Pool heater will not fire

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  #1  
Old 02-11-08, 02:05 PM
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Laars LX400 Pool Heater High Limit Switch

My heater is coming up with an error message. It says I have a high limit switch problem. I have the manual and it shows the parts blow up diagram, but I cannot tell where this switch (I think there are two) are located. I am fairly well adept at using a volt/ohm meter for troubleshooting. Perhaps someone can tell me where to find and access these switches, and what resistance they should read. Don't know whether they are normally open or normally closed switches. I also noted in the forum that cobwebs can be a problem. Well, I have some good black widow webs in my unit. Could that be the source of my problems. I am going to spray before I get into this too much, but perhaps these webs are the source of the problem? This problem came after a long period of rain storms so perhaps also moisture got into the unit a bit. Unit is about 4-5 years old and was installed when the pool was built. Any help is appreciated.
 
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  #2  
Old 02-11-08, 02:52 PM
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Wink

tgodrich Best to make your own post here . Not add to a old one. This spider webs talked about here would be like in the venturi of the burners and up in the pilot light. You say high limit. Id jump it and see if the burner comes on. Then move to the next check. A limit will be closed for sure when the unit is not on.
 
  #3  
Old 02-11-08, 04:57 PM
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Tgodrich, I moved your post so we can better help you, let us know how it goes when you try what ed posted. We'll get ya going...
 
  #4  
Old 02-12-08, 08:24 AM
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limit switch

I got your suggestion. Does this mean that the limit switches (there are two in series on the schematic diagram) are both normally closed and would open in the case of over-temperature? Per the schematic, that would appear to be the case. It would do no good to have them normally open in series. One is 135 degrees F and the other 150 degrees F. I am not sure why you would need the 150 switch if the 135 was working as once it opens, the 150 is disconnected. Perhaps it is a failsafe in case the 135 fails to open.

Anyway, This weekend I will be opening up the unit for diagnosis. If I can simply jump the switches to bypass and see if the unit fires, that will at least confirm or eliminate them as the cause of failure.

The model I have is the Laars LX400.
 
  #5  
Old 02-12-08, 08:30 AM
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Yes you can bypass all the safetys in the loop, however you never want to leave any safety bypassed. Just do it to diagnose.
 
  #6  
Old 02-12-08, 05:16 PM
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both switches are normally on the water inlet / return plumbing side. as previously mentioned they are normally closed and open when there is a high temp condition, so with the heater off , & cold , remove the connections on each switch , test the two connectors on the switches with your ohm meter , it should zero out, there is continunity and good, if not its bad, replace it.

steve
 
  #7  
Old 02-13-08, 09:02 AM
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Excellent advice

Thanks,

I will diagnose this weekend (when it is light out and I am home). I work in electronics, so the electronics part of this I am good at. I just wanted to make sure I am interpreting the schematic correctly. I will check the switches for continuity and if open, bypass and see if I get the heater to fire. I doubt I have multiple problems, and it has only not been working a few weeks now. Could also be a poor connection as I suspect that the switch assembly plugs into the main wiring harness somewhere, and the harness plugs into the control board, both other sources of poor connections exist. The check of the switches is a good place to start.

I have Leslie's Pool Supply as my local shop. Are they OK to order stuff like this through, or is there some better place on the web?

Thanks for the advice. Always nice to tackle a problem knowing a little bit of what to expect.
 
  #8  
Old 02-16-08, 08:14 AM
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Laars LX High Limit Switch Problem

I am having a similar problem with my Laars 400 LX heater. After about 4 years of perfect service I began to get error messages and the heater would shut down and not turn back on again. The heater stated that the High Limit Switch was faulty. I have had those switches replaced 4 times in the past year. In the beginning the new switch would last 3-4 months, now only a few minutes before they blow. On the most recent incident, I had both switches replaced, and the wire harness. I fired up the spa and the water temp hit 80 degrees and boom- the heater shut down with the same error code.

I have spoken with technicians and all they do is replace the switch, but they cannot diagnose what is causing the problem. I have called Teledyne and they tell me it is possibly due to low flow, but I cleaned the filter, etc, and flow seems to be fine. They state it cannot be electrical, such as a power surge, and that these switches burn out over time, not right away. They were of amazingly little help.

There is no leakage anywhere.

Is it possible there is an internal buildup of calcium or something like that at fault? The heater is worthless to me right now, and I cannot find anyone who can tell me what is causing the problem.

