LJ or LD? Natural gas?

The rated minimum is 5.5"WC. You may also have a stuck internal bypass. How are you measuring the rise? Pete's plug with thermometer as designed?

Repair Guy:

LJ
Natural Gas
Manual says Supply Pressure minimum is 5.5" WC and Manifold Pressure ("Nominal") is 4" WC.
Measuring outlet temp with thermometer in Pete's plug on header.

Puget Sound Energy technician report:
"Checked gas pressure @ pool boiler. Found 4" WC while running. This is adequate according to manufacturer. To further check out problem w/ boiler, contact outside service co. regarding temp rise, etc. I ran boiler for a few minutes and it was running OK @ 4" at this time."

I get around 1 degree per hour increase in water temp when bringing the pool (32,000 gal.) up to temp. I'm mainly concerned with potential damage to the heater if I'm not getting the proper temp rise across the header and, to a lesser extent, that I may be wasting gas if the heater is running too inefficiently.

I'm still wondering about the potential damage to the heater if the temperature rise is below the specified minimum.
Any more ideas on this?

where are you measuring from?

Scott

The built in bypass is designed to handle up to 125gpms. Adding a manual bypass is only reccommended if your flow exceeds 125gpms. If you are running the manual bypass wide open, you are probably not passing enough water through the heat exchanger. Try closing the manual bypass and checking the temperture.

A rule of thumb that we have used to adjust a manual bypass with a system that exceeds the 125 gpm rate or if we are doing an infloor cleaning system is:
Check filter gauge pressure with bypass closed.
Open bypass untill you achieve a 2 psi pressure reduction.

Ran a test this AM. With the bypass fully closed and the heater running for several minutes, the temperature rise was 31 degrees F. This is the difference between a thermometer reading at the Pete's plug location on the heater (downstream of the heater manifold) and the temperature reading on the digital display of the heater (incoming water temp). Prior to turning on the heater, both readings were the same.

This is 2 degrees below the minimum specified in the manual. Is this a potential problem?

What is your elevation above sea level?

Check if all baffles are in place.

Mike-

My elevation is 500 ft.
What baffles do you mean?

Mike-

Never mind about the baffles. I figured that out from my heater manual and drawings. As far as I know, all baffles are in place, as received.

3 Winters ago, I had to replace one of the headers (cracked from freezing), but I didn't remove or replace any of the baffles. I could take the top end apart again and double-check that all parts are properly in place. Is the problem serious enough to warrant this?

It may not be a big problem but bothers me as to why. The baffles are there to hold the heat on the heat exchanger just a little longer, increasing the efficiency a little. I'm just reaching for possibilities.

Have you looked on the bottom to see all burners running with nice blue flames?

The gas pressure on low-nox heaters is critical, but your LJ has more of a fudge factor. Try bumping it up to 4.5 inches.

Another thought: the wrong spring may be on the internal bypass. They are color coded for each size heater. A 400,000 is black.

I checked the burners: all were running with nice blue flames.

I'll maybe get the gas company to come out again and check/increase the gas pressure.

Thanks for your help.