Pentair Mastertemp 125 cycling btwn "service system" and heating

levin.philip

New member
Jan 31, 2021
2
Oakland CA
Pool Size
1140
We have a Mastertemp 125 heating our spa.

The heater works, but is clearly having issues.

It cycles between "heating w/ blinking light" (~10-20 secs) ---> "heating with solid light" (~10 secs) ---> "service system" (~20-40 secs) and then back to heating again. The tub eventually heats up but slowly because of this cycling. Sometimes there's a clanking noise when it goes to "service system"

What might be wrong here?

Here's a video: IMG_3690.mov
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
24,082
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
Welcome to TFP.

First thing I would check is your filter pressure and clean your filter. Your heater is showing symptoms of low water flow causing the water to boil inside, which is the knocking, and overheat causing it to shutdown. Once it cools down it restarts.

If not a dirty filter then check your valves or it could be a bad thermal regulator or bypass valve.

It helps us to know your equipment. Please create your signature with details of your pool and equipment.
 
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levin.philip

New member
Jan 31, 2021
2
Oakland CA
Pool Size
1140
Welcome to TFP.

First thing I would check is your filter pressure and clean your filter. Your heater is showing symptoms of low water flow causing the water to boil inside, which is the knocking, and overheat causing it to shutdown. Once it cools down it restarts.

If not a dirty filter then check your valves or it could be a bad thermal regulator or bypass valve.

It helps us to know your equipment. Please create your signature with details of your pool and equipment.
Thanks so much! We recently changed the filter, but I'll give it another look. Will check the board for any error messages too.
 
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