Is thermostat setback energy effecient ?


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Old 02-12-15, 10:19 AM
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Is thermostat setback energy effecient ?

I live in a 75 yr old two story house with an oil fired boiler/furnace and cast iron rads. Its only about 1600 square living space so its not huge, but I was wondering if it would be more efficient to stop making big swings in the thermostat. Heres our normal routine. 62 all night and some of the day hours until my wife comes home around 3 pm, then she sets it up to about 68-70 until we go to bed at 9-10 oclock. It goes back down to 62 at that point. My question is that it takes about two hours of burning oil and circulating to get the temp raised that six degrees. Is that more efficient then keeping the temp a bit higher all day long so it doesnt have to work as hard later?

Another question is that I have a new unused gas furnace in my attic that is two years old and it was retrofitted along with my airhandler when we had AC installed. I would like to convert to natural gas at some point but wondering if the payoff would be worth it and if forced hot air from ceiling registers would be better heat then my cast iron rads(I know thats a matter of opinion)

I already have an old gas line coming into my basement from the street because it appears someone many years ago converted back to oil, but I would have to pipe gas to the furnace in the attic and I would still need a hot water heater unless I just kept my boiler furnace and ran two systems.

Does this sound rediculous or what?

The other bonus is that if I got rid of my rads, I could free up a little more floor space.
1600 sq. is not that big, but it works for us.
 

Last edited by NJT; 02-12-15 at 03:46 PM.
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Old 02-12-15, 12:59 PM
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if forced hot air from ceiling registers would be better heat then my cast iron rads(I know thats a matter of opinion)
It's pretty much a given that the radiators are a superior way of heating over forced heated air from the ceiling.

You have a two year old natural gas furnace in the attic that was converted and now you want to convert it to natural gas. Did I miss something ?

Converting the old boiler to natural gas makes more sense to me. I'm lucky... I've always had natural gas here and all my appliances use it. If I had an oil burner and could get natural gas..... I would have converted yesterday.

As far as the the thermostat.... I don't believe in setbacks of more than five degrees.
 
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Old 02-12-15, 01:24 PM
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PJ, you missed the part where I said the gas furnace was installed as part of our AC air handler and we got a better deal on the whole unit instead of just the handler.We dont use the gas furnace part, but it could be hooked up if I chose forced air over hot water rads. The other part of this I didnt mention
is that the gas furnace is in an unconditioned attic which is ice cold so would that matter? Being only a few years old, Im thinking the unit is well insulated for an area like that? My bigger question is if I chose forced hot air instead, which way to go for my hot water?
 
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Old 02-12-15, 02:38 PM
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If it is a condensing furnace then I don't believe you can use it in an unheated area.

Right now your entire house is heated by radiators. Your entire house is cooled from the A/C - furnace in the attic. Cold air settles so that is a good setup. Heated air doesn't settle so I doubt you could heat the house from the attic unit.

if I chose forced hot air instead, which way to go for my hot water?
Which way ? Not quite sure what you want to with the water.
 
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Old 02-12-15, 02:59 PM
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Almost everybody in Midwest areas that that have had natural gas available for many decades use a stand-alone gas water heater for domestic water heating - whether they have hot-water heat, forced warm air, new units, or old units. I'm aware that in those areas without a tradition of natural gas, this seems foreign to many people.
 
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Old 02-12-15, 03:45 PM
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As to the question of the thermostats, in a big old drafty home I would bet that the setback savings would be pretty much a 'wash'. If the home is not well insulated and high heat loss, it will cool quickly when you set back, then start to cycle again. Yes, there will be some savings during the period of time that it's set back because the temp difference between indoor and outdoor is not as great... BUT, when you kick the t'stats back UP again, as you say, the boiler runs for hours to get back to where it was. Probably burning up anything you saved.

If the home were really tight, lost heat slowly, then there could be long periods of time that the burner didn't fire at all after a setback. There might be a little savings if this were the case.

If you've got working heat, the first thing you should do is improve the building envelope as much as possible with AIR SEALING and INSULATION. Work at keeping the heat you pay for INSIDE the home. Caulk, weatherstripping, and insulation is fuel you pay for ONCE!

