Boiler only stays on for a few minutes, what could it be?
Hi there, My friend has a Burnham V904 boiler, and the burner was converted from burning oil to gas last fall, and since it was put into summer water-heating-only mode, the boiler only kicks on for a few minutes – not enough time to make hot water. So now the aquastat on the hot water…
Hi there,
My friend has a Burnham V904 boiler, and the burner was converted from burning oil to gas last fall, and since it was put into summer water-heating-only mode, the boiler only kicks on for a few minutes – not enough time to make hot water. So now the aquastat on the hot water tank is set at 140 (like it normally is), and the aquastat on the boiler at 212 (supposedly it should be set to 190), so that it will stay on long enough to make hot water. So now there is steam running through the heating pipes near the boiler and it seems very inefficient.
A guy looked at it and advised to replace the aquastat, which did nothing. I suspected that maybe the water pump wasn’t working at full strength, and thus the boiler was clicking off because the heated water was not being moved out of the boiler quick enough. However, my friend says that this is unlikely, since the boiler apparently behaved the same way when the backup pump was used. Any ideas? Is this normal? It’s only hot in the bathroom nearest the boiler and in the unit above it, do they just have to endure?
Thanks in advance!
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Thanks very much for your replies guys, I’ll take another look at the boiler later this week when I get a chance.
Summer water heating mode should be a simple circuit. Boiler cut in at 140 deg and pump on. Boiler cut out at 190 and pump off. Make sure these things are happening in the right sequence. Check your relays if applicable.
-SteamMan
Also, not 100% clear from your explanation of the set-up, but if the boiler has a coil and the coil is very old, it could be covered with sediment which cuts down on the transfer of heat from the boiler water to that inside the coil. I went through a similar problem… replaced the aquastat, then the mixing valve and still the problem persisted. Finally replaced the coil and voila, problem solved!
Most aquastats we see (including the ones I use) are made by Honeywell and have nearly a 30-degree range of error (plus or minus 15 degrees from their setting).
That 212 setting is the problem. You’re boiling water and making steam unnecessarily. That’s all loss.
Set the aquastat to 180 and then figure out why that’s not getting it done, if that’s the case. I agree with your diagnosis there may be a flow issue especially if you’re using a Super-Stor indirect water heater or similar. There is too much resistance to flow in those tanks for traditional pumps. It gets complicated.
While we’re at it, converting small oil boilers by replacing the burner with a gas-firing one is never a great idea. Make sure some alteration to the flue was made or your friend could be set up for a carbon monoxide problem.
Me:
http://www.GatewayPlumbing.com
Try cleaning or replacing the low water cut-off sensor. When dirty or malfunctioning this device may false read a low water situation and shut down the boiler. These units are designed to self test at the start of a heating cycle and that may explain why the boiler only runs a minute or two before shutting down.
Art Malfitano
http://www.amconsultations.com
Possibly a bad mixing valve??