What is a cycle re: compressors

Discussion in 'General Discussions' started by ChrisJ, Apr 2, 2011.

  1. ChrisJ

    ChrisJ Active Member Forum Leader

    The statistics on my heat pump say the compressor has run for 4813 hrs and 5757 cycles. How can it have more cycles then hrs run? What constitutes a cycle?

  2. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    On / off

    On / off twice in an hour is 1 hour run. 2 cycles.
  3. ChrisJ

    ChrisJ Active Member Forum Leader

    Thanks, I just hope my compressors don't cycle themselves to an early death.

    The numbers given were my stage 1 compressor, the stage 2 compressor has 1245 hrs, 4200 cycles. Seems like it runs for shorter time spans.

    I have on demand DHW, takes less then an hour to reheat tank.

  4. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    If your stage 2 compressor consists of a Copeland Ultratech 2 stage scroll, then no worries about many short 2 stage cycles - Ultratech shifts-on-the-fly
  5. ChrisJ

    ChrisJ Active Member Forum Leader

    I believe my dual compressor unit uses two single stage Bristol compressors. One being larger then the other.

    For the first few months the radiant floor was used it was short cycling the HP. 20-30 min on, 8-12 min off, when floor was calling for heat. Re-plumbing the buffer tank solved that problem.

    Anytime there is a call from the other tank for DHW both compressors run. It may take 30 min to get tank to 120*.

    I just thought those numbers showed a lot of cycles for the # of hours run. I wish I had started collecting info earlier then Jan/11, HP has been running just over a year. I finally got a palm pilot that can read the Georgia control board.

  6. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader


    I think you are worrying too much. If you did not have the app you would not know the numbers.

    If you have solved the radiant floor issues vs. run time then let the machines do the work.

    Geo stuff is like the tortoise and the hare, slow and steady wins.

    With out knowing the control board, equipment or how the system was piped, I would just take comfort if you are comfortable. Bristol's are OK and cheap to replace. If you need to worry look at the delivery system.

  7. ChrisJ

    ChrisJ Active Member Forum Leader

    I know I worry too much!!
    I am about to shut down the radiant till next fall and am already thinking about changes, might even cut my slab to get a thermal break across the area where my 2 sliding glass doors are, slab runs under doors to be in contact to outside air.

    Makes me wonder what people do in garages where the cement goes out under the doors. Do they some how seperate the slab from the aprons under the door? In my garage I am trying to heat the 6"-8" of cement that sticks out under the doors.

    I know now we should have used more tubing in both basement and garage, too late now.


    Attached Files:

  8. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader


    I tend to LOAD the areas of a slab near large windows and doors. Your install looks to be 12 inches on center. I would have started with 6" O/C for a couple of loops then 9" to about 4 feet off the doorway and then finally switch to 12" O/C then as much as 18" in the center of the slab.

    I did not see your manifolds. If they are adjustable you could lower the flow to the center of the slab and maybe get better performance.

    Adding a thermal break might help.

  9. ChrisJ

    ChrisJ Active Member Forum Leader

    Is it worth it? To cut out a 2" trench infront of the doors and put in insulation. The slab has 2" rigid around the sides where it meets the foundation, just not infront of the 2 doors, about 14'. In the garage I have 2- 9' doors and a 3' entry door with no break from the cement sticking through the doorways.

    My manifolds are very simple copper things, see picture. They are set up so I can seperate them into 2 zones in basement, 600' and 600' of tube. The doors would be in the half of the basement I want to make into an In-Law appt. The 5/8" pex feeds the garage manifolds in second picture.

    I know now how it should have been done, heavy near doors and walls. Hopefully someone doing radiant w/geo will learn from my mistake (not a complete disaster, it does work).


    Attached Files:

  10. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    It may be possible

    to make this system work better. Do you have heat loss calcs for the two zones?

  11. ChrisJ

    ChrisJ Active Member Forum Leader

    The cals were done as if the basement was 2 zones. The area with the doors and one window showed 7500, approx 15'x40', the other area same size no windows or doors, but has open staircase to main floor, showed 5400.

  12. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    I found all three copies

    of one of my favorite books. The book is called Hydronic Heating Helper It is printed as a service of Burnham boilers. It is my first go to for crunching numbers.

    Given your heating load of just under 13,000 BTUH I was looking for how large the piping needed to be to handle the load. Half inch pipe will carry 17,000 BTUH @ 20* delta T, and 1.7 GPM. So your 5/8" Supply and return to the manifolds will do the trick.

    It would be very difficult to add more tubing as the system is cast in concrete. There are several things we can do to increase the effectiveness of your system.

    The first thing we need is the ability to measure what is going on. The cheap or best value added way to do that would be up-grading the manifolds. I would go to manufactured manifold that are equipped with thermometers and flow gauges. I will try and add a photo.

    Once we can measure, we can fine tune the floor(s). A cheap infrared point and shot thermometer will allow you to "see" the heat in the slab. Poured in slab radiant systems are high mass systems and as such the stratagy for their use is differant than low mass fast floors and air delivery systems. In slab is slow to heat, but can provide a very effective storage system.

    When I design such a system I start loading the slab with heat as soon as the leaves start turning color. The entire geo system is dedicated to getting the slab up to tempurature while the other loads are low. The magic number is somewhat elusive as I tend to control my floors with ambiant air thermostats that everyone is used to dealing with.

    The rule is no warmer than 85* at the surface of the slab.

    Since we can not add tubing we need to increase the BTUH to the floor. I disagree with those hear that alow the buffering tank to control the floor temps. I use either a fixed or motorized mixing valve.

    Sorry I did not get back to this thread earlier, but I could not find my books.

    Please feel free to contact me if you need more details.

    Warm regards,


    Attached Files:

Share This Page