Sand Filter Valve Melted / Heater gets hot when off

[tthorson]

The six way valve on my sand filter is deformed and leaking. I think the pilot light on my pool heater is heating the water enough to melt the valve. Is this possible?

I recently added a timer to the pump. This includes a fireman's switch.
I have the timer set to run from 7am to noon, and 5pm to 10pm.
Everything seems to be working properly.
The heater comes on after the pump is running, and only when the pump is running.
The heater turns off when the pool reaches the proper temperature.
The fireman's switch turns the heater off about 20 minutes before the pump turns off.
The pipe from the filter to the heater is cool to the touch when the pump is running, whether the heater is on or off.
The hose from the heater back to the pool is warm, but not hot, when the pump and heater are both running. It is cool when the heater is off and the pump is running.

Hours after the heater and pump have been off, both the pipe to the heater and the hose from the heater get really hot. Not soon after the pump is off, but hours after the heater and pump have been off.

The six way valve started leaking out of the waste line. I took it apart and found the inside features melted and deformed.

Where is all this heat coming from?
Am I supposed to be able to use a timer with my setup?

I have purchased a new valve, but I am afraid to even have the pilot lit on the heater without the pump running full time.

What am I doing wrong?

Thanks for any advice.

 

[Bama Rambler]

Welcome to TFP.

Can you post a picture of your equipment pad with the heater and filter piping shown?

My initial thought is that the heater is too close, plumbing wise, to the filter. A pilot light will get the stagnated water pretty warm, but it shouldn't get real hot.

One option would be to kick just the pump on every two or three hours for a few minutes.

 

[tthorson]

I am having trouble posting the picture. I get the message that the upload failed. I will try again, after work.

The sand filter is right next to the heater, about as close as it could be.
There is a 6" length of 2" gray CPVC coming out of the heater. This transitions to 1-1/2" white PVC, which goes right to the sand filter.
It is about a 2' length total. The white pvc is discolored from the heat.

 

[Bama Rambler]

I would re-plumb that whole setup and move the heater about 5' away from the filter and use about 1' to 2' of stainless steel pipe right out of the heater. You at very least need CPVC right out of the heater (That's what the gray pipe is).

Can you measure exactly how hot the piping is getting now? A good rule of thumb is that if you can force yourself to hold your hand on it for 8 seconds, it's less than 150ºF.

Another option would be to get a new heater that doesn't have a standing pilot.

 

[Pool Tool]

There should also be a check valve inline between the heater and filter to prevent hot water from backing up into the filter. This would not help much with the system getting hot from the pilot, but if you're replumbing its worth adding. You could go straight down from the filter elbow horizontal to install the check the elbow up back in the heater. That would give you around 4-5' of piping without physically moving the equipment if you're space constrained. That is a lot of heat being generated. Just my $.02, good luck.

 

[zimm]

That filter is the intake side to the heater right? So run heater and feel with your hands if the pvc is actually getting hot....

 

[jblizzle]

Even being that close, I would not think much heat should be reaching the filter at all.

To confirm, the water does come out of the top of the pump into the filter and then out of the filter and into the heater and then out of the heater to the pool?

I just can not see how the heater could be affecting the filter, although I could certainly be wrong.

 

[Pool Tool]

I'm not the OP, but looking at the picture one can just barely make out the inlet arrow on the heater - just on the top of the black, cast block where the piping/hose from the filter attaches.

Just a thought; would the fireman's switch installed override the heater's pressure switch if the heater was turned off by something other than the timer? For example, my pump has timer and a separate switch to turn off the pump for routine tasks like clearing the strainer basket, backwash, etc. and I am guessing most pumps do too. If I were to turn off the pump with the heater running the pressure switch would immediately notice the pressure/flow loss and shut down the heater. Also it would shut it down if a backwash was needed and flow slowed to a point of damaging the heater. I don't run my heater but for weekends, parties so it is off unless i am monitoring.

TThorson, do you run this on Propane or Nat. Gas? If propane, does it have the correct orifice(s) in there? Running propane through a natural gas orifice would deliver a lot more flame/heat that it should. Just grasping at straws, hard to believe a pilot could heat the water to that extent.

 

[ps0303]

First off, if the water is back feeding for some reason, the flex PVC and the union, and the elbow, and the reducer would have melted or be deformed. That would be the first thing to go if in fact is was back feeding hot water in to the filter. Second, the fittings used are DWV and not schedule 40 which is what should be used. Third, why is their a piece of romex running to the heater to provide power. Bad choice and illegal in most parts of the country.

If you have no automation system and you have the heater turned on all the time, then you probably have an issue with the pressure switch. It is not sensing that the pump is off thus allowing the heater to stay on. However if that is the case, I would have expected a huge meltdown. If you do not have automation and just a plain old timer clock of sorts, then the heater should be connected to the same terminals on the clock as the pump. This would kill power to the heater and thus turning it off completely.

You have some cleaning and changing needed on this pad. I've seen heaters just about as close as yours but the installer did run the pipe from the filter in a U shape. So out of the filter towards the ground, short section, and then back up towards the heater.

