Max-E-Therm 400

Jump to latest Follow Reply
M

Michigandad3

0
Aug 25, 2018
25
The Woodlands/Texas
My Max-E-Them heater runs for a few hours then the service heater light comes on. If I turn off the heater and wait a couple hours, the heater will come back on. Also, the effectiveness of the heater decreases the longer it is on. For example, the temperature in the pool raises from 70 to 80 degrees in approximately 1 hour, but from 80 to 81 may take one hour, the I get the service heater light. My pool flow is normal, and there are no rat nests in the heater. I borrowed a neighbors old board and swapped it out, and the behavior did not change,
 
What is the heater rating in btu/hr?

How old is the heater?

What does the display show?

Are any of the diagnostic LEDs on the back of the control board coming on?

There's no way that the pool is gaining 10 degrees per hour. Even if the heater is 400,000 btu per hour, the best that you can get is 1.8 degrees Fahrenheit per hour.

What set point are you setting the heater to?

Is the temperature displayed getting to the set point?
 
Last edited:
The heater is 400,000 BTU/hour, and is approximately 3 years old. The display shows 'Service Heater". There are no LEDs illuminated on the back of the board. I may be mistaken about the heat rate, but I can turn the heater on in the morning when the temperature is 70 degrees, and by evening it is 92 degrees when the heater is working properly. Now the rate of heating decreases the longer the heater runs, and then gives a service heater error. The pool is set to 92 degrees. The temperature does not make it to the set point without a service heater light coming on if the time to reach the set point takes more than 4 hours. If I turn of the heater for approximately one hour, and re-start the heater, I can eventually reach the set point. The Spa will reach the set point of 98 degrees approximately 50% of the time without getting a service heater code. The vent is facing up, and is outdoors. I asked about a vent cap when the when the heater was installed, but I was told that it was not necessary. The vent is very rusted. This version has a copper heat exchanger.
 
So, it just stops heating before the water temperature gets to the set point with no error codes or LEDs lighting up?

Check the Fenwal Ignition Control Module to see if the red LED is on or flashing.
 
Hello,

The heating rate slows, then a Service Heater" error code appears on the from of the board, there are no LEDs lighting up on the rear of the board. I will check the Fenwal Ignition Control Module.

Additional information
I opened the heater approximately one year ago, and found two frog skeletons, 5 gecko skeletons, and load of gecko droppings. When I opened the heater a couple days ago, I found several gecko skeletons, a load of gecko droppings, and hundreds of dead snails.
 
Last edited:
If I have to replace the heater, I am considering going with a commercial heater. I live in Houston, and we heat the pool year round. I am considering these two heaters"
Raypak Digital ASME low NOx, commercial ASME heater 400,000 btu, Natural gas
Hayward H400FDNASME Natural Gas Commercial Pool Heater

Am I on the right track, or there better heaters out there
 
If the "Service Heater" comes on, a diagnostic LED usually lights up as well.

Check the back of the board and note all LEDs that are lit.

The following are the LEDs:

1.....PS (Pressure Switch)
2.....HLS (High Limit Switch)
3.....SFS (Stack Flue Sensor)
4.....AFS (Air Flow Switch)
5.....AGS (Automatic Gas Shutoff).
6.....Service System
7.....Thermistor
8.....Heating
9.....Pool On
10...Spa On
11...Service Heater

If not, that might point to loss of flame rectification, which should cause the LED on the ICM to flash.

What is the model number of the ICM?

Check the Manifold Bypass Valve and the thermal regulator.

The Raypak is a good heater, but I don't think that the ASME version would be better than the regular residential unit.
 
Last edited:
A 400,000 BTU heater will heat a 22,000 gallon pool around 2 degrees an hour.

Check that the heat exchanger is not rusted and starting to have pinholes that leak water as the heater runs.
 
The symptom of the heater heating well until it gets into the 80's is a sign that your thermostatic by-pass is failing to operate properly and the heater is over heating and shutting down then restarting (cycling). That's why it wont continue to heat at the previous rate, because it is always shutting down then starting back up (though fan may continue to run). When you shut it down for a while, it gives the heater, and its components (by-pass) a chance to cool down a bit. Checking this part is not hard. If it has any corrosion, even a little, it is probably the cause. Also look for discoloring, an aqua, teal or tourquise color on the bulb indicates a crack that may or may not be visible.
 

Enjoying this content?

Support TFP with a donation.

Give Support
I agree that it's probably the thermal regulator or the Manifold Bypass Valve.

It might also be low flow due to a variable speed pump running at too low rpm or an external bypass.

However, the OP is reporting that there are no diagnostic LEDs lighting up.

I suspect that the high limit LED is probably lighting up and the OP is missing it somehow.
 
Last edited:
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply