A few questions for those in the know

[uncleblaine]

Originally posted by dash
Imporovements saving 5% on cooling,and 11% on heating.[

That's like buying a half of SEER more ,and going from an 80 to a 90 % furnace.

Well hopefully doing the a 90+ furnace and several SEER on the AC can save that much again. Perhaps I need to hope for cold winters and hot summers so I can have a quicker payoff.

[dash]

Originally posted by uncleblaine

Originally posted by dash
Imporovements saving 5% on cooling,and 11% on heating.[

That's like buying a half of SEER more ,and going from an 80 to a 90 % furnace.

Well hopefully doing the a 90+ furnace and several SEER on the AC can save that much again. Perhaps I need to hope for cold winters and hot summers so I can have a quicker payoff.

Don't forget the higher utility costs more likely than the weather changing that much.

[dan sw fl]

Originally posted by uncleblaine
Okay, I've done the manual J, and here's the whole house results if anyone is interested.

With current windows:
S/Gain L/Gain T/Gain T/Loss
15,596 3,417 19,013 53,612

With new windows, patio door and front door:
14,659 3417 18,076 47,427

That's just shy of 6200 BTU less heat loss. To me that seems quite substantial, but I'm a laymen. And in all actuality, the only changes made in the program were to lowE glass, and vinyl frame. The old windows leak like seives so the real difference may be greater.

Back to studying recommended links...

Blaine,

Why would you have existing 100,000 BTUh capacity and
53,612 BTUh need per your analysis ?

I believe your have performed analysis which does
not show Total BTU loss.
Infiltration is a huge contributor to this difference.

Say house is 30 x 50 x 20 foot tall = 30,000 Cubic feet
Using a "Quite LOOSE" value 0.6 ACH yields
~ 300 CFM infiltration.
Q= CFM * dt * 1.08
1.08 = constant

Q= 300 CFM * 81 'F dT * 1.08 = 26,400 BTUh
Estimated Current Load
26,400 + 53,600 = 80,000. BTUh MAX ( 81 'F dT)
Of course, review of heating energy bill would be quite useful at this point.

You could obtain infiltration of 0.25 ACH or 125 CFM with
new windows and significant caulking / spray foam effort.

Q net savings = 175 * 81 * 1.08 = 15,309 BTUh
at design temp of -11'F
----------

WINDOWS
Q= U * A * Dt
U= 1.0 for Old perhaps
U= 0.3 for New ? ONLY As an example

A (Total window area) might be 200 Sq.Ft per floor
Dt = -11'F + 80 = 81'F

Qnew windows = 0.3 x 200 x 81 = _4,860
Qold windows = 1.0 x 200 x 81 = 16,200

Energy Savings per 200 Sq. Ft.= 11,340 BTUh
---------------

I would expect > 20,000 BTUh total savings given this
set of ASSUMED values ( adjust as appropriate)
which may "get you in the ballpark"
of a Energy Saving$ goal.

Perhaps, purchase of a ~70,000 BTUh 90% efficient furnace
(63,000 BTUh NET)
is what you may be able to pursue with integrated improvements in housing Envelope AND Heating equipment.

[uncleblaine]

Hi Dan,

Why would you have existing 100,000 BTUh capacity and
53,612 BTUh need per your analysis ?

I don't know. I questioned it too, but just used the software. Of course it was my first time. Infiltration is listed at 15956 BTUH total loss. Perhaps I should run through my entries to see if I've made a major gaffe. I'll also try plugging my measurements into your calcs to see what I arrive at.

edit to add

Infiltration numbers are shown as .4 summer and .7 winter, on 2752 square feet. This is using average/loose construction figures built into the software.



[Edited by uncleblaine on 10-09-2005 at 11:53 AM]

[Freezeking2000]

I am wondering if during the coldest windy nights did your existing furnace EVER run for 30+ minutes?

I know that when -20F with 30 MPH winds the heating equipment get a good run. You do not want to be short capacity in Minn. when temps drop below design temp. I would get a 2 stage system so the heat will run constantly and go to high fire when exreme temps hit.

Also I hear the 90+ units are not as reliable, but I hat be incorrect since I am a Refrigeration man. I do know you cant go without heat for more than a few hours in Minn.

Ask the contractors what they recommend for the severe winters you have! They are the ones that have to make it work on the cold winter night when it is -20.

[uncleblaine]

Originally posted by Freezeking2000
I am wondering if during the coldest windy nights did your existing furnace EVER run for 30+ minutes?

I know that when -20F with 30 MPH winds the heating equipment get a good run. You do not want to be short capacity in Minn. when temps drop below design temp. I would get a 2 stage system so the heat will run constantly and go to high fire when exreme temps hit.

