Help needed - Replacement pool/spa heater

[Geeper]

Had a pool put in about 2.5 yrs ago. Builder put in a Laars LT400 heater for pool/spa. At the time, I figured this was a good heater having had an older Teledyne heater heating a spa only at another house I owned with no issues. Have consistently had problems with the spa heating to full temp. Have been back and forth with the pool company and gas utility who each blame each other, but I have been told my problem is due to the "safety" design of the heater requiring at least 5 water columns of gas pressure to the heater. Have had it measured a few times and we are getting over 5 water columns until the heater jets kick on, then it dips just below 5. Seems the computer in the heater then gets freaked and shuts the heater off causing only a partial heat of the spa. Wierd thing is that this happens most, but not all, of the time. Sometimes it fires right up to a toasty 103-104 degrees water temp, other times, kicks off at 98. Tonight it go to 101, then settled at 99.

Based on conversations with my pool guy, I really don't think it is a malfunction of the heater itself, but a problem due to the "safety" features deigned into the unit

That all being said, I am looking into a replacement heater due to our gas pressure issue and looking for recommendations. We use an Aqualogic PS-8 control system with salt cell, Jandy 60 sq ft DE filter and Jandy Pro Stealth pump and valves.

Thanks
Geep

[mas985]

As you said it may not be the heater but it could be the supply line. How far is the heater from the meter and what size line is it? With a 400k BTU heater, you probably need at least a 1" gas supply line. Simply replacing the heater may not solve your problem if the supply line is too small.

Also, measuring the pressure with the heater off does not give you an accurate reading as like with water, gas loses pressure as it moves through the pipes. Since it dips when turned on, it would seem there is a restriction up stream from the heater which would indicate the supply line again.

Another thing to check is the gas filter screen in the heater. When mine was installed, there was a small amount of dirt in the gas line which plugged up the screen. Once it was cleaned it worked perfect.

[Geeper]

Mark,

Thanks for your reply. We have a 1.5" line running just under 50 feet. My pool guys stated he would not have installed this particular heater if it was up to him and that he would have installed a larger line from the meter. In the end, neither of these really matter since our line "should" be big enough and we already have the heater. Replacing the supply line is not an option as it would require digging up my yard, destroying me deck, etc which we are not looking to do.

I'm looking for recommendations on heaters that can operate on 4" wc pressure that I have consistently. Due to the features of the LT Laars unit I have, it will not.

I'll check the screen issue, but in the end, I may need a different heater. Call it poor design of the system on the builders part, restrictive design constraints by the heater mfr, whatever. In any event, I have just under 5" sc pressure to work with and need to find a way to make it work. Otherwise I have a $2500 boat anchor waiting to happen.

[mas985]

I assume that you also have a big enough gas meter since the gas company was of no help. The meter should be large enough to handle the heater plus any other gas appliance that may be used as the same time.

Although I am not completely sure, I would expect that all 400k BTU heaters to require the same the gas pressure since the flow rates are the same. One alternative is to go with a lower BTU rating which would require less pressure. It just means longer warm up times.

[msm859]

Your 1.5" gas line is plenty big. Are you having problems when you have other gas appliances running? Maybe it is your meter size and/or it is having some restrictions.

[Geeper]

No problems with anything else, Had the gas meter "upgraded" when we got the pool, have gas heat and a gas cooktop in the house and a large gas grill in the backyard.

The issue is the pressure being right at and under 5"wc. My pool guy doesn't like this particular heater b/c it is so finicky with the input pressure, so I'm looking for alternatives.