MAINTAINING a lower temperature, that is ALWAYS keeping the t'stat set lower, inside any building will ALWAYS result in a savings.
 
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Old 02-12-15, 03:46 PM
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PJ brought up a good point.

You probably don't know if the gas furnace in the attic is enough BTUH output to heat the home.
 
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Old 02-12-15, 03:48 PM
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already have an old gas line coming into my basement from the street because it appears someone many years ago converted back to oil,
I'm not sure you should count on that gas line even being USABLE if it's been abandoned for many years.

It may not even be sized properly (big enough) to provide enough gas for the furnace...

Do you even know if it's connected to the main still? It could be abandoned in place.

Is there still a gas meter anywhere?
 
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Old 02-12-15, 03:51 PM
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I would still need a hot water heater
I believe I'm reading this to mean that you are making your domestic hot water with a 'thankless coil' in your oil unit?

That right there is a huge waste.

The only way of making domestic hot water for a home that is worse than that is a kettle on a wood stove.

VERY inefficient.
 
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Old 02-12-15, 04:05 PM
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In my area, the gas company owns the underground line from the street to the meter. If for any reason, that line needs to be replaced, the gas company does it. Your situation may be different.

Our original gas line, installed 60+ years ago was steel, presumably coated and wrapped - it was later abandoned and replaced by the gas company with copper. Now the gas company is in the process of replacing copper pipe with plastic, their present standard. We've been served by three different gas companies as they bought out each other.
 
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Old 02-12-15, 04:09 PM
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In the Northern part of the state where I live and Public Service (P.S.E. & G.) is the provider.... they are also responsible for the gas line up to the meter.
 
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Old 02-12-15, 04:27 PM
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Im not sure what you mean by a thankless coil. You mean I dont have a tank inside the furnace? I dont know how it's set up, but I believe I have a small hot water tank in there. All I know is when I call for hot water, the burner usually kicks on within a minute or two and runs so long as Im in the shower. The furnace is a 92 yr model so I hope thats not terribly in-efficient but in the winter with temps around freezing or below, I go through about 100 gal of oil a month for this two story home. I use another 50-100 the rest of the year just for my hot water. There is no meter near the few gas pipes in the basement so maybe the house was just built with
the option but several years ago, they were repaving our street and asked if we used gas so they could shut it off out there which they did. I guess like the other gentleman said, heating from the attic through ceiling ducts might not be efficient even if everything is setup that way, because its really best for the AC alone at this point. I would say the envelope to this house is pretty tight for a 75 yr old. Double pane vinyl windows and aluminum siding about a decade old. Ive done a lot with weatherstripping and caulk too as well as rigid foam in some basement areas.Still working on beefing up the attic insul.
 
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Old 02-12-15, 04:34 PM
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I know they offer a lot of incentives to new customers PJ. I wonder what they would they would do for me if I got a new gas furnace as far as hooking it up if these current gas pipes were not usablr and opening up the street to turn it on.
 
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Old 02-12-15, 04:49 PM
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I doubt that you'd have to pay anything to have the gas company run a new line from the street and install a meter. I'm sure that they have a distance limit how far they'd run a line without an extra installation charge. That's just my experience, but why don't you call the local gas company? Whatever they say trumps whatever you assume or that you are told on an Internet forum.
 
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Old 02-12-15, 05:01 PM
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Im not sure what you mean by a thankless coil. You mean I dont have a tank inside the furnace?
"Thankless" is tongue in cheek... usually called Tankless... No, there's no tank inside the boiler. There's a coil of copper tubing behind that plate that the domestic pipes go into and out of.

Looks like this typically:


image courtesy slantfin.ca

Downsides to this are the fact that the boiler has to run 24/7 and keep itself warm, like leaving your car idling in the driveway in case you need to run out for a pizza later.

The output of these coils is usually no more than 3 GPM at BEST, and decreases over time as the coil gets 'limed up' from minerals in the water precipitating and coating the inside of the tubing, reducing the output.