 

[tthorson]

Wow! I am very excited to see all of the responses. Thank you for trying to help. Let me try to answer all of the questions.

Water flow: Water flows out of the pool through the in-wall skimmer, down to the pump, into the sand filter, then into the heater, then back to the pool. I think this is normal and correct, right?

If the pump is running, the PVC does not get hot, whether the burner is on or not. I can run the heater and pump continuously, without a problem. This is what the previous owner did. He did not have a timer.
The problem is when the pump is not running. The plumbing into and out of the heater gets very hot, even when the burner is off.
There is heat damage on all of the plumbing components near the heater. I think the filter valve is the weakest link. It appears to be ABS plastic.

Check Valve: I do not have a check valve. I shouldn't need one, right? But, it may help with the problem I am having. I looked at the cheapo Menard's PVC check valves. They just have a rubber flapper. 1: I didn't think it would hold up to the heat. 2: I wasn't sure it would stop the convection flow, I think is happening. 3: If it did stop the flow, I think the heat may just conduct through it. I hear rumors that Jandy makes a good check valve designed for pools. Does anyone have experience with these? Would they stop the heat transfer?

I think the U shaped plumbing may help. It may stop any convection flow as the hot water would not want to go down the U.

Pool Heater details: The pool heater runs on natural gas. The valve, burners and pilot orifice(s) are all for natural gas. The pool heater runs on a millivolt system. There is no power to the pool heater. That is not romex in the picture. It is a 2 conductor wire running to the fireman switch. The millivolt system is powered by the pilot light. The pilot light heats a thermopile which produces about 750 mv. This is the electricity that powers the control circuit. All of the controls are wired in series. If any of the controls are not closed, the burner will shut off, or not light. The controls include; a pressure sensor, on/off switch, thermostat, temperature limit switch, and fireman switch. If the fireman's switch is open, the burner will not run. If the fireman switch is closed, the burner will only run if all of the other controls are also satisfied. None of the controls can override another.

The purpose of the fireman switch is to turn the burner off 20 minutes before the pump stops. This allows everything to cool off with the water still flowing. According to the manual, the fireman switch is not required. The pressure sensor will turn the burner off when the pump stops. But, this can be hard on the equipment because the heat exchanger is hot and the water is not flowing.

It could be something wrong with the pressure switch. I have never seen it malfunction. I have never seen the burner on when the pump was not running. But, that would explain the symptoms. The fireman switch is only open (off) for 20 minutes prior to the pump shutting off. After the pump is off, the timer closes the fireman switch. I don't know why, that is just how my timer works. The only thing keeping the burner off is the pressure switch. If it closed for some reason, the burner would come on. It would stay on until the pressure switch opened or the thermostat was satisfied, or the max temperature limit was reached. I have the thermostat at about 84 F. That should not be damaging the filter. I don't get it.

I am also having a hard time believing that the pilot light is causing all of this heat. I have been trying to adjust the pilot light down as low as I can and still get enough voltage for the burners to fire. I will try to do a deeper study this weekend, measuring temperatures over time, making sure the burner doesn't come on when it is not supposed to.

I appreciate all of the ideas to fix the symptoms, such as check valves and longer distance between the filter and heater, I will probably have to implement one of these. But, I am curious if there is something am I am doing wrong. My setup is supposed to work, right? Something must be malfunctioning?

Thanks again.

 

[ps0303]

Well the thing is, if the previous owner had this same setup then why is this just now happening. You didn't move any equipment? A millivolt system wouldn't put out enough heat with just the pilot burning. It also makes no sens that when the heater shuts off via the fireman switch and then the pump runs for 20 minutes, that is long enough to cool the unit down. Can you take a picture of the pilot while it is lit? I wonder of a portion of it is broken and the flame is super huge. Still don't see it as being enough to super heat the pipes like you are saying. But then again, you have a rather old heater. So when everything has been off for say a few hours, can you put your hand on the top of the heater? Is the top of the heater really hot?

 

[tthorson]

Nothing has been moved. Only difference is the timer.
When the burner is on, the top of the heater is boiling hot. If you splash water on it, it boils.
When everything has been off for a few hours, the top of the heater is warm. You can touch it without burning yourself, but it is noticeably warm. I was working near the equipment and touched the top and it caught my attention. Didn't seem like it should have been that warm.

I took some pictures of the pilot light in the dark. It seems kind of large.





I plan to measure some temperatures, tomorrow.
I am going to shut off the valves to and from the pool.
Remove the top of the filter valve.
Place a thermocouple in the water.
Light the pilot light, with the heater switch off.
Then, measure the water temperature over a few hours, with just the pilot light.

If I don't see anything abnormal, I will put it all back together, and run the pump and heater for a while.
I will have to measure the temperature on the outside of the pipes, then.
Next, shut down the heater, with the pump still running, and measure the temperature for 2o minutes.
Then, shut the pump off, and measure temperatures for a while.

Any other ideas or measurements I should take?

