Raypak 2100 Heater heats for 10 minutes, then shuts down

[dave dutkowsky]

My 1996 vintage Raypak 2100 heater needs help.

I have replaced the Unitherm governor, and the bypass valve in the entry header. I have cleaned the heat exchanger tubes and have replaced the thermistor in the entry header.. Now the heater fires on POOL setting only but does not fire on SPA setting. On Pool setting, the heater runs for about 10 minutes then the service light goes on and the heater shuts down. I have all of the supply valves wide open so water flow is at a maximum level. On the control PCB, the SENSOR FAIL led lights up when the shutdown occurs. On SPA, the service light comes on immediately as does the sensor fail light on the control board.

What could be causing these issues and how should I fix them?

Thanks for the advice.

 

[ajw22]

Welcome to TFP.

You can download your RP2100 manual from Raypak Swimming Pool Heater RP2100 User Guide | ManualsOnline.com

You will find troubleshooting information in the manual. There are three versions of the 2100 heater - Millivolt, IID (Atmospheric), and IID (Low NOx). Wiring diagrams for each of them are on pages 26-28.

If you cannot figure out what sensor is failing from the display then you need to jumper the sensors one by one and to see which are causing the shutdown. Only jumper the sensor for test purposes and do not let the heater run for any length of time or you can damage it.

At over 20 years old it may just be time for a new heater. Open it up and post pics of what it looks like indie the burner and wiring areas.

Let us know what you figure out.

 

[dave dutkowsky]

Welcome to TFP.

You can download your RP2100 manual from Raypak Swimming Pool Heater RP2100 User Guide | ManualsOnline.com

You will find troubleshooting information in the manual. There are three versions of the 2100 heater - Millivolt, IID (Atmospheric), and IID (Low NOx). Wiring diagrams for each of them are on pages 26-28.

If you cannot figure out what sensor is failing from the display then you need to jumper the sensors one by one and to see which are causing the shutdown. Only jumper the sensor for test purposes and do not let the heater run for any length of time or you can damage it.

At over 20 years old it may just be time for a new heater. Open it up and post pics of what it looks like indie the burner and wiring areas.

Let us know what you figure out.

Thanks. I have the original copy of the manual (had to believe that we have kept it around for 25 years!) and have been using it to get to the point that I am at in the rebuild. I know that a new heater would be the easy way but now it has become a challenge and I'm not going to let this machine outwit me! My grandkids are coming for Thanksgiving and I would like to have the pool a little warmer than the current 58 degrees for their visit.

I plan to jump the temperature sensors on the inlet header first followed by the one on the exit header next. Does this make sense?

 

[ajw22]

I plan to jump the temperature sensors on the inlet header first followed by the one on the exit header next. Does this make sense?

Inlet temperature sensor is a thermistor which can be replaced by a 10K resistor to force it to read 76F.

Temperature Sensors - Further Reading

www.troublefreepool.com

Hi Limit sensors in the outlet can be jumpered for test purpose only. If Hi limit is the problem you then need to determine if it is a sensor failure or the sensor is doing its job and you have an internal problem causing high water temperature.

 

[1poolman1]

The "Sensor Fail" is the temperature sensor, a 10k thermister. It is brand specific so you need one for that RayPak. Should be part #009577F. It should have three wires; 1 black and 2 green.
The hi-limit switches are just that, switches that react to heat, open/close.

 

[dave dutkowsky]

New Input.

Today when I turned on the power to the heater along with the pool pump, the SENSOR FAIL led on the control board (lower left in the picture) does not go out. In the past, this led would be out and then I could switch on the heater to POOL and the burner would light and continue to burn for about 10 minutes before it would shut off and the SENSOR FAIL led would be on when the shutdown happened.

I was able to measure the resistance in the thermistor. Both sides of the thermistor were very close in resistance and the resistance value was in line with the temperature of the pool water which was flowing through the heater. (I measured 15.5 ohms at approx 59 degree water temp.)

