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Jack_in_VA
Premium
join:2007-11-26
North, VA
kudos:1
Reviews:
·Millenicom
reply to cowboyro

Re: [HVAC] Manual J and heat pump sizing

said by cowboyro:

If I were to do it I'd put the 5-ton unit. Yes some will disagree, but if you have a variable speed blower the humidity issue will be taken care of.
You'd probably save more from being able to use setbacks than from being super-efficient and having all the savings wiped by just one very cold day. Not to mention that having a system blowing warm air is nice.
During a very cold day I use over 100kWh of electricity in addition to 7gal of oil.
My oil heat cost is $4/gal and 7 gal make 780k BTU, so 28000BTU/$ give or take.
Heat pump would give me 45000BTU/$ even with a lousy COP of 2
For the difference in cost of 1 day ($10 cheaper if I could produce the heat with the heat pump) I can run a dehumidifier for over 5 days (not that I would need, the system takes care of the humidity).

You have a fixation on the variable speed blower. I have a variable speed blower so what. Most all newer systems utilize that technology now. Your posts contradict all accepted HVAC design and operation.

At zero the other day My 3 ton with heat strips used 160 kWh. About $16. Removing the cost of the strips the 3 ton HP itself would be about 75 kWh or $7.50. There is no way 2 more tons (5 tons) would be enough at zero degrees.
Do your own math...


cowboyro
Premium
join:2000-10-11
Shelton, CT
You have a fixation that heat pumps must be shitty and HVAC people look out for your best interest. Reality check, HVAC people are in the business of making money and an undersized system in the name of efficiency will bring them business. An undersized system will only wear faster needing service sooner. An undersized system will make people unhappy and call backs aren't free. Heat pumps can deliver all the required heat even at freezing temperatures if they are big enough, it's all about finding the balance for the lowest TCO.


Jack_in_VA
Premium
join:2007-11-26
North, VA
kudos:1
Reviews:
·Millenicom
said by cowboyro:

You have a fixation that heat pumps must be shitty and HVAC people look out for your best interest. Reality check, HVAC people are in the business of making money and an undersized system in the name of efficiency will bring them business. An undersized system will only wear faster needing service sooner. An undersized system will make people unhappy and call backs aren't free. Heat pumps can deliver all the required heat even at freezing temperatures if they are big enough, it's all about finding the balance for the lowest TCO.

That's bull. My system has a 10 year parts and labor warranty. It would not be in "THEIR" interest to even think what you post.

You going to revise the capacity charts at given temperatures and given tonnage to match your statement?