Carpenter with an HVAC question re Weil mcclain oil burner - Contractor Talk - Professional Construction and Remodeling Forum

Whiteshadow · 07-01-2009, 11:35 PM

Hey all I need some assistance with an issue I have next to zero knowledge about. I have a Weil mclain home oil burner, two zone (upstairs and downstairs), with no external hot water tank. The problem I have is that the burner makes enough hot water to last about 45 seconds if I run straight hot water from the kitchen sink. The hot water IS adequately hot for about 30 seconds but then begins to quickly cool down. Also, it takes the burner a good 2 minutes to kick on after the hot water has run nearly cold. The burner is about 15 years old, and the high/low thermostat is set at 180/120. The model number on the boiler says "68 boiler". Is this the proper setting for the high/low, and would raising tho low prevent the water from running cool so quickly and also allow the burner to kick back on before the water runs cold? Please let me know if u guys have any info that would be of help! Showers have been a nightmare for some time for obvious reasons!

beenthere · 07-02-2009, 05:44 AM

Yep. Your low temp is too low.

Should be a min of 140.

Does your piping have a tempering valve on it?

NickTech · 07-02-2009, 09:33 AM

was it working well in the past and then all of a sudden this happened, or are you new to the home? if it was working well before then the problem it could be a variety of things. first compare the actual water temp to the a-stat settings. run water until it kicks on, the temp should be what the cut in is set for. shut the water off and watch until the burner stops, this should be the cut out setting. you mentioned the unit wont kick in until 2 min after the water gets cold, this suggests either the a stat in not working right or the internal watercoil is dirty and not exchanging heat addequately. it could be internally crudded up, or externally caked up. hows your water out there? 120 is kind of low for boiler temp, 140-160 is the norm.
suggestion:
in the meantime electrically disconnect the cirulators (assuming its FHW) and about 5-10 min before your hellish shower turn the heating t sat up, the hi limit a stat should regulate the water temp. like beenthere mentioned check for a tempering valve. hot and cold coming in, warm coming out. the valve could be clogged or malfuntioning. if this doesnt do it, it sound like dirty water coils. good luck

Whiteshadow · 07-02-2009, 11:22 PM

Thanks for the quick response guys. I will raise the low temp and see if this is a quick fix. Im not sure if the system has a tempering valve but i will find out and check it if so. I will go down the line with the troubleshooting that you guys recommended and let you know what i come up with. To answer your questions, this system is at my parents house and to the best of my knowledge this has been a problem that has become increasingly worse over the past few years, and not something that happened all of a sudden. But i do know my father messed with the high and low settings in what i believe was an attempt to get better efficiency out of the unit and it seems to me that it was all down hill from there. If it is a problem of the internal watercoil being caked up, is this something i can tackle on my own???? Thx again for the help!

beenthere · 07-03-2009, 05:53 AM

The chemicals for cleaning a coil. Are harsh, and if applied incorrectly. Will completely clog the coil.

Your call on how brave you want to be, as far as trying to cook it out yourself.