Product review (4 stars): Fan Delay Relay (FDR circuit) for a Trane WCH036B100AA Heat Pump.
The heating and cooling cycles on my heat pump worked fine, but the blower fan (known as an air handler) would continue to run after the compressor would turn off.  During the heating cycle, the house would heat up, then start cooling off because the air handler would not shut off and eventually start blowing continuous cold air, cooling off the house at which point the thermostat would start the heat cycle again, heating up the house again, then cooling off again, and the fan would never shut off running continuously.

For my heat pump (and most others), there are two components responsible for turning off and on the air handler;  A single large start capacitor and a Fan Delay Relay circuit, or, FDR as it is referred to on the schematic.  If either of these components have problems, the Air Handler might never turn off, or, not turn on at all.

The original FDR in my Trane WCH036B100AA was a Honeywell 21C144385P01 which I replaced with this RLY02807 and it works perfectly.  However, these components do not look at all alike, nor are the connections even close.  Therefore, you have to pay particular attention on how to connect the wires from the bad 21C144385P01 FDR to this new RLY02807 FDR.

While doing this, there are several things to keep in mind:

1. Safety first!!!!  - Make sure the BREAKER IS OFF.  There are 220Vac mains voltages that can kill things like people.  If this bothers you in any way, or you do not understand any part of this, call a service tech.

2. You are not working with DC voltages, but AC voltages.

3. You really need to read the schematic and have a full understanding of the FDR and how it is wired to proceed.  This TERRIFIES most people because they have never looked at a schematic before so it looks so confusing.  Foreign languages and computer programming look "so confusing" until you've learned something about itsame thing applies to electronic schematics and everything else for that matter.

The schematic for your heat pump is usually printed somewhere in or on the unit.  Mine was printed on the access panel that I removed for access to the electronics.

If you try to wire the new FDR circuit, like the old FDR circuit, you'll probably send 208Vac to the new RLY02807 and your wall thermostat, which will destroy both.

The wiring for this RLY02807 is as follows:

TURN OFF THE CIRCUIT BREAKER AND/OR PULL THE FUSE DISCONNECT AND GIVE THE CAPACITORS 10 MINUTES TO DISCHARGE.

Find the transformer.  There are two secondary wires from a STEP-DOWN transformer.  These are 24Vac lines.  The 220Vac side has THREE wires, with the WHITE center tap wire capped or isolated from use.

 One of the 24Vac wires, the (probably BLACK) wire, goes to terminal A.
 The other 24Vac wire (probably BLUE) goes to terminals B and 4.

 The White wire goes to terminal 6  Defrost detect
 The GREEN wire (Low Voltage Terminal Block - LVTB) goes to terminal T  Thermostat
  This is labeled LVTB on the schematic.

 The fat RED wire, goes to the CENTER POST marked COM on the relay.
 The other RED (dual) wire, goes to the OUTTER POST marked NO.

Once againthis is for MY TRANE heat pump, PROBABLY NOT YOURS.  You really need to confirm the above configuration, by reading the schematic for your heat pump, and verify that the connections I used will match the connections you need.  The most important thing is. DO NOT CONECT ANYTING WITH 200+ AC VOLTS TO ANYTHING OTHER THAN THE TWO TERMINALS LOCATED ON THE RELAY!!!

While you are at it, the FDR MAY indeed be the problem, however as I mentioned earlier, it may also be the start capacitor.

If you are going to replace the FDR, I HIGHLY RECOMMEND YOU ALSO DO THE FOLLOWING:

While you are in there, replace the large motor start capacitors.

My Trane WCH036B100AA Heat Pump uses the following:

 CPT00091 - 135MFD  330Vac  Air Handler
 CPT00668 - DUAL - 40/5MFD 440Vac Compressor and condenser fan

These capacitors are for a Trane WCH036B100AA Heat Pump and DOES NOT necessarily mean that YOUR UNIT uses the same size capacitors.  Write down the specifications for your start capacitors that are found on YOUR capacitors, or, verify the values on YOUR schematic, then order your replacement caps based on what you currently have installed, or better yet, what the schematic says.  A wrong MFD rating can shorten the life of your heat pump motors, while an incorrect voltage rating can destroy your brand new capacitors.

This is an easy fix and will save you $$$HUNDREDS$$$ on service call fees, but only if you feel comfortable in the process and follow the schematic.

I gave this RLY02807 FOUR STARS because the electronic assembly of the PCB is, substandard.  The electrolytic capacitors on the board have not been soldered flush with the PCB.  Therefore, be careful while handling the RLY02807, because if any of the capacitor wire connections break, you get to start all over.