Have whole house load numbers but nobody cares

10 years ago

Long story short. I ran two whole house load calculations for my heating needs, no A/C necessary, one quick and dirty calculator gave me 13,492 btu/h. Another more comprehensive calculator using wall, window, door, floor square footage, air volume, insulation r-values, exposure, siding, etc., gave me 12,289 btu/h for my whole house load. My input numbers are accurate as I know my way around houses. Plus, it's my house and I know every stick in it.

I have existing basement central forced air ducting and hope to continue using it. 1917 house, 1500 sf 2-story, smallish rooms, lots of doorways, so a mini-split system might work but would cost a lot more than a simple gas furnace. All ducting is in conditioned space. I'm slowly remodeling (new everything!) and already have r-50 foam attic, new windows and doors, and will have r-30 foam walls when I am finished.

So why, in getting bids for a new gas furnace for my central forced air, does everyone say I need an 80,000 btu unit? This simply does not feel right to me. They do not seem interested in hearing my whole house load numbers or in helping me size my heat source to what I actually need. Or do I actually need a 80,000 btu furnace? What piece of knowledge am I missing here?

Sort by:Oldest

Comments (7)

tigerdunes
10 years ago
Someone is wrong, either you or the dealers.

What size and efficiency is existing furnace?

What is your location?

Ask dealers to justify their sizing with a load calculation of their own. Then make comparison to your results.

Just an opinion based on the info you ave provided, but I think your calculation is too low but you certainly don't require an 80 KBTU furnace either.

BTW, your fuel source is nat gas?

Post back.

IMO
0
rmtdoug
Original Author
10 years ago
Currently have a Thermopride oil OL5-85 with 85k btu output nozzle, installed in 1998. This furnace rarely runs more than four or five minutes and then shuts off, and I recently learned about steady-state efficiency and how that plays into furnace sizing and how it is more desirable for a furnace to run longer at a lower output than shorter at a higher output.

Location is near Seattle. My delta T is 44. I've averaged 240 gallons of oil over the last 5 years, which if my calcs are correct is 21,152,000 btu's per heating season. This is in a house that still has zero insulation in the walls. That will change completely in the next two or three years.

No dealer has run a load calculation. They come in, shine their flashlight around, and hand me a brochure. I'm not being a know-it-all either. I keep my mouth shut and answer their questions and let them assess what I need. Right now, I'm just feeling like this is a huge disconnect from what I have learned over the last year about high-R houses, heating, cooling, and indoor air; however I still consider myself pretty ignorant about a lot of this.

The energy audit guy that came a few weeks ago said I probably could heat the entire house with a one or two-head mini-split system, but I'm still skeptical. I still favor the idea of using my existing ducting because of how the rooms and doors are configured and used.
0
Related Discussions
Whole Foods is coming, should I care?
Q
Comments (24)
Debra, it depends on how far Trader Joe's is to know if it's worth going just for nuts. I do, but I'm walking distance to two of them. :) If you stock up, they'll do better if you vacuum seal them. They have individually wrapped packets of almonds (in a big bag that looks like the rest, so you have to pay attention), which are great for throwing in a travel bag or purse for when you don't know if there will be meals. My absolute favorite is Simply the Best Trek Mix (cashews, almonds, pineapple, cranberries and tart cherries). One great thing about the nuts and seeds is that you can get them raw or unsalted roasted. They also have unsulphered apricots. I think I had to get sour cherries at Whole Foods though. Those were put up in boxes by the grocery department, not in packets or bulk. Whole Foods does target their offerings to the neighborhood. The one in my neighborhood is geared toward upper middle class families. There's one I don't like in an upscale apartments neighborhood that's geared toward overworked yuppies and dinks. Many more prepared things, less actual food. There's one near a university with a lot more vegan ready to eat, sweets, and a more reliable supply of mildew fighter. :) With both places, if you're not familiar with the products and packaging, and the mindset of the merchandise managers, it takes awhile to acclimatize. You also have to be prepared to have certain personal favorites disappear from lack of sell through. TJ's no longer has dried sweetened hibiscus flowers, and I can't find another good source, so I bought a big bag of plain dried. So far I've made agua de jamaica, but haven't gotten around to trying to soak them in simple syrup and see if I can approximate my old fave. I can't seem to get my Whole Foods to reliably keep tomato puree on the shelves, though they have plenty of room and many types of whole, diced and crushed. I can't get D'Oni Bold As Love honey habañero mustard or OooWee barbecue sauce at WF anymore, and I don't want to bother with making my own when these are so good, so I order them from the makers, and I get my favorite cleanser that was from Whole Foods, from Amazon. Still, I forgot to buy lentils the other day, so stopped into Whole Foods today and got organic green lentils, organic green split peas and organic hard red wheat berries from the bulk section. I also got some tomatillos and nopales to barbecue, and almost bought some eight ball squash, but remembered I had yellow squash at home that needed using. They also have tamarind pods, whole turmeric, lemongrass, cherimoya, and stuff like that, most days. And they had lovely, early cherries today. There might be different demand near you, but if you express interest, they might get it. You do have to read the signs and labels. There are always both organic and conventional bananas at both stores, and usually the same is true for peppers, berries, tomatoes, aspargus, etc., though sometimes it's one or the other. Will Whole Foods lure you away from Wegman's? From what I've heard about the Wegman's, probably not. Might it be an interesting place to shop now and then, or to look for what Wegman's doesn't have? Possibly.
...See More
sewer smell in whole house
Q
Comments (3)
The post clearly states the washer pumps up to the drain line, therefore I think we can rule out floor drains. That leaves me with two questions: 1. How did they connect the washer to the drain line? 2. What is the diameter of the drain line that is receiving the discharge?
...See More
Nobody is home at the bathroom forum today
Q
Comments (7)
I hang out there but "those people" don't participate like kitchen people do. And I know for sure the same people are over there. My bathroom shower is enclosed. That cement board stinks! Starting the countdown for the kitchen! Be sure to keep posting. We've had a flood and more rain coming Friday night. Our county has been declared a disaster area. Sigh... I have lakes in my pasture. It will likely die after it's under water for so long. I JUST got it going again after a flood a couple of years ago. This is just not right. It never used to be like this. Let's clear cut some more forest. Clear away more vegetation for more parking lots. That's sure to help. We have electricity and running water but no sewer of any kind. I thought tonight I'd hook the garden hose up in the basement and let the sump pumps take care of it. OR outside in a dog run but that's such a long way to go to adjust the water temperature! Compared to the people who have 4 feet of water in their basement or a tree across their house, I am just fine.
...See More
When you have company do you clean the WHOLE house?
Q
Comments (56)
Returning to pipe in and say that I always clean the house from top to bottom before we leave on a trip. If something happens to us, no one will be thinking we were slobs (although, the house is usually pretty tidy anyway) and I love, love, love coming home to a clean house. It's like someone upthread said - it's like getting another week of vacation! Of course, by the time we bring in our luggage, groceries (always go shopping on the way home because no food in the house), mail and whatnot, it looks like a hurricane went through. Unpacking and putting everything away often takes a full day. But, we usually either do our laundry or send it out to be done before we come home. That way, we don't have to do a mountain of laundry when we get home. I always find having to do that after a lovely vacation a real downer.
...See More
rmtdoug
Original Author
10 years ago
p.s. Yes, I would be running natural gas for fuel, although it is not currently in the house. The cost of hookup would be negligible.
0
tigerdunes
10 years ago
You will find it difficult to locate a small furnace.