Anyone have a similar problem and if so, can you share your solution?


Thanks
 
  #9  
Old 02-16-08, 11:03 AM
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I know you don't want to hear it but it does sound like a flow issue. Though the water in the spa is 80, the water in the heater is much hotter and with low flow through heater it gets even hotter possibly causing your issue. Have you taken the buckets off heat exchanger and visualy inspected? Could be corrosion, bad bypass, anything that would prevent normal flow. Does heater pop (bang) when on or shutting off???
 
  #10  
Old 02-16-08, 06:20 PM
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Thanks Todrut

I wish I was that handy to do those things you mention. I did clean out the filter today, and it was quite dirty. Turned the heater back on, and it worked great. Got in my spa when it hit about 96 degrees, and I was a happy camper. But then I noticed the water was no longer coming out hot. I checked the heater and again, the High Limit Switch code, with the heater shut down.

I am sure you are correct about flow being the problem. Is it a big deal to take the buckets off the heat exchanger? I am sure I will end up calling a technician again, but I am so tired of them simply replacing the switch without trying to find out why the heater is faulting. I would like to do some of my own diagnostics myself before calling them.

Thanks for your help.

Doug
 
  #11  
Old 02-16-08, 07:15 PM
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When you say clean out filter, what exactly are you doing and what kind of filter is it? Also what is the code you are gettin? Is it always the same code?
 
  #12  
Old 02-16-08, 11:12 PM
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Todrut---

Up until now I have been getting a High Limit Switch error about once every 2-3 months, which shuts down the heater and it will not light up again. I had both switches replaced this week. Today I started the heater and it worked fine until the spa was at about 80 degrees, and then the heater went off. This time the code was AGS (automatic gas shutoff). This was the first time I had ever seen this code. I did some checking and found this is most likely due to low flow. So I took my cartridge filter apart and cleaned all four cartridges thoroughly with a high pressure garden hose. They were obviously quite dirty, but I got them nice and clean. I then restarted the system and the heater worked fine. I got the spa nice and hot to about 96 degrees and I went in. It felt great and I thought all was ok. However after about 15 minutes I noticed the water was no longer coming out hot. I checked the heater and saw it had shut down again, but this time it was my friend the High Limit Switch code again.

That is about all I can tell you. I suspect that the dirty filter was partially at fault, but now it is cleaned out thoroughly, so I fear there is corrosion or some type of internal blockage that is causing a low flow and therefore the internal water temp goes high enough to trip the high limit switch.

Is it possible to actually look inside the heater to see if there is a blockage? IS that something an amateur can do?

I really appreciate your expert advice.

Doug
 
  #13  
Old 02-17-08, 10:16 AM
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If you're only cleaning filters with water hose, here is what you should try. Take filters out and soak in a bucket of hot water with 3tbls of cascade (yes dishwasher detergent) for a few hours, then rinse very good and replace. This takes out all the oils in the filter which is most likely the problem.
Let me know how it goes...
 
  #14  
Old 02-17-08, 06:58 PM
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Doug, Todrut has you pointed in the right direction, Id like to see you try something a little different, remove the cartridge elements completely, then put your filter back togeather, this will tell you witj out a doubt if the problem is with the filter, what size is your filter and what kind of circulation pump & hp do you have,? there are other issues that may be involved, the bypass may be allowing too much water to bypass the heat eachanger , thus the water in the exchanger would get too hot , therby causing the hi limit to open the circuit, also the heat exchanger itself may be restricted with calcium deposits, [ we call this liming up ] if thats the case the heat exchanger tubes would need cleaning , that would be a job for a qualified service technitian, the thermister or thermistat could also contribute to the problem , ...... stay the cours your heading untill you know for sure if its the filter / flow problem

steve
 
  #15  
Old 02-18-08, 12:20 PM
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Great Advice Everyone Thanks

I took all your advice. The cartridges are currently soaking in Cartridge Cleaner. I have a Pentair Clean and Clear Plus filter with a total of 320 SF of filter cartridges (4-80 SF cartridges) for my 15000 gallon pool.

I put the filter back together and am running the system with NO cartridges in it. I also thoroughly cleaned out the baskets in the filter pump, which had a fair amount of debris caught in the strainer. I should say that the guage on the top of the filter is reading the same number (20) that it did with the cartridges in place, so that is a little puzzling.

