Heating cost program

Bryan_16

in on your conversation, but this thing works excellent. I have been plugging in different numbers and everything makes sense. Thank you for the help. Bryan

S Ebels

Heating cost program

A couple years ago someone, I don't remember who, e-mailed me an excel spreadsheet that you could figure out a rough cost to heat a building using different fuels. It had a line for HDD data as well as variable price per unit of different fuels. I saved it but must have dumped it in the recycle bin inadvertantly. Anyone have it or something like it yet?

Brad White_71

I do not think it was me, Steve, but

see if the attached does not help you. I develped it using the conventional DD formula. I prepped this one for another Wallie in South Dakota. If you want Michigan data let me know what location is nearest to you.

This is an Excel template file (.xlt) so you can save it, tear off a sheet and get to work. But you have to fill in your local data, fuel costs, Cd factor and so-on. One tab is blank the other filled in as an example.

Hope it helps.

Brad

S Ebels

Nope

That's not it but It looks interesting. I'll save it and play with it.....see how it does. I have a couple buildings that I track actual use and degree days on and I'll see how close it comes.

Thanks Brad

Brad White_71

The plant efficiency entry is the real wild-card

You can change it to reflect your actual usage, sort of a test and fit scenario to back-calculate to known variables from your fuel bill. Where in Michigan are you located? I have PDF weather data for several locations I can post.

Brad

S Ebels

Why

Why does the fuel cost go up as you lower the design day temp difference (column E) How would you reflect an indoor temp of........60*f ? When I lower the number in (E) the fuel cost goes up and it should go down unless this doesn't reflect what I think it does.

S Ebels

Your HDD data

Is darn close to what we have here. We average about 7200 annually.

Brad White_71

Delta T

The delta T function is the same as used to calculate the heat loss. It is part of the formula divisor as a means of cancelling out that aspect from the heat loss itself. (Brings it to "BTU's per hour per degree difference"). Hence if you decrease it, being a divisor, you will obtain higher usage numbers.

Key is that it has to be the same delta T that was used in calculating the heat loss in the first place. Remember if your delta-T was less, so would be your heat loss.

And when you lower the efficiency, yes the cost will go up.

Does that make sense?

Brad White_71

Here is a selection of data

Complete Engineering Weather Data Packages by name and WMO number;
Monthly High Resolution Binned Temperature Data (by Hour)
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANN

ALPENA 726390

BATTLE CREEK 725396

DETROIT CITY 725375

FLINT/BISHOP 726370

GRAND RAPIDS 726350

HOUGHTON 727440

JACKSON/REYNOLDS 725395

K. I. SAWYER AFB (CLOSED) 727435

LANSING/CAPITAL 725390

MARQUETTE 727430

MUSKEGON 726360

PELLSTON/EMMET COUNTY 727347

SAULT STE. MARIE 727340

SELFRIDGE ANGB 725377

Tim_33

Constantine..

Had a spread sheet called "Sizer"? I think that sounds like what you're looking for. Maybe he'll provide you a new copy.

Brad White_38

Glad it is working for you, Bryan

Sorry it took so long to get it to you. Have fun!

Brad

S Ebels

Brad

I'm not following what you are saying, probably because I'm thinking column E (design temp diff) is something different than what I am imagining it to be. I'm looking at it like this....... If I have an indoor/outdoor temp difference of 70* it takes xxxx amount of fuel. If I lower that temp diff to 60*, it should take less fuel and the opposite is true if I raise the temp diff number. The program works backward to that scenario. Raising the temp diff number lowers the fuel use and lowering it raises fuel consumption. I'm thinking that I'm thinking wrong about what that column actually represents.


Thing number 2: What is the Seasonal correction factor and where/how is that number established?

This looks like it will provide a basic guess at the least for determining fuel usage and that's what I was after. I think that the program I had a couple years ago was written by or came from someone who worked at Wirsbo IIRC.

Brad White_38

Steve-

I know you have never used this particular tool before because this is the first time I have shared it with anyone. Only Bryan in SD had used it before I published it here on the Wall. The formula is basic, just the standard DD formula we all use by hand:

(BTUH x DD x 24 Hours) / (Delta-T x Eff. x Fuel Value) xCd

(See Burnham's Heating Helper, p. 55 also.)

Siggy's HDS has a module that also is rooted in the same formula if I am correct.

The difference here is that I broke it down month by month so that one could adjust for efficiency and over-sizing but also to better track usage in more realistic time increments. The degree-day data is a 30 year average.


Just remember that the delta-T number is what you used to calculate your heat loss in the first place. You do not change it independently. It is not a "what-if" variable.

Say you have a design heat loss of 90,000 BTUH based on an outdoor temperature of -10 and indoor temperature of 70, (80 degrees, obviously). You enter 90,000 in the heat loss column and 80 degrees in the delta-T column. That's it.

Now, say you decided that you really wanted to maintain the house at 72 (82 degree delta-T). But if you do this, you HAVE to change your heat loss accordingly to an 82 degree delta-T equivalent, in this case, 92,250 BTUH. Try that, you will see the costs go up.

If you changed only the 80 to an 82, without changing the associated heat loss, yes your costs would go down, not up, because your heat loss stayed the same.

You can see that if you were to change the delta-T at all, and not the heat loss figure, it would not reflect the basis.

The Cd factor is empirical and is graphed as a lazy "V"; it changes with the actual degree days. In general terms, in the 5000 to 7000 DD range, the Cd factor ranges from 0.6 to 0.65. That is right about where the V bottoms-out. Warmer climates the value is less (0.30 range IIRC) and in colder climates also less (0.50 IIRC).

I do not have the knowledge/ability at this point to incorporate a pivot table or database to catalog and fill that in automatically as the DD values change. Someone out there does! And I would welcome that.

You are right, this is not a complex tool. It is basic but the core formula is nothing unusual.

I hope this helps!

Brad

Constantin

Maybe you meant this?

Steve, this is my unfinished Sizer program. It has a lot of work left to do, but if it's useful, great!

Cheers!