Raypak 206A Millivolt Trouble Shooting

TVGREEN23

New member
Jun 18, 2020
4
Roswell, GA
New to the Forum but not completely new to pools.

Lucky enough to grow up with one in my backyard and Pops had me working on it young. Now that I have moved back into my childhood home with my fiance, I am trying to knock off the dust a bit lol. Im good with cleaning the pumps and filters but never had much experience with the Spa heater. Enough introduction I am here because I need help and dont want to keep throwing money at the problem.

We have an older Raypak 206A millivolt spa heater, with the manual thermostat & on/off switch. When I first got to working on this thing I realized the gas valve was not opening properly. I have since replaced the gas valve completely and the pilot assembly. Additionally I pulled the burner tray out to clean it up a bit and remove any surface rust as the unit is outdoors. Now that I have everything reinstalled the pilot works great and I have a constant and strong blue flame. I was thinking the source of my issues was fixed however now I cannot seem to get the burners to kick on. I have read through the manual a couple times and it seems as though some common problems are the rollout switch, and water pressure switch. I already ordered a new rollout switch. I am about to buy the water pressure switch as well. But just curious if anyone else has had a similar issue and knows if I am maybe overlooking something. I also noticed when i removed the panel to access the water pressure switch, what looks to be my thermostat sensor is showing signs of corrosion. I have attached an image below. When I try to turn on the heater I flip the switch and then begin to adjust the thermostat to spa levels as the manual instructed me to. I do not hear any additional gas flowing all I can hear is a faint click every time it hits the orange range on the thermostat. Again not sure if anyone knows what could be the source of my issue but any help would be awesome.
 

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swamprat69

Well-known member
Mar 30, 2019
415
Las Vegas, NV
Just offhand it looks like your gas valve is in the "off" position. Push down and rotate the knob on the gas valve 180 degrees counterclockwise so that the "on" designation on the gas valve knob is lined up with the protrusion on top of the gas valve that has a red dot on it.
 

Pool Clown

In The Industry
Sep 5, 2008
2,187
Silicon Valley, CA
Faint click is a good sign. Tells me the thermostat is working,. but not necessarily calibrated. You have no temp numbers printed on the thermostat so, no worries there. Test pressure switch. You can remove the wires from the pressure switch and connect your continuity meter to them and turn the pump on. You should get continuity once the pressure comes up.

Clean filter, and good flow coming out the returns of course.

I'm assuming that you took that picture before you lit the pilot as you would not be able to achieve even a pilot with the gas valve in that position (off). Once you got pilot, rocker switch below thermostat to off, then continue rotating knob to "on" then try to fire (rocker to on).
 

JamesW

TFP Expert
Mar 2, 2011
24,051
Check for 500 mv dc coming from the pilot generator (thermopile). Red and white wires. Red pilot generator wire goes to the TP terminal. White pilot generator wire goes to the TP/TH terminal.

If that's good, check for 500 mv dc from the TP terminal to the TH terminal with the violet wire.

If that's not good, you have something open on the limit string.

The limit string is a series of on/off switches that all have to be on for the voltage to get from the TH/TP terminal to the TH terminal.

The red wire connected to the TH/TP goes to the roll out switch, you should measure 500 mv dc between the TP terminal and the other side of the roll out switch.


The red wire leaving the roll out switch should go to the water pressure switch. You should measure 500 mv dc to the orange wire leaving the pressure switch.

The orange wire leaving the pressure switch should go to the first high limit. You should measure 500 mv to the out terminal of the first high limit switch.

From the first high limit switch, there should be a black wire to the second high limit switch. You should measure 500 mv to the out terminal of the second high limit switch.

Leaving the second high limit switch should be a black wire going to the thermostat. You should measure 500 mv on the out terminal of the thermostat.

Leaving the thermostat, there should be a yellow wire going to the on/off switch. You should measure 500 mv on the out terminal of the on/off switch.

