Lochinvar Burner meltdown

[gman994]

I have a Lochinvar CH1800 hot water heating boiler that I've serviced for the past 6 yrs. I was onsite today on an unrelated mission when I noticed it was having a hard time igniting. Disassembled and pulled the burner panel out to inspect it. Of the 20 burners, 8 of them were totally incinerated, 4 were severely cracked, and 8 were okay (in the area of stgs 3 and 4). a similar meltdown occurred 2 yrs ago, with which I was involved in the repair and burner setup. The factory says that the burners are overfired. I just had those out 2 mos ago, and there no visible sign that any of these burners were getting too hot. Anybody ever had this problem ? The unit is an early 90's vintage.

[chuckcrj]

Possibly the heat exchanger getting plugged. Look at the TOP side of the HX.

Another possibility is the entering water temp is too low and the HX is condensing and raining on the burners.

[Zeke XI]

Flue gas condensation. Had a School with Geo that couldn't heat. Contractor decided to add a shell and tube HX to the Lochinvar pool boiler to help heat up the building loop. Looked like someone threw a hand grenade in it.

[fitzyfitta]

X2 on the low water temp causing condensation issues. Seen it many times.

[gmanss454]

I agree about checking the heat exchanger for dirt and corrosion. Also check for air leaks around the burner compartment door as the burner compartment is under a positive pressure. Also when checking your manifold gas pressure be sure to take into account the static pressure of the burner compartment. I service a apartment building with 4 of these boilers for heating.

[gman994]

Well, replaced the burners yesterday. Brushed and blew out the heat exchanger, but it really didn't appear dirty enough to cause problems. The condensation theory, though solid, isn't a factor in this system. The hot water loop is pretty short and it heats up pretty quick. This is a 4 stg machine that I try to maintain 170 deg supply water, the temp rise thru boiler is adequate. Are you sure about compensating for the static in combustion chamber? The manual doesn't allude to that. I'm more concerned about the draft. It is very unstable even after it heats up, sometimes remaining at 0 before going to -.03 then 0 then -.05 then 0 .... and so on. I'm measuring this in the flue 16" above boiler. i'm thinking about adding an additional 6' to the flue.

[Betabass]

Check the boilers design delta t,


Beta

[CityHvac]

Check the boiler room combustion/fresh air

[HvAckid82]

From experience, sounds like its being over fired. We have a meat plant that we have 13 of their copper fin boilers and on average we replace 4 tubes per water heater. Unfortunately we have to over fire them to keep up with their load. They are replacing all of the boilers shortly with condensing water heaters.

[n-e-w Jerz!]

Interesting. Just wondering from anyone with extensive hydronic experience if repiping these boilers with a primary/secondary loop would help with low water temp issues? Might be talking out of my rear here.....

[HvAckid82]

If you want to see if you have condensation issues just look for green streaks all ove the heat exchanger. To have 4 burner tubes severely cracked over 6 yrs is not bad at all. Just wear and tear.

[gravity]

I learned from a wiseman how to correct this problem. I recommend taking Jim Davis' class.

[HvAckid82]

What is your combustion readings? What's your inlet gas pressure and manifold readings, do you have a barometric damper? The tubes will fail, only a matter of time. If you get a hairline crack it will only get worse. Those tubes are such a thin stai less material. Also what is your temp rise during each stage?