The furnace is a 92 yr model so I hope thats not terribly in-efficient
It's a BOILER, not a furnace. We refer to SCORCHED AIR as a furnace, hot water is a boiler. But I'm just being picky...

What's the make and model?

No, the unit itself is not going to be terribly inefficient, just the way you are making domestic hot water is.

I go through about 100 gal of oil a month for this two story home. I use another 50-100 the rest of the year just for my hot water.
100 G a month is not 'terrible' for the heating season. But think about how much you are spending for a few gallons of hot water a day in terms of that "50-100" gallons the other nine months.

That's a pretty big spread by the way... is it closer to 50? or to 100?

Let's say it's 100 G for 9 months. At 3.50 (cheap) a gallon, that's $350 ... divided by 9 is 'about' $40 a month, which is 'about' what my ELECTRIC water heater costs to run. Oil is going to climb back up and escalate faster than electric rates.

Nat Gas is going to be WAY cheaper than that.

You might consider as a first step having gas line run to the home and installing a gas water heater. You'll probably need a 'direct vent' model because you probably don't have a chimney flue to vent it into. You can't vent it into the same flue as your oil boiler.

Then, convert the oil boiler to 'cold start' (controls change).
 
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Old 02-12-15, 05:03 PM
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I doubt that you'd have to pay anything to have the gas company run a new line from the street and install a meter
This is NJ Gil! We have to pay for EVERYTHING here!

But it's worth a telephone call for sure!
 
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Old 02-12-15, 07:02 PM
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Trooper, I looked and found this boiler is a Slant/fin Liberty L30 installed in this house in April, 1992 long before I was here. The owner kept detailed paperwork for everything they purchased here. Curious what the typical life span of most oil fired boiler systems is, although I guess you could swap new parts for life if you wanted, like an an antique car. I took a pic of the old gas pipes that are just plugged. Would these still be used if I converted back to Gas? As far as tankless water heaters, I thought that only worked with Gas, because electric coils couldint put out enough juice to flash heat a continual source of water for a faucet/shower? Can you throw some figures at me regarding cost of a new gas boiler and hot water heater conversion? 5K? 10K?
 
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Old 02-12-15, 07:16 PM
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typical life span of most oil fired boiler systems is
30 years or more for cast iron boilers...

I took a pic of the old gas pipes that are just plugged. Would these still be used if I converted back to Gas?
I can't see where you posted a picture, without being there to inspect the piping, there's no way that anyone could tell you if they are OK to use or not. For all you know, they have been out of service for 30 years or more. Probably all crudded up inside. You are better off getting new IMHO.

I wasn't talking about the new variety of "Tankless Water Heaters" that hang on the wall. They can be either GAS OR ELECTRIC.

The coil inside your boiler is ALSO called a 'Tankless' water heater, because it has no tank, but it has absolutely NOTHING in common with the (mostly) pieces of junk (MY OPINION!) they are pawning off as tankless water heaters these days. Some ppl love their tankless heaters... I think they 5uck.

I would say you would be looking at between $5 and $10 K ... shop carefully!

If you DO end up with a new Gas boiler in the future (your old boiler has plenty of life left in it though), what you would want to do is have an INDIRECT WATER HEATER installed with it.

This is but one manufacturer:

HTP Indirect Water Heating Appliances

Click here to let me google "Indirect water heater" for you
 
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Old 02-13-15, 03:58 PM
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You can figure out if the set back is saving you any money. You will have measure your oil usage and use degree days. Trooper can help you set up your boiler to measure the amount of oil you have. I can explain the rest if you are interested. You can go a week with your set back, and then another week without and see if you have any savings. I can tell you that when I went from having a set back to not having one, the house was much more comfortable because the walls and furniture were the same temp as the air. I was able to set my thermostat back a couple degrees permanently.

I'm paying about $.92 per therm for natural gas with NJNG. Multiply that by 1.38, which is $1.27. That is the equivalent cost to a gallon of heating oil. Instead of paying $300 a month, you would pay $127 a month.
 
 

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