example that setback doesnt always reduce gas usage

GusHerb

Hi everyone i havent posted in a long time but i have been observing closely and i wanted to share with everyone my personal experience with setback vs no setback on our hot water heat system in our early 1900s 3 story apt bldg with 2 apts on the top 2 floors and a storefront on the 1st floor, the hot water system only serves the apts, new boiler put in in 2007 and the system is controlled by a programmable thermostat and a tekmar 256 outdoor reset, so now to the point in december the system was running with multiple setbacks a day 70 morning 68 day 70 evening 68 night and the gas bill came in quite high it used 589 therms and thats quite high for december so i tried 70 continously for the month of january, most of december was in the high 20s while january was in the low teens & single digits and even up to 17 below zero here in chicago so i thought the bill and usage would be a nightmare but it just came and it used less gas than december! i was amazed it only used 583 therms and this in a much much colder january, from now on i will be keeping it at 70 all the time now plus no more complaints from the 3rd flr tenant about being cold at night great!

jonathan

Big Ed_4

Varibles

You first should figure fuel usage savings by a degree day fomula .Which will give you a better usage factor. And then clock the meter your self. Was your bill a estimate from the gas company? I would take out a careless meter reader from the equation... What about hot water usage ? Can this be pulled from experiment ?Was the top floor cold and running a oven to supplment heat. Zoning would be something that will save fuel. Better yet, break up the system with independent boilers and gas meters and walk away

Gordy

Variables

Have to agree with Big Ed on your calculations.

Lots of variables to consider in your scenerio. The first one is an estimated reading. NICOR usually estimates every other month, unless you send in your own reading. This estimate is taken from last years usage. If the estimate is off one way or the other then it is made up the next reading.

Then you need to weed out any other NG burning appliances that would be in the mix of the reafding.


You say the floor level store front is not on the boiler, but was the temp in this area always the same? Being a store front was in, and out traffic the same?
Solar Gain?


I like to use a Btu per degree day per square foot formula.


The most accurate way is to be able to put a timer on the boiler gas valve to time burner on times.


Take the burner run time for a 24 hour period * the gross Input of the boiler = Btus for 24 hour period used.

Btus used for 24 hour period / Degree days for the 24 hour period = Btus Per Degree Day.

Btus per Degree Day / Square Feet of heated space = Btus per degree day per square foot of heated space.


You can substitute (gross boiler output) with the (net boiler input or DOE heating capacity) to nock off what goes up the stack, and only to the dwelling.


This formula not only tells what you are using for comparing an apples to apples scenerios, but also tells the performance of the envelope you are heating.



Gordy

steve_29

Thanks Jonathan, I've been saying that forever.

Set the thermostat and forget it. I've had to deal with more problems with people screwing around with thermostats.

2* might not sound like alot, but with 0* temps outside, it maybe a big deal, especially where your heating up the entire mass of the building and furnishings.

Unknown

Big fan

I am a big fan of reset and constant circulation with no setback.

GusHerb

big ed gkaske thanks for the information, the place has four gas meters 1 for the store 2 for the two apts serving the stove and the dryer and 1 for the boiler and (your gonna laugh) just a average 50 gallon water heater not even high recovery and yes i think it has to go in trade for a much better indirect, my dad owns the building and my mom has her store in the 1st floor so i manage the temps in their too the store just has a horribly noisy and disgusting forced air furnace (put in by the last owners not me!) (and i do have plans to convert back to hot water with its own boiler though) and the thermostat there is set for 67 during business hours and 57 for setback and theres a large radiator in the backroom connected to the boiler just for supplemental heat because its very drafty back there, that gets turned off at night though. the second and third floor are not insulated either and i dont think the walls can be insulated as there attached straight to the brick and if the third floor ceiling were insulated i would be afraid that would throw the whole heating system off balance. the apts are about 1200 sqr ft each and the boiler serving them is a buderus ga244 thats exactly 156,000 btus input and 128,000 out and we did a heat loss calc before this was put in so its not oversized and then on the back of each apt there was a screened in porch that was converted to living space about 10 years ago but had no heat when we got the bldg so during the boiler project we added heat to that while the boiler was being done thats on it own zone but im trying running the whole system as one zone so far its going good. We considered splitting the system up but decided against that as this is an old gravity system and we would have to tear into the walls and the tin ceiling that we restored in the store. oh and about the gas bill part we dont get estimated usage readings we get the actual reading every month the meters in the buildings here in bridgeport are wireless so they just drive through the alley for the reading though i will do what you guys suggested. sorry for the long post i just wanted to get this out of my head.

jonathan

GusHerb

timer

where would you get and what kind of timer would you use on the boiler?

thanks jonathan