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Laarx LX Pool/Spa water heater runs for an hour or so then errors with AGS

Laarx LX Pool/Spa water heater runs for an hour or so then errors with AGS


Old 01-21-13, 04:03 PM
Thread Starter
Join Date: Jan 2013
Location: USA
Posts: 2
Laarx LX Pool/Spa water heater runs for an hour or so then errors with AGS

1) Before anything is turned on a "Low Pressure" message flashes.
2) Spa can be turned on and from that cold start it seems to fire up and run for a while (approx. 50 minutes) then cuts off with AGS flashing.
3) With the AGS flashing the burners shut off and it blows cool air from the blower
4) If I cycle the Pool-Off-Spa switch to off and back to Spa(sometime I have to cycle it a few times) it will fire the burners again and continue for another 30-50 minutes erroring out again with the AGS.
5) I then turn the Spa off and once it finishes the delay it goes back to flashing the "Low Pressure" message.

FYI: I just replaced the Electronic Controller as the display was not fully working and the buttons at the bottom wouldn't work.
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Old 01-21-13, 11:01 PM
PJmax's Avatar
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Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 47,567
This is a small Laars unit......for a spa......not a pool ?
Can you leave me the model number.

AGS = automatic gas shutdown. Not terribly helpful. Several things can trigger it.
Low water flow/pressure
Low propane or nat. gas pressure
Dirty flame sensor.

In your case it sounds like the low pressure it's displaying is low water pressure. It could be an actual flow problem or it could be a pressure sense switch.
Old 01-21-13, 11:38 PM
Thread Starter
Join Date: Jan 2013
Location: USA
Posts: 2
Model is the LX400N

What I don't understand is what the Low Pressure message is measuring. The unit is not running and the pumps are not running, basically the system is "off" but the Low Pressure still blinks. So it seems weird that it would be water pressure if the pumps aren't running to create the pressure. I could see the gas pressure being an issue as it may be able to measure that constantly. It looks like the incoming gas line is 1 1/2 or 2" and gets reduced to 3/4 going into the heater. Not sure if that is the right size. No installation documentation left after the setup.

When you press the Spa button on the indoor controller everything kicks in and runs for 50 minutes or so(starting at a water temp of 56ish and turning off with the AGS error at around 98ish). If I cycle the heater through Pool - Off - Spa a couple times it enters the "Heating" mode once again for another 40 or 50 min. When I say "a couple times" pressing the button, it is because usually I can switch it to Off-Pool-Spa and it will run and the igniter glows red but you don't hear the "woosh" sound of the gas being fed to the burner and ignited. Thus the spa begins to cool down as the water circulates. After a couple rounds through it decides to fire up. So I'm not sure why runs that long before the AGS happens again. One would think that low water pressure or gas pressure would be recognized at the start and therefore not fire up at all. I monitor the pressure in the filter regularly and while a backwash or cleaning may be in order, it appears to have a "normal" pressure reading.
Old 01-22-13, 08:30 AM
todrut's Avatar
Join Date: Jun 2007
Location: USA
Posts: 1,212
Low pressure is for water flow only. If pump is off and heater on then it will show low pressure.
AGS error if there is fire before this message, either flame proving rod or fenwal ignition control is your problem. I can walk you through testing if you have volt meter and want to attempt it.

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