Results 1 to 8 of 8

Thread: What have I?

  1. #1
    I'm a new home owner and I'm having problems with a dual fuel Carrier system and I thought I'd start out by asking the simple stuff first: I hear talk of everything from 1 speed HP and 1 stage furnace to a 2 speed HP and 2 stage furnace. By reading the literature that was left with the house and looking at it I have no way to tell which this system is. I've listed the model numbers of the equipment. Can anyone tell me what this system is from the numbers? I don't feel like I can even ask intelligent questions unless I at least know this!

    HP: Carrier 38QF
    Furnace: Carrier 58DH
    Optimizer II Control: 38CQ/HQ/RQ ?

    Any help is appreciated.

  2. #2
    Join Date
    Sep 2004
    The books I have dont list those model numbers

    [Edited by ct2 on 02-04-2006 at 01:34 PM]

  3. #3


    Isn't that a necessary component of a dual fuel system?

  4. #4
    Senior Tech Guest
    Yes, you need a furnace...auxillary heat, emergency heat ring a bell? Not a Carrier guy but when one happens along they will probably want the entire model and serial number as opposed to partial.

  5. #5
    Join Date
    May 2000
    Indianapolis, IN, USA
    That was a really nice system in its day but it is pushing past 20 years old so problems are to be expected. That's a single stage heat pump with gas backup. That's a good way to heat a home these days. If I recall right, the DH furnace is 80% model.

    If budget doesn't permit replacing all, a tech needs to find the culprit and replace that aspect of the system.

    What's it doing or not doing?

  6. #6
    Thanks for the replies. Budget is really the operational word here.

    Initially, I found that, in heat mode, the HP and outside fan was running without the inside fan running. This happened only on occassion and didn't seem to be connected to a defrost cycle. I had a contractor come out (Of course it wouldn't do it when the tech was here.) and the tech looked at the Optimizer unit and said a wire was loose. (I'm always suspicious of that being the solution.)

    It did it again, so I had them come out again. This time, (Of course it wouldn't do it when the tech was here.) he seemed to think that it was in the Optimizer Unit and suggested replacing that with the Carrier Dual Fuel Programmable Thermostat. This morning I noticed that the return line (the small dia. one) was frosted near the furnace, and was very cold. The outside unit was running and the inside fan was running. The larger line didn't seem to be warm. I switched it over to auxillary heat at that time, fearing that there was something wrong that might damage the compressor unit.

    I'm not looking for diagnosis here, more for the most cost effective and correct way to go about diagnosing and fixing it. I also have some questions about procedure on service calls of this nature.

    Regarding the service calls: The tech didn't do any check of the outside unit and didn't seem to try running it through any tests, or take any measurements. Just ran it in HP Heat mode and, on the second visit, stated that he increased the fan speed some on the inside unit. Isn't there a way to check the condition of the entire system, such as line pressure, etc? Is there a "normal" procedure for analyzing a problem on this type of system?

    Would it make sense to go ahead and replace the Optimizer Unit with a new Dual Fuel Thermostat as a way of eliminating a potential source of the problems? (I know I'll have to do that anyway with any update of the system.) If so, are there any further checks of the HP unit that can be done before that?

    A lot of questions, I know. I'm just new to this, and I don't have a lot of money to spend right now. I'm just trying to figure a good route through this, or what my options are. Any help is appreciated.

  7. #7
    Join Date
    May 2000
    Indianapolis, IN, USA
    You could go with Carrier's dual fuel stat or with a Honeywell Vision Pro. Carrier's can do much more, the Vision Pro is about as easy as they come. This would rule out optimizer problems (it sounds like you were cooling for a while) and could be used later if you replace the system.

  8. #8
    Join Date
    Aug 2001
    bogart ga.
    You could also go with a bill porter fossil fuel board and a regular h/p t-stat

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event