Pentair Ultratemp rapid cycling

meatty

Active member
Jun 22, 2019
30
Austin, TX
Hello. I lurk here occasionally, and tbh, wish I'd checked here before building my pool last year, but I didn't, so here we are!

I have an Pentair Ultratemp 120 H/C heatpump (heat/cool) that is acting very strangely. I'm in Texas, trying to heat my spa currently. I have it set to 104. It runs for about an hour, and then stops. The temperature this brings it to is inconsistent, and seems to have more to do with ambient temperature than anything else. Following that (without changing settings) it begins rapidly cycling. It seems to try to start and then fail. The best way to understand the problem is to view the "history" screen from Screenlogic ("solar" is what Pentair uses for heatpumps):

1579668290961.png

With this chart, we can see it's not shutting off because of the ambient temperature (It turned on at noon, ran until 1:19, during which time the ambient temperature went up). The water temperature at 1:19 was 94. Testing at different times, I've had it shut off at a different temperature (eg. 88), so it's not related to the actual temperature - it doesn't think it's hit 104. And you can see once it starts rapid cycling, it no longer heats. If I try to run it several hours later, it runs for a much shorter time at the beginning (I tried running it just after 9 pm - it ran for 6 minutes before rapid cycling. And it is VERY rapid cycling and not consistent. Here it is during a 4 minute period:

1579668956596.png

Anyone seen anything like this before and/or have any ideas?

I haven't yet called Pentair or my builder (incompetent), and I can't find anything that matches this pattern in the manual. I wondered if anyone here had seen it before calling Pentair.
 

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meatty

Active member
Jun 22, 2019
30
Austin, TX
Yes, this is a fairly recent development - it was used in the summer as a chiller and would run for a long time to cool the pool.

Ive tried a varity of flow speeds with the same result. This screenshot was taken with my Intelliflow VSF at 32 GPM.
 

JamesW

TFP Expert
Mar 2, 2011
16,955
There are two different temperature sensors. One for the system and one in the heat pump. Check the heat pump temperature sensor and temperature display.

Maybe a bad internal check valve bypass.

Maybe low flow.

Maybe an obstruction in the heat exchanger causing most of the water to go through the check valve bypass.

Check the pump suction, baskets and impeller.

A suction clog or clogged impeller will make the gpm reading inaccurate.

So, even though the reading is 32 gpm, it might be lower.
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
15,323
Bedford, TX
M,

Seems to me we have seen this before.. Something to do with how the heat-pump is being controlled by the EasyTouch.

Is your heat-pump connected to the automation using the RS-485 com port or just the fireman's switch?

Thanks,

Jim R.
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
15,323
Bedford, TX
M.
JamesW's idea of letting the pool builder take care of it makes the most sense..

But.. If you are senseless, like me, you could disconnect the RS-485 or shut off the external control and try to run the heater by itself. If it worked fine, then at least you would know the heater is ok and the problem is in the automation or the RS-485 connection.

Thanks,

Jim R.
 

panic_button

Bronze Supporter
Jun 23, 2019
38
Navarre, Florida
I have the same unit and an EasyTouch just installed in December, but have the opposite issue. My set temp for the pool is 82°, but it will not shut off until 84° or higher. I have Pentair look at the setup for the past week and they can't figure it out. Everything is calibrated correctly as in the heater and ET temperatures match.
 

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meatty

Active member
Jun 22, 2019
30
Austin, TX
M.
JamesW's idea of letting the pool builder take care of it makes the most sense..

But.. If you are senseless, like me, you could disconnect the RS-485 or shut off the external control and try to run the heater by itself. If it worked fine, then at least you would know the heater is ok and the problem is in the automation or the RS-485 connection.

Thanks,

Jim R.
This is a good next step for debugging. Thank you, I will try this!
 

meatty

Active member
Jun 22, 2019
30
Austin, TX
But.. If you are senseless, like me, you could disconnect the RS-485 or shut off the external control and try to run the heater by itself. If it worked fine, then at least you would know the heater is ok and the problem is in the automation or the RS-485 connection.
Jim,

This worked like a charm! Disabling RS-485 and setting the heat pump directly allowed the spa to come up to heat.

So, with this knowledge, I think we can eliminate the heat pump itself (which is great - at least I can manually set it). The temperature registered is off by 1-2 degrees between the two systems, but both seem to be registering consistent temperatures - that's just a minor calibration issue that I'm not worried about.

Given that it seems to be tied most closely to the time run, rather than the temperature of anything registering, it feels to me like some component in the automation is hitting a failure point. almost like a resistor is shorting (by overheating) or something.

Is my understanding correct that the "solar" thermometer is really only there to confirm that it's present as a resistor, and it's not actually using the temperature from there? In which case, it's likely a prime suspect for the problem. Does this seem sound?
 

JamesW

TFP Expert
Mar 2, 2011
16,955
The heat pump can be configured as Solar but it doesn't have to be.

Go to Settings, go to Solar and disable Solar. Then, go to Heat Pump and enable.
 

JamesW

TFP Expert
Mar 2, 2011
16,955
In Settings, you can choose Solar Yes/No. If you choose Yes, you can then choose Solar is Heat Pump Yes/No. Choose No for both.

Then, go to the different Heat Pump section and choose Yes.

Go to "Heat Pump Com" in settings (Separate from Solar) and select enable Yes, Heating Yes, Cooling Yes.
 
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meatty

Active member
Jun 22, 2019
30
Austin, TX
In Settings, you can choose Solar Yes/No. If you choose Yes, you can then choose Solar is Heat Pump Yes/No.

Choose No for Solar. Then, go to the different Heat Pump section and choose Yes.
That automatically checks the solar box as well (at least in my setup). And if I then uncheck solar, it automatically unchecks heat pump.
 

JamesW

TFP Expert
Mar 2, 2011
16,955
Select No for Solar.

Then, go to the completely different Heat pump section (not part of solar) and check enable yes, heating Yes Cooling yes.