Leaving the on/off switch should be a violet wire going to the TH terminal.

So, basically, the voltage needs to get through the entire string in series to power the gas valve.

You can remove the red wire from the TH/TP terminal and remove the violet wire from the TH terminal and check the resistance of the entire limit string.

The entire limit string should be closed and show low ohms.

If open, you can go in series as described above checking to see which limit is open.

If high ohms, a limit might be bad or a connector might be bad.

Note: TP means thermopile. TH means thermostat.

The gas valve has two solenoids. It has a pilot valve solenoid and a main gas valve solenoid.

The pilot valve solenoid is powered by the TP and TH/TP terminals. The resistance of the pilot valve solenoid should be about 9 to 11 ohms.

The main gas valve solenoid is powered by the TP and TH terminals. The resistance of the main gas valve solenoid should be about 1.5 to 1.7 ohms.
 
Last edited:

TVGREEN23

New member
Jun 18, 2020
4
Roswell, GA
@JamesW @Pool Clown @swamprat69 @agw22

Thank you all for the responses. Sounds like I am headed on the right track. Going to get a continuity meter today in order to test the limit string as suggested. Glad to hear that it is not the thermostat itself as that was a major concern of mine. All of this was extremely helpful information I will let you know when I got heat!
 

Sendero

Member
Jan 22, 2017
5
B.C. Canada
I have the same heater & experienced the same problem. I mentioned it to my neighbour who has the same heater & he said it’s the rollout switch, bypass it. I tried that & it fired right up. I have since ordered a new switch but haven’t installed yet. You could check continuity through the switch to confirm if you have a meter.
 

TVGREEN23

New member
Jun 18, 2020
4
Roswell, GA
So just to follow up guys I replaced the rollout switch and the water pressure switch after running a few continuity test. The heater is up and running now and my girl couldn't be happier. I am experiencing two problems though that I would love some expert advice on. First off seems as though when the heater kicks off once it reaches the desired temp or for whatever reason, when it comes back on it seems to have a gas build up of some sort. Its very strange and only seems to happen when the heater is already hot and turning back on not for the initial start up. I've removed the vent hood a couple of times now in order to try and create more open ventilation for the gases to escape and this seems to help a bit but still will get the occasional build up that will knock off the pilot from time to time. Probably sounds a lot worse than it actually is but sure can make you jump during a relaxing evening in the hot tub.

One last thing is sometimes it can be temperamental trying to turn it back on while its hot or will kick off early when the water temperature hasn't reached the set temp from the heater. This leads me to believe that the thermostat sensor might be going bad as there are some signs of corrosion on it and its the only thing that I have not replaced yet on the heater besides the burner tray itself.

Sorry for the long post but any thoughts? @swamprat69 @ps0303 @Pool Clown
 

swamprat69

Well-known member
Mar 30, 2019
415
Las Vegas, NV
You replaced 2 parts. Were they both showing no continuity? The rollout switch is a fusible link, non-resettable temperature safety that melts a metallic bridge ( that maintains the circuit ) at a specific temperature. If the rollout switch was open, the condition(s) that caused the rollout switch to open must be corrected before the rollout switch is replaced. The rollout switch opens if there is an overtemperature condition at the entrance to the firebox. This is normally caused by a restriction to the flow of combustion byproducts ( flue gas ) from the firebox through the heat exchanger and out the exhaust which backs flue gas out of the entrance to the burner box.. This can be due to a sooted heat exchanger ( due to incomplete combustion ) or debris/blockage on the downstream side of the heat exchanger in a non-assisted (atmospheric/ non fan ) system. A less likely cause would be deterioration of the firebox itself. If the heat exchanger is blocked by soot it must be cleaned and the cause of the sooting also corrected. Incomplete combustion can be due to dirty burner slots, spider webs/debris inside the burner tubes, spider webs/debris restricting the gas manifold orifices or incorrect gas pressure to the gas manifold. If you seem to have a buildup/restriction that is preventing normal operation it would seem that all of these should be checked and corrected if needed.
 
