Heat Pump Suplemental Ht and Digital Thermostat

[keith welchel]

My home has a 5 ton Carrier heat pump (40YR060300) that was installed in 1991. I just had it serviced and the tech made several statements that I'd like some advice on...

1. Leaving the Fan On will actually help my units efficiency by maintaining a more constant temperature mixture. I have three rooms with 25 ft vaulted ceilings (4000 heated sqft)

2. Install a "two stage heat/one stage cooling" Digital Thermostat. I purchased a Honeywell RTH8500D. I'm a EE and very versed in wiring and I wired it in myself. I'm sure the wires are connected per the instructions.

The thermostat is selected for "Multistage Heat Pump."

Question: I'm not sure I have selected the correct System. My lights dim periodically (I haven't timed it but about every 10 minutes) as though the strip heat or compressor is constantly cycling on, even when the thermostat shows "Heat On" and not "Aux Heat On". As I was writing this, the lights dimmed and the thermostat cycled from "Aux Heat On" to "Heat On". Now it appears the compressor is not running (freon pipe never gets hot.)

Thanks,
-Keith-


[Edited by keith welchel on 02-13-2005 at 09:46 AM]

[karsthuntr]

Call your tech back and have them install a real t-stat, not that Home Depot crap.

Is this the one?

[keith welchel]

No, that's not it...

What's a real one...

Are all Lowes/Home Depot Digital thermostats... not real...

[Edited by keith welchel on 02-13-2005 at 09:49 AM]

[karsthuntr]

They sell cheap Homeowner grade t-stat's at Home depot. The one's you buy fro a contractor are better quality and have more features. Plus you will get a warranty on one installed by a contractor.


You get what you pay for.

[keith welchel]

I understand... but saving money isn't the issue... nor is debating real thermostats...

I'm following the techs suggestion... it's installed and I'm not going to call them yet...

I'd really like some help on the problem at hand...

Thanks,
-keith-

[beenthere]

You may have to change your cph

Or you may have miss wired it.

Check the install instructions, and you see where it mentions some system changes may have to be made.

[beenthere]

To say much more then we have, would be step by step instructions to a DIYer.

[docholiday]

Since you are an electrical Engineer (I assume EE is just that), you could probably do the math and figure that running the fan constantly costs more, not less so unless somehow the heat from the motor costs less than the HSPF of the unit itself, I suspect you have received a less than correct information. It may, and I cant comment on your system, be a comfort issue but it is not an efficiency issue.

The thermostats at HD or L are defeatured versions designed to look like the ones you can have installed by the contractor but at a price that appears to be competetive. Technicaly they work most of the time by switching on and off equipment but thats about it. If you are looking for technical support for that thermostat call HD or the 800 number on the box.

I understand for you the cost is not the issue but you have to admit, a few dollars saved up front have ultimately cost you more in unnescessary resistance heat operation and agravation.

[keith welchel]

well... I installed the original thermostat and still no compressor heating... time for a service callback...

[BaldLoonie]

Is anything running outside?

[keith welchel]

yes... the outside appears to be running normally... the Fan is running and it sounds normal...

on Friday when the tech was servicing my unit he thought the unit had been overcharged from a previous service (another company). he wasn't totally sure about the over charging and said that I need to have it checked again when the temp is over 70degF.

thanks,
-keith-

[BaldLoonie]

Doesn't sound stat related, compressor isn't starting for whatever reason. At 14 years old, could be getting towards the end of its life. Hard start kit or super boost could give it a little more life.

[fat eddy]

As a service technician for a large equipment dealer I would say,

The compressor is not working and it is probably going off on internal overload then cools down about every ten minutes and tries to restart again this is why the lights are getting dim. Turn the whole thing off for an hour then fire it back up if it still doesn't come on then you will need to have the compressor checked sounds lke it is either hard starting or already dead.

[keith welchel]

the HVAC tech checked it today and said the compressor is dead.

here's what's happened in the last week...

The outside unit has been making loud noises and vibrates when in defrost mode for about two months or so...

I called a service repair company that I have never used before but is on the HVAC manufactures list of recommended service companies...

the unit was checked last Friday and the tech stated the unit was significantly over charged... some Freon was removed...

the unit seemed Okay until Sunday (but now my son says our lights dimmed more than usual on Saturady)... on Sunday morning I noticed the lights were dimming about every ten minutes...

I called the service company to come back out today (Monday)
------------------------

it seems very possible the compressor has been so stressed that it finally died... the unit is 14 years old

but, i'd like to take the unit out another 5 years...

Questiom:
are refurbished compressors an option?

are refurbished compressors a big risk?

could the unit just be out of Freon? I don't think the tech today hooked up the meter... but I'm not sure.

if a new unit is the only/best option, I'm considering a Carrier Infinity or Trane similar system... any thoughts or recommendations...

Thanks,
-Keith-

[beenthere]

Either system will be a good choice.
Don't bother having the compressor changed, that isn't always a inexpensive a way to go as it first seems.

[jesup]

Leaving the fan on can help keep temps more even (increasing comfort and potentially reducing costs, since you don't need to set it according to the "worst" room), but mostly this is in the case of a house that has serious imbalances or poorly positioned thermostat, or if the fan is a modern variable-speed fan (they can run at a low speed continuously using a lot less juice). We run our modern units in fan-on mode, since our house in inherently highly unbalanced from room-to-room in terms of heat loss/gain (lots of windows (75+, many large), differing levels of insulation and exposure to outside walls, etc).

[keith welchel]

thanks for the input...

I've invited several companies to bid on replacing my Carrier 5 ton.

One other question... the main trunk is duct board... should this be replaced... it's clean and no mold... I've heard that these disintegrate over time...

[beenthere]

If its still in good shape, no reason to replace it.