MasterTemp 400 cuts out entirely

Jump to latest Follow Reply
N

NeedCoffee

Active member
Dec 12, 2020
35
SoCal
Hi all,

I've lurked for a little while but this is my first post. I have a MasterTemp 400 with an odd problem. I only use it to heat our spa, as we have a pretty good solar heating system that keeps the pool warm enough for most of the season. So heater comes on per normal when we run the spa. It heats up reasonably well. But after a while the whole heater just shuts off as if someone pulled the electrical plug... except that the blower still runs (and no heat). Keypad on the heater goes completely dark... no temperature, error code, or indicatior lights illuminate. Typical conditions when that happens:
  • CP3000 control system indicates spa temp 104 (where I set it)
  • a thermometer bobbing in the spa indicates 99-100 (controller has read ~4 higher for as long as I can recall)
  • Heater control pad indicates the water temp is only 88 or 89
  • Heater flue outlet temp is good at 304
I ran it in service mode this afternoon to witness the symptoms. It shut off sometime after the controller read 104. Heater was off and the heater light on the CP3000 was off. I had to wait for the temp to drop to 103 and then the CP3000 let me restart the heater. It ran for a couple minutes and then went dead again (except for the blower). I did this a couple times in a row. heater flue temp never got above 300 and heater never indicated water hotter than 89. I always had to wait for the controller to drop from 104 to 103 before I could restart.

Many months ago I replaced the thermistor as it was cheap and easy. Made no difference. Today I inspected the thermal regulator. It looks OK-ish. I ran it under hot water in the sink and it barely opened a crack. Sink water was around 115. Putting it in a bowl of hotter (140) water it opened readily. I gave it a hot/cold cycle several times.

I can order a new thermal regulator and try that. I could also try a new HLS. But that doesn't explain why the whole unit just goes dead. Any suggestions? Thank you!!
 
Welcome to TFP.

The CP3000 is controlling the heater using the "firemans switch". When the CP3000 sees its temperature sensor reach the setpoint it shuts off the heater.

Heater Control with Automation - Further Reading

www.troublefreepool.com www.troublefreepool.com

It sounds like your water temperature sensor is reading high so the CP3000 is shutting the heater off when it thinks the water is at 104.

The CP3000 water temperature sensor is a 10K thermistor. You can test it using a multimeter. Read Temperature Sensors - Further Reading

Amazon.com: Pentair 520272 Air/Water/Solar Temperature Sensor with 20-Feet Cable Replacement Pool/Spa Automation Control Systems and Pump: Garden & Outdoor

Amazon.com: Pentair 520272 Air/Water/Solar Temperature Sensor with 20-Feet Cable Replacement Pool/Spa Automation Control Systems and Pump: Garden & Outdoor
www.amazon.com
 
Thanks very much! That definitely makes sense. Looks like it consistently reads 5 degrees high no matter the actual water temp. Inspecting it just now I can see that some insulation has rubbed away where it was zip tied to the inlet of the spa jet pump. So for a $22 part I'll just go ahead and replace it.
 
OK, so I attempted to replace the sensor. I installed the recommended sensor, but when I did so I got an Err1 on the CP3000. The sensor has a red and a white wire, while the board indicates green and red (old sensor was green/red). No matter which way I connect the new sensor I get the error. When I put the old sensor back in I no longer have the error. But I do have air in the system now, I think because the new sensor has a larger diameter and I had to drill out the hole. Now that the old sensor is back in it doesn't seem to seal well. Hopefully it's just the air that got sucked in while the sensor was out, though it's been running for several minutes now and still bubbling at the outlet into the pool.

So are the sensors compatible? Doing a search on here leads me to believe they are not. My old sensor looks like this one: Pentair Temperature Sensor TS5L
 
Yep, You want a TS5L sensor (linear), not the one that has all numbers as the part number (520272). Note: When putting the system into "Service" mode and hitting the heater button, you are turning the heater on with no automation thermostatic control, only the thermostat limit entered at the heater (104).

If the heater shuts off before automation say so, and the heater light is still illuminated at the top of the indoor controller, your heater has the issue, not the CP3000.

If you want to calibrate the temp display:
1.Press the Program key.
2. Press the Spa Heat Source key.
3. Enter correct pool temperature (using the up and down arrow keys) and press Spa Heat Source key.
At this point, you can just hit the Program key and exit calibration.
4. Enter correct solar temperature and press Spa Heat Source key.
5. Enter correct air temperature and press Spa Heat Source key.
6. Enter number of days between backwash and press Spa Heat Source key.
7. Enter number of minutes to backwash and press Spa Heat Source key.
8. Enter floor cleaner valve cycle time and press Spa Heat Source key.
9. Press the Program key to end.
 
Pool Clown said:
Yep, You want a TS5L sensor (linear), not the one that has all numbers as the part number (520272). Note: When putting the system into "Service" mode and hitting the heater button, you are turning the heater on with no automation thermostatic control, only the thermostat limit entered at the heater (104).

If the heater shuts off before automation say so, and the heater light is still illuminated at the top of the indoor controller, your heater has the issue, not the CP3000.

If you want to calibrate the temp display:
1.Press the Program key.
2. Press the Spa Heat Source key.
3. Enter correct pool temperature (using the up and down arrow keys) and press Spa Heat Source key.
At this point, you can just hit the Program key and exit calibration.
4. Enter correct solar temperature and press Spa Heat Source key.
5. Enter correct air temperature and press Spa Heat Source key.
6. Enter number of days between backwash and press Spa Heat Source key.
7. Enter number of minutes to backwash and press Spa Heat Source key.
8. Enter floor cleaner valve cycle time and press Spa Heat Source key.
9. Press the Program key to end.
Click to expand...
Thanks very much. I orderd and installed the new TS5L but I now doubt I needed it. I didn't realize I could calibrate the sensor until I installed the new one and it read 3 degrees even farther off than the old one. I recalibrated but have not run the spa yet to see if it solves the issue.

One thing I do notice is that the heater's water temp sensor appears way off. The heater itself never showed higher than 89 degrees, while the spa water was 99-100. Seems odd to me. As for service mode, I'm not sure I have the level of control you mentioned. After the controller registered 104 the heater shut off, and I was unable to turn on the heater until the CP3000 registered less than 104. And it shut down consistently at 104. Perhaps that's because 104 is the legal limit? I don't recall if the inside panel still had the heater light illuminated. I'll look for that when I try it this evening.
 
You should check the temp sensor of the heater. You will know immediately if it has failed if the sensor is cracked.

The Compool temp sensor and the heaters sensor are not one in the same. And they don't communicate with one another either. Set, or calibrate your automation temp with a known accurate thermometer. And see how that goes.
 
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply