• Hey Guest!
    British Car Forum has been supporting enthusiasts for over 25 years by providing a great place to share our love for British cars. You can support our efforts by upgrading your membership for less than the dues of most car clubs. There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Upgraded members don't see this banner, nor will you see the Google ads that appear on the site.)
Tips
Tips

Any HVAC gurus here?

Share this page

NutmegCT

NutmegCT

Great Pumpkin
Bronze
Offline
I'm looking for guidance on specs for some window units for our museum library.

Four rooms about 250 sq feet each, one north facing wall in each, cement block, not well insulated. Will need to provide fresh air, humidity/dust control, and good circulation. Must be individually timer-controlled, and bring 85F degree air down to 75 . I can find BTU estimators, but nothing so far on how units handle air flow around obstacles (cabinets, shelving, etc.).

Any takers or references?

Thanks.
Tom
 
I'd look at LG units, seems like everything else is junk. GE and Fridgidaire only have styrofoam separating inside from out. You can see light through them....a lot of it..:eeek:

If you have obstacles and poor insulation, I'd go with at least 8k per room if not 12K. IIRC, a 12K LG was ~$300. I don't know if mine's timed or not.

I am by no means an AC expert, I just lived in the south. I miss the old units that would hurt your hand if you held it in front too long.

This is the one I have. https://www.homedepot.com/p/LG-Elec...ir-Conditioner-with-Remote-LW1212ER/203147366
 
Have you looked into mini-splits? Not window units but much better air circulation and much less noise. If its window units only, I have had good luck with LG as well. Just make sure that you don't go too big or humidity control will suffer.
 
Thanks for the suggestions. I've heard good things about LG and Mitsubishi also.

One thing that puzzles me about the "split" units. Where do they get fresh air? Seems the only thing through the wall is the refrigerant pipe. We're in a concrete block building with no windows - so no fresh air. Standard window units would have to go into a hole in the block wall, but at least those units provide ventilation.

Also concerned with air flow in one of the rooms; it's got a divider panel (with built in shelves) in the middle of the room, that "blocks" half the air flow. Don't know how to handle that. Imagine a room 20 feet by 20 feet, with a 10 foot floor to ceiling divider in the middle, five foot open space on either side.

Would the a/c unit at one end have a problem with pushing/pulling air into the opposite end of the room?

Tom
 
I have a Mitsubishi split unit in my house. They don't need fresh air...I didn't know any AC unit did. The room air stays in the room and is recirculated and the hot air stays outside. A split unit looks and works in the same way a window unit looks and works; it's just in to separate housings instead of one rectangular box. The only thing that really needs to pass from cooled space inside to heat dump outside are the refrigerant pipes and electrical wires. They could pass through a space about 1½" tall and did in some of the older window AC units we had when I was younger. Some AC units have a tiny vent that opens to the outside but from the point of air exchange, they're about useless.

You might be able to circulate air around that divider with a couple of fans...a lower one moving air into the the space and a higher one moving it back with the AC outflow directed toward the end of the divider with the fan blowing in....it's a thought.
 
Just reading all this and thinking that, while education is good - it is probably worth either getting a consultant in, or getting some expertise as part of a couple of bids. Then you won't be blamed for being the guy that got too little or too much or only one side of the room AC.
 
Thanks. Sorry I wasn't clear about the fresh air bit. As I mentioned before, the rooms are in a concrete block hangar. There are no windows. We need to ventilate the area at least some of the time. Standard window units allow you to recirculate, or to ventilate. Seems you can't do that with the split units.

Edit: JP - your post popped up as I was posting the above. I've called in consultants already, but they only deal with full duct work or the split units. Lowest proposal so far is $60,000 - which is ridiculous for our space. And none of those systems allow any fresh air! Can't find anyone who wants to "consult" for the system design I need, and which I can afford.

Tom
 
Typical window AC units don't ventilate. That just isn't the way they are designed. As noted above the better sealed they are the better they work at cooling.

If you need ventilation AND AC then you are probably going to need something like a heat recovery ventilator. Some of these come with HEPA filters and can be used in a recirculation mode when the neighbors experiment with Cajun cooking on the barbeque grill. I installed a HRV last year and am considering a second. They work but when the outside temp gets ~0o F I can feel some temp drop.

Edit: I don't sell HRV's but they work so well that I'd conswider them mandatory for any new construction and would retrofit any house I buy in the future with one - including rental units.
 
I'm wondering why you need ventilation. An A/C unit should pull as much moisture out of the air as you need.
 
Bring in a couple of reputable hvac contractors. They should design a system with the hope of getting the job.
 
Put the unit blowing straight into the side of the divider. Use the divider to split the ac discharge, that way both sides get equal air.
 
kellysguy said:
Put the unit blowing straight into the side of the divider. Use the divider to split the ac discharge, that way both sides get equal air.
Click to expand...

Thanks - that divider is most of my worry.

If the air blows straight onto the divider, won't that just reflect the air back to the a/c side of the room?
 
John Turney said:
I think he meant blow straight at the edge of the divider.
Click to expand...

Now *that* makes sense. But I don't have that option. A/C has to go into the outside wall, which is parallel to that divider wall.

hmmm
 
NutmegCT said:
Now *that* makes sense. But I don't have that option. A/C has to go into the outside wall, which is parallel to that divider wall.



hmmm
Click to expand...


O.K, then mount it far to one side where it will blow through one of the openings on side of the divider. On the other side of the divider in the opposite corner, put a fan blowing through the other side of the divider back towards the wall with the a/c in it. It should circulate air through both sides of the divider as well as along both faces of the divider. Kinda "yin/yang".
 
Thanks for the ideas. I like the "yin/yang" concept, and I was already thinking of two fans at the divider sides (push and pull).

Mini split evaporator is certainly feasible, but I really like the idea of the fresh air inlet you see on window units. Sometimes called fresh air, exhaust, vent, etc. Usable when desired. In the window-less concrete block environment we're working in, access to fresh air is important. Currently there is *no* fresh air at all; with only one door - an inside door to the civilian aviation hangar - we're probably breathing the same air we breathed there five years ago.

gasp choke
 
Back
Top