Boiler Max/Min Setting Questions

[Dave Gallant]

Hello:

When I purchased my new boiler 18 months ago for my hot water baseboards and domestic use, the service guy wrote "summer" and "winter" settings on the back of the Aquastat cover. He basically said that I should set it at 140LO/160HI for the summer when I don't need baseboard heat and then up it to 170LO/190HI for the coldest winter months when the heat is really needed for the baseboards.

Speaking with family and friends with identical requirements (baseboards and domestic), none of them seem to make the temp change. Some had never heard of making such changes, while others shrugged them off.

Questions: Is this a common practice? Is there any benefit to me actually increasing the temp? Presumably, this shortens the cycling time when the system calls for heat, but would use more oil to keep the higher temp - so is there any financial benefit? Any other reason for doing this?

Thanks for the help!

Dave

[Handi]

I've asked this question before myself Dave and received a variety of responses.

What it boils down to (pun intended) is your climate. We live in Atlantic Canada and some days in February it can get as cold as -28 C. Last winter I played with the settings on our boiler, reducing the max temperature because our heating system boiler doubles as our domestic hot water heater. The high water temperatures were causing the occassional scalding.

After lowering the max temperature to 150/160 (min/max) I discovered the boiler had to run longer and I couldn't seem to get the room temperature comfortable.

Today after reading your posting I noticed that our boiler settings were set to 160/170 and I adjusted it up to 160/180. Perhaps the furnace will now run less now but I'll have to keep an eye on the domestic hot water temperature.

Y'know what I really should do is add a thermostatically controlled water mixer to our domestic hot water system. This would safely insure that it doesn't reach dangerous levels.

later...

Handi

[HA HA Budys Here]

This may have been suggested in order to supply ample domestic hot water during peak winter useage when the boiler is "just barely large enough", given that you were given this advice unsolicited and not as a solution for low heat / hot water supply problems.

You could try not making the upward adjustment during the coldest winter months and see if you notice any shortage of hot water.

My old oil burner/hot water baseboard system used to run constantly (Not the burner, just the circulator pump) during cold snaps, not because the boiler was undersized but because there wasn't enough linear baseboard to provide the needed BTUs for the coldest of cold snaps. That's somewhat correctable by increasing the boiler temperature.

[John Barry]

Hi, Dave.

Probably not, unless you use a setback thermostat, and your recovery rate is too low. Excepting the ability to recover, the optimum aquastat setting is such that, in the coldest hour of the year, the pump runs 60.0 minutes. Additionally, the burner nozzle size would be such that for the same hour the burner was running for 60 minutes, and just holding temp.

Slower is better.

John