Short cycle and system damage?

Discussion in 'General Discussions' started by Eric D, Jan 15, 2008.

  1. Eric D

    Eric D Member

    Web Base Geothermal Consumer Information

    To help people understand the benefits of geothermal over other more common heating and cooling systems has anyone come across any exceptional websites that you might like to share the link to? Might be fun to have folks vote for their favorite website and to rank them on the GeoExchange. Might even convince GeoExchange to have a special excellence award for the best site!:rolleyes:...just a thought!
  2. Guest

    Guest Guest

  3. Eric D

    Eric D Member


    Thanks for the link to OurCoolHouse. This is a very cool site! I spent way to much time looking it over.


    Eric D
  4. Guest

    Guest Guest is a pretty well done site
  5. Guest

    Guest Guest

    More sites...

    I might suggest these 2 sites to look at; is interesting as they have an A to Z section across the top which is like a short course in this technology. Check it out! Then, look at the systems that does. I'm psyched on this stuff.
  6. geome

    geome Member Forum Leader

    Sometimes our geothermal system may be on for a very short period of time when I want to turn it off. For example, in heating mode, the system may have just turned on when I am just about to walk out the door in the morning of a sunny fall day. I know the house temperature will be fine when I return, so I would prefer to have the system off to save a little money.

    Could the system, including the compressor, be damaged if I immediately (after the system turns on) override the thermostat program by setting the thermostat a few degrees lower (a temporary program override) to get the system to turn off? The timing of turning the system off can be anywhere from 5 seconds to a few minutes after the system turns on. Could this hurt the geothermal system? Thank you
  7. teetech

    teetech Member Forum Leader

    May I suggest a programmable thermostat instead of turning the thermostat up and down.
  8. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    Yes yes and No.

    With a heat pump be it geo or air to air, let the machine do the work. Do not mess with the thermostat.

    Set it and forget it.
  9. geome

    geome Member Forum Leader

    teetech, already have and use a programmable thermostat. Overrides would be outside of the program we set.

    Mark, guess I still have a furnace mentality. That is, thinking small thermostat changes will save a lot of money.
  10. gabby

    gabby Member Industry Professional Forum Leader

    I know what you are saying and it is hard for us on autopilot (past experiences dictate a certain response) to remember that geo is lower heat and longer response time to recoup. A few cents saved is a dollar or two lost.
  11. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    Most Geo systems are

    child proof. The controls are designed to protect the machine at all costs. Even if you want to change the action there will be built in safe guards.

    If you are thinking air furnace, turn that off. One needs to think, hot water/gravity, when doing a heat pump.

    The objective is to use the cheapest fuel first. Heat pumps do the job, but not this second, they take time. They take low grade heat and pump it up to usable heat.
  12. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    Getting back to the original question:

    No harm in shutting unit off immediately after it has started. Once it has started, whether it runs for 5 seconds or 5 hours makes little difference.

    Avoid calling for another cycle a few minutes after the system shuts down - that is harmful, but that's not what the OP was asking, IMO
  13. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    Ditto Engineer.
    While I often subscribe to the set and forget philosophy, We have had sunny days around 60* here this year where solar gain has kept the house comfy til evening. I have no objection to shutting a system down as you leave.....however, the other guys points are not without merit and suggest you turn the stat back up as soon as you return (vs waiting until you are cold).
    good Luck,
  14. geome

    geome Member Forum Leader

    Good side point. Should the subsequent cycle wait 5 minutes or would longer be better, maybe 6 to 10 minutes? I believe WF Envision has a built in 4 minute cycle delay. I have 5 minutes set in our thermostat but have no problem increasing it.
  15. gabby

    gabby Member Industry Professional Forum Leader

    The delay is to protect the compressor during electric outages in most systems.The subs have auto resets that test for faults in the load side before restoring full power. If the rush current is too high, it will shut down and retest again...not good for starting and stopping compressors.

    You don't want to do anything that interferes, or disrupts the cycle time. The duty cycle of a system is designed to run for an extended period, testing if set point is reached before bring on the next stage. During a cold snap if the duty cycle is short relative to normal operation and you increase the delay start too much, the machine will struggle to recover. A minute or two longer in delay should do nothing to the overall performance...just don't get carried away.
  16. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    The basic concept of restart delays is to allow several minutes for refrigerant pressures within system to equalize. This reduces startup load on compressor.

    There is also an advantage of allowing heat buildup within compressor motor winding coils to dissipate during the start delay.

    Coil wires are insulated. Insulation is degraded by heat. Less heat = longer lasting compressor.
  17. geome

    geome Member Forum Leader

    Engineer, given all of this, what delay would you suggest using? 4, 5, 6 minutes or something else? Thanks!
  18. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    I've come across recommendations for 3-5 minutes. I wouldn't go any lower than the four minutes you say WF recommended.

    Adding a minute or so wouldn't do any harm. I might be tempted to do so perhaps in the case of larger, 5+ ton units, my theory being larger units might exhibit longer pressure equalization times, and the larger compressor might take similarly longer for its wiring to cool.
  19. geome

    geome Member Forum Leader

    Thank you. I believe the 4 minute WF off time is programmed into our Envision units. I made it 5 by programming the thermostat to do so (it won't send a new "on" signal for the time specified (even if there is a call for heat or AC). I just checked our Prestige thermostats. The minimum off intervals are 0,1,2,3,4,&5 minutes. I'll stick with 5. Thanks again.

    Glad there is no danger in shutting off the system after a brief "on" time. I'll do my best to leave the thermostats alone. My success will probably be limited. :lol:

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