Pentair MasterTemp 400 not working

[Ed LaCrosse]

Hello all,

I have a Pentair MasterTemp 400 heater for my pool/spa. I decided to use it a couple days ago and couldn't get it working. I've done some troubleshooting myself and it's still not working so I have a call in to a local tech. Meanwhile, I thought I'd check in with the experts here to see if I could get some advice.

When I initially tried to turn on the heater, everything sounded normal. Blower fan came on, gas flowed and ignited, and heater "worked" for a few seconds, then shut down with error code E05. I was able to look that up and discovered it was a problem with the flue stack sensor, so I replaced it.

After replacing the flue stack sensor, I tried to get the heater working again, but, again, no joy. This time, the heater progressed as before, gas ignited, it ran for a few seconds longer than before, but then shut off with the "service heater" LED on. This time there was no error code.

I will add that when I removed the panel to access the stack flue sensor, I noticed a fair amount of debris in the box, including leaves and acorn shells, indicating some animal had taken up residence at some point. Whatever it was chewed the wires on the sensor which certainly rendered it inoperative. I saved the sensor, thinking I could splice some wire and a couple plugs onto it in case I needed it sometime. The sensor itself looking in pretty good shape.

I cleaned most of the debris out of the box, but there is still a bit lying around on the bottom. I wondered to myself if it would be wise to get the hose out and hose down the inside of the box to clean it out, but stopped short of doing that, thinking I'd do more harm than good with all the electrical connections.

I've scanned the inside of the box from one side and did not notice any loose wires or anything suspicious. I have not removed to the top of the heater to view the main board, nor have I removed the other side panel.

Anyway, any thoughts from the group on what I might try next would be helpful. I'm going to keep the ticket open with the local tech just in case things end up over my head.

Thanks in advance!

 

[1poolman1]

Hello all,

I have a Pentair MasterTemp 400 heater for my pool/spa. I decided to use it a couple days ago and couldn't get it working. I've done some troubleshooting myself and it's still not working so I have a call in to a local tech. Meanwhile, I thought I'd check in with the experts here to see if I could get some advice.

When I initially tried to turn on the heater, everything sounded normal. Blower fan came on, gas flowed and ignited, and heater "worked" for a few seconds, then shut down with error code E05. I was able to look that up and discovered it was a problem with the flue stack sensor, so I replaced it.

After replacing the flue stack sensor, I tried to get the heater working again, but, again, no joy. This time, the heater progressed as before, gas ignited, it ran for a few seconds longer than before, but then shut off with the "service heater" LED on. This time there was no error code.

I will add that when I removed the panel to access the stack flue sensor, I noticed a fair amount of debris in the box, including leaves and acorn shells, indicating some animal had taken up residence at some point. Whatever it was chewed the wires on the sensor which certainly rendered it inoperative. I saved the sensor, thinking I could splice some wire and a couple plugs onto it in case I needed it sometime. The sensor itself looking in pretty good shape.

I cleaned most of the debris out of the box, but there is still a bit lying around on the bottom. I wondered to myself if it would be wise to get the hose out and hose down the inside of the box to clean it out, but stopped short of doing that, thinking I'd do more harm than good with all the electrical connections.

I've scanned the inside of the box from one side and did not notice any loose wires or anything suspicious. I have not removed to the top of the heater to view the main board, nor have I removed the other side panel.

Anyway, any thoughts from the group on what I might try next would be helpful. I'm going to keep the ticket open with the local tech just in case things end up over my head.

Thanks in advance!

When the "Service Heater" indicator lights an LED on the back of the board should also so the same thing. It will tell you which circuit is not allowing the heater to stay lit. It won't be the pressure switch as that will cause a "Service System" light to come on.

 

[Ed LaCrosse]

Thanks for the link the very helpful video. This afternoon, I did some more testing with the following results:

I turned on the pump, observed the start-up sequence on the heater's display, 888 138 r 13. I let the pump run for a minute, then pressed the "pool on" button. I immediately got the "Service system" light, which I had never gotten before, and there was no further progress. Looking at the back of the board, the "PS", or "pressure switch" LED was lit.

I accessed the flow switch and tapped it a few times then tried to restart the heater. No joy. I switched the system water flow valves to put water only into the spa and take it only out of the spa, thereby increasing the pressure at the filter (and presumably at the heater). No joy when trying to restart the heater. Finally, I bled the air out of the filter and tried again. This time, I didn't get Service System LED and the heater progressed and fired up. It ran for about two minutes the stopped with "Service Heater" LED lit. The blower continued to run for awhile and eventually the Service Heater LED cleared and the heater fired up again. This on/off cycling occurred several times before I gave up and shut the heater off. Before doing so, I observed that the HLS, or high limit switch, LED was lit.