I am running the spa with the heater on, and so far so good, but only up to 70 degrees at this point. If the heater continues to run up to the 100 degree setting and sustains it, then I think we have the problem isolated to an obstruction to flow.

Once the cleaned cartridges are put back in place I will try again. If the heater shuts off again, I will purchase 4 new cartridges (these are 5 years old) and try with the new cartridges.

If none of this works, I will call a technician to come out again and check the bypass and heat exchanger to look for calcium buildup and clean if needed.

Does that sound like a good plan to you guys?

Thanks again.

Doug
 
  #16  
Old 02-18-08, 01:25 PM
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Update

Spa is now at 100 degrees. Heater still working, no codes noted. I will leave it on all day to see if it hangs in there. Once cartridges are soaked for 5-6 hours I will rinse them and reinstall to see if it continues to work. If so, the problem is solved. If not, I will purchase new cartridges.

I have my fingers crossed that this will work. Any further advice would be most welcome.

Thanks to everyone for your help.

Doug
 
  #17  
Old 02-20-08, 08:45 AM
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More on the switches

Last weekend I took the switches out (quite simple) and found the 150 degree switch open. I could push on it and it would come and go. So I have one of these on order. I bypassed the switch and the system has worked fine the last couple of nights I have used it. Still protected by the 135 degree switch, since they are in series. It would very improbably to get both switches to fail at the same time as when one fails, the circuit is disabled and the heater shuts off. Not quite sure why two switches are needed, unless just a safety precaution in case one does not open when over-temperature occurs.

I noted some corrosion on the end of the switch when I pulled it out. I think that perhaps some water got in there and caused the Aluminum to corrode over time. I will clean the switch area thoroughly before I put the new switch in and see if that cures my problem. These switches are not cheap, and are in fact rediculously expensive when you consider what little is inside them. Captive market I guess.

On the thread below with the filters...
I have replaced the filters once, and cleaned them multiple times. They are expensive, but browse the internet for good prices. Actually, I got a goot price on the internet and went to Leslie's and they gave me the same price on the same filter. They had to special order, and the first attempt came in with the wrong size. Their computer system had the wrong part number for the ones I needed. By the description below, I have the same filter system as dcappiello. My pool is 13,600 gallons (measured when I filled the pool once by watching the meter).
 
  #18  
Old 02-20-08, 08:58 AM
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Pool plaster

Not the same forum, but I thought I would throw this out there. My pool plaster is discoloring. I have tried every conceivable test to determine what is causing it. It is not metallic, and not related to any of the different algaes (sp?). None of the test kits identified the source of the discoloration. It is of a brownish appearance, and is embedded into the plaster such that scrubbing with a pumice stone has difficulty removing it.
At the suggestion of a pool place, I drained some of the water out of my spa and applied muriatic acid with a spray bottle directly to the plaster, let is soak for perhaps half a minute, and rinsed with the garden hose. It cleaned the plaster nicely. The pool place said if that works, then the entire pool needs to be drained and acid cleaned by a professional. They quoted about $1800 to do that. Any ideas what is the cause of this type of problem? I don't want to clean it and then have to do it in 4 more years again.

A bit of history on this plaster...
When the pool was first installed, I was told I had to brush the pool three times a day for 3 weeks to keep the plaster smooth. I did this religiously and brushed is every day. I could always see a cloud of plaster dust come off in the water when brushing. This plaster dust got less and less each time I did it. The problem was, the plaster NEVER became smooth as it should be. In fact, it was so rough, it would abrade your skin if you brushed against it. It was not smooth. After a long battle with the plaster company, they finally agreed to come out and drain the pool and sand the whole thing down to make it smooth. This did make it smooth, but I am worried that there was something inherently wrong with the plaster to begin with that is now causing it to discolor. I don't know squat about plaster, so I am at a loss. Any ideas?
I am also told not to drain the pool until the end of the summer season before it rains so that I do not run too much risk of it popping out of the ground due to water in the soil. The prospect of that just sounds expensive to fix.
 
  #19  
Old 02-20-08, 02:21 PM
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several things here,
1. first it appears the brown stain might be iron or colbalt at any rate you allready know the acid wash will remove it.