Do you want 80% or high efficiency model?

No AC?

IMO
0
rmtdoug
Original Author
10 years ago
I assumed I would go with a 2-stage 95%+ furnace. I'm now trying to learn as much as I can about modulating units. I see some of them go as low as 20k'ish btu's on the lowest setting, but I don't know if one would be appropriate for me or not. I've read of some concerns about running them on low all the time. Don't know how valid these concerns are, although the idea of a furnace that adjusts to your heating load while maintaining its highest efficiency seems like a good one.

No A/C. It's just not hot long enough here, plus I'm by water and there is usually a breeze. I just turned the heat off two weeks ago. We heat 8 mo's a year and have 4 months of pure bliss.

Got another dealer coming at noon. I have four or five more I could call from my list.
0
udarrell
10 years ago
By all means switch from Oil heat to lower cost Natural Gas.

With your winter design temps, I think your Whole House Load-Calc is quite accurate.

You can go 50% above the load-calc with heating.

I would stay in the 40,000-Btuh range or lower.

Longer runtimes provides a lot better efficiency.

Those contractors should be using A load-Calculator; here is as "Free Online Whole House Calculator" they can use; but they should use a room by room calc.

Here is a link that might be useful: Free Online Whole House Calculator
0
rmtdoug
Original Author
10 years ago
Thank you both tigerdunes and udarrell. I used that same calculator for one of my figures.

Well, the dealer rep from yesterday really knew her stuff. When I did bring up the subject of my load calc, she understood immediately and also agreed that my numbers were pretty close to what she would expect, but she still came back with a 60k 2-stage Coleman unit. This was after we discussed a mini-split system and telling me she would go with a two-head 18k Daikin system.

When I asked her why everyone previously was suggesting an 80k furnace and why the oil furnace was 85k, she said it's simply that my ducting was built for that, so I at least learned about that. She said running a smaller furnace would be absolutely no problem in a house my size with all the ducting in conditioned space.
0

Have whole house load numbers but nobody cares

Comments (7)

tigerdunes

rmtdoug
Original Author

Related Discussions

rmtdoug
Original Author

tigerdunes

rmtdoug
Original Author

udarrell

rmtdoug
Original Author

COMPANY

BUSINESS SERVICES

GET HELP

CONNECT WITH US

Have whole house load numbers but nobody cares

Comments (7)

tigerdunes

rmtdougOriginal Author

Related Discussions

rmtdougOriginal Author

tigerdunes

rmtdougOriginal Author

udarrell

rmtdougOriginal Author

COMPANY

BUSINESS SERVICES

GET HELP

CONNECT WITH US

rmtdoug
Original Author

rmtdoug
Original Author

rmtdoug
Original Author

rmtdoug
Original Author