New Pool heater woes

[Qwaxalot]

The 4.5" WC with the heater fired is right at the edge for the current generation of Legacy heaters. That said it should work. Is it possible that some other large appliance in the house might be running from time to time? And what size is the house gas meter? From what's been said so far it sounds as if everything in your installation is being pushed right to the limit.

In those kinds of situation even something as innocuous as a booster pump kicking in can cause a problem.

 

[swimcmp]

Not sure but 4.5 fired isn't enough, gas should maintain 5.5 minimum

 

[evanwellens]

I don't understand. The pressure says 5-10 , it doesn't say when fired. I'd imagine any line that puts out 5-10 fired would be much higher not fired ( then one would probably need a regulator ) and really pushing the legal pressure limit of dwelings. According to the gas util now we are at the limit , + a 1/2 turn ;-) So far things are working , but the need isn't really there at the moment so we just test and turn it off shortly afterward as the water is 90 and the air temp higher. Then again I'm far from an expert on the matter. I do think it should be sufficient since our last heater was a laars lite 2 400K ,10 years old and no problems. I'm hoping things keep working , not sure what I can do to up the pressure any higher. It doesn't seem to be an option unless we need to run a new 400 ft line, which is not an option.

Who knows perhaps the water heater was kickin in at the same time, wouldn't that be a funny cause. Thanks again guys for all the input , it's amazing the wealth of knowledge on this forum !!!