Noob Needs Help w/ Hot Water Baseboard Heat

Old 01-16-09, 08:47 AM
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Noob Needs Help w/ Hot Water Baseboard Heat

Just bought my first house, so there have been a lot of "first's" for me lately. My largest homeowner deficiency is in the area of my homes oil-fired, hot water boiler. Not sure of the year of installation, but I would estimate less than 7 years.

I currently have the main living level (2nd floor) set to 62 during the day, 68 in the evening, and 65 at night. The finished basement and bedrooms (3rd floor) all stay at around 62-64. I have three zones -- one for each level of the house, minus the finished attic.

Here are my questions:

- If the house, for example, was 60 degrees and I set the thermostat to 68, why does the boiler run and turn off before getting the room to temperature? I'm assuming that because this is not forced hot air, what matters is the temperature of the water in the system, and therefore the boiler will only kick on when it reaches a certain level. (Just checking..)

- My boilers water temperature is set to 170F, is this sufficient for NJ winters? If not, I'm unsure on how to adjust it, but I think I can search for that on the Peerless site.

- How long should it take for a room to get to temperature, assuming I have decent/average insulation? It seems that if I set the thermostat to 70, it goes up incredibly slowly (may even take a few days). I've had the system purged, and there is no banging, so I don't think air is the problem.

Many thanks for the advice! :P
Old 01-16-09, 10:15 AM
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I'm far from an expert but just got a new boiler installed so am a bit dangrerous with my newfound info. I have cast iron baseboards and i have the same recovery issue you do. Didnt change from new vs old boiler. When i get home from work and the setback goes from 66 to 67 degrees, it can take 2-3 hours for just that one degree. I guess you have the same 'situation' as me and will learn not to set back for too many degrees or else you never will recover. My installer told me never setback more than 2-3 degrees.

On the other hand, i've seen people on here that set to 60 and then 68 and it recovers in 30 minutes! So all our systems are different. I have a low mass boiler and i'm sure that's part of the difference

MY guess is 170 is right for your boiler. My old was set at min 160 max 180. But I'm not familiar with your type of boiler so i may be wrong.

Question: how long does it take to get from your 62 day to your 68 evening temp? Your last thought wasnt clear to me. Are you saying it takes days to get from 68 to 70 or from the 62 to 70?

I just ask because if it takes hours for you to get up to the 68, it probably pays you not to set back all the way to 62. Do you get any overshoot? ie it goes over 68? I know i had a problem when i jacked it up 5 degrees and it turned off, it would shoot up 2-3 degrees sometimes beyond that temp!

Now ill sit back and wait for the pros to chime in
Old 01-16-09, 04:10 PM
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When the boiler fires on a demand for heat, the water circulating pump will start running water through the pipes, and the burner will fire. The boiler water will probably heat up faster than the house. When the boiler water reaches IT's setpoint the BURNER will turn off, but the CIRCULATOR will continue to run if the demand from the thermostat is not satisfied, and until it is.

If the heat call is long enough, the boiler water will cool. When the water reaches the DIFFERENTIAL temperature of the limit control, the BURNER will fire again and re-heat the water.

This sequence will continue until the thermostat is satisfied.


The dial that you are reading 170 on... is that inside a gray box, about 4" x 6", with a Honeywell 'badge' on it? If so, that is your AQUASTAT and there is a 'bulb' inserted into the boiler that measures the water temperature. That silver dial with the temp markings engraved on it will turn. 170 is probably adequate. If you find that the boiler runs for extremely long times just to MAINTAIN the temperature in the home, you CAN increase that temp setting. I would say not to go over 190 though... remember that the higher that setting, the more fuel you will use. If you can heat the home with 170, leave it there. Don't be tempted to decrease it ... this can cause other problems with the boiler... you probably can go down as low as say 160 though... but ONLY if you know that the water returning to the boiler from the baseboards is above say 130 (playing it safe here...). If the water returning is too cold, you can have a condition known as 'flue gas condensation' where the flue gases actually will condense inside the boiler and the flue pipe and create an acidic brew that will eventually and ultimately EAT your boiler. You don't want that!


I can't imagine it taking DAYS to recover from a setback period! Something terribly wrong if that's the case.

What type of heat emitters are in the home? If they are copper tube with aluminum fins (aka 'fintube baseboard') and the fins have not been recently cleaned (most are NEVER cleaned!) the buildup of dust/lint/pet hair can seriously decrease the heat output of the baseboards. The baseboard covers snap off to reveal the heating element. Using a brush with long bristles, a vacuum cleaner, and whatever else you can think of to get between the fins, get as much of the dust and debris out of there as possible. Compressed air with a 'blow nozzle' works best, but is messy... if you have a compressor and want to use this method, keep the vacuum cleaner running and use 'bursts' from the nozzle... suck up the dust as soon as it comes out...

If there is wall to wall carpeting in the home, there should be around 2" of clearance between the carpeting and the bottom of the baseboards. Less than that and there won't be enough airflow through the element to produce the rated heat output. Try not to block the baseboards with draperies and heavy furniture. (obviously you need furniture! but leave a little space for airflow if you can)

My general thermostat setback rule is 1/2 per hour of setback, and not less than a 5 hour setback period. Any more than that and it seems that it takes as much (if not MORE) energy to recover from that setback. Homes with HOT AIR heat can generally setback farther, and will recover faster... the amount of savings from a setback schedule is highly dependent on recovery time. If you setback say 6 for 6 hours, and it takes 4 hours to recover, what have you really saved? not much... if anything... there are many naysayers out there that will dispute this, but I have tested for the past 4 years in MY home and found this to be MY truth. Your mileage may vary.

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