Equipment:
Thermidistat: Carrier TP-PRH01-B
Heat Pump: Carrier 25HCD336A310
Oil Furnace (Aux/EM Heat): ThermaPride OL11-105RDA
Humidifier: April Aire 560 (ByPass Humidifier)

We recently moved to this new house and now winter time is coming and I'm trying to get the humidifier up and running. It currently is controlled via a humidistat in the basement connected to a air pressure switch connected to a relay. I don't like this setup because the humidistat is in the basement and even though connected to plenum, seems to read humidity level in the basement and not in the living space.

So, according to the thermidistat manual, I just need to connect a wire from HUM on the control board to one side of the solenoid at the humidifier and C on the control board to the other side of the solenoid. I have tried this and nothing happens. System is calling for both heat and humidity.

Control board wiring below. Any suggestions?

 

Welcome to the forums.

What is powering the EIM board..... the air handler or a separate transformer ?
You need to get the C from the same place the EIM does.

I keep seeing this in the installation manual diagrams.....
* Indicates connection may not be required/available.
I'm not intimately familiar with that system so I'm not sure what this means.
It's almost like this feature (of which humidifier is) is not available on all these stats.

Install manual (pdf)

 

Thanks for the Welcome PJmax.

That makes sense that I need to get power elsewhere and let the EIM just switch the HUM terminal on/off. Any thought on which wire/terminal connection I can follow to determine that?

I'm guessing it's the terminal below the EIM (see picture attached). There is also another group of wires lower down under this Honeywell cover that I think is related to the oil furnace (see second picture).

As far as the *indicates connection may not be required/available, the asterisks are on the Humidifier, Outdoor air sensor, and remote air sensor connections. So I just interpret it as not every system will have these components (for example in mine I do not have a remote room sensor-wish I did).

Let me know your thoughts about where the power is coming from. Thanks again for your time.


Picture 1: EIM to connections immediately below (my guess where the power source is).

 

Didn't need the second picture. Those connections are shown on your first picture.

We've got a problem..... there are splices behind the EIM. I see wires changing colors.
See if the red and white TT wires are connected to Rh and W in the EIM.
If they are..... tell me what other cables are used in that same cable and what they connect to.
The additional colors/wires are:
C which looks like black
Rf - blue
Y - yellow
G - green

 

Thanks for your continued help with this! I followed the wires you labeled TT. And your prediction was right.
Red: Rh
White: W
Yellow: Y/Y2
Green: G
Blue: Rc
C (black): connected with a wire nut behind EIM with 3 other wires:
1. Black from other cable bundle that leads to outside Heat Pump
2. Blue from other cable bundle that leads to outside Heat Pump
3. White (short) that connects into the C Terminal on the EIM

Attached picutre from back of EIM if that's helpful and ot show the connections via the wire nut.

 

Pictures are very helpful.... thanks.

Ok.... here's the problem..... your HUM terminal is supposed to supply 24vac from Rh on a call for humidity. Your Rh terminal doesn't have 24v on it. Your Rh terminal is a T connection.

I'm going to check further but it looks like a 24v relay will be needed to handle the TT wires. Then we tie Rh and Rc together. Now on a heat call..... W closes the TT relay and the humidifier gets its power from the 24v Rh/Rc connection. It sounds complicated..... it's not. Let me know if this is something you'd want to do. Any 24v SPST or SPDT relay will work.

I do see something puzzling. I see two white wires on W/W1. You confirmed one is a T wire.
Where does the second one go to ?

Example of 24v relay.

 

Thank you again for the continued help. To answer your last question, the other white wire on the W/W1 connection is part of the cable bundle that goes to the outside Heat Pump Unit.

As far as the relay, that does seem complicated but I want this to work so full steam ahead! I think I already have a relay we can use; see pictures. This is currently being used to power the humidifier. It's use in line with the humidistat and air pressure switch.

Let me know what connections you suggest I make. Thank you again and Happy Thanksgiving!

 

Happy Thanksgiving to you too.

Ok.... that white wire does go to the outside condenser.
That is there so that the furnace will run during a defrost cycle.
That's a 24v transformer in your picture.

I'm going to work on this further.

 

Just circling back to this. What’s the difference between a 24v transformer and a 24v relay? Just trying to figure out if I need to buy a relay or if we can use the transformer.

Looking forward to your guidance on this. Thanks again!

 

I purchased and received the relay you suggested. So I’m all ready for how best to connect. Thank you

 

Be sure to power the system down before wiring.

Ok.... follow your red and white wires from TT to the EIM. They should be on Rh and W.
Disconnect them from the EIM and connect them to terminals 2 and 4 on the relay.
Since it's AC.... there is no polarity.