I've stopped fiddling around for now and will look forward to my tech arriving. I'm pretty sure I'm over my head but I thought I'd post my results here in case someone thinks there are other things for me to do.

I suspect a problem with the manifold is causing the pressure switch and high limit switch (both of which mount to the manifold) to read incorrectly. I've never had a problem with this unit running correctly with the pump and filter arrangement I'm using. There has always been adequate water pressure for the system to operate.

 

[1poolman1]

Thanks for the link the very helpful video. This afternoon, I did some more testing with the following results:

I turned on the pump, observed the start-up sequence on the heater's display, 888 138 r 13. I let the pump run for a minute, then pressed the "pool on" button. I immediately got the "Service system" light, which I had never gotten before, and there was no further progress. Looking at the back of the board, the "PS", or "pressure switch" LED was lit.

I accessed the flow switch and tapped it a few times then tried to restart the heater. No joy. I switched the system water flow valves to put water only into the spa and take it only out of the spa, thereby increasing the pressure at the filter (and presumably at the heater). No joy when trying to restart the heater. Finally, I bled the air out of the filter and tried again. This time, I didn't get Service System LED and the heater progressed and fired up. It ran for about two minutes the stopped with "Service Heater" LED lit. The blower continued to run for awhile and eventually the Service Heater LED cleared and the heater fired up again. This on/off cycling occurred several times before I gave up and shut the heater off. Before doing so, I observed that the HLS, or high limit switch, LED was lit.

I've stopped fiddling around for now and will look forward to my tech arriving. I'm pretty sure I'm over my head but I thought I'd post my results here in case someone thinks there are other things for me to do.

I suspect a problem with the manifold is causing the pressure switch and high limit switch (both of which mount to the manifold) to read incorrectly. I've never had a problem with this unit running correctly with the pump and filter arrangement I'm using. There has always been adequate water pressure for the system to operate.

Pressure in the filter = no or less waterflow, not better waterflow. That's not a flow switch in the manifold but a pressure switch. Low waterflow = not enough pressure to close it. Low waterflow will also cause a HLS to trip if the flow is just enough (or you tap it) to close the pressure switch but not enough to draw enough heat from the heat exchanger, overheating what water there is there.
Did you clean the filter before trying anything else? That is the first thing to do as over 90% of all service calls on heaters have nothing to do with the heater but are a system issue; low water flow.

 

[Ed LaCrosse]

Pressure in the filter = no or less waterflow, not better waterflow. That's not a flow switch in the manifold but a pressure switch. Low waterflow = not enough pressure to close it. Low waterflow will also cause a HLS to trip if the flow is just enough (or you tap it) to close the pressure switch but not enough to draw enough heat from the heat exchanger, overheating what water there is there.
Did you clean the filter before trying anything else? That is the first thing to do as over 90% of all service calls on heaters have nothing to do with the heater but are a system issue; low water flow.

Thanks for your feedback. I take your point about pressure in the filter vis-a-vis waterflow to the heater. I did try running the heater pushing water through just the spa and through the entire pool, so I did end up testing it with maximum waterflow to the heater. I'll also note that this heater has worked well for several years in both configurations. There has never been a water flow issue.

And yes, the filter was brand new last summer and thoroughly cleaned just about a month ago. Pressure at the filter is "normal" -- about 15 psi with water flowing into and out of the whole pool.

Seems like something has happened in the heater vs. the filter to me, but I'm no expert. I'll look forward to the tech's diagnosis and will report back here in case others are interested.

 

[Ed LaCrosse]

Thanks for your feedback. I take your point about pressure in the filter vis-a-vis waterflow to the heater. I did try running the heater pushing water through just the spa and through the entire pool, so I did end up testing it with maximum waterflow to the heater. I'll also note that this heater has worked well for several years in both configurations. There has never been a water flow issue.

And yes, the filter was brand new last summer and thoroughly cleaned just about a month ago. Pressure at the filter is "normal" -- about 15 psi with water flowing into and out of the whole pool.

Seems like something has happened in the heater vs. the filter to me, but I'm no expert. I'll look forward to the tech's diagnosis and will report back here in case others are interested.

Well, the pool tech was here and fixed the problem yesterday. His initial diagnosis was a defective high limit switch, but, on getting into the repair, I see he also replaced the thermal regulator. He invariably comes out when I'm not home and I rarely get the opportunity to ask him questions, but I'm wondering if it's common for both of these items to require replacement simultaneously.

A couple questions: First, the reason the flue stack sensor failed is some animal chewed through the wires. If I got 'hold of a couple of the right connectors and spliced the chewed wires, will it work again? If so, I'll save it for a spare. If not, I'll just toss it.

Should I use a blower or water hose to clean out the inside of the heater where all the rodent debris is? I cleaned most of it out by hand, but there is a fair amount of debris on the bottom of the heater and in random other areas.

I appreciate the insight I received from the experts here.