Mini split question

[42769vette]

Thinking of doing a mini split in a large shop. The main room is 80'x40', with a 20'x20' side room, so basically 3600 feet.

The room has 10' ceilings on a insulated concrete pad. 6 windows, and a 10' overhead garage door that will rarely be opened. Closed cell spray foam sidewalls, and blown in insulation in the attic.

Any advise on what this room will require? There is not much info on 3600 foot rooms.

 

[tmschuller]

You’re set on a mini split? If so a multi evaporator set up or 2 systems running dual evaporators. Without seeing a floor plan it’s hard to say..

 

[ChristianPatriot]

Thinking of doing a mini split in a large shop. The main room is 80'x40', with a 20'x20' side room, so basically 3600 feet.

The room has 10' ceilings on a insulated concrete pad. 6 windows, and a 10' overhead garage door that will rarely be opened. Closed cell spray foam sidewalls, and blown in insulation in the attic.

Any advise on what this room will require? There is not much info on 3600 foot rooms.

Not sure one mini-split would give you enough dispersion to maintain temp in the whole space. That’s a big room for a unit with no ductwork.

One condenser with three or four heads may work if they’re spread out enough.

Or just a traditional split system with some ductwork.

 

[42769vette]

I'm not set on a mini split at all. Just exploring options. This is for a building I'm donating to the local wrestling club, so trying to keep cost down. I need it to get cool enough to not kill anyone, but heat is more important than cool.

As far as floor plan, it's simple. 60x80 building runs east west. South 40x80 is 1 room. Right in the middle of that space is an extra 20x20 section with garage door. It's shaped like a T..

 

[Leo]

If you are working in the whole room, you need air circulation in the whole room. For athletics you might want to over size the air handlers. Don't forget that heat from lighting needs compensation.

Body heat loads the system also. Add 500 BTU per hour per person. I have spec'ed 5 tons for a single 600 square foot conference room, and when 35 people walk in for a 2 hour meeting, the unit keeps up but runs the whole time.

Do you already heat it?

 

[Mark-DuCo]

First off: I AM NOT AN EXPERT IN HEATING AND AIR.

Now, from what I understand about mini splits, they are not the best option for a building like this. They are designed to work with a small room or several small rooms using a multi head unit.

We are installing one in the living quarters in my brothers shop, his will be a 3 head unit. One in each bedroom and one in the living area/kitchen. The total is 900 sqft.

 

[Hardscrable]

I have a 32’ X 30’ , 10’ ceilings, etc. in my retired guy shop at my house. It works fine for me but I agree with others in thinking that I would look at other options for your sq. footage, etc. System should have Distribution and cold return in my totally not a professional HVAC person opinion.

 

[DocIndy]

What kind of power is available? Single or 3-phase? Gas available?

 

[rhamersley]

You really need to have a load calculation done, especially with the heat load of athletes in the space. It's a really large space, and I'd guess that it'd need more tonnage than you'd get in a mini-split unit to keep up. Also, as said above, distribution would most likely be necessary in a space that large. I'm guessing that a ground mounted gas pack unit might be the most satisfactory solution with a main trunk going in and splitting both directions of the long area, with a branch into the 20x20. Hard to know without doing a design on it, but I think you'll not be real happy with minis in this application. Just my two cents as an MEP engineer.

 

[cg21]

So……. I tried a mini split (mr cool from Home Depot diy kit) not only does it NOT run when it is cold out (something freezes and won’t run under a certain temp when you actually need it) AC worked OK when it was working now it is throwing a code.

i would highly NOT recommend. Cheaper up front headache the whole time.

 

[42769vette]

Thanks for all the replies.

To answer some questions. The coldest we will ever want it in the room is 85. In wrestling you have to sweat a lot, and that's hard to do in a 70 degree room.

There will be times there are 60 kids on the mat with another 10 adults, that's a lot of body heat, but like I said, it's not like we want it cold in there.

My original plan was ceiling mounted electric heaters, and no air, just open windows/garage door. I was working in there a week or so ago, and I know it got to 100 degrees mid day. I'm all for keeping it hot, but I don't want heat stroke hot.

Sounds like mini splits are not the right answer. I appreciate the advise.

 

[DocIndy]

A ground mounted package unit would be the best solution. You will need outside air to meet ventilation code requirements and can do that much easier with a economizer on the package unit.

 

[cg21]

Thanks for all the replies.

To answer some questions. The coldest we will ever want it in the room is 85. In wrestling you have to sweat a lot, and that's hard to do in a 70 degree room.

There will be times there are 60 kids on the mat with another 10 adults, that's a lot of body heat, but like I said, it's not like we want it cold in there.

My original plan was ceiling mounted electric heaters, and no air, just open windows/garage door. I was working in there a week or so ago, and I know it got to 100 degrees mid day. I'm all for keeping it hot, but I don't want heat stroke hot.

Sounds like mini splits are not the right answer. I appreciate the advise.

Maybe just run the gas heaters and then open doors and turn on barrel fans like they have at TSC or any farm store a couple of those wouldn’t cost near as much as air conditioning and if you don’t want it under 85….. I think they’d do just fine you could get fancy and plug them into a thermostat…..

 

[rhamersley]

Thanks for all the replies.

To answer some questions. The coldest we will ever want it in the room is 85. In wrestling you have to sweat a lot, and that's hard to do in a 70 degree room.

There will be times there are 60 kids on the mat with another 10 adults, that's a lot of body heat, but like I said, it's not like we want it cold in there.

My original plan was ceiling mounted electric heaters, and no air, just open windows/garage door. I was working in there a week or so ago, and I know it got to 100 degrees mid day. I'm all for keeping it hot, but I don't want heat stroke hot.

Sounds like mini splits are not the right answer. I appreciate the advise.

When we design a HV system like you were wanting, the design criteria we use is outside ambient + 10 degrees, then calculate the airflow to a 95 degree outside condition (105 indoor). Even if you had "perfect" ventilation, on a 90 degree day you'll have a 90 degree space (impossible due to walls retaining the heat, etc.). You're stuck having some type of mechanical air conditioning if you want to keep any type of setpoint.

With a gas package unit, or even an electric package unit if gas isn't available, you have the cooling and heat being distributed throughout the building. And as DocIndy said you need a minimum amount of outside air introduced to the building per person to meet code, which this type of unit allows.