I was also able to confirm that there is continuity through each of the switches on page 26 of the manual. This continuity was measured at the connector where all of these switches connect to the control board. (Also, the led associated with each of these sensors was not lit confirming that the sensor is working I think)

What is left to check before buying a new control board?

 

[1poolman1]

Have you visually checked the condition of the temp sensor? You may find that it has one or more cracks it in or it is corroded. The rust at the well that it is in is an indication that it may have failed. Many times, when they fail, they will work for a few minutes then give a faulty reading that the board senses as failure. Won't hurt to look.

 

[dave dutkowsky]

Thanks. I installed a new thermistor temp sensor and get the same results. Sensor continues to show proper resistance per the specs in the book. I also looked at the thermistor and do not see any rust or cracks.

 

[skimmerswimmer]

I have the millivolt version so I can't be much help for your issue. I did have a very strange similar problem with my heater early on and thought it had to do with the temperature sensor or pressure switch. It was a very intermittent problem. With the millivolt version of this heater, the entire safety circuit is one long series circuit. Turns out, my analog temperature control potentiometer was the issue. Once I jumped it out of the circuit, the heater worked properly ever since. I never did replace it. I just manually turn the heater on when I need it, and turn it off when the water reaches swim temperature.

 

[dave dutkowsky]

Thanks for the idea. I tried to jump out the rheostat for the temperature control and it did not make any change. The sensor fail led on the control board continues to be lit and as a result the unit will not fire. Since this is a new temp sensor thermistor and it is reading the correct ohms for the water temperature then, per the troubleshooting tree in the manual, it seems my next step is to replace the control board.

Does this make sense or is there something else that I should try first?

 

[ps0303]

I looked at the pictures you posted and in the last one I see what appears to be a hole in the bottom of the heater. If the bottom is rusted out to the pad, it's time to replace the heater. It has lived a full life and with holes in the bottom creates another issue, fire hazard. So, is it rusted out on the bottom?

As for a new board, not sure you can purchase another like that and not so sure the new version will work in that older unit.

 

[dave dutkowsky]

Thanks. I found a replacement control board on e bay that is the same PN that is in this unit. Will see how it works.

Yes, there is rust on the bottom. I will pop rivet a piece of sheet metal over the rusted spot if I can get the unit to heat the pool.

 

[1poolman1]

Thanks for the idea. I tried to jump out the rheostat for the temperature control and it did not make any change. The sensor fail led on the control board continues to be lit and as a result the unit will not fire. Since this is a new temp sensor thermistor and it is reading the correct ohms for the water temperature then, per the troubleshooting tree in the manual, it seems my next step is to replace the control board.

Does this make sense or is there something else that I should try first?

Please, listen to PS0303. Your heater is 25 years old. That is a long life for anything pool related. If it is rusted out at the bottom, it is time to get a new one. You are dealing with an item that is very safe when used properly, very dangerous when modified or un-approved repairs are made. Bypassing heater controls is another way to cause great harm or damage.

 

[skimmerswimmer]

Please, listen to PS0303. Your heater is 25 years old. That is a long life for anything pool related. If it is rusted out at the bottom, it is time to get a new one. You are dealing with an item that is very safe when used properly, very dangerous when modified or un-approved repairs are made. Bypassing heater controls is another way to cause great harm or damage.

I agree with this. My old Raypak heater was about 15 years old when it started making noises in the inlet header. I probably could have fixed it, but the unit was quite rusted and I was in the process of resurfacing my pool and there were other minor issues with the pump and filter, so I just went ahead and replaced everything at a cost of about $15k including the new pool finish. Despite the severe hit to the wallet, I'm glad I did it.

 

[dave dutkowsky]

I bought a new control board and installed it today. Pool heater fired right up and is heating the pool nicely. Turned out that both the thermistor and the control board were bad. With those two electronic parts plus a new Unitherm valve and a new bypass valve, the heater is now working like new.

Thanks for all of the help.