Fuel use question?

wrxz24

Looking at the following numbers, just curious if there is something I should do to improve my system for next year. Triangle Tube 110 propane.  Radiant slab and baseboard mix and 50 gallon indirect HW.  Design temp -9, outdoor reset. Heat loss 90k.



From Feb 3rd to March 5th, 31 days I used 322 gallons to heat my 3,400sq/ft home.

1400 degree days  

During that time, the boiler ran for both heat and hot water priority for 400 hrs(330 for heat, 70 for hw) or about 13hrs a day.

So as I was burning about 10 gallons a day, the boiler was running about 13 hrs a day. 

so 10.3 gallons x 91,500= 942,450/31=/ 24= 30,401 btu/hr/3400sq/ft=8.9 btu/hr per sqft

Does this sound correct?

On the other hand the boiler was burning 10 gallons a day running for an average of 13hrs.  If it (87k for lp) ran full tilt at 95%, it would burn 82,650 btu/hr.  x 11hrs( just for Heat) = 909,150= 37,881btu/hr/ 3400sqft= 11.1 btu/hr/sqft.  T

So in the end, I heated my house this month on 8.9btu a square foot and if the boiler had run at 100% it would have heated my home at 11.1 btu a square foot.  So is it safe to say, the boiler did its job and modulated? 

SWEI

The best number for overall system efficiency

is BTUs per square foot per degree-day.  I get 6.19 using your monthly figures.

wrxz24

that sounds better

How did you get to that number?

SWEI

Just use the monthly numbers

322 gallons X 91,500 BTU per gallon / 1400 degree-days / 3,400 square feet

ChrisJ

Ouch

I keep coming up with 18.2 for mine.

ced48

Seems About Right-

If I remember right, this puts you in the 88% group-only 12% of homes have a better efficiency than you-

ChrisJ

88%

If the OP is in the 88% group, what am I in? The leaky sieve group?

ced48

75.5%

of homes are more efficient than yours-but you are better than 9.8%-so you are in the bottom 24.5%-

ChrisJ

Mistake

Ah! apparently as others have told me in the past the HDD reported by the gas company may be way off.



Using a local weather station from weatherunderground I came up with a number of 12.45 for one month and 14.7 for another.



I feel a little better now.



I really like this thread, I've learned an easy way to compare changes and improvements to my home.

ced48

That Puts You

at 50%-right in the middle-

Gordy

Here's one benchmark article.

http://www.homeenergy.org/show/article/nav/consumerinformation/page/2/id/825



The census was in 1997 but it gives you an idea. I would suspect those percentages have changed for the better 16 years since then.

wrxz24

I forgot to add that

the 10.3 gallons a day figure also includes cooking stove and dryer so I am not doing too shabby.

I still need to dial in the boiler though.  I am having a bout 20 ignitions a day and that includes a 30 minute burner delay.  I sort of wish I had all zones into one with constant circulation.

wrxz24

I saw that when I was

doing some research with my useage.  10 gallons a day seems like a lot but when I have to heat 3400 sq/ft, it isn't that bad.  

SWEI

Degree days

I make sure to collect them from the closest (or most similar) PWS.  I go to www.degree-days.net, download daily data for the previous two (or more) months, then prune the data so it matches the meter reading or tank filling dates and sum those up.



Two things you need to consider:  One is base temp -- for newer, better insulated houses, 65ºF is not a good assumption.  The other is non-heating appliance use.  Add up the gas or oil use over 3-4 non-heating months and divide that by the number of days to get an average daily use number and subtract that (multiplied by the days in the billing period) from the usage during the heating season.

wrxz24

Update.

From Nov 26 to Jan 9, 45 days, I used 385 gallons of fuel for heat, hw, cooking and about 15 dryer cycles. That comes out to about 8.5 gallons a day. 2453 hdd's.

The tank was filled to 85%. Boiler ran 13hrs at about 50% firing rate. So I assume, I must have burned about 5 gallons of propane. Checked gauge and it read about 80%. So according to that, I used 25 gallons in 24 hrs. I must assume that the gauge is wrong?

wrxz24

Here is the firing chart

Gordy

Have no faith in propane tank gauges. I'll bet it sticks if you tap on the Gauge too. I remember once I was on LP ran out on a Sunday tank said 45% till I tapped the gauge dropped to zero.

BobC

I feel the same way about oil tank gauges, rough indicators at best and often outright liars.

I used a timer on my Becket AFG for many years and always knew where I was within a couple of gallons.

Bob

Gordy

If you want to know your fuel usage track boiler run times, and calculate using gross input.

Jamie Hall

If it cheers you all up any... I use 0.42 gallons per day per degree day; on a day with the outside temp at 0, I can quite happily (?) run through almost 28 gallons. For a 7,000 square foot building. Which, considering that the place has minimal insulation and a lot of infiltration isn't too bad, I suppose...

My oil company, however,simply can't wrap it's head around that number. I'm constantly having to call them to get me a delivery NOW (it's supposed to be automatic). Which they didn't do Friday, so I suspect I will run out tonight... at which point I will be polite, but no friendly.

wrxz24

Gordy said:

If you want to know your fuel usage track boiler run times, and calculate using gross input.

I tried using the boiler log. 13 hrs at about 50% which is about 43k/hr. Temp outside was 5. That is about 5 gallons used, yet gauge went down 5%. According to the tank, about 25 gallons....

Gordy

Your not using Gross INPUT. your using DOE output. 1/2 of 97k is 48.5K. use input to track fuel consumption, and output to track envelope consumption.

wrxz24

Gordy said:

Your not using Gross INPUT. your using DOE output. 1/2 of 97k is 48.5K. use input to track fuel consumption, and output to track envelope consumption.

