[Jpcd]

Hello,

I'd like to potentially determine the cause for no aux heat during the defrost cycle on our heatpump and correct the strip staging.

Given: I have a Honeywell TH6220 Stat, Trane XL14i condenser and 4TEC3F60B Air Handler with 3 strips BAYhtr3415000. The condenser has an ODT-A, TAYSTAT250B. I have traced the wires and found no shorts.

From what I have read I believe the issue with the Defrost/No Aux Heat is with the following wiring at the ODT---Air Handler:

Air Handler-----ODTa--Condenser
.....................Pin1----X2
.....................Pin2 no wire
W1W2W3------Pin3

Stat----Air Handler
W2-----W1W2W3

It appears that the X2 will only call for aux heat during defrost if the ODTa is closed, it appears to be set around 25 degrees. Shouldn't Pin2 be connected to W2W3 only at the air handler and if it is real cold ODT circuit closes and all heat called for during defrost?

For staging shouldn't W1 be separated from W1W2 and connected to Stat w2? W1W2 connected at Stat to E?

Comments welcome?

 

[beenthere]

Tranes aren't my normal unit.

Houston204, or HVACTECH126 may have info on them. Hopefully one of them sees this thread.

 

[Jpcd]

been there,

Can you explain the wiring for the ODT? The install sheet says... Assure that lead wires are attached to terminals 2 ie. common lead wire and 3 ie. cold lead wire and that dummy terminal is attached to terminal 1 ie. warm dummy terminal.

Thx

 

[beenthere]

I would need to see the instructions for both the heat pump and ODT.

 

[zappa]

Can you tell us some history. New install, stopped working, are you adding the ODT to an existing system. The ODT's can be wired a couple of ways. What do you want it to do?

It sounds like you are breaking the defrost heat signal to the air handler until below 25 degrees which will give you a blast of cold air during defrost.

 

[Jpcd]

Odt

I am seeking to rectify original installer's hookup. Aux heat never worked during defrost cycle and a blast of cold air always occurred. There would be a temp. drop and the stat would call for aux to recover after defrost. Second installer replaced the defrost board, didn't fix it, said he was a tinman and professed after he had little experience with Trane. There is only 1 ODT. I want staged aux to come on during defrost (defrost --aux via W2, below 25 defrost --aux via w1+w2 as ODT is closed).
I suspect the current wiring doesn't call for aux at air handler at all, as the x2 connects to ODT & circuit is open, it will only call for it when circuit closed at temp below 25 degrees. I believe another wire is needed for X2--W2 and can be passed through the ODT device?

 

[Jpcd]

ODT docs

I am attaching the installer guide for the ODT. I don't understand the language used for wiring install? Also, pic attached of the ODT temperature setting for review.

Thx

 

[zappa]

I think I understand. One stage of heat at all temperatures until it gets below 25 then another stage along with the first stage.

I'm stabbing in the dark now without schematics. First stage would be passed along unmodified just like you didn't have a ODT. You are correct about needing another wire from outdoor unit to air handler, which I don't know if you have. That signal would go through the ODT to select the additional stage.

 

[hvactech126]

you have electric aux heat, so... are you currently staging the aux heat using the ODT? There are many ways to wire it up. Here is what I think you are looking for in a schematic...

X2 from heat pump is powered during defrost and must terminate on w2 without using the ODT. Using 1 or 2 ODT's you can wire per the diagram. It all really depends upon how many Kw you have for aux heat.

 

[Jpcd]

Thx for the schematic, but I need to clarification on the wiring through the ODT.

"X2 from heat pump is powered during defrost and must terminate on w2 without using the ODT."

1. Does the ODT allow a pass through circuit of the X2 call for heat on a pin at all times? Pin2 is called a common? or just bypass for x2--w2w3? Can you explain the 3 pins on the ODT?
Would this work?

Air Handler-----ODTa--Condenser
.....................Pin1----X2
W1------------Pin2
W2W3---------Pin3

The A/H has 15Kw on 3 strips. Currently a call for aux heat from the stat energizes all 3. Last installer wired all of them together. I will stage as follows: Aux will call for 10Kw and E call for the additional 5Kw?

Stat---------Air Handler
Aux------------w2w3
E--------------w1

Alternatives welcome?

 

[zappa]

Yes, X2 needs to be wired straight through, follow it on the schematic. Also notice the wirenut and a jumper going from X2 to the common pin #2 of the ODT. The ODT is like a single pole double throw switch. When cold, #2 and #3 are connected together. When warm, #2 and #1 are connected but you won't use that combination.

 

[zappa]

BTW, the schematic is showing a different style of ODT without pin #1.

 

[Jpcd]

ODT Wiring

Thanks for the explanation of the ODT, clears things up considerably!

Given the logic sequence would this combination not work and a separate x2 bypass not needed?

Air Handler-----ODTa--Condenser
.....................Pin1----X2 (Warm> 25deg) circuit:1&2
W1------------Pin2 (Cold <25) circuit: 1&3
W2W3---------Pin3

 

[Jpcd]

Schematic

The schematic simplifies the installation of the ODT. The 3 pin ODT in my understanding replaces the extra wire x2---Air Handler? Given the sequence logic you provided, the current installation is: (Warm> 25deg) circuit:1&2 completed (but 2 not connected to AH, thus, no aux heat during defrost). (Cold <25) circuit: 1&3 completed w1w2w3.

 

[zappa]

Sorry, I'm having trouble following what you are saying.

X2 to W2 never gets broken. That is the factory connection without a ODT.

You can't use pin#1 of the ODT.

The ODT is simply adding another heat stage to W2.

You might be happy with W2 only and might not even need the ODT.

 

[Jpcd]

Given the sequence logic you provided, the current installation is: (Warm> 25deg) x2 on Pin1 to Pin3, no circuit when warm via P1P2!

(Cold <25) x2 on Pin1 to Pin3, no circuit when cold via P2P3. Thus, no Aux Heat.

Proposed Solution: Connect x2 to P2!

Air Handler-----ODTa--Condenser
.....................Pin2----X2
W1------------Pin1 (Warm> 25deg) circuit:2&1
W2W3---------Pin3 (Cold <25) circuit: 2&3

 

[Jpcd]

P2 acts as the common. Is this ideal?

 

[zappa]

You can't permanently jumper any of the W's together. You could break X2 to W2 with the ODT but why would you want to do that? That's the way it is wired now and you will get A/C only and no heat until it gets lower than 25*.

 

[zappa]

Follow the schematic that 123 posted but disregard the lower optional ODT. Use pins 2 and 3 of your ODT and wire it like the top ODT.

 

[Jpcd]

wiring

Zappa, I will try to provide clarity:

Right now current setup X2 to P1 breaks the circuit and it is never closed with the ODT, thus no aux heat ever called?

Proposed Soln: Connect X2 to P2 and establish a staged circuit when warm or cold to call for Aux.
P1 wired to W1 at AH = staged 5kw
P3 wired to W2W3 at AH = staged 10kw

Stat Aux wired to W2W3= staged Aux 10kw
Stat E wired to w1 = staged Aux 5kw.

Thoughts?