Zone too warm - Oil fired - HW base board and Domestic hot water

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Old 12-01-08, 01:03 PM
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Zone too warm - Oil fired - HW base board and Domestic hot water

I have an oil fired furnace that provides one zone of hot water baseboard heat and the domestic hot water service. The furnace has a Honeywell Triple Aquastat - Relay Type L8124A,C L8151A and the hi-low cutoffs are set at 180 and 160.

I have a very small home and it's always too warm, no matter what the thermostat is set at. It appears that the burner runs once or twice an hour to maintain the domestic hot water temp. The radiators are always warm as though the circulating pump is running whether or not the thermostat is calling for heat. This seems to be quite a waste of energy. Any suggestions on next steps to help define the problem and then address the issue?

Another thing I would like to be able to do, is to turn off the domestic hot water portion of the system when I am going to be away from the cabin for any length of time. It seems a waste to burn fuel to keep water hot, that no one is going to use. Any suggestions on how to do this?
 
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Old 12-01-08, 02:07 PM
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If your home only has one zone and the circulator and triple aquastat control are OK then the culprit is most likely a faulty flow control valve which is allowing hot water to migrate past the flow valve and gravity feeding the radiators. An easy way to check this is to close a valve somewhere in the heating loop ( Anywhere on the supply or return heat line) and see if this cures the problem, if it does you will need to replace the flow control valve which is usually mounted on the supply line somewhere in your boiler room. If you take pics of your boiler and boiler room and post them it should be easy to point out the flow control valve.

As far as the domestic hot water question, don't turn anything off just turn the low limit on the aquastat all the way down (Around 100 degrees) when you aren't using the cabin.
 
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Old 12-01-08, 03:24 PM
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faulty flow control valve
or a non-existent one ...

I wouldn't close any valves and let the boiler fire though ... I don't think the circ will be too happy about being dead-headed...

Willy, the flow control valve prevents 'gravity' or 'convection' or 'ghost' flow in the pipes. Even when the system is not running, there can be flow from a hot boiler into the system. The hot water is less dense, and 'floats' up the pipes, pushing the cooler water back to the boiler ... heating the house, and cooling the boiler... both are exactly what you don't want, obviously...

Can you set up a free account on Image hosting, free photo sharing & video sharing at Photobucket and upload some pics of the system ? Provide a link here so we can look and see if you have a flow valve...
 
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Old 12-01-08, 06:21 PM
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"I wouldn't close any valves and let the boiler fire though ... I don't think the circ will be too happy about being dead-headed..."

Oops, Good Point. If the house is overheating and the temperature in the house is above what the thermostat is set at there won't be a call for heat and the circulator won't run but just to be safe, turn down the thermostat before closing any valves.
 
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Old 12-02-08, 09:01 AM
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speaking as a non hvac guy, if you have a properly functioning zone valve, would not that be closed when there is no call for heat, and if it is closed, how can there be flow through that loop? i ask because the way my system is set up, the zone valve is located just before the common return line and acts like an open/close faucet. of course, my system has no bypass allowing some mixing of supply and return water to prevent shock to the sytem. if your system has no bypass, i do not see how water can constantly flow through the loop. do you have a correctly functioning zone valve?
 
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Old 12-02-08, 11:06 AM
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If you only have 1 heating zone I don't know why the installer used a zone valve instead of a flow control valve but zone valves can go bad too and hot water can gravity past them as well. The upside of using zone valves is that one circulator can be used to heat multiple heating zones but since your home only has 1 zone I don't know why someone would go through the trouble of purchasing and wiring a transformer and zone valve unless the supply and return lines in the heating system were stubbed out for provisional heating zones. (In the event that an addition was added on to the house)
 
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Old 12-02-08, 04:52 PM
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I'm confused... I didn't think Willy had any zone valves ?

You _could_ use a zone valve in that fashion, but every bit of complexity that you design into something, cuts down the 'mtbf' (mean time between failures) of the system. KISS (Keep It Simple Simon).

Bleeve itornot, it is possible to have two way flow in one pipe. Steam systems do it all the time... hot water can do the same thing, just not to the extreme that steam can. Yes, in ONE PIPE, hot water can flow on the top in one direction, and cool water can flow back along the bottom.
 
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Old 12-03-08, 07:00 AM
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probably my confusion. when i read the post i thought he had a separate water tank for hot water, as i did. if his is integral he wold not have a zone valve. my mistake.
 
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