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Old 03-05-2020, 12:55 PM   #1
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Why is it So Difficult


I had no idea attempting to find the average KW / monthly usage of a air to air heat pump properly sized for my house heating for 4-5 months in zone 3 would be so difficult. Our utility co. is worthless in that respect.



I thought maybe in the attached link I could find useful information but they require microsoft word to ask questions and fill out information that may be useful. Now I suppose I need to be a computer whizz. I'm bout to the point of just whizzing on the whole idea.
https://www.energy.gov/energysaver/h...rce-heat-pumps
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Old 03-05-2020, 01:12 PM   #2
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Re: Why is it So Difficult


You have to do it yourself.

Need to know:

Existing usage for heating and efficiency of the furnace
Heat loss/gain, btu per degree F drop in temp.
Capacity and efficiency of new heatpump at various outdoor temperatures, if electric backup is required and how much.
Temperature bin data, how many hours at x degrees

Even with all the info it's not that accurate due to defrost cycles, duct loss, and cycling on and off.

In most areas, at today's prices it's much cheaper to burn natural gas than run a heatpump.

You also need to factor in extra repair costs over a straight a/c as well as upgrading to a 200 amp service if you need strip heat. (or extra cost of getting a furnace and doing a duel fuel setup)

Now if the existing source of heat is oil, propane or straight electric a heatpump can save a lot.

You may not like the lower capacity and supply air temps of a heatpump if you're used to fossil fuel heat.

They're very good when properly installed and used in the right applications.
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I am not in the business of any trade I give advice on. I have non-professional hvac experience + good knowledge of theory. Attempt repairs at your own risk. Never jump out safeties - especially pressure switches - on a furnace for testing with fuel supply on; use a meter. Do not troubleshoot with live line voltage present unless there's no alternative.
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Old 03-05-2020, 01:32 PM   #3
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Re: Why is it So Difficult


Quote:
Originally Posted by user_12345a View Post
You have to do it yourself.

Need to know:

Existing usage for heating and efficiency of the furnace
Heat loss/gain, btu per degree F drop in temp.
Capacity and efficiency of new heatpump at various outdoor temperatures, if electric backup is required and how much.
Temperature bin data, how many hours at x degrees

Even with all the info it's not that accurate due to defrost cycles, duct loss, and cycling on and off.

In most areas, at today's prices it's much cheaper to burn natural gas than run a heatpump.

You also need to factor in extra repair costs over a straight a/c as well as upgrading to a 200 amp service if you need strip heat. (or extra cost of getting a furnace and doing a duel fuel setup)

Now if the existing source of heat is oil, propane or straight electric a heatpump can save a lot.

You may not like the lower capacity and supply air temps of a heatpump if you're used to fossil fuel heat.

They're very good when properly installed and used in the right applications.
I could see the need for all those calculations being run for each individual house if all were unique. But in a zone, as large as 3 is, there's millions upon millions of single story 1,800 sq ft. 8' ceilings brick veneer houses, with 2x4 construction, 6/12 hip roof, 4" of fiberglass insulation and 6-8 Andersen dual pane windows. How difficult can that be? Well, I am assuming real difficult.
I'd consider doing it myself but I can estimate the end result wouldn't be KW usage but an estimated size unit needed.


Thanks for your time.
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Last edited by SeniorSitizen; 03-05-2020 at 01:36 PM.
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Old 03-05-2020, 01:45 PM   #4
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Re: Why is it So Difficult


Performance varies by heatpump model even of the same size. Some units are weak at heating.

You're right that it's possible to get an average for a specific type of house, but it would still only be an average that can vary a lot.

As a starting point, you can just get the cop data for the typical 14 seer hp and just calculate heating cost per delivered kw or 100k btu of heat, compare to what you have.
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I am not in the business of any trade I give advice on. I have non-professional hvac experience + good knowledge of theory. Attempt repairs at your own risk. Never jump out safeties - especially pressure switches - on a furnace for testing with fuel supply on; use a meter. Do not troubleshoot with live line voltage present unless there's no alternative.
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