slow fan trane xv95

[central nj]

Hello.

I have a newer trane xv95, mated to a 15 year old single stage trane air conditioner in three zones. Last summer the air conditioner worked great. The heater works great – I set the honeywell TZ-4 panel to first stage for one zone, second stage for 2-3 zones.

This early summer/spring the air conditioner works well, but after 1 ½ hours or so, the fan speed slows down, and cooling of the house slows. I know this because the weighted bypass damper arm falls down/closes implying that there is much less pressure in the system. If I turn the unit off for 15 minutes, and restart --- the pressure/fan is back to full speed for another other hour or so.

Thank you so much for your time. The service tech said that the air conditioner is working perfectly, but I didn't realize at the time that I should have turned the unit on for a few hours before he came out). Any hints I could give him when he returns would be appreciated.

Steve

[bobboan]

You could be loosing air flow. A few things come to mind:

1. coil icing up
2. zoning/damper problem
3. blower motor problem

I would recommend doing just what you said: have the tech check it after it's been running long enough for the problem to show up.

[mark beiser]

When the fan slows down, is the outdoor unit running?

It could be that the supply air temperature is going below the limit set for it, causing the zone panel to turn the AC off.
It only kills the power to Y, but still powers G to the equipment, so the indoor fan would ramp down to the continuous blower speed.

[bobboan]

When the new furnace was installed, it could have been setup to run on low cooling speed when only one zone is calling. You can't do this with a single stage outdoor unit: it's gotta have fulling cooling speed any time there's a cooling call.

[bobboan]

Hello.
I set the honeywell TZ-4 panel to first stage for one zone, second stage for 2-3 zones.
Steve



I think that is your problem: you only getting low cooling speed when one zone calls.

[central nj]

Thank you so much.

I don't think it is the zone issue (i'm activating only one zone in the tests i've done, and the blower is nice and strong for the first 1 1/2 hours)

It was nice and hot a few days ago, so i don't think the condenser was below temp.

Icing perhaps? But it seems like it shouldn't disappear with only a 15 minute break---then reappear sort of magically around 1 1/2 hours.

[beenthere]

May not be icing. But could still be falling below the DAT setting.

Do your test with all zones calling, and see if it still does it.

[central nj]

Again, thank you.

What if there is no DAT sensor attached to the honewell tz4? How would that change your opinion of the problem?

[beenthere]

Would have to be there and check it.

[central nj]

Thank you all for your time. Steve

[central nj]

As follow up, and a thank you, the tech found freezing of the line. Says there is a leak, causing icing. I'm not going to spend the time and money on this older system. Getting the unit replaced. Thanks!!!!!!!