires on the the airhandler terminals and the diagram of the airhandler. Just to check the inside connections.


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## Wilbits (Mar 11, 2017)

Check post #10.


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## Bluejean (Sep 7, 2017)

Wilbits said:


> The condensing unit does not need a transformer. I would remove the transformer and see what size it is, should say something like 40 VA. Let us know.
> 
> Did you check the fuse on the inside transformer?


Why does it not need its own transformer if that is the way the blower relay box is wired? Please see the photos below. 1st picture is inside the blower relay box. Second picture is of the diagram on the front of the blower relay box and the third picture is a close up of the instructions on the relay box and the fourth photo is from the diagram on the furnace referring to the the relay box that is installed.


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## Bluejean (Sep 7, 2017)

Wilbits said:


> The condensing unit does not need a transformer. I would remove the transformer and see what size it is, should say something like 40 VA. Let us know.
> 
> Did you check the fuse on the inside transformer?


Which transformer would you like for me to check? 
Fuses are fine.


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## Bluejean (Sep 7, 2017)

Wilbits said:


> The condensing unit does not need a transformer. I would remove the transformer and see what size it is, should say something like 40 VA. Let us know.
> 
> Did you check the fuse on the inside transformer?


The transformer on the AC unit is 40va
The old transformer that was on the furnace was also 40va. This has since been replaced with one that is 90-T40F3. The bigger transformer was installed by the tech who was unable to get the 24volts at the airhandler.


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## Wilbits (Mar 11, 2017)

You can use 2 transformers but they both need to be in the furnace. Check the one in the outside unit.


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## Wilbits (Mar 11, 2017)

There's only one fuse on the transformer it is purple with a red and yellow wires going to it.


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## Wilbits (Mar 11, 2017)

Go ahead and remove the transformer outside.


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## Bluejean (Sep 7, 2017)

Wilbits said:


> The transformer only has 1 fuse, its purple with a red and yellow wires going to it.


The purple fuse is intact.
For thirteen plus years everything worked perfectly. There was always one transformer in the furnace section and one on the condenser.


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## Wilbits (Mar 11, 2017)

Well then leave it there and good luck.


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## Bluejean (Sep 7, 2017)

Wilbits said:


> You can use 2 transformers but they both need to be in the furnace. Check the one in the outside unit.


Would you say that the wiring of this transformer to the contactor and thermostat wires is correct?


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## Bluejean (Sep 7, 2017)

Wilbits said:


> Go ahead and remove the transformer outside.





Wilbits said:


> Well then leave it there and good luck.


If I turn everything on and call for cooling and check to see if the contactor engages is there a way to do this without burning up the transformer?


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## Wilbits (Mar 11, 2017)

Can't really tell from that pic. I have seem 100s of condensing units and never seen one with a transformer in it.


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## Wilbits (Mar 11, 2017)

Bluejean said:


> If I turn everything on and call for cooling and check to see if the contactor engages is there a way to do this without burning up the transformer?


Do not start the unit with the transformer wired in.


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## user_12345a (Nov 23, 2014)

The condenser unit should get it's signal to turn on from the low voltage wiring coming into it.

It should be getting 24v ac which energizes the contactor's coil so it can pull the contacts in.

The only instance you should ever have a transformer outside is if it's a communicating system and there aren't enough conductors to have a common and power from the indoor unit.

Your unit is not communicating.

-----

You're dealing with crooks and have a real mess on your hands.


A decent contractor doesn't go and replace a unit because the low voltage wiring is messed up from thermostat replacement.

They don't go putting transformers into straight cool, non-communicating condenser units either.

You get it done because there's a freon leak or the compressor failed, or you want something more energy efficient.

If you're comfortable with electrical you may be able to straighten that part out.

But it's unlikely that the refrigerant charge is correct or that they at least changed the metering device out at the coil, going from 6 to 10 seer to 13.


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## Bluejean (Sep 7, 2017)

user_12345a said:


> The condenser unit should get it's signal to turn on from the low voltage wiring coming into it.
> 
> It should be getting 24v ac which energizes the contactor's coil so it can pull the contacts in.
> 
> The only instance you should ever have a transformer outside is if it's a communicating system and there aren't enough conductors to have a common and power from the indoor unit


The system is very old. I think there was originally only electric heat and later the AC was added. All I know is that the old condenser had a transformer in it and the blower relay box ad well as the furnace have instructions for two transformer system. The thermostat is also wired without the jumper isolating the r and rc.

All I can do is try. I am comfortable with doing this. I just need someone to tell me if the transformer in the condenser will do the job of energizing the contactor coil and complete the circuit back the way that it is currently wired... 
I have been reading and trying to find anything possible to help, such as this:
1 or 2 Transformers for Heating Cooling System ? 2 Transformer Heating and Cooling Systems

There are some situations where a new air conditioner is installed where there is an existing boiler system. It is not uncommon to find these combinations of HVAC systems with two transformers. The boiler system utilizes its very own control wiring and circuits while the air conditioner does the same and each separate system has its own transformer. In that case, each system can have its own thermostat or if a single thermostat is used for both systems there must be RC and RH terminations in the thermostat to keep the two control/transformers circuit(s) apart. I have observed both types where there is a single thermostat and where there are two thermostats. It is important to note in the systems that two thermostat to make the occupants aware that with two thermostats it is possible to have both systems on and fighting each other in which they are going to use a lot of energy which means their bill will be high.


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## user_12345a (Nov 23, 2014)

Even when there are two transformers, it's not normal to have the second one in the outdoor unit.

Best to do it properly and eliminate that outdoor transformer, have two wires to the condenser, a transformer/relay combo (fan center) indoor for indoor fan and condenser.

Fan center is an add on for old indoor units and has a transformer and relay.

I've attached a messy mspaint diagram with basic low voltage wiring for this.



Preferable to have a licensed pro sort this out.

it probably won't cool right with that old coil and metering device.

impossible to figure out without being there and mis-wiring controls, especially on high voltage side can cause safety issues -> ie back feeding heating elements and more.


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## supers05 (May 23, 2015)

Please refer to your other post for the wiring correction. 

Personally, I would have changed the indoor air handler at the same time and have you a heat pump if and ONLY IF the outdoor unit was beyond reasonable repair. We can't know at this point if it was necessary, but something does sound off. 

Cheers!


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## tvengineer (Oct 2, 2020)

I know this post is 3 years old, but wondering if there was ever a resolution to this? I have the same type setup and trying to replace a hunter digital thermostat with a Honeywell WiFi. I can't seem to figure out the wiring coming from the furnace. 
The current thermostat is working, just looking to upgrade.
Thanks


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