Pool heater will not fire up

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  #1  
Old 06-07-05, 06:42 PM
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Pool heater will not fire up

Hi, have a Laars LX250 pool heater, 4yrs old.

Have the schematic diagram, have checked the sensors - they seem ok.
Problem is that when setting on to POOL or SPA, the fan starts up but the gas valve doesn't open. (after a few minutes, the 'service' LCD lights up and 'AGS' (auto gas shutoff)

Late in the season last year I called a heater tech in and he left a $150 bill in the mailbox and said it wouldn't start because of cob-webs. That may have been true last fall - but at that time the gas valve was opening - but intermittently.

This year the problem is solid - no gas smell at all. (I have since turned off the gas while troubleshooting this problem)

Tried putting a volt meter on the wires going to the gas valve while turning on the heater - and during the entire time - nothing - 0.00v (not sure what voltage it uses - but have tried both AC and DC settings, low and high.)

Tried unplugging some of the sensors - but the LCD panel points me to the sensor - so they are obviously working. The water pressure from the pump is about 14psi - tried backwashing - still no heater flame.

Saw 24VAC across the leads of the transformer - looks OK.

Is there a relay or something along those lines that supplies the voltage to the Honeywell gas valve?

Any ideas? (aside from 'call the heater tech back' :-))
Thanks, Graham
 
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Old 06-08-05, 07:52 AM
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Is this a new pool? Or an old pool with a new heater? Is your heater natural Gas? Check your gas line sizing and check your gas meter size. Newer heaters need gas volume. Natural gas heaters run at around 5-10 WC on the inlet side of the gas valve. That is equal to less than 1 PSI. Post back and we can go from there…
 
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Old 06-08-05, 09:32 AM
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Hi, thanks for responding.

The heater and pool are 4 yrs old. The natural gas pipe should be within specs as it worked OK the last 4 yrs. Is it possible to have a blockage?
The heater is about 50 feet from the gas meter at the side of the house.

However, shouldn't the gas valve at least try to open despite what pressure might be available? I recall hearing a destinctive 'click' when the valve opened (back when it was working properly). Now the click does not happen - as I couldn't see any voltage on the wires connected to the gas valve coming from the controller card.

Thanks, Graham
 
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Old 06-08-05, 04:02 PM
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check the hot surface igniter, disconnect from connectors first. using your ohm meter , should zero out when you connect one lead on your meter to one wire and one lead to the other , of the igniter, if no conunity, replace it . if you have continunity , check the hose going to your air switch , check the switch itself, n.o. when the fan comes it should close completing the circuit, [ hot surface igniter must be good . ]



steve
 
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Old 06-09-05, 03:45 PM
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The spark ignition starter was 56 ohms (must be OK).

The blower switch closed when the fan came on (must be OK)

I noticed the Fenwal auto ignition system. Is this an assembly that can cause this type of problem?

Graham
 
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Old 06-09-05, 07:15 PM
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yes the ignition control can be the the problem, but first go back to the hot surface ignighter should zero out when connected to ohm meter if not its BAD



steve
 
  #7  
Old 06-10-05, 06:55 AM
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Hot surface igniter - I measured 56 ohms on the igniter - not quite zero but certainly not open connection. Is 56 ohms OK?
Are there any voltage check points on the ignition control?

I have the schematic diagram but not a lot of voltages are mentioned.

BTW, the gas installed left a tag inside that mentioned the diameter of the gas pipe -> 1 + 3/4.

I noticed Laars has a 5 yr. warrany on these heaters. (It's only 4yrs old - so I may be able to get parts under warr.)

Graham
 
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Old 06-10-05, 08:58 AM
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Originally Posted by gprentice
Is 56 ohms OK?

