Pentair Mastertemp 400HD - Manifold Design & Operation

[Naples34114]

Hi Folks,

As a new poster but a user for many years I enjoy the site and all the great info. Recently I had my Temperature Regulator fail in my relatively new Mastertemp 400HD due to bad water balance and resulting corrosion. For reference I had an HLS fault that started the process with the unit cycling at approximately 83 degrees with a spa setpoint of 102. You knowledge experts know the drill.

In any case the regulator was replaced and I am back in business.

As an inquisitive guy I am working to understand the working aspect of water flow in the manifold; incoming water, outgoing water, heating coils (6 loops). More specifically the interaction of the bypass valve, temperature regulator (120 D) and the baffles manufactured into the regulator. I have searched the web and found disassembly videos and read the wiki which is essentially the Pentair manual which leaves out the detail. It seems to me with the thermostat (i.e regulator) stuck closed caused the water in the manifold to exceed its 135 D sensor set point and shut me down.

Again my question is related to water flow however and the relationship of water flow from incoming to outgoing and mixing. Pressure versus Temperature.

Thanks for the help. Mark

 

[ajw22]

Welcome to TFP.

Sounds like you have read the available information on the MasterTemp. I am not sure what you want to know.

 

[Naples34114]

Welcome to TFP.

Sounds like you have read the available information on the MasterTemp. I am not sure what you want to know.

Good Morning,
I am interested in the water flow in the manifold. How does the water flow at startup (cool) to make its way into the heat exchanger and then as the initial water heats and pressure builds to 120 f the thermostat and bypass begin to operate in unison at steady state. It seems as though there are four operating sections of the manifold. Incoming cold, return heated. These are balanced by the bypass valve and the thermostat creating I think the potential for four different flow patterns depending upon pressure and temperature. I’m sorry if it doesn’t make sense as it is difficult to explain. The manifold insert (portion between exchanger & incoming/return) is really what I’m trying to understand .

 

[Naples34114]

Hi Folks,

As a new poster but a user for many years I enjoy the site and all the great info. Recently I had my Temperature Regulator fail in my relatively new Mastertemp 400HD due to bad water balance and resulting corrosion. For reference I had an HLS fault that started the process with the unit cycling at approximately 83 degrees with a spa setpoint of 102. You knowledge experts know the drill.

In any case the regulator was replaced and I am back in business.

As an inquisitive guy I am working to understand the working aspect of water flow in the manifold; incoming water, outgoing water, heating coils (6 loops). More specifically the interaction of the bypass valve, temperature regulator (120 D) and the baffles manufactured into the regulator. I have searched the web and found disassembly videos and read the wiki which is essentially the Pentair manual which leaves out the detail. It seems to me with the thermostat (i.e regulator) stuck closed caused the water in the manifold to exceed its 135 D sensor set point and shut me down.

Again my question is related to water flow however and the relationship of water flow from incoming to outgoing and mixing. Pressure versus Temperature.

Thanks for the help. Mark

UPDATE:
After studying a couple video repairs for either the regulator or bypass it seems to be the following. Any confirmation or comments from others appreciated.
As the COLD water from the pool return enters the chamber it flows directly to the top three of six heat exchanger tubes via a baffle in the manifold (clockwise flow).This warmed water is redirected back to the manifold hot side and reenters the bottom three tubes in the heat exchanger (counter clockwise flow) . This warmer water now is in the chamber where the thermal regulator (aka thermostat) resides. As the water warms to 120 F the thermostat opens and the water is now able to flow to the pool or spa. This whole investigation on my part was understanding why the HLS error was so easily fixed by replacing the regulator. My regulator failed in a closed position, not allowing the hot water to flow out to the pool. This caused the water temp in the regulator to exceed 135 F causing the error and shutting down the unit.

Comments welcome.

 

[1poolman1]

UPDATE:
After studying a couple video repairs for either the regulator or bypass it seems to be the following. Any confirmation or comments from others appreciated.
As the COLD water from the pool return enters the chamber it flows directly to the top three of six heat exchanger tubes via a baffle in the manifold (clockwise flow).This warmed water is redirected back to the manifold hot side and reenters the bottom three tubes in the heat exchanger (counter clockwise flow) . This warmer water now is in the chamber where the thermal regulator (aka thermostat) resides. As the water warms to 120 F the thermostat opens and the water is now able to flow to the pool or spa. This whole investigation on my part was understanding why the HLS error was so easily fixed by replacing the regulator. My regulator failed in a closed position, not allowing the hot water to flow out to the pool. This caused the water temp in the regulator to exceed 135 F causing the error and shutting down the unit.

Comments welcome.

Water does not sit in the heat exchanger until hot and then allowed to flow to the pool/spa. The bypass valve is spring-loaded to allow "just enough" water into and through the heat exchanger to get the best heat transfer. It then mixes with the water that is being bypassed and the water entering the pool/spa should be about 6 degrees hotter than the body of water.
If it fails too little goes into the heat exchanger, comes out too hot, and the HLS or AGS will open so that the water entering the pool will not burn someone. So little can enter the exchanger that it will flash boil and you get a loud knocking noise and I've seen the whole heater bounce, due to the steam pressure of the boiling water.
The thermal regulator acts in a similar way, but is there to allow just enough water into the heat exchanger so as to keep it around 100 degrees so that condensation doesn't form on the outside of the exchanger.
If either fail, there is too much water bypassing the exchanger, the water coming out of it is too hot, 135 or more, and the HLS opens. If it doesn't then the AGS should at 140.