External Heater Bypass

[W.J.Christy]

Not sure if this should be here or under everything else, please move if needed.

I recently had a failure of the bypass valve in my Pentair MasterTemp 400 heater. A potential reason as to why this occurred was there was to much flow going through the heater according to some posts (here New Construction Started - Willis, TX (north of Houston)) I have found on this forum, but I have also found contradicting posts stating the bypass is capable of handling a high flow rate from a VS pump (can't find the posts).

I was hoping to get clarification on the necessity of the bypass as I will hopefully be having my heater repaired soon and in the process want to install the bypass if its needed.

 

[wireform]

The bypass we speak of is to avoid the water going through the heater core altogether such as for a repair but not so much as to limit which way the water passes to the pool while the heater is working.

 

[W.J.Christy]

The bypass we speak of is to avoid the water going through the heater core altogether such as for a repair but not so much as to limit which way the water passes to the pool while the heater is working.

thanks for the response. I understand its typically only used for maintenance, but in the post mentioned above, my setup was specifically shown as an example of excessive flow that was a probable cause for the failure of the internal bypass valve of the heater.

I am hoping to find out if I need the external bypass or not and if I don't install one will I keep experiencing failures.

 

[wireform]

Why can you run it a some lower rpm and call that the upper limit. This would be needed to be calculated which is beyond my pay grade.

 

[W.J.Christy]

Why can you run it a some lower rpm and call that the upper limit. This would be needed to be calculated which is beyond my pay grade.

Not sure what that limit would be. I do know that I need to run around 1500 rpm to get enough flow to have my spa spill over just slightly. From my understanding, that's quite high and may be the issue. The pump also primes at a fairly high RPM when it starts so I am not sure if the issue is the priming rpm or the rpm I use to chlorinate the pool.

Unfortunately, it would seem its above my pay grade as well.

 

[1poolman1]

Not sure what that limit would be. I do know that I need to run around 1500 rpm to get enough flow to have my spa spill over just slightly. From my understanding, that's quite high and may be the issue. The pump also primes at a fairly high RPM when it starts so I am not sure if the issue is the priming rpm or the rpm I use to chlorinate the pool.

Unfortunately, it would seem its above my pay grade as well.

Unless you were exceeding 120gpm, the design upper limit on your heater (not likely), excessive flow is not what caused the internal bypass to fail. They fail. That's why I keep one on my truck. I replace one or two a year and they are not always easy to get quickly. Your heater manual will tell you the maximum flow

 

[ajw22]

Not sure what that limit would be. I do know that I need to run around 1500 rpm to get enough flow to have my spa spill over just slightly. From my understanding, that's quite high and may be the issue. The pump also primes at a fairly high RPM when it starts so I am not sure if the issue is the priming rpm or the rpm I use to chlorinate the pool.

Unfortunately, it would seem its above my pay grade as well.

You likely cannot hit 120 GPM with your plumbing setup. Your VSF pump can display the flow rate.

 

[W.J.Christy]

Thank you for all the replies. I think I'm going to forgo the bypass valve for now and just get the heater repaired.