Thermostat setback efficiency

[Patman]

I'm off work for a few weeks so today I decided to check the temperature of my house to see how I should set the thermostat during the day (when I'd normally be at work) At 7:30am when I turned the furnace off, the temperature in my house was 72F, outside temperature was 14F. It was a cooler than normal day here actually, it only got up to 18F (normal high is 28F, normal low is 16) although the sun was shining for about half of the day, so that probably helped our house's inside temperature. The temperature in my house never got down below 65F all day, and the furnace was off the entire time. I'm going to turn it back on now (3:30) to simulate a normal work day where I'd be home by 5pm, so I'll see if the house comes back up to 72 by then.

So the way it looks to me, for my house, the best temperature setback is to go from 72 down to 65 for an 8 hour period of time during the day, and then while I'm sleeping (since it's a shorter period of time where the temperature will be set lower, from about 11pm to 5am) I'll have the thermostat kick it down to 67.

So my furnace will be pretty much completely turned off for 8 hours during the day and probably most of the time while I'm sleeping too. This way I figure I can still run it warmer while we're home, so we're more comfortable, but I won't spend a fortune on natural gas either.

 

[Quattro Pete]

On a related note, how much are you guys paying for gas right now (not counting delivery charges)? Out here, natural gas has gone up from 33 cents/therm in September to 68 cents/therm in January. I understand the price is driven by demand to a large extent, but that's still quite a hike.

 

[Gary Allan]

Originally Posted By: brianl703
Originally Posted By: Gary Allan
I will then run continuously for up to an hour at above 212 (pressurized) with the radiators putting out great heat ..and wait even longer until the thermostat sees it. This will then overshoot the set point


The Honeywell Chronotherm III (I have one) is capable of learning how long it takes for your heater to warm the space to avoid overshooting the preset temperature.

The Honeywell Chronotherm III is also an old design (1995? Edit: No, 1989!), so any newer Honeywell thermostat probably does the same.


Yeah, it can learn the pulsing to make the curve fit the prescribed contour, but it's more complicated than that. They're not always respondent to quick changes in ambient temp. I've observed a smart Honeywell (can't recall the model) thermostat over a month long period. It maintained the set point fairly well except where the actual room temp changed rapidly. It appeared to be making a speed or course correction on an ocean liner that had all the time in the world to react.

They may have advanced enough in adaptive PID loops, but even with tight control, the fixed output of a residential steam boiler makes them lousy in terms of efficiency below a certain rhythm. So, you will save money and energy at lower setpoints, it won't be much.

My boiler isn't a high mass boiler. That makes turning the aquastat up to like 180f-190F practical for shortest time to heat production from ignition.

The worst experience was having the wife decide that it was "fresh air day" and having her slam the thermostat down and opening the back door when we were in some transitional temp swing where you can have a 62F daytime temp (fine while you're moving around doing neurotic tasks for the sake of toil - dogs in and out ..happy time

) ..and then have her leave for work and realizing that it's now 7pm and it's getting cold inside due to it being 40F outside. Stone cold boiler ..stone cold house....and hours to re-stabilize.

I don't know of the controller that will compensate for purposeful and assertive sabotage.

 

[Patman]

Originally Posted By: Quattro Pete
On a related note, how much are you guys paying for gas right now (not counting delivery charges)? Out here, natural gas has gone up from 33 cents/therm in September to 68 cents/therm in January. I understand the price is driven by demand to a large extent, but that's still quite a hike.


Our rates just dropped down actually, to 12.95 cents per cubic meter. Not sure how that compares to the rate you just quoted though.

We typically pay about $120 to $140 per month in the cold months to heat our 1800sq ft townhouse. In the warm months, the gas bills are under $60/month (during that time, that's just for the water heater and it's $25/mo rental fee)

 

[Quattro Pete]

Originally Posted By: Patman
Our rates just dropped down actually, to 12.95 cents per cubic meter. Not sure how that compares to the rate you just quoted though.

I think 1 cubic meter = about 0.36 therms, which means 1 therm = 2.78 cubic meters.
So, you're paying about 36 cents per therm (12.95 x 2.78). I wonder why such a big price difference between US and Canada. Looks like Nicor is ripping me off.

 

[Gary Allan]

Yes ..but you're DEMANDING it ..they're annoyed at you.

 

[JustinH]

Originally Posted By: Quattro Pete
Originally Posted By: Patman
Our rates just dropped down actually, to 12.95 cents per cubic meter. Not sure how that compares to the rate you just quoted though.

I think 1 cubic meter = about 0.36 therms, which means 1 therm = 2.78 cubic meters.
So, you're paying about 36 cents per therm (12.95 x 2.78). I wonder why such a big price difference between US and Canada. Looks like Nicor is ripping me off.


The lowest that I paid per therm is .46, the highest was .88. It usually hovers in the .60 range..

This is New York, buying though a third party provider.

http://www.ecny.org/gas/residential.html

 

[Quattro Pete]

Originally Posted By: Gary Allan
Yes ..but you're DEMANDING it

Certainly, but I'm sure Canadians are demanding it, too, yet their local gas provider doesn't seem to jack up the rates.

 

[Gary Allan]

Originally Posted By: Quattro Pete
Originally Posted By: Gary Allan
Yes ..but you're DEMANDING it

Certainly, but I'm sure Canadians are demanding it, too, yet their local gas provider doesn't seem to jack up the rates.


No. Patman is just asking. It's a cultural distinction (sorry for leaving off the gremlins

)

 

[Quattro Pete]

Originally Posted By: Gary Allan

No. Patman is just asking.