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phreaq 11-20-2007 07:12 AM

Thermostats for Oil Furnaces?
Hey folks,

Last Spring I changed my thermostat to one of the wireless models that the hydro company can dial into and lower the setting on those hot days during peak hours. I can honestly say I had my A/C on for only 3 hours total for the entire season (you gotta loves trees around the house), so it’s not crucial for me to have.

It’s hard to compare exactly, but the new thermostat ‘behaves’ differently than the last one I had hooked up, as it seems to cycle more often. It’s almost as if it comes on every 10 mins and stays on as long as it needs to raise the temperature to the set temp. This can range from a few mins to several more, obviously depending on the outside temperature.

The new thermostat does have an electric/gas/oil setting, and I have it set to oil since that is my source. (actually, I had to ask the installer how to do it, as it was not documented in the instructions).

My question is; are there thermostats out there that are better for oil furnaces?

I believe the electric/gas/oil setting adjusts the ‘swing’ setting, but are the swing variances standard from one thermostat to another?

thanks in advance,


glennjanie 11-20-2007 10:12 AM

Hello Steve:
You need the installer to come back and calibrate the thermostat. If you can't get him back, I can tell you how to do it but it takes an ammeter and most of us don't own one. Short cycling is not good for the furnace.
Please let us know how it goes for you and if we can be of further help.

phreaq 11-21-2007 07:03 AM

Thanks Glenn,

The installer is loooong gone. He came to install it in the early spring, when a sense of 'I'm doing something good for the enviroment' flooded over me, and as such i wasn't able to 'test' the heating side of things.

Now I wouldn't call it a short cycle per se, it just is different, and I'm not sure it's a good or bad different ;)

glennjanie 11-21-2007 09:53 AM

Hi Steve:
Your thermostat is fine for the use intended. If it is a digital thermostat it will be much more sensitive than the older ones. The old ones had a 3* window; starting at 1 1/2* below the set temp and kicking off at 1 1/2* above, whereas the digital wants to nail the temp exactly to the selected temp, therefore, you get more activity with the digital.

Hube 11-22-2007 07:11 AM

The "short cycling" that you are describing may not be entirely the T stats fault at all. It may be your burner nozzle is too large and this will bring the temp up quickly because of "overfiring" .....
if your burner has a, say....65 nozzle, try a .50 in it and compare the run times. A good burner run time should be perhaps approx 6-8 minutes at outside temperatures a few degrees above design temp for your local, and occur only 1 or 2 times in an hour.

phreaq 11-22-2007 10:54 AM

Thanks for the comments Hube!

I had the furnace serviced last fall, whic included a new nozzle. I have used the old thermostat with the new nozzle, so that part is consistant.

When the installer put the new nozzle in, he referred to it as being 75L/hr, I think? not sure if that's correct or if that's how you measure the flow (I'm in Canada, so we'd have a slightly different measuring method than the US, perhaps, like mpg vs L/100km)

phreaq 11-22-2007 10:54 AM

Actually that doesn't sound right at all, perhaps it's 7.5L/hr?

Hube 11-22-2007 03:46 PM

Well,since you say it worked ok before with the old T'stat, then the current nozzle size should be ok.
I also live in Canada (Central Ont, Owen Sound area.)
I have an oil furnace too. I have been in Hvac for 50 years(now retired)

Most popular make of nozzle is a Delevan. The typical residential sizes are; .50, ,65, .75, 1.0
They are measured in GPH (gallons per hour) and more than likely that measure is in U.S. measure.(80 % of ours)
Actually in the last couple of weeks, I too have been interested in Hydro One's
offer to install a new T' stat so that they can control the setting to help out when power is near a shortage period.
Most popular models of t'stats have an adjustable "cycles per hour setting" (cph) The older ones also had an "anticipator" which when set properly could control any 'overide' to the temp setting.

Most t'stats have several types of anticipators, but the most common are the "fixed" and the "variable" The "variable is generally set to give a 3 minute burner 'on' cycle. An ammeter is used to adjust this cycle setting. Oil setting is usually .20 amperes.

Since I do not know what type the Hydro put for you it is hard to say if you have a cph adjustment or not. You would be BEST to get more info on this stat from Hydro and see if you can get it set up to give you longer burner cycles without getting more than .5 to 1 max degree of over-ride.
Please let us know how you make out.

phreaq 12-06-2007 11:43 AM

Hey folks,

Just thought I'd give a quick update on my issue.

The other night the thermostat was really getting under my skin. It was running the 'night' program, which is a temperature setting of 18 deg C, with the room temperature being 21 deg C (it just switched into night mode, so the house was still warm). Well, the furnace would turn on for 3 – 4 mins, and then turn off. After another 3 – 4 mins of no activity, the furnace turned back on again, the room still being 21. No idea why.

So the next morning I ordered a new thermostat from Home Depot online, and waited with excitement for its delivery (gotta love next day, free shipping). During the day the old thermostat seemed to be running fine. Regardless, I put in the new thermostat (a Honeywell) and I’ll see how it ‘feels’ over the next few days.

There’s a really cool feature in the new thermostat I didn’t know about when I ordered it. It’s called “Adaptive Intelligent Recovery”, which allows you to program the on/off settings slightly different than normal. Instead of programming the time the furnace should turn on in the morning to preheat the house before you get up, you program what time you actually wake it. It figures out how long it takes your house to preheat, and turns the furnace on at the correct time so the house is the set temperature when it reaches your ‘wake up’ time. It says it needs about a week to figure out your heating system, weather, and the other factors involved. I’m not sure how it will handle vastly different temperature changes from day to day that we have here, one day could be -15C, the next -5C.

Hube, I’m always amazed at how small the WORLD Wide Web is. I live about 30 mins south of Coolingwood, just north of Shelburne. I love hiking up in Tobermory, absolutely beautiful! I never believed Canadian waters could look so stunning! It’s like you’re in the Caribbean.

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