Also I hear the 90+ units are not as reliable, but I hat be incorrect since I am a Refrigeration man. I do know you cant go without heat for more than a few hours in Minn.

Ask the contractors what they recommend for the severe winters you have! They are the ones that have to make it work on the cold winter night when it is -20.

You know the more I think about it, the more I'm wondering if the units are oversized, and perhaps the ducting undersized. To be honest I've never really paid attention to how long the furnace runs in any given cycle, but I'm going to start now. And oversized or not, the two-stage has been in the front of my mind for a more even temp and its comfort, if no other reason. That would also make my air cleaner do its job better. Though 2 of 5 animals have passed on since that was put in, so it already has less work to do.

[uncleblaine]

Dan,
I'm getting lost in your calculations, but I have 21392 cubic feet in the house. I attempted to get my gas usage numbers from the online bill pay, but what I can access right now does not include Oct04-Feb05, which are going to be the ones that really count. I should be able to get them tomorrow during business hours and will post gas usage then.

I'm not sure if I'm ridiculously off on my load calc, or if the equipment is ridiculously off. It wouldn't be the first thing about the house that was half-a**ed.

[dash]

Unit oversized ducting undersized,that's normally the case.Sad but true.

[uncleblaine]

Gas usage in therms for the last year total 866. Based on the gas usage for no-heat months, I'd estimate about 20 therms are used for hot water each month. That leaves me 626 therms used on heat with my current 80 efficiency furnace.
626 Therms = 62,600,000 BTU

[edited to reflect correct efficiency numbers]

62,600,000 *.63 = 39,238,000 BTU into the house

To get 39,238,000 BTU with a 92 AFUE divide by .92 right?

That's 42,867,391 BTU

divided by 100,000 = 429 Therms. Or a savings of about 197 therms.

I definitely like these numbers better.

[Edited by uncleblaine on 10-20-2005 at 09:40 AM]

[tbox8098]

Blaine,

I am currently working on finalizing your proposal, I will have it finished up tomorrow. I should be able to help with some of the additional questions when we get a chance to talk in a couple days.

Talk to you soon,

Travis

[uncleblaine]

Originally posted by tbox8098
Blaine,

I am currently working on finalizing your proposal, I will have it finished up tomorrow. I should be able to help with some of the additional questions when we get a chance to talk in a couple days.

Talk to you soon,

Travis

Hey, I was wondering what happened to you! Even at a couple of days from now, you'll probably still be the first bid in hand.

Don't forget to add on for that placebo stat from the other thread.

[tbox8098]

It takes a while to get the options put together. I will give you a call tomorrow.

Travis

[uncleblaine]

Sounds good Travis. Use the cell number as before.

Thanks!

[tbox8098]

Blaine,

For your knowledge the furnace was only produced between 1972 and 1975 according the Preston's guide to furnaces, it also gives an estimated efficiency between 60.2 and 62.9% AFUE. The air conditioner wasproduced between 191987 and 1991 with a SEER rating between 9.2 and 9.4.

I hope this helps

Talk to you later,

Travis

[uncleblaine]

Travis,
Thanks for that info! That makes me feel much better that I'm doing the right thing.

[kjones]

Hey Travis, as long as you have that guide book dusted off, could you see what it says about a Premier GA150?

Thanks,

KJ

[troyorr]

Go back to your fourth grade math class. 125,000 in and 100,00 out. Sounds like 80%.

[Noel Murdough]

You don't know Dash. He'd recommend pet porcupines if Carrier branded them.


I'll have to check the brand on this one.

Living in the boondocks, you have a lot of time on your hands......

Noel

[tbox8098]

And old furnaces never lose efficiency. Or do they?

[uncleblaine]

Originally posted by troyorr
Go back to your fourth grade math class. 125,000 in and 100,00 out. Sounds like 80%.

Well gee, I'm not sure if this is meant for me or not. Prior to the post saying I could divide the numbers, they meant nothing to me, a homeowner. Then I had that post saying 80, which I went by. Until, that is, my local professional who is *bidding* on the job and actually looked at the furnace posted on this forum that its estimated efficiency is 60-63 based on the Preston guide. That means troyorr, you are calling one of two of your colleagues a liar, and me an idiot. I guess I can live with being called an idiot, but I'd be very interested to know which of the hvac pros are lying! Or "confused" if you prefer? Or is it a question of efficiency as new, versus efficiency at 30 years of age. What does *your* Preston guide say?

[Edited by uncleblaine on 10-20-2005 at 03:24 PM]