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Considering replacing a working furnace...

Posted by seattleCraftsman (My Page) on
Wed, Sep 18, 13 at 19:27

Background:
I'm looking to preemptively replace an ~18 year old natural gas furnace.
House is 102 years old, located in Seattle. Living sqft 3,000, that includes finished basement.
Had attic taken to R49 and dense pack cellulose blown into the exterior walls.
Double hung windows on first floor (~20) are original, single pane. Basement and upstairs are double-pane. House is better sealed than when I got it, but certainly not drum-tight.

I don't think I want an HVAC, space, noise, cost, generally mild summers.

Questions:
* Looking to contact a well-reviewed Carrier installer in the area. What other brands should I consider?
* Anyone hazard a guess at $$ ballpark for Infinity 98 or 96? Looking at them for the quiet as much as the efficiency, plus slightly better rebates.
* Is something like the Infinity air purifier worth the investment, or one of the step-down models adequate? Or skip it?


Follow-Up Postings:

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RE: Considering replacing a working furnace...

Having lived in the Seattle area (Silverdale) years ago for three years, I've got to ask.

With the generally mild weather in Seattle, why preemptively replace a working furnace? If it were to die in mid-Winter someday, I suspect you could survive for a few days until a replacement could be installed.

I/ve never owned a furnace that needed replacement at anytime near as early as yours.

YMMV


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RE: Considering replacing a working furnace...

Real motivators are that this sucker (Plus 80 Payne) is noisy and to help with room layout revision. Wouldn't mind a more efficient model either. Had thought gas furnaces were good to maybe 20ish years, so didn't think I was really throwing in the towel on this thing too early. I may be way off.

It currently vents up through chimney and intake from the basement. My hope - so correct me if I'm wrong - with a new furnace, one that does intake through the exterior wall, I could make a solid and sound-insulated wall where I currently have the bifold doors. We watch TV in the rec room and that is difficult when ole' Payne fires up. Less of a concern is the bedroom on the other side, which is an infrequent guest room.


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RE: Considering replacing a working furnace...

What size and efficiency is existing furnace? You have AC as well?

How is home's insulation qualities, ext walls, attic, basement, etc.

Any hot/cold spots? Typical winter temp averages?

Location of existing furnace?

Post back.

IMO

This post was edited by tigerdunes on Thu, Sep 19, 13 at 8:38


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RE: Considering replacing a working furnace...

I know you have gas, but a heat pump there might not be such a bad idea and worth investigating. I seem to remember that the Seattle area had really low electric rates.


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RE: Considering replacing a working furnace...

Re the heat pump. If thinking about that, examine the costs and scope of possibly needing to upgrade the electric service.


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RE: Considering replacing a working furnace...

Re the heat pump. If thinking about that, examine the costs and scope of possibly needing to upgrade the electric service.


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RE: Considering replacing a working furnace...

If OP will provide his rates, I will be glad to run the fuel comparison numbers.

I think it would be well to note OP's home is 102 yrs old. This raises the question of the home's insulation properties. If good, then consider a HP paired with 80% eff two stg VS furnace. If poor, I would forget the HP and stay with nat gas for heating.

IMO


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RE: Considering replacing a working furnace...

Thanks for the questions. A point against a heat pump is where to locate it - no AC currently, no real room next to house, not much out back, they're loud(ish) and the windows are thin...

Some answers:
Insulation from original post:
Had attic taken to R49 and dense pack cellulose blown into the exterior walls.
Double hung windows on first floor (~20) are original, single pane. Basement and upstairs are double-pane. House is better sealed than when I got it, but certainly not drum-tight.

Electical rates:
We currently use ~500 kWh per 30 days, our roughly 17 a day.

Summer Billing Cycles
(April - September)
First 10 kWh per day at 4.66¢ per kWh
All additional kWh per day at 10.71¢ per kWh

Winter Billing Cycles
(October - March)
ENERGY CHARGES:
First 16 kWh per day at 4.66¢ per kWh
All additional kWh per day at 10.71¢ per kWh

Gas
Feb 2013 Delivery charge - 89.39 therms @ $0.3924 per therm = $35.08
Feb Feb 2013 Delivery charge - 89.39 therms @ $0.56627 per therm = $50.62


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RE: Considering replacing a working furnace...

By all means do a whole House load-calc on your home for sizing any new furnace or A/C or heat pump.

Use the calculator & use .4 or .5 Air changes per Hour (ACH) * cu.ft volume of your home to get the CFM...put in the blank___CFM; when U think U have it right print it; U can't save it; unless U use 'Snipping Tool' to capture the screen image of it.

Here is a link that might be useful: whole House load-calc


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RE: Considering replacing a working furnace...

Depending models, heat pump condensers are no louder than straight AC condensers. That's a fact.

If AC is unimportant for the time being then just stick with a good nat gas furnace. I would go with a two stage var speed model. The question would be whether high eff 95+% efficient or standard 80% efficient.

I'm not even going to run the fuel comparison costs unless you are interested in HP for the AC mode. You will have to tell me.

Perhaps I overlooked it -the size of your existing furnace.

Post back.

If you are interested in AC, I would look at a HP paired with nat gas furnace. If not stay straight nat gas furnace and perhaps you might add AC at a later date. Just tell me the direction you are leaning.

IMO


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RE: Considering replacing a working furnace...

Not interested in AC now. Higher efficiency, 95%+

Payne furnace, 395cav048111
input 110,000, output 89,000


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RE: Considering replacing a working furnace...

Get a load calc to confirm sizing.

I would think an 80 KBTU 95%+ model with a 4 ton rated blower. That would give you the option to add a 4 ton AC condenser for the future if so inclined.

What size living area in the basement is included in the 3000 sq ft? Basement below grade? Insulation properties if any ?

I would look at Carrier/Bryant, Trane/AmStd, and Rheem.

IMO


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RE: Considering replacing a working furnace...

Thanks for the recommendations. Appreciate the help from everyone.

Basement is just shy of 1,000 sqft with 7 foot ceiling. About 2/3 below grade with ~5/8 of walls insulated with R13. Carpet on floor, but no insulation.

Load calc with some guesses. Cool tool, I'll have to more accurately measure things and give it another go.


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