Coleman Horizon 400 Won't Stop Heating.

[jbailey]

I have a coleman Horizon 400 that continuously heats the water. I have the temp set to 80 (lowest setting), but it stays between 104 and 108. If I leave the cover off, it will sometimes come down to about 101. I run two, three-hour filter cycles per day. Spa is located outside in a screened, covered porch - outside temp averages mid 90's during the day, mid 70s at night. Is there a water temp sensor that may have gone bad?

[PreservedSwine]

If it's set to 80, and it's reading 80, and maintaining 104=108, yes- either a bad t-stat of thermistor.

But if it's seat at 80, but reading the water temp accurately, and displaying 104-108 and the water IS 104-108, then the thermostat is fine.

Try backing off on the filter cycles to 2hours a day, and vent the spa for one or two nights, see if it cools off.

Is it digital?

How long have you had it?

[jbailey]

It is set to 80, it is reading 104-108 and the temp IS 104-108, so then it is not the thermostat. Yes, it is digital, the tub is at least 10 years old. I will adjust the filter cycles and see if that works.

[n1oty]

Stuck relay.

John

[PreservedSwine]

Stuck relay.

John

I doubt it would consistently maintain a temp to within ~4 with a stuck relay.

[n1oty]

Stuck relay.

John

I doubt it would consistently maintain a temp to within ~4 with a stuck relay.

Re-read the OP's last post. The tub is NOT within a few degrees of set point. He stated that he set the temp to 80, the water temp is actually 104 to 108 and the display is reading the temp as 104 to 108. That sure sounds like a Coleman Horizon 400 that is cycling on the high limit sensor. A stuck relay is easy to check.

John

[jbailey]

John, please explain where the relay is located and how to check it.

Thanks,

[PreservedSwine]

Stuck relay.

John

I doubt it would consistently maintain a temp to within ~4 with a stuck relay.

Re-read the OP's last post. The tub is NOT within a few degrees of set point. He stated that he set the temp to 80, the water temp is actually 104 to 108 and the display is reading the temp as 104 to 108. That sure sounds like a Coleman Horizon 400 that is cycling on the high limit sensor. A stuck relay is easy to check.

John

lol- re-read my reply. I said it wouldn't maintain "a" temp to within 4 degrees, not the set temp. I never say never, but it's highly unlikely a stuck heater relay is going to have that kind of consistency to maintain a temp, then still be able to open and close that for any length of time and maintain that temp. ( Even when that temp is much higher than the set temp- the consistency is what's remarkable)

If it's stuck, and stays shut to reach 108, assuming it gets "unstuck" by itself, how does it close again at 104, while it's set at 80, to reach 108, at which point it opens again, over and over? I didn't read that it was going into overheat protection mode- maybe I'm missing something here.

[n1oty]

Stuck relay.

John

I doubt it would consistently maintain a temp to within ~4 with a stuck relay.

Re-read the OP's last post. The tub is NOT within a few degrees of set point. He stated that he set the temp to 80, the water temp is actually 104 to 108 and the display is reading the temp as 104 to 108. That sure sounds like a Coleman Horizon 400 that is cycling on the high limit sensor. A stuck relay is easy to check.

John

lol- re-read my reply. I said it wouldn't maintain "a" temp to within 4 degrees, not the set temp. I never say never, but it's highly unlikely a stuck heater relay is going to have that kind of consistency to maintain a temp, then still be able to open and close that for any length of time and maintain that temp. ( Even when that temp is much higher than the set temp- the consistency is what's remarkable)

If it's stuck, and stays shut to reach 108, assuming it gets "unstuck" by itself, how does it close again at 104, while it's set at 80, to reach 108, at which point it opens again, over and over? I didn't read that it was going into overheat protection mode- maybe I'm missing something here.

The mistake you are making is assuming that the relay that normally opens and closes to turn the heater on and off is the one that is opening at 108 degrees. The high limit relays normally stay closed at all times and only open on a signal of 108 or 109 degrees. One high limit relay opens if excessive temp is detected by the temp sensor. The other high limit relay opens if excessive temperature is detected by the high limit sensor. I suspect that one of the limit relays is actually opening, then resetting when the tub drops into a normal range (104 or less), at which point the heat runs away again because the normal temperature relay is stuck. Newer firmware tubs will not often reset themselves, but older tubs like this will automatically reset the limits once temp drops to 104 or less.

This older board probably has open relays and the stuck relay, if stuck, will be readily observed by shutting off power to the tub and visually checking for stuck contacts. On boards with closed relays, check for continuity from "common" to "normally open" with the power off. Any relay with continuity from C to NO with power off is stuck.

John

[PreservedSwine]

Stuck relay.

John

I doubt it would consistently maintain a temp to within ~4 with a stuck relay.

Re-read the OP's last post. The tub is NOT within a few degrees of set point. He stated that he set the temp to 80, the water temp is actually 104 to 108 and the display is reading the temp as 104 to 108. That sure sounds like a Coleman Horizon 400 that is cycling on the high limit sensor. A stuck relay is easy to check.

