Luxaire Package heat pump

[sean88]

I'm a bit stumped. I installed 4 Luxaire 2 ton BAUA024 208/1 package heat pumps with 5 kw strip heat. I got three out of the 4 to start up no problem. However, the last one I tried to start---didn't. Here's what happend.

1. Turned on main power - 5 AMP fused on fan board blew. Figured I may have shorted the t-stat wire. Checked wiring no shorts.

2. Put another 5 AMP fuse in - transformer pops. Check low side of x-frmr it's ok. Check high side and it's gone. Checked input of x-frmr getting 208 V, wire is on 208 lead of x-frmr. OK figure bad x-frmr.

3. Get new trasformer. Turn power on blows last 5 AMP fuse. Check t-stat wiring again - measured ohms across stat getting 1.9 ohms - ok figure bad stat.

4. Get new stat, pull new wiring, (found serveral nicks in old wiring). Install new stat. Turn main power on blow another 5 AMP fuse.

5. Disconnect t-stat wires from fan control boad. Put in 10 AMP fuse. Fuse doesn't pop. Check voltages across fan board terminals going to stat- getting 24 across hot and common.

6. Reconnect t-stat, turn on main power. X-fromer pops. Primary side is gone again. Secondary side is ok.

7. Place a call to factory--suggest it's a bad fan control board get new board, install it--repeated steps 1 through 6.

WTF? I'm at a loss. Any suggestions?

[Wild Leg]

Get a supply of fuses, or a minibreaker.
Leave all the stat wires off.
Use jumpers instead of the stat.
Put it through its paces, using jumpers.
Connect them one at a time.
See when it happens.
Watch the amps.


Are you sure your stat agrees with the equipment?

What is the common terminal on the unit & stat?

Don't hook up the common until you see everything else work.


[Edited by bwal2 on 05-16-2005 at 05:18 PM]

[sean88]

Using a Honeywell Stat CT70 for a heat pump. Common on stat is X common on unit is C.

Will have to go to supply house to get more fuses.

Thanks

[service guy]

At what point does the fuse blow? like a call for heat or a call for cool or a call for fan only. sounds like something is raising your amp draw Ex: shorted coil on a contactor or bad solinoid on reversing valve just wanted to add my two cents.

[sean88]

The fuse blows as soon as I put power to the unit. I haven't checked amp draw because everything points to a dead short. BUT I CANT FIND IT!

[service guy]

I don't understand why you keep losing the primary side of transformer? I read your first post again and realized I may have answered to quickly. Sounds like the issue is some where on the line voltage side, let me ask you this Is your blower motor getting power from this board? Use your meter use your brain I have Faith you will find the problem.

[Wild Leg]

Originally posted by sean88
The fuse blows as soon as I put power to the unit. I haven't checked amp draw because everything points to a dead short. BUT I CANT FIND IT!

Sean, did it blow the fuse with the all of the t-stat wires disconnected?

[sean88]

No the fuse didn't blow with the t-stat wires disconnected.

BUT--it did blow when ONLY the hot and common where connected.

I ohmed out the t-stat wires while they were connected to the t-stat (set to cool fan ON). I got resistance on R to O, Y, G and W but no resitance from R to common.

Pushed contactor in and compressor and condenser fan started.

The blower motor is getting power from this board.

Here is the wiring diagram for the unit. See page 24.

http://www.luxaire.com/PDFFiles/036-21312-002-A-0104.pdf

Thanks for all the help.

[Wild Leg]

Originally posted by sean88
No the fuse didn't blow with the t-stat wires disconnected.

BUT--it did blow when ONLY the hot and common where connected.

I ohmed out the t-stat wires while they were connected to the t-stat (set to cool fan ON). I got resistance on R to O, Y, G and W but no resitance from R to common.

Pushed contactor in and compressor and condenser fan started.

The blower motor is getting power from this board.

Here is the wiring diagram for the unit. See page 24.

http://www.luxaire.com/PDFFiles/036-21312-002-A-0104.pdf

Thanks for all the help.



Will it run without hooking up the common terminal on the stat?
The only thing the common does is run the clock & lights in the stat.

It sounds like either a misapplication of the stat, or a bad stat.

What wire are you hooking to X on the defrost control?

[sean88]

Haven't tried disconnecting the common from the stat yet. I'll do that tomorrow.

I'm not hooking any wire to the defrost control. It's a spade on the defrost board not a screw down. I know the drawing shows to field connect x on the defrost to x on the stat but the x on the stat is common. Here is the stat I'm using.

http://customer.honeywell.com/Techlit/Pdf/69-0000s/69-0866.pdf

[Wild Leg]

Since you have three just like it, you might want to move the stat & see if the problem moves with it.

Also, look closely at the way the wires connect to the stat.
If one is a little long, it could touch something it shouldn't.

Try removing the stat from the wall, and hooking the wires back onto the unit.

That will tell you if there is a problem in the wires.

Happy hunting.

[sean88]

FOUND THE PROBLEM!!! My wife said the same thing bwal2, maybe the new stat could be bad. So I got a new stat installed it and the unit works fine.

I ohmed out the first new stat and found the x and R where shorted. I'll never trust a new stat again.

[Wild Leg]

Good Job!

I hate to condemn new parts, but when they're bad, they're bad!

Don't forget to charge enough. :)