Isn't the gross input for the lp 110 87k? if the boiler runs at 50% for 13 hrs, I would take 13 hrs x 43.5k = About 565k btu and divide that by 91,500 which comes out to about 6.1 gallons.

During that time, 13 hrs, the boiler was putting out 41,760 btus/hr which is about 12 btu/sqft.

So for a 5 degree day, my heat loss is 41,760 btu/hr during that 13hrs of run time.

Gordy

97k for the LP.

Gordy

So 6.89 gallons

JUGHNE

Square footage... where at? I want to compare fuel usage by this formula but what area are we looking at? I have 2366' living space on grade.....1806' finished heated bsmt ...1008' of garage/shop connected to house that gains heat thru one uninsulated bsmt wall, 55to 60 degrees, never freezes. Granted we throw out the garage/shop. Do we call this 2366 heated or add the bsmt (2-3' wall showing above grade for bsmt) which would total 4172' (8' ceilings) ??

wrxz24

I'm in Vermont. Design day is -9.. Total heated space is 4100 sqft including the garage. The garage does not use a Tstat as I combined that zone with the house zone. It gets 90 degree water in the floor anytime the house gets heat. Did this to cutdown on short cycling.
Gordy, so what is the output? I thought I saw 76k for the net output.

wrxz24

Gordy said:

So 6.89 gallons

So, for my 4100sqft house plus garage, I used 6.89 gallons and the gauge on the in ground tank said I used 25.

The latest firing chart which shows about 23 ignitions in a 24 hr period. Boiler ran 16 hrs between about 20% to 50 %. My tekmar Tstat 519 with slab sensor has pulse width modulation. How many cycles per hr does this thing do?
Wonder If I should jack the Tstat up and rely on the Odr? That would cut down on the cycling, although 23 cycles isn't bad in a 24hr period. Worse when you factor in just how long the boiler actually ran in that 24hr time frame.

Gordy

wrxz24 said:

Gordy, so what is the output? I thought I saw 76k for the net output.

87k is DOE, 76k is ibr

Gordy

Pretty darn good. NFW you used 25 gal in 13 hours unless you have a leak some where between the tank and the boiler. Might be worth a check.

wrxz24

Gordy said:

Pretty darn good. NFW you used 25 gal in 13 hours unless you have a leak some where between the tank and the boiler. Might be worth a check.

So after another day, the fuel tank gauge still read about 80%. So guessing it is the gauge. Will look every morning to see.

Another question about the tt 110. During post pumps and delay settings, if the boiler isn't firing but the pumps are on, does that add to the CH run times?

For example, if the boiler fires for 30 minutes with a 30 minute post pump, is total ch run time 60 minutes?

icesailor

Fuel level gauges on LPG and oil tanks are there for the convenience of the person who wishes to know if the tank is empty, or an approximate level in the tank. The size and shape of the tank make it impossible to accurately gauge the fuel usage by the reading of the gauge. The only way you can accurately gauge a oil tank is with a stick. Hard to do with a LPG tank.

wrxz24

Very true, I am going to keep a daily log this billing period to see how close I can keep the actual use once I determine the run time feature on the boiler.
Anyone know if ch post pump time is part of ch run time for the tt solo 110?

wrxz24

I am stumped here...
Since my fill-up on January 10, my boiler has run for 53 hrs and the firing rate has been around the 50% on average. So if I do the math...53 x 48.5k divided by 91,500, that comes in around 28 gallons in 3 1/2 days.
However, the gauge is at 77% on the tank which is 385 gallons. At 85% is 425, therefore, I have used 40 gallons in 3 1/2 days.
That is a 12 gallon difference.
Could it be the boiler is not burning efficient?

RobG

Anything is possible, however as Ice said above, those gauges are more for and idea about how much fuel you have, rather than how much fuel you've used. Think about the gas gauge on your car, it may be a 20 gallon tank reading empty when you pull up at the pump and it only takes 18 gallons to fill it.

wrxz24

I do know the tank started at 85% and now it is down to 77 or so. Regardless, it seems the rate of use is kind of high but I do get your point.
The thing is though when they filled the tank, I was down to 3% and they put in 407 gallons to get it to 85%. So if you do the math, 3 % of 500 is 15 gallons which was left plus the 407 they put in, comes to 422 gallons which is about 85%.
I am starting to think that my boiler is using more than it should.

ced48

I think the only way to gauge LP usage is to keep track of deliveries. Even this has some guess work, as they fill to partial full, to allow for expansion.

If your boiler continues to operate a pump after the call for heat has been satisfied, than that time is not counted. This is assuming you are not cycling on and off during a single call for heat, in which case I'm not sure how the boiler counts the pump time.

wrxz24

I just went out and took a dental mirror to peer into the flame view port, I saw flashes of what appeared to be an orange/yellow flame when the boiler was at 68% firing rate.
I have looked before when the boiler was on full fire and the flame was blue. Should the flame be all blue at any firing rate?

Gordy

Dont beat yourself up that tank gauge is ther so the delivery guy does not over fill it. When I was on LP I think it was 90% on a 500 gal tank. Temperature may effect the gauge also especially as the tank reaches a higher degree of emptiness.

SWEI

As mentioned above, LP tank gauges are pretty much useless. The only way to come even close to tracking LP use is gallons filled on what date, assuming it was a top-off. Even that is dodgy, because the "full" determination is dependent on both the person filling and the ambient temperature. Averaging over several fills is about as good as you can get without a flow meter.

JUGHNE

Did you consider a propane gas meter? Google that and there are a lot and not that spendy.