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swamprat69

Well-known member
Mar 30, 2019
415
Las Vegas, NV
I have the same heater & experienced the same problem. I mentioned it to my neighbour who has the same heater & he said it’s the rollout switch, bypass it. I tried that & it fired right up. I have since ordered a new switch but haven’t installed yet. You could check continuity through the switch to confirm if you have a meter.
You should reference my response to TVGREEN23 regarding replacing the rollout switch without correcting the problem that caused its failure
 

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Pool Clown

In The Industry
Sep 5, 2008
2,187
Silicon Valley, CA
Majority of roll out fuse/link opens are from a blocked burner (spider webs). Gas from the jet hits the web and backs up. Cleaning the burners with a stripped wire (solid not stranded) should get the gas flowing in the right direction THEN replace the roll out sensor. Would not advise jumping sensor "till the fuse arrives" as that could cause a fire.
 

Sendero

Member
Jan 22, 2017
5
B.C. Canada
In regards to the rollout switch/ fusible link. Both my neighbours & my Raypak heater were installed in new pools in July 2017 & both switches failed within 2 years. There doesn’t appear to be any soot & there are no blockages in the burner tubes. For what it’s worth the man who installed the pool told us he finds that an open rollout switch is a common fault with this heater, but there must be a reason for it to fail.
The problem we do have is high winds at times. Because of cooler temperatures this year we have been using the heater frequently & I find I’m having to relight the pilot at least once a week. Could the wind be the cause of flame rollout? I haven’t installed the new fusible link yet so I haven’t tested that theory.
I’m now looking to purchase & install a stack kit which I hope corrects the problem with the pilot light & hopefully the rollout issue.
 

swamprat69

Well-known member
Mar 30, 2019
415
Las Vegas, NV
The stack hood could help alleviate problems caused by excessive winds interfering with the flow of flue gas because the construction of the stack hood allows for dilution air to the flue gas which acts similar to a vacuum breaker on a water system by reducing/eliminating backflow.
 

ps0303

TFP Expert
In The Industry
Jul 6, 2011
4,049
FL
High winds would be cause for this issue and a stack hood is what you need.
 

TVGREEN23

New member
Jun 18, 2020
4
Roswell, GA
So I have seemed to fix the gas build up problem thanks to yalls help however the heater is still very tempormental. Not sure what the driving cause is behind this but seems as though getting it initially started is a breeze. Once it starts warming up it will usually kick off around 94-95 degrees. I cannot get it to turn back on for about 30 -45 minutes after this and once I do it will only stay on for another 30 mins to an hour. This usually gets the hot tub to the desired temp. but I have to believe it could be performing a bit better. Seems as though this will become an issue towards the fall and winter as I will not be as willing to leave the warm water to go mess with the heater until it decides to kick back on. Any suggestions? I still think it might be the temperature sensor as this is one of the only components I haven't replaced besides the burner tray itself which was extensively cleaned. But as you can clearly tell I am no expert and am crawling back to you guys for wisdom lol. Refer back to my original post for pictures of what I believe to be the extremely corroded temp. sensor. @swamprat69 @ps0303 @Pool Clown
 

Pool Clown

In The Industry
Sep 5, 2008
2,187
Silicon Valley, CA
Check the pilot assembly. While it is burning, the flame should be pointing to, or near the first burner rail. If partially blocked, it may still be lit, but pointing away from the rail. This, when warm can initially cause ignition failure, but then once enough gas fills the area, it finally ignites, and this is when you may or may not get the "WHOMP". It may fire, or it may blow out the pilot. At this point, since you reported that you are no longer getting any roll out, you may want to verify that all the burners are igniting. Especially the rail next to the pilot. If either the jet for that rail or the rail itself is blocked, you can get the same result (WHOMP), as the dirty pilot.
 
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