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Old 03-28-18, 06:31 AM   #1
Steve Hull
 
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Default need advice from group

Looking forward to your wisdom and experience. People who have installed are especially welcome.

Time for me to heat and cool shop with a minisplit. Shop is 40 x 60 and built with SIPS (structual insulated panel system). Both roof (R 30) and walls (R 20) are SIPS. Thus, it is very efficient and has low infiltration.

With no supplimental conditioning, shop may drop to 40 F in winter and in summer rarely goes above 85F (central Oklahoma)

I currently use a 1 ton geothermal heat pump - almost 30 years old for some HVAC. But the COP is poor (maybe 2.5) and a low SEER (13-12).

There is an office, separate enclosed in the 40 x 60, of about 250 sq ft. I currently use a 120 V electric resistance heater to keep it warm in winter as it is located on the cold NE part of the building.

I am thinking that a 24 K BTU (2 tonn) will do well for shop interior and 1 ton for office (likely oversize). A standard manual J calls for a bit more, but moisture control is more important than narrow temp control.

Why change now? My livestock feed business has rapidly expanded (feed stored in shop) and feed needs controlled temps- especially in summer. Secondly, I also use the office for business meetings and feel that it does not do me good encouraging energy efficiency in a hot summer office!

One central outside condenser and two wall mounted (small one in office) distribution units, larger one in main shop area, are anticipated

I will install myself and have a HVAC contractor on board who will "sign off" on install for any potential warrantee issues.

Now, what brand, model, specs do you recommend? I am very impressed with these units with high COP and SEER.

Your collective wisdom is FAR better that me starting fresh.

Thanks in advance.

Steve

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Last edited by stevehull; 03-28-18 at 06:38 AM.. Reason: typos
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Old 03-28-18, 09:33 AM   #2
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If you want to go over sized and have humidity control you should get an inverter based unit and they are much more efficient than fixed speed on/off units.
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Old 03-28-18, 12:01 PM   #3
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Definitely go with inverter systems, the price premium is worth it in efficiency. I have an older Carrier single speed 9k installed and wish I would have gone with an inverter. Surplus city liquidators sometimes has good deals on minisplits so thats one avenue to get cheap equipment.
As for brands, most people say the Daikin and Mitsubishi are the cream of the crop when it comes to mini splits. I've had quite a bit of experience with the Carrier units and they are pretty reliable in a light commercial environment.
If you want to play around with manual J a good website to go to is coolcalc.com It can help you fine tune your calculations and is completely free
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Old 03-29-18, 06:20 PM   #4
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In some case a inverter model will not save much money over a non inverter unit
For a non inverter I would size to your homes average winter BTU consumption and no higher. My non inverter 12000 BTU model runs 24-7 throughout winter heating 900 sq.ft of a 1900 sq. ft two story house so im my case I would see little savings if the heat pump had a inverter. For me not enough of a savings to warrant the price of a inverter pump.
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Old 03-30-18, 07:14 AM   #5
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Guys, I am not interested in this going on for a discussion of manual J (already done), but hard advice on models, the ability to put a 1 tonn and 2 tonn on one minisplit condenser, and who to buy from.

Read my original posting, not just the last one for details on the shop.

There are SO many on line dealers and I would like to know which have you found helpful.

I have followed many of your threads (xringer, pinball and others) over the years.

Steve
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Old 03-30-18, 06:21 PM   #6
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I will tell you my next route in the next house I want to buy a Senville or equivalent 12k inverter split off eBay for about $1000 mount the split myself but hire a Hvac guy to plumb it for the warranty.

I expect it will cost around $200 to have a certified person plumb the lines. My guess.
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Old 03-31-18, 11:18 AM   #7
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I have 2 senville units, they work great.
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Old 04-19-18, 01:08 PM   #8
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Quote:
Originally Posted by ecomodded View Post
In some case a inverter model will not save much money over a non inverter unit
For a non inverter I would size to your homes average winter BTU consumption and no higher. My non inverter 12000 BTU model runs 24-7 throughout winter heating 900 sq.ft of a 1900 sq. ft two story house so im my case I would see little savings if the heat pump had a inverter. For me not enough of a savings to warrant the price of a inverter pump.
I would always go with the inverter unit -are they really more expensive at this point?

A single speed unit operates at nameplate (with temperature (reality) related capacity curve) - but the inverter units can actually supply their nameplate output at lower temperatures than the non-inverter units, by over-speeding the compressor.

If you size to average heat demand, all of the periods in winter with more demand (colder than average) mean your unit will not be able to maintain setpoint.
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Old 04-20-18, 12:20 PM   #9
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Quote:
Originally Posted by stevehull View Post
Looking forward to your wisdom and experience. People who have installed are especially welcome.

Time for me to heat and cool shop with a minisplit. Shop is 40 x 60 and built with SIPS (structual insulated panel system). Both roof (R 30) and walls (R 20) are SIPS. Thus, it is very efficient and has low infiltration.


Steve
SH,

Aren't you a certified engineer and an energy professional with 28 years of professional experience under you belt?

Why are you asking a bunch of amateurs for advice?

Puzzled,

-AC_Hacker

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