Page 3 of 3 FirstFirst 123
Results 27 to 32 of 32
  1. #27
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,755
    In my area, most 1600 sq ft house of the same time period could be easily heated with a 60,000, 90%er. We usually get a little colder.(but not these last 2 years)

    What size was the old furnace. A load calc can be fudged to say a size a contractor wants it to say.

    Is it wired for 2 stage operation, or do they have it on a timer that it goes to second stage every cycle.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  2. #28
    Join Date
    Nov 2005
    Posts
    40
    3 contractors sized it when I got independant quotes. You saying all three fudged the numbers?

    Also the previous furnace was an 85k, but yet another contractor. AND the original furnace was 80k. The previous furnace (85k) was removed due to issues with not turning on the blower when the DX ran. The contractor could not fix that issue.

    Since I helped install and wire the furnace, I know it is right. I also ran the thermostat in test mode to double check. All delta T's across the HX were right smack in the middle of the manufacturer's specs for temp rise (both speeds), without changing speed taps. External static pressure is fine, and no my house is not a wind tunnel. Actually I hear slightly less noise than the other furnaces while airflow is comparable and not excessive or too low. My curtains (shears actually - not my choice) move only slightly when the fan is on, similar to the other furnaces. Everything matches up. The only issue is the indicated temperature never changes and the excessive on-off cycles. My Robertshaw/Invensys Insight thermostat would show the temp change. I had the opportunity to watch as my VisionPro was out for repairs. And yes, the thermostat is in a very good location.

    With 1 CPH being set, it NEVER changed indicated temperature over the 1/2 hour it ran this morning while I watched. This was after recovery on both days. I know my other stat would have and did show temp variations more than 1 degree during a similar runtime with the same furnace. I do admit the temperature is more even with the VisionPro, but it is not worth the extra wear and tear on the equipment.

    This weekend will be the test as we will be in single digits. I know the current setting is good for the balmier temps, like this morning. So, we shall see what colder temps do.

    I am glad to have the ability to set CPH, but I still would like a more thorough description as to what algorithm it uses to determine when to cycle on and something more than second stage comes on when it thinks it needs to or sees the temperature drop. PID loops are nice for even temps, but they also make the equipment wear out faster.

    Basically, I like the thermostat as it is easy to use and setup. I also like the touch screen. Just the quirk of control.

    Is it possible to email them for answers?

  3. #29
    Join Date
    Feb 2008
    Location
    Danville, IN
    Posts
    47
    Quote Originally Posted by y2kjackal View Post
    Definitely not over sized. My Robertshaw/Invensys Insight 2-stage thermostat works it just fine. My thoughts are that it just has a very small dead-band since it tries to maintain a constant temp (i.e. less than 1 degree). It turns on even when the display is at setpoint. Hence more cycles. If I could get it to drop 1 degree before it turns on, I'd be happy. Why should the furnace come on when it is at setpoint? Certainly not an over sizing issue.

    Over sized means it would shut off right away, which it does not. It runs for a while after it starts. Just no noticeable droop or dead-band. What this thermostat does is it makes the furnace comes on too early making for more starts per hour or counts or whatever.
    Thermostats actually read in tenths of a degree, you should never see the room temp move if the anticipation circuit is working correctly. You need to measure the cph before assuming oversized unless of course its grossly obvious as I'm sure we have all seen a time or 2.

  4. #30
    Join Date
    Feb 2008
    Location
    Danville, IN
    Posts
    47
    Depending on the brand of furnace--most upstage to hi-fire after 7 to 10 mins.

  5. #31
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,755
    Quote Originally Posted by comfortking88 View Post
    Depending on the brand of furnace--most upstage to hi-fire after 7 to 10 mins.
    Not if your not using the timer.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  6. #32
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,755
    Quote Originally Posted by beenthere View Post
    Not if your not using the timer.
    Not saying they fudged the nmbers, just that its easy to do.

    When it gets down to the single digits, time how long it runs. It should be Almost continous.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

Page 3 of 3 FirstFirst 123

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