A/C vs Heat Pumps

gary68

5 ton A/C with 10 KW heat strip running 20hrs a day when temperature get in the 40`s. do I need to upgrade my heat strip or go with a heat pump? Only have 150 amp service panel. (2100 sq. ft.)

Hot_water_fan

You need to supply more information to get useful help, as situations vary widely by location. What’s your location? How much is your electricity? Is the house comfortable during the winter? How about during the summer? How old is this AC? How many hours a day does the AC run when it’s really hot? 

A heat pump is more efficient than electric resistance strips - at 40 degrees, 3-4x more efficient. A heat pump can easily be the same size or greater than 10kw (34,000 btu), which sounds about right for your heating needs if the design temp is around 40. That said, if you don’t have very much cold weather, who cares if the strips run 20 hours a day and the house is comfortable. Pay the charge and move on, until the AC needs replacing. Then, just add a heat pump. Shouldn’t cost any more than a replacement AC. 150 amps is plenty - a heat pump that can supply what you have now probably needs 30 amps or less. 

ratio

Bigger heat strips aren't going to use less electricity, if that's your goal. Averaged over time, 20 kW for 10 hours will use exactly the same amount of electricity as 10 kW for 20 hours, but the heat will cycle on & off more often.

gary68

The unit is only 18 months old and all new ductwork. My concern is that when the temperature gets in the 30's which is about a couple of months a year here in NOLA it won't be able to maintain a 76 degree temperature. Forgot to mention we are also running an electric fire place set at 74 degrees. The unit is still under warranty and had the tech that installed it come check it after my electric bill jumped $100. He said that the air handler was pushing 2000 cfm and was to much for the 10kw heat strip and suggested a 20kw strip. I was told by an electrician that the full house load was 140 amps and would have to upgrade to a 200 amp panel with more space to accommodate an additional 60 amp breaker for the 20kw strip. $2500 for 200 amp panel and $500 for 20kw strip. I was wondering if it would better to go with a heat pump and keep the10kw strip since they are more efficient we have mild winters hear in NOLA. Probably can get $1000 dollars for the a/c unit to offset the cost of the heat pump.

neilc

76* heating setpoint ?
NOLA !

Hot_water_fan

I lived in NOLA too - highest heating bills of my life despite the warmest place I’ve ever lived. But 30 for months at a time? Ha c’mon now. 

I’m sorry they messed that up so badly -  a heat pump should have been installed at the jump. If you can swing it, get the heat pump. If not, you might have some 74 degree nights and pay a few hundred more per year. You can keep the 10kw strips if you want, or toss them. 

I’d highly question that 140 A load, is your panel 100 or 200 currently? Either way, without the 10kw strips, you’ll have room. 

gary68

We have two 50 gal water heaters to accommodate for the jacuzzi and 50 amp circuit to a work shop. The current panel is 150 amps. The house is 40 years old and bought it 6 months ago. Had no problems with a/c.

Hot_water_fan

Well no matter, a heat pump won’t take up any more room on the panel. 

gary68

A couple of months! I've lived here all my life we have 30 to 40 degree temperature swings form one week to the next. Anything below 70 is cold to me. Jan and Feb are the coldest dipping into to the low 30's. Seen some cold Mardi Gras. I'm retired now and this inflation thing have to save any where I can.

Hot_water_fan

I've lived here all my life we have 30 to 40 degree temperature swings form one week to the next.

I sure remember that. The decision is - spend money on a heat pump to replace a nearly new AC for a small portion of the year. I don’t think the 20kw makes sense if the 10kw is turning off during cold weather. 

HVACNUT

Why wasn't a heat pump discussed 18 months ago? What's done is done but it just seems weird to me that it wasn't considered. Or was it?
I saw 2000 CFM which is 5 ton drive but what's the size of the system and what's the SEER rating?
Was a Manual J done? It might be oversized.

gary68

https://www.timeanddate.com/weather/usa/new-orleans/historic?month=1&year=2018

gary68

I've only been in the house 6 months and ask myself the same question. It's a 5 ton 14 seer and a manual was done.

pecmsg

gary68 said:

I've only been in the house 6 months and ask myself the same question. It's a 5 ton 14 seer and a manual was done.

Where is this house and how many Sq Ft?

Hot_water_fan

Even if a manual J was done, and done well, manual Js don’t account for people keeping the house at 76. 

Back to the decision. New heat pump or live with it - which way are you leaning? The pros of the heat pump are efficiency. The cons are that New Orleans isn’t that cold, so there’s less time to be efficient. If you save $3000/ year it is a no brainer. If you save $300 probably not. 

Hot_water_fan

10 KW heat strip running 20hrs a day when temperature get in the 40`s.

How did you clock this run time? Is that 20 hours at 10kw or is it a staged strip?