Now we need to add a jumper across Rc and Rh. A little piece of bare thermostat wire is fine.
Using a short piece of thermostat cable..... connect terminals 1 and 3 of the relay to Rh/Rc and W.

Here's an easier alternate method. Locate the red and white wires labeled TT down by the burner. Cut them. Connect the red and white from the EIM to 1 and 3. Connect the red and white from TT to 2 and 4. Again... no polarity on the relay terminals. Add a jumper between Rc and Rh on the EIM.

Now your humidifier will work using HUM and C.

 

Thank you Pete. Made some progress but ran into problems with the Aux Heat.

I followed the easier alternate method. Worked great when the heat pump was active. Could use the Carrier Thermidistat to control humidity. However, when the aux heat was supposed to kick on, the oil furnace did not power up nor did the blower fan; the humidifier was still running though. I ensured that the oil furnace reset was not tripped and tried to manually reset it, but no luck.

I was going to try the more complicated method too before replying but I wanted to make sure we weren't missing something first. I also wasn't 100% sure about the connect terminals 1 and 3 to Rh/Rc and W. I would connect 3 to W but for the Rh/Rc does it matter which one? I assume no since they are jumped together but wanted to confirm.

I wired it back to baseline so let me know your thoughts. I think we're close and I appreciate your assistance more than you know.

 

Sorry... my mistake.

Rc/Rh = 24v. When W is active..... it's also 24v. That will never trip a relay.

Using the easier method..... leave the white wire from the relay on W.
Move the red wire from Rh to C.
So the relay will get 24v switched from W and common from C.
Still need the Rc to Rh jumper.

 

No apology necessary.

So to confirm:
Terminal 1-->W (white wire)
Terminal 3-->C (red wire previously at Rh and moved to C)
Terminal 2-->White TT wire from burner area
Terminal 3--> Red TT wire from burner area

Still add Rc to Rh jumper
Still connect humidifier to HUM and C

Thank you again

 

Make that terminal 4 on the relay.
Everything else is correct.

 

Oops, dumb typo on my end. Thanks Pete.

Plan to attempt this evening, I'll message back with an update.

 

Took me a little longer to make the changes. Yesterday, heat pump was not going into defrost cycle and icing up and aux oil heat not kicking in. Turns out, the red Rc wire was not connected in the EIM so I don't think the defrost cycle could be energized. I believe this is fixed as of yesterday evening.

I made the change to the relay connections as suggested. Humidifier appears to be turning on/off with both heat pump and aux oil heat as controlled by the humidistat. I have not been able to test when the switch from Heat Pump to aux oil heat due to demand or defrost cycle yet because the weather is too warm (40s today). But plan to monitor over the next week or so. The only thing I don't like is that when the furnace turns on the humidifier starts running immediately even though the blower fan is delayed with the fan limit control switch. I think this is expected behavior but just seems like waster water.

One thing I am noticing with the furnace, is that when it's energized the blower fan is off until it reaches 100 degrees per fan limit control switch. But then the fan kicks on for about 10s and off again for a few minutes. Repeats this cycle twice before staying on. In this expected or suggestive of a failing fan limit control switch? Happy to post this elsewhere just on my mind.

Thanks again for the help. I'll update in a week or so as well.

 

Having the humidifier running slightly before the air is heated is ok.
Not really much of a way around that.

You have a wire from G on the EIM to G on the fan center. Power on that wire will bring on the blower. It's possible that power on G is high speed.... for A/C only.
If you have a meter..... check from G to C on a call for heat. See if it becomes 24v.
My guess is that it won't and that there is a fan/limit control inside the furnace that controls the blower in heat mode. That fan/limit control is usually adjustable.

Page 6 in the manual discusses the location. If you find it..... pull the cover off. Hold the silver disc from turning and adjust FAN ON setting slightly higher. Give that a try.

Thermo Pride downloadable manual

 

I do have the fan limit switch. When the oil furnace kicks on and I watch the dial spin. What seems to happen is:

1. Spins and when it his the Fan On at about 140* fan kicks on for 10-30 seconds
2. Will jump down to below 140* BUT still ABOVE the Fan Off Limit at 90*
3. This will repeat 1-3 times before the fan stays on

When the furnace burner turns off, the fan will continue to run and then turn off at the Fan Off limit. It may come back on 1-2x while the furnace remains off; I think this piece is normal behavior but the cycles from 1-3 above seem abnormal. There also is no cover over the fan/limit control so wondering if this is now faulty and needs to be replaced?

Do you still recommend increasing the Fan On limit? The 140* it's set on seems a little high to me as is.

Thanks for continued help. Humidifier seems to be functioning as expected.