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QUESTION: Hi!
I'm curious to know more about two things:
- How far apart my intake and output can get with a minisplit
- Is a minisplit more efficient to run when the temperature difference is less?

To give you some context, I want to do two things:
- Run a minisplit with a coolbot (http://storeitcold.com/howitworks.html) to run a 6x8 walk-in cooler to 2C
- Run a minisplit to keep a grow room at 21C year-round

The temperatures where I live go from an average -10C in the winter, to 8C in the spring, 18C in the summer and 4C in the fall.

Both the rooms that I want to heat&cool are inside of a barn that has a bit of a temperature buffer when it comes to the extreme temperature swings and the rooms are about 20ft away from eachother.

I was thinking of putting the output from the minisplit for the cooler right in the grow room to help with the heating and then to put the output from the miniplit in the grow room in the barn, so that when the temperatures outside go below 5, the minisplit isn't affected so much.
am I right in thinking that the multizone minisplits generally don't coordinate temperatures with each other and is it a good idea to create those synergies between rooms? Maybe this approach doesn't make any sense, I'd like your opinion.

thank you!
Tori

ANSWER: First of all I have never heard of a Coolbot.

I am not sure what you mean buy intake and output.  

What temp. difference are you referring to?

Please refer to the parts of the unit as the evap. (indoor section) and cond. (outdoor section).  You will be less confused by my answers when you know what is what.  

Clear that up for me and I will do my best help you.

---------- FOLLOW-UP ----------

QUESTION: Ok!  
So I will re-word the first two questions so they make more sense:
- How far apart my evap. and cond. can get with a minisplit
- Is a minisplit more efficient to run when the temperature difference between evap. and cond. is less?

...Answer, briefly, what a coolbot is:
a coolbot is a unit that you can buy that will bypass the electrical controls to get enough cooling out of an AC or minisplit to get a small room down to 2C without freezing up and record less $/BTU than a normal walk-in cooler compressor/condensor/evaporator.

...And put the right words into the last question:
I was thinking of putting the cond. from the minisplit for the cooler right in the grow room to help with the heating and then to put the cond. from the miniplit in the grow room in the barn, so that when the temperatures outside go below 5, the minisplit isn't affected so much.
am I right in thinking that the multizone minisplits generally don't coordinate temperatures with each other and is it a good idea to create those synergies manually between rooms?

thank you so much for your time and expertise!
Tori

Answer
Mini-splits have a limit to the length piping between the units.  You will have to refer to the manufactures directions for that bit of info.

The efficiency  of any system will vary as the temps start to change. The hotter it is outside, the less efficient the unit gets.  The efficiency rating is based on certain operation conditions, which can vary.
There has be a certain amount of difference in temp for them to work.  Mini-splits can cease to operate when the outdoor temp gets to a certain temp, you can refer to the manufacture for that as well, as it can vary greatly.   Systems are installed and designed based on user needs.

The issue of placing the cond. unit inside is heat rejection.  Is the space you are rejecting the heat to large enough?  For every 12000 btus of cooling, expect round 15000 btu's of heat rejection. The colder the set point the longer the unit will run and the larger the unit has to be to get there.

There are ways out there to use heat that is generated from refrigeration systems to heat spaces when need and reject the heat outside when not needed indoors.  

I would stay away from the coolbot.  If something like that was really all it is cracked up to be, it would be used in the field more.  If mini splits were really designed to run as cold as it says it will, the manufactures would sell them out of the box to do what the coolbot does.


Craig  

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Craig HVAC Expert

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I have been in the HVAC field for the past 18 years. I can help with most HVAC questions. I work on commerical buildings for the most part, and have yet to find anything I could not troubleshoot and repair, when repairable. I work on small 1 ton units to a 2500 ton chiller. Troubleshoot air flow, elect, and control problems. I attend regular classes to keep up with the latest and greatest.

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I work on commerical sites, hospitals, gov't buildings. I can troubleshoot just about anything in the HVAC business.

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5 years trade school, VFD training classes, Liebert factory training, some York and Trane factory training.

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