2. thr rough plaster may be attributed to the plaster mix, quality of the white cement , low total alakinity, low sustained p h

3. when you originally filled the pool you should have added a sequestering ageant , such as staintrine, [ applied biochemists brand ]

4. if & when you do acid wash , use a sutiable sump pump , rubber boots, gloves, mix 2 parts water with one part acid , add a small amount of liquid dishwashing soap , [ this will facilitate the solution staying on the walls & will prevent the solution from etching the plaster , it will also cut down on the smell / fumes ] , pour the acid into the water not the other way around, use a watering can [ plastic / rubber ] walking around the perimeter pouring from the bottom of the tile this is a two man job if for no other reason safety should be your main concern, before pouring the acid solution remove your pool light & or metal rail / ladder be sure to dispose of water in an approved method, check with your city building dept. [ in our local we can despose into the p-trap / sewer .]
do not try to remove every stain and or discoloration , as you may destroy your plaster. when applying the acid in the shallow end you will notice the mixture will take a certain path to the deep end , be sure to keep this wet as when the solution travels down this path several times it will have a tendency to roughen the plaster.

$1800.00 ? ? sounds high a 15 x 30 pool here [ so. cal. would run you apx. $850.00 - $1000.00 ]

be sure to add a sequestering ageant when re-filling , there will not be plaster dust.

steve
 
  #20  
Old 02-20-08, 04:32 PM
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plaster

When I tried the metal stain kit it did not remove the stain, so I made the assumption it was not iron, cobalt, or some other aspect of degrading metal fixtures.

Swan pools did the pool and had a person come out and initially balance the pool and keep reign on the chemicals for the first month. I did nothing in that time other than brush the plaster. So I am not sure if they used a sequestering agent.

Is acid cleaning a common thing that needs to be done to plaster pools over time? Nobody told me about it when I was looking to get a pool. Nor have any of my friends with pools had to do it. And nobody in my neighborhood has had the same problem with their pool plaster. This is why I believe that they may have not done the plaster correctly. Don't know, though, since I am plaster illiterate. I do not plan to do it myself, and will hire someone to do it for me. I am in Livermore, California, so will likely try to find a reputable company in my area.

Thanks for the input.
 
  #21  
Old 02-23-08, 08:20 AM
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Tgodrich--

Your story sounds so similar to mine that it is spooky. I also have a 15 x 30 pool, built by Swan Pools. I live in Northern Cal in the Bay Area- Danville. Are you near here?

I had a similar problem with a brownish discoloration on my plaster. I came to find out it was from impurities in the salt I was adding to the pool. I recently had to have the pool drained due to a leak in the wall between my pool and spa, and during that repair job, which Swan graciously covered, they also did a light acid wash and it all came out. From now on I will only use high quality pool salt that is finely ground, so it dissolves quickly and does not sit on the bottom of the pool for very long.

Do you also have a salt chlorine generator (I have AquaRite)? If so, this is likely the problem for you as well.

Regarding the high limit switches, as stated previously, I have had to replace them several times over the past year. I have the old parts and in each case there is corrosion on the surface of the switch, as you describe. I was recently told the problem is that my chlorine generator is placed too high and once the pump turns off, super chlorinated water from the Aquarite can flow backwards into the heater and destroys the switches. So, lately I have set my computer to go into Spa mode for the last 30 minutes of each day. I noticed that when it is in Spa mode the Aquarite is not generating, so I figure it will wash out all the chlorine during that time. Does that make sense to anyone? Or am I just kidding myself?

Thanks all. This is a great resource. You have all helped me a lot.

Doug

Doug
 
  #22  
Old 03-24-08, 03:35 PM
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plaster discolor.

Wow,

I live in Livermore. And Swan from Walnut Creek did the pool. I also have the Aquarite chlorine generator. What is it about the generator that might discolor my plaster? Swan is mum on this one.

I have been using pool salt from Leslie, which is quite fine and appears to be of good quality.

The acid wash seems to be the fix, I just wish I knew how to keep the stain away. My last quote was for $1800 to drain, wash, and re-fill the pool. Can't do until the end of summer now. Don't want to take a chance of the pool popping out of the ground when it is empty. I don't know where the water table is, but right after winter it is likely high.

I usually turn on my spa for a short while at the end of the day's cycle, but for a different reason. Birds like to sit on the waterfall from the spa to the pool and drink and bathe (then crap on the side of my spa). By running the spa, the water level goes down enough to be out of reach of the birds, and they don't do it anymore.
 
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