Concerns about heat exchanger cracking

[Coz]

I'm a first time pool owner and am wondering if I need to be concerned about cracking the heat exchanger in my Pentair Mastertemp 400. I have a leisure pools ultimate 35 with a built in spa. I am able to heat the spa separately, or pool, or both. My concerns center around the temperature difference in the water when I heat the spa and not the pool. When I am done with the spa (usually around 102 degrees), will I do damage to the heat exchanger if I reconfigure the valves back to filter both pools?...this allows very cold water back through the filter and heater.

Another question I have relates to the LCD screen on the Mastertemp 400. It got down to 9 degrees last night and now the screen shows all black cursors and does not read digits. The heater will work, but I have no idea what temp is set. I know LCDs can stop working when they get cold, so thinking it should start working when it gets warmer, but totally ticked that a heater screen isn't working when I need to use the heater most. Ideas?

 

[ajw22]

I'm a first time pool owner and am wondering if I need to be concerned about cracking the heat exchanger in my Pentair Mastertemp 400. I have a leisure pools ultimate 35 with a built in spa. I am able to heat the spa separately, or pool, or both. My concerns center around the temperature difference in the water when I heat the spa and not the pool. When I am done with the spa (usually around 102 degrees), will I do damage to the heat exchanger if I reconfigure the valves back to filter both pools?...this allows very cold water back through the filter and heater.

You should give the heater a 5 minute cool down after you turn off the heater and before changing the valves back to your pool.

How do you reconfigure the valves back to filter both pools?

Another question I have relates to the LCD screen on the Mastertemp 400. It got down to 9 degrees last night and now the screen shows all black cursors and does not read digits. The heater will work, but I have no idea what temp is set. I know LCDs can stop working when they get cold, so thinking it should start working when it gets warmer, but totally ticked that a heater screen isn't working when I need to use the heater most. Ideas?

I don't know how you are using your heater in these conditions but the Pentair MasterTemp Heaters manual says:

• Operating this heater continuously at water temperatures below 68° F. (20° C) will cause harmful condensation and will damage the heater and void the warranty.
• When starting the heater for the swimming season with a water temperature below 50° F (10° C), the heater may be used to heat the water; however, make sure that the heater operates continuously until the water temperature reaches the heater’s minimum setting of 68° F (20° C).

 

[Coz]

You should give the heater a 5 minute cool down after you turn off the heater and before changing the valves back to your pool.

How do you reconfigure the valves back to filter both pools?



I don't know how you are using your heater in these conditions but the Pentair MasterTemp Heaters manual says:

• Operating this heater continuously at water temperatures below 68° F. (20° C) will cause harmful condensation and will damage the heater and void the warranty.
• When starting the heater for the swimming season with a water temperature below 50° F (10° C), the heater may be used to heat the water; however, make sure that the heater operates continuously until the water temperature reaches the heater’s minimum setting of 68° F (20° C).

Hmm, 5 min cooldown probably won’t help in my situation. When I heat the spa solely, I drawn water from spa and return it to the spa. When I am done with the spa, the water is still around 102 degrees. Am I ok switching the valves at that point and allowing 50 degree water from the pool skimmer to enter the filter and heater? If not, I guess I can leave the spa water to cool down before reconfiguring the valves, though it means one more trip outside later.

I appreciate the information from the manual. I wasn’t aware of that restriction. Sounds more like a restriction on minimally heating a pool. I turn on the heater to heat the spa (water temp has been around 45-55 degrees) and it comes up to 102 degrees in about 30 mins. The heater will then cycle on and off to keep the spa at temp. If I can’t use the heater in this manner it totally eliminates any reason to have the spa in the winter. Thoughts?

 

[ajw22]

When I am done with the spa, the water is still around 102 degrees. Am I ok switching the valves at that point and allowing 50 degree water from the pool skimmer to enter the filter and heater? If not, I guess I can leave the spa water to cool down before reconfiguring the valves, though it means one more trip outside later.

Temperature inside the heat exchanger can be 300F or more. The 5 minute cool down is to allow the heat exchanger to cool down to the 102F water temperature.

The temperature differential between 50 and 102 is not a problem. The differentail between 50 and 300+ can be a problem.

Let the heater cool down.

I appreciate the information from the manual. I wasn’t aware of that restriction. Sounds more like a restriction on minimally heating a pool. I turn on the heater to heat the spa (water temp has been around 45-55 degrees) and it comes up to 102 degrees in about 30 mins. The heater will then cycle on and off to keep the spa at temp. If I can’t use the heater in this manner it totally eliminates any reason to have the spa in the winter. Thoughts?

You are using the MasterTemp heater in a way it is not designed for. That may shorten its lifespan.

A heater designed to be used in winter conditions will have a Condensation Management system in it. Other heaters do and the MasterTemp does not.

Heater Condensation - Further Reading

www.troublefreepool.com

 

[1poolman1]

If you have automation, it will do a cool down automatically, turning the heater off and continuing to pull water from the spa for its cycle. If you don't have automation, do it manually, turn the heater off and continue with the valves in "spa" position for at least 5 minutes (this pulls residual heat from the heater), turn the pump off, set valves for pool and you're done. If, after that cool-down, the pump starts pulling water from the pool it shouldn't hurt anything. According to all heater manufacturers, a heater that is properly cooled will last about 50% longer than one that isn't.

 

[Coz]

You are using the MasterTemp heater in a way it is not designed for. That may shorten its lifespan.

Argh! Thank you for the information. I was totally unaware and apparently my pool installer is too. I will add this to a long list of his shortcomings.

At this point I really have no choice but to carry on and see how long it lasts.