Most HSI (Hot Surface Igniter) Devices test normally in the 37-70 Ohm range, at ambient temp. Do not test warm or hot as reading will not be accurate.
Are you getting Voltage to the HSI? did you test their leads while ignition sequence is starting up? (should be in the 120v AC range). If you are, and your HSI is testing good you should move on to the next step. Check for output to the gas valve 24-28 volts AC is common.When testing, make sure to unplug the leads from the valve in case it is shorting internally! They will apply power to the Gas valve after all other ignition module sequences are completed and satisfied. If you have no output before it shuts down and throws the error then most likely it is the relay inside the Ignition Module at fault. and the entire module is to be replaced (you should never attempt to replace any components inside any control parts PLEASE) If for some chance you DO have power out to the Gas valve, but it won't open then you know what's next. Since you stated you turned OFF the gas for testing I must congratulate you on using common sense!!!

As far as your service call last year and recalling the same individual out Beware.... CobWebs were and are a major no fire problem with any unit with a Pilot! HSI's, other than being cracked or broken heat up to 2900 deg F and I've yet to see a spider web that would keep that from happening. most likely you had an Intermitent module all along.

The 5 yr Warranty you are refering to is for the case of the heater none of the control parts share in that . When your unit was built a 2 yr parts and labor on system parts was offered (Sorry)
 

Last edited by poolspapro_com; 06-10-05 at 09:52 AM.
  #9  
Old 06-10-05, 10:50 AM
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The case is warranted for 5yrs - but NOT the electronics - I guess that is what 'limited' means.

Yes, I think is was a good idea to turn OFF the gas before troubleshooting. Don't want to get blowd up.

I'm all for having qualified service techs do their good work, but after the last guy, I thought I would be an informed consumer and troubleshoot it myself as far as I could. (I've fixed a lot of electronic devices over the years as I spent 15 years with Honeywell as a field tech.)

You don't have to worry about me testing the HSI hot because the heater doesn't work.

I earlier tested for voltage across the leads going to the gas valve and saw zero volts through all stages.

I'll make the final checks tonight and post the results - so far I'm guessing the relay in the ignition module is the culpret. I saw the module on a parts web site for about $200US. (pretty close to last year's service call).

Thanks very much everyone for your help.

Graham
 
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Old 06-10-05, 04:00 PM
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if you don't have an owners manual or repair, diagnostics chart, your still stabbing in the dark somewhat, go to your local pool supply an ask them for this valuable information.

steve
 
  #11  
Old 06-11-05, 08:08 AM
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It must be the Ignition Control Module.

There is 0.4VAC constant across the IGN terminals (should be between 60-120VAC)

I will order the replacement module - thanks again to all.

Graham
 
  #12  
Old 06-15-05, 05:41 PM
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Well, good thing I didn't order the ignition control board.

Turned out to be the hi limit sw shorting out to GND.

Thanks to Richard from PoolandSPA for the extra persistance. The sensors metered out OK but there was a bit of corrosion and they were shorting out to GND - lowering the voltage from 28VAC down to 2VAC.

Removed the sensors from their housing and the gas valve got proper 28VAC upon heater on mode.

Thanks again to all!

Graham
 
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Old 06-15-05, 06:31 PM
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Graham,

You did all the Work! I didn't even have to break a sweat for a change. Glad to have helped.
 
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Old 11-21-07, 06:50 PM
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Same issues different heater

WOW, I'm amazed at the wealth of knowledge on here!
Very good stuff.

But now a new problem ...
We have a Laars lx400 and spent over $1000 in parts so far in the last year (a little at a time...).
So far, we've replaced the Ext Switch, the blower switch, the heat sensor, flame sensor, HSI (twice), the ICM and the whole display and board on top of the unit. ( I don't give up easy )

Most recently (today) we replaced the entire control board and display. This solved our gas valve problem not opening. Woo hoo!, but we still don't have ignition. 2 weeks ago we replaced the ICM but didn't get fire because we didn't have any gas (but now I think of it, we never did test the ignitor since we figured out we weren't getting any gas).

What else can prevent voltage from firing the HSI? We tried 2 ignitors which Ohmed good, 2 ICM units, and still no fire. From the power block, we're getting 120VAC but from the ICM we get nothing. No power or ground from the IGN terminal. I have to belive this is going to be so simple, I'm going to feel stupid for even asking, but I'm having a real brain fart. (we also checked continuity on all the wires, they're ok too.)

Any help is VERY appreciated!!!
 
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