 

[ps0303]

Looks to me like the pilot assembly needs to be replaced. That flame looks way too big. It should be a nice blue flame as well. No one has been messing with the gas valve?

 

[tthorson]

Yes, I have totally been messing with the gas valve. I did not intend to leave out that very important detail, but did, until now.
Everything had sat unused for a year. I could not get the pilot to light. No gas was coming out of the pilot orifice. It had rusted shut. I clean the orifice with a wire brush.
I was able to light it, and it would stay lit, but the thermopile was not generating enough voltage to power the circuit.
I checked every component in the circuit.
I started messing with the pilot adjustment. Still no luck.
I replaced the thermopile. It was generating more voltage, now. But, still not enough to power the circuit.
I cleaned and greased every connection, and replaced a couple terminals that broke from my messing with them.

Bingo, it worked! I then proceeded to turn the pilot light down as low as I could and still power the circuit.
The pilot adjustment screw is 180 degrees open from full closed.
I get 430 mV across the thermopile, with the circuit all hooked up, but no call for heat. This is below the recommended 500 mV, but it is working.
I get 290 mV across the thermopile, with a call for heat.

The pilot is a blue flame with 1/2" yellow tips. It is actually like 3 flames. The pictures at night, make it look like more yellow, than in person.


I ran my experiment:
I shut off the valves to and from the pool. I took off the lid of the filter valve, and placed a thermocouple in the water.
The pump is not running, the heater is not on, no water is moving.
I lit the pilot light. The water in the filter valve went from 70 F to 150 F in 1 hour. It was still on the rise, but I shut it down.
The heat deflection temperature of ABS plastic is around 190 F.
Just the pilot light is causing enough heat to damage my filter valve.

I ran the experiment, again. This time with the pilot adjustment screw only open 45 degrees from closed. Just barely enough to keep the pilot lit. Not enough to run the circuit.
The water temperature rose to 127 F after 1 hour. I am not sure if it was still on the rise. I didn't take a lot of data points, this time.


So, a new thermopile is barely making enough voltage to power the circuit, at the same time, the pilot is making too much heat and melting my filter valve.

I probably need a new pilot burner assembly, but I don't see how it is going to make enough voltage to power the circuit without making too much heat.
There is probably too much resistance in the circuit, too.
I have more troubleshooting to do.


No one else has this problem?
Does anyone have a heater with a pilot and a pump on a timer?

 

[zimm]

My old millitvolt heater needed a new pilot assembly (it didn't run) and when we fired it up the pilot flame was tiny. Not enough to heat anything up, but it worked properly. You have a bunson burner going on there. I would try a new pilot burner assembly with probe.

I've since switched to a Raypak heater so no more pilot lights for me, it auto ignites.

 

[Kiss4aFrog]

Maybe what you need is a new pilot assembly with a much smaller flame and to adjust the location of the thermocouple so it's engulfed in the smaller pilot. I think having the pilot orifice rusted shut and then reopened is allowing too big a flame and it's not directed at the thermocouple but that's just a guess.
I like the idea of adding the downward "U" to help with isolating heat from the MPV.
Pilot assy. $120. http://www.parts4heating.com/SearchResults.asp?Extensive_Search=Y&Search=xlg3
Thermocouple $67. http://www.parts4heating.com/SearchResults.asp?Extensive_Search=Y&Search=W0036901

 

[gtemkin]

I have the same heater, except the next size larger (250K BTU). The thermopiles (generator) can be pretty poor and I've had to change them out frequently. It's not a surprise that a new one might be marginal so I'd agree with others that you should just go ahead and replace it again. The pilot on these models is much larger than most other pilots but your's seems adjusted extra high. I know the thermopile bracket doesn't have or allow any adjustment for position but you should take advantage of whatever slop there is in the mounting to get it closer to the flame. And yes, you want to clean every one of your electrical connections 'cause you're dealing with such low voltage.

You're plumbing isn't in compliance with the installation manual, in that your supposed to have a minimum of 6" of CPVC coming off the header. I estimate you have about half that. I know that doesn't have much to do with the excessive heating but if you re-plumb, you should fix that. Although it doesn't state it as a requirement in the manual, every illustration shows the pipes routing down. This will lengthen the piping distance to your multiport. The current piping length is way too short. I think these heaters were designed when filters more commonly had side mount multiport valves, which generally required plumbing to be routed downwards.

I think you have a perfect storm of too short a piping run, that runs uphill, and an energetic pilot light.

EDIT: "Uphill" is relative to the reverse flow of pilot heated water when the pump is off.

 

[gtemkin]

I just went out and felt the header and pipes of my Laars/Jandy Lite2 250K millivolt and sure enough, they are warm (96F measured with contact thermocouple), even though the heater and pump have been off for at least 12 hours. I wouldn't have guessed that beforehand, but indeed the pilot will deliver enough heat to get them warm.

I have the optional install stainless steel downpipes, so by the time you get a foot or so down, the pipes feel room/water temperature (75F measured at bottom of pipe).