Heat pump cycling -- is this bad for the unit?

[jeffr47]

I do not run my pump at night, so when it comes on in the morning, the water in the pipes is cold and the heat pump thinks there is demand, so it clicks on. About 60 seconds later, the water in the pipes is cleared and the pump clicks off, since the pool is already quite warm. Is this type of cycling bad for the unit? I'm not sure how to get around this, other than to run the pump at low speed all night.

My guess it would cost about $20/year to keep the pump running over night. That's negligible, but I don't know if I'm worrying about an issue that doesn't really exist.

 

[swamprat69]

Repeated "short cycling" ( repeated quick on/off cycles with very little time in between ) can be very detrimental to the life span of a system (usually eliminated by the inclusion of a time delay in the circuit in most modern systems). A single quick on/off cycle may have a some detrimental effect on the system (difficult to quantify) as once the system starts up it is normally meant to run for an amount of time that allows the system to stabilize at normal operating parameters. It would not hurt to run the pump overnight to see if that eliminates the one minute run time in the morning considering the cost to do so compared to the cost of the system.

 

[ajw22]

I think if you observe your Heat Pump you will see that the fan turns on but there is a delay before the compressor turns on and the HP is shutting down before the compressor engages. If that is so then there is no real wear over the cycle of just the fan running for a minute.

 

[pjt]

the heat pump thinks there is demand, so it clicks on

Can you simply leave the heat pump off until you want to use it?

 

[jeffr47]

Repeated "short cycling" ( repeated quick on/off cycles with very little time in between ) can be very detrimental to the life span of a system (usually eliminated by the inclusion of a time delay in the circuit in most modern systems). A single quick on/off cycle may have a some detrimental effect on the system (difficult to quantify) as once the system starts up it is normally meant to run for an amount of time that allows the system to stabilize at normal operating parameters. It would not hurt to run the pump overnight to see if that eliminates the one minute run time in the morning considering the cost to do so compared to the cost of the system.

Like most ac/heat pump units it does have a compressor lockout to prevent rapid cycling. But that doesn't stop that initial cycle when the pump starts or primes.

I wish the heat pump had a built in delay from when the water flow sensor triggered and when it started running, or a way to schedule it for certain times of day. It's definitely more efficient when it's hot out, so in a perfect world I'd run it in the middle of the day. I suppose I could use an Intermatic to do that, but might be very limited improvement.

 

[jeffr47]

I'm fairlt

I think if you observe your Heat Pump you will see that the fan turns on but there is a delay before the compressor turns on and the HP is shutting down before the compressor engages. If that is so then there is no real wear over the cycle of just the fan running for a minute

sure it's the compressor

I think if you observe your Heat Pump you will see that the fan turns on but there is a delay before the compressor turns on and the HP is shutting down before the compressor engages. If that is so then there is no real wear over the cycle of just the fan running for a minute.

I'm fairly confident it is the compressor, both from the sound and the current draw I can from my Sense monitor.

 

[ajw22]

I'm fairly confident it is the compressor, both from the sound and the current draw I can from my Sense monitor.

That is unfortunate. I have seen some HPs have a start up delay and a countdown on the panel. I was hoping yours was smart enough.

With a VS pump and SWG I woudl run your pump 24/7 and adjust your SWG output. Even without a HP I run my pump 24/7 and I like my water always filtering and getting some chlorine.

 

[jeffr47]

That is unfortunate. I have seen some HPs have a start up delay and a countdown on the panel. I was hoping yours was smart enough.

With a VS pump and SWG I woudl run your pump 24/7 and adjust your SWG output. Even without a HP I run my pump 24/7 and I like my water always filtering and getting some chlorine.

Yes, I am leaning towards running the pool pump 24x7 and letting it fall below the heat pump's low flow cutoff at night. I will have to check, but I don't think my Intermatic T220 can handle the current demand of the heat pump. That would be another option.

A startup delay would be awesome. Will have to check - maybe it's buried in a menu somewhere, but I don't think so.

 

[swamprat69]

According to the manual https://s3.amazonaws.com/AWSProd/sites/raypakcom/documents/6000.56.pdf on page 31, the heater has both compressor short cycle protection and a minimum run time protection built in. "Compressor Start Delay: The control is equipped with a compressor start delay to prevent short-cycling of the compressor. The control will not energize a compressor unless the compressor has been off for at least 3-minutes. When this situation arises, the display shall read “Comp Start Delay” until the timer clears and the compressor starts. Minimum Run Time: To ensure proper operation of the compressor and longest life, the control has a minimum run time for the compressor of 3-minutes. If the setpoint is reached within 3-minutes, the compressor will continue to run for 3-minutes unless (1) the high pressure switch trips, (2) the water pressure switch trips, (3) the high temperature limit is reached, or (4) the user selects “OFF” mode". The only reason that I see for it to run only one minute would be one of the 4 exceptions to the 3 minute minimum run time.

 

[swamprat69]

According to the above, even if the heater set point is reached after only 1 minute the heater should continue to run until the 3 minute minimum run time has been satisfied.

 

[jeffr47]

Right... so the 3 minute compressor protection is satisfied, because the heat pump has been off all night due to no flow. Then it clicks on, and runs for the minimum time, and clicks off because once the cold water in the pipes is cleared, there is no demand.

So in the absence of a way to introduce a startup delay after minimum water flow is satisfied, I don't think this can be solved on the heat pump itself. Either I need an external timer to have the heat pump energized a few minutes after the pool pump starts, or keep water circulating.

 

[jeffr47]

According to the above, even if the heater set point is reached after only 1 minute the heater should continue to run until the 3 minute minimum run time has been satisfied.

Agreed, that matches my observations. Thanks for looking that up.

 

[swamprat69]

If the control voltage on the circuit board ( through the safeties etc.) is 24VAC, then a time delay relay (delay on make) such as this https://www.grainger.com/product/4E...c6g6F7h2ow57dxMs0P4aAmbWEALw_wcB&gclsrc=aw.ds wired in series with the downstream side of the pressure switch (normally open) which would be the first thing that the board should look for to initiate the heater startup/call for heat would delay the heater startup for the timing of your choice. Please note that terminal #3 is the line side from the water pressure switch normally open and terminal #1 is the load side which would connect to the ciruit board.

 

[swamprat69]

In other words, the water pressure switch makes the time delay relay but doesn't tell the circuit board until the TD relay timing has completed the circuit.

 

[swamprat69]

The only problem would be that if all of the safeties are in series and one of them is open, the delay on make TD relay would never initiate as it needs a load path to ground in order to work. If you are aware of this, you would still be able to troubleshoot any problems.

 

[jeffr47]

The only problem would be that if all of the safeties are in series and one of them is open, the delay on make TD relay would never initiate as it needs a load path to ground in order to work. If you are aware of this, you would still be able to troubleshoot any problems.

I would not have the first idea where to install this!

 

[jeffr47]

In other words, the water pressure switch makes the time delay relay but doesn't tell the circuit board until the TD relay timing has completed the circuit.

Love the idea, and did manage a current sensor for my SWG so it doesn't get power unless pump is running (as a back to the flow switch), but I I have no clue how to install something like this.