Latest Discussions : HVAC


12:15PM | 12/11/05
Member Since: 12/10/05
2 lifetime posts
I have an oil fired hydronic heating system in my 1600 sq foot, 70+ year old house in Annapolis, MD (moderate climate, hot summers, some snow in the winter). I would classify the insulation as resaonable. A good portion of it has been replaced with pink fiberglass and I'm eliminating as many drafts as I can (replacing windows, weather stripping, new insulation, etc). The boiler is about 20 years old and am considering replacing it. The same boiler also supplies domestic hot water. We've only lived here one year so I don't have much history with this particular system. Any advice or answers to these questions are appreciated.

1) It makes a loud noise and vibration when it shuts off. It seems to be getting worse. Is this normal or a bad sign?

2) It seems to burn about 150 gallons of oil per month during heating season which seems high to me. Does anyone have any rules of thumb on how much oil I should be burning or how boiler efficiency degrades over time? This would help determine how much of a decrease in oil consumption I could expect if I replace it and what the payback period would be.

3) There seems to be a big variation in temperature from the first floor to the second floor. I'd like to separate them into 2 zones. All the pipes lead to the basement so the plumbing won't be that difficult. I can't imagine the control system being all that complicated either but is it a standard type of thing or would it be completely custom to run both zones off one boiler?

4) I am also considering adding radiant floor heating in one of the bathrooms when I redo it. I'd like to embed the tuding right in the tile floor when I level it. According to the thermometer on the boiler, it runs at about 190 degrees F which I believe is too hot for that type of radiant flooring. Does anyone have any experience tying these two kinds of systems together.

Thanks in advance...

The Sail Boffin

Annapolis, MD


05:25PM | 12/11/05
Member Since: 12/10/05
2 lifetime posts
Thanks for the response. I'll get the oil company out to inspect it. One other question about the flue, there is an exposed section between the boiler and the wall that has a "T" with a weighted flapper in it which doesn't want to stay closed. What does that flapper do?

29000 btu/hr (I think this is the correct number 150 gal per month/720 hours per month*138,000 btu/gal) sounds high to me. Correct me if this isn't right, assuming 85% efficiency, specific heat of 0.018 BTU/ft^3 * deg F and 8 foot ceilings, that amount of energy would be able to raise the temperature in the house 106 degrees or heat the volume of air in the house from the average MD winter temperature of 40 deg F to the interior temperature of 70 deg F 3.5 times.

Is it possible to quantify the efficiency by measuring the exhaust gas temperature?

The house has radiators, not baseboard and I have tried turning them down. The problem is the temperature extremes up stairs are worse than downstairs. Downstairs ranges from 69 deg F to 72 deg F. If I turn the radiators upstairs up, it becomes like a sauna when they are on. If I turn them down, it gets too cold before the heat comes back on.

Separating the piping into zones (and the hydronic heating subloop for that matter) are fairly straightforward. The issue as I see it is the control circuitry. It's easy to wire the zone valves to come open with a thermostat but the boiler and the circulating pump still need to come on. It's that control loop that I'd like to purchase and not build. I guess a couple of simple solenoids or transistors would do the job. Is that how something like that would typically be done?

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