I have a PacFab MiniMax Plus 400 natural gas pool heater that is giving me some issues. I am not the original home owner, but I know the system is about 12 years old. I have never used the heater very much; just occasionally to heat the spa alone. I have copies of the Operation & Installation Manual and the Service Manual. I am trying to troubleshoot and diagnose the problem in hopes that is something I can handle without bringing in a technician.
When I try to use the system, it immediately starts cycling on and off approximately every 20 seconds. When in the “on cycle”, the status indicators lights are as follows:
Front Control Panel (outside):
• TSTAT – green
• AUX. – green
• PRESS – green
• HEAT – green
• POWER – green
• SERVICE – off
Inside Control Panel:
• HI TEMP – green
• TFUSE – green
• MV – green
When the system trips and the heater shuts off (i.e., the “off cycle”), the status indicators lights are as follows (atempted to underline the state changes on the ones that were affected):
Front Control Panel (outside):
• TSTAT – green
• AUX. – green
• PRESS – green
• HEAT – off
• POWER – green
• SERVICE – red
Inside Control Panel:
• HI TEMP – off
• TFUSE – off
• MV – off
A few other things to note that might help:
- This quick cycling occurs independently of whether the Thermostat Selection/off switch is toggled to “POOL”, or to “SPA”. Of course, the temperature dials/potentiometers need to be turned up to start the pilot and the cycling.
- This occurs across a wide range of pump speeds on my variable speed pump; at 1600 rpm, 2000 rpm, 3200 rpm – it doesn’t matter. I noticed that, even at 1600 rpm (what I run the pump at when I am using the salt chlorinator), the PRESS status light on the Control Panel remains lit green. I have not done any test of how low the pump needs to run at to trip the PRESS indicator off. Should I try this type of test?
- This occurs independently of any adjustments to the bypass valve at the heater input.
- I checked some of the wiring, and there are no obvious problems. I cleaned connectors where possible. This may need a better inspection, but I am not sure.
- I have not attempted any further electrical trouble shooting by attaching jumpers or meters across any electrical components. There is no direction on how to do this in the manuals, so I was hoping for some directions here, if this is required.
Here are my initial thoughts on the possible root causes, and where I am looking for the opinion of some experts.
1. Flow Valve – I have not removed yet to inspect; I did not want to create a leak where I did not have one already. I have since bought a new gasket in preparation for possibly removing to take a look. I would assume that, if the valve is preventing water from getting to the unit, it shuts down the burner.
QUESTION: since the PRESS indicator light remains lit through both my on and off cycles, would this indicate that the flow is not the problem? Or is this logic flawed, i.e., is it just the Pressure Switch that drive the PRESS indicator status light, or does the Flow Valve actually play here?
2. Pressure Switch – I assume there is no problem here, as the indicator status light remains green. I have not used a jumper to actually bypass this switch. Should I? What would I expect if the switch is good/bad? Note that the outside case of the switch does show some rust. Does this component just screw in and out easily?
3. Hi Limit Safety Switch – this is where I was heading, if the Flow Valve is diagnosed as fine based on the PRESS status light indicator. My guess would be that, if the system thinks the water is dangerously hot, it will keep shutting down the burner. That said, I am confused by one thing:
QUESTION: there are 2 Hi Limit Safety switches; are they independent? Since I get the same symptoms whether I am using the POOL thermostat or the SPA thermostat, does this eliminate the Hi Limit Switches as the cause?
If this is the issue, do I just go ahead and replace both – or is it possible and worth it to figure out which of the two are bad? Do these components just screw in and out easily?
4. Thermostat Circuit Board – I guess what all else fails, blame the board. Could this be it? How do I tell?
Any help on how to narrow this down? I would rather not sink the cash into replacing everything.
When I try to use the system, it immediately starts cycling on and off approximately every 20 seconds. When in the “on cycle”, the status indicators lights are as follows:
Front Control Panel (outside):
• TSTAT – green
• AUX. – green
• PRESS – green
• HEAT – green
• POWER – green
• SERVICE – off
Inside Control Panel:
• HI TEMP – green
• TFUSE – green
• MV – green
When the system trips and the heater shuts off (i.e., the “off cycle”), the status indicators lights are as follows (atempted to underline the state changes on the ones that were affected):
Front Control Panel (outside):
• TSTAT – green
• AUX. – green
• PRESS – green
• HEAT – off
• POWER – green
• SERVICE – red
Inside Control Panel:
• HI TEMP – off
• TFUSE – off
• MV – off
A few other things to note that might help:
- This quick cycling occurs independently of whether the Thermostat Selection/off switch is toggled to “POOL”, or to “SPA”. Of course, the temperature dials/potentiometers need to be turned up to start the pilot and the cycling.
- This occurs across a wide range of pump speeds on my variable speed pump; at 1600 rpm, 2000 rpm, 3200 rpm – it doesn’t matter. I noticed that, even at 1600 rpm (what I run the pump at when I am using the salt chlorinator), the PRESS status light on the Control Panel remains lit green. I have not done any test of how low the pump needs to run at to trip the PRESS indicator off. Should I try this type of test?
- This occurs independently of any adjustments to the bypass valve at the heater input.
- I checked some of the wiring, and there are no obvious problems. I cleaned connectors where possible. This may need a better inspection, but I am not sure.
- I have not attempted any further electrical trouble shooting by attaching jumpers or meters across any electrical components. There is no direction on how to do this in the manuals, so I was hoping for some directions here, if this is required.
Here are my initial thoughts on the possible root causes, and where I am looking for the opinion of some experts.
1. Flow Valve – I have not removed yet to inspect; I did not want to create a leak where I did not have one already. I have since bought a new gasket in preparation for possibly removing to take a look. I would assume that, if the valve is preventing water from getting to the unit, it shuts down the burner.
QUESTION: since the PRESS indicator light remains lit through both my on and off cycles, would this indicate that the flow is not the problem? Or is this logic flawed, i.e., is it just the Pressure Switch that drive the PRESS indicator status light, or does the Flow Valve actually play here?
2. Pressure Switch – I assume there is no problem here, as the indicator status light remains green. I have not used a jumper to actually bypass this switch. Should I? What would I expect if the switch is good/bad? Note that the outside case of the switch does show some rust. Does this component just screw in and out easily?
3. Hi Limit Safety Switch – this is where I was heading, if the Flow Valve is diagnosed as fine based on the PRESS status light indicator. My guess would be that, if the system thinks the water is dangerously hot, it will keep shutting down the burner. That said, I am confused by one thing:
QUESTION: there are 2 Hi Limit Safety switches; are they independent? Since I get the same symptoms whether I am using the POOL thermostat or the SPA thermostat, does this eliminate the Hi Limit Switches as the cause?
If this is the issue, do I just go ahead and replace both – or is it possible and worth it to figure out which of the two are bad? Do these components just screw in and out easily?
4. Thermostat Circuit Board – I guess what all else fails, blame the board. Could this be it? How do I tell?
Any help on how to narrow this down? I would rather not sink the cash into replacing everything.