John

lol- re-read my reply. I said it wouldn't maintain "a" temp to within 4 degrees, not the set temp. I never say never, but it's highly unlikely a stuck heater relay is going to have that kind of consistency to maintain a temp, then still be able to open and close that for any length of time and maintain that temp. ( Even when that temp is much higher than the set temp- the consistency is what's remarkable)

If it's stuck, and stays shut to reach 108, assuming it gets "unstuck" by itself, how does it close again at 104, while it's set at 80, to reach 108, at which point it opens again, over and over? I didn't read that it was going into overheat protection mode- maybe I'm missing something here.

The mistake you are making is assuming that the relay that normally opens and closes to turn the heater on and off is the one that is opening at 108 degrees. The high limit relays normally stay closed at all times and only open on a signal of 108 or 109 degrees. One high limit relay opens if excessive temp is detected by the temp sensor. The other high limit relay opens if excessive temperature is detected by the high limit sensor. I suspect that one of the limit relays is actually opening, then resetting when the tub drops into a normal range (104 or less), at which point the heat runs away again because the normal temperature relay is stuck. Newer firmware tubs will not often reset themselves, but older tubs like this will automatically reset the limits once temp drops to 104 or less.

This older board probably has open relays and the stuck relay, if stuck, will be readily observed by shutting off power to the tub and visually checking for stuck contacts. On boards with closed relays, check for continuity from "common" to "normally open" with the power off. Any relay with continuity from C to NO with power off is stuck.

John

That fits, but I thought it would throw an overheat code in that situation?

[n1oty]

Stuck relay.

John

I doubt it would consistently maintain a temp to within ~4 with a stuck relay.

Re-read the OP's last post. The tub is NOT within a few degrees of set point. He stated that he set the temp to 80, the water temp is actually 104 to 108 and the display is reading the temp as 104 to 108. That sure sounds like a Coleman Horizon 400 that is cycling on the high limit sensor. A stuck relay is easy to check.

John

lol- re-read my reply. I said it wouldn't maintain "a" temp to within 4 degrees, not the set temp. I never say never, but it's highly unlikely a stuck heater relay is going to have that kind of consistency to maintain a temp, then still be able to open and close that for any length of time and maintain that temp. ( Even when that temp is much higher than the set temp- the consistency is what's remarkable)

If it's stuck, and stays shut to reach 108, assuming it gets "unstuck" by itself, how does it close again at 104, while it's set at 80, to reach 108, at which point it opens again, over and over? I didn't read that it was going into overheat protection mode- maybe I'm missing something here.

The mistake you are making is assuming that the relay that normally opens and closes to turn the heater on and off is the one that is opening at 108 degrees. The high limit relays normally stay closed at all times and only open on a signal of 108 or 109 degrees. One high limit relay opens if excessive temp is detected by the temp sensor. The other high limit relay opens if excessive temperature is detected by the high limit sensor. I suspect that one of the limit relays is actually opening, then resetting when the tub drops into a normal range (104 or less), at which point the heat runs away again because the normal temperature relay is stuck. Newer firmware tubs will not often reset themselves, but older tubs like this will automatically reset the limits once temp drops to 104 or less.

This older board probably has open relays and the stuck relay, if stuck, will be readily observed by shutting off power to the tub and visually checking for stuck contacts. On boards with closed relays, check for continuity from "common" to "normally open" with the power off. Any relay with continuity from C to NO with power off is stuck.

John

That fits, but I thought it would throw an overheat code in that situation?

Newer board firmware, yes. The OP indicates that this is a Coleman Horizon 400 that is at least 10 years old. It may, in fact, be closer to 15 years old as the model was prevalent from the mid 90's to around 2000 or so. Some of those old Coleman boards would not throw a typical "OH" code, especially if it is a 200r1a or 400r1a board. And, if the OP does have a stuck relay and the board is as old as I think it is, those boards are NLA. Maax Arizona does have a conversion board to replace it with, but you have to change the topside as well.

John

[PreservedSwine]

Good to know. Thanks John

[john T]

I have a similar problem - my coleman horizon 400 spa heater not turning off. I set temp to 80 but heater heats water until high temp sensor shuts down spa (usually around 110 degrees) sn1 and after a while after cooling I get the OH code and than I can restart the spa. But, the heater seems to continue to operate. I hear a hum from the heater area as if the heater is always on. I shut down the whole spa over night to cool.  When I turned on the spa again, the heater got hot to touch pretty quickly - the water temp this morn was 104 degrees at startup, the hight temp sensor triggered again.  any idea. hope you understand.

[RDspaguy]

You should start a new thread. 

Did you do any of the things you read in this thread? If so, what?

[Pool Support LLC]

Same problem. Filter cyles set to 1 hour each with no heat. Low speedjet comes back on and drives the temp up. I can open relay with jet button and it cuts off for 5 seconds, then it cuts back on. Been getting OH error, now SN1 error. Should I replace hi-limit or is it a board issue? TY, Steve 

[RDspaguy]

On 4/7/2020 at 12:50 PM, RDspaguy said:

You should start a new thread.