Question: Air Conditioning System

[pastorables]

I have a question concerning central air cooling, etc. We have central air at my business. It's a 4 ton unit cooling 3,000 sq. feet. The problem is as follows:

Today, it's around 90 degrees outside and 84 degrees inside the building. This problem has been ongoing for a couple years now. The building just will not cool better than 5 degrees of the outside temperature. The building is block and metal with no ceiling insulation. The ceiling temperature has been checked at 20 degrees above average temps. I've had the air unit checked twice to no avail. The answers have been anything from unit too small for building to ceiling could need insulation, etc. Any help would be greatly appreciated as the building is just too hot. I've seen it over 90 inside when the outside temperature is over 100.

Thanks,
pa

[dolfan]

Gee whiz, PA, coming from a family of A/C people and electricians, I think you've answered your own questions. I'm sure some insulation in the ceiling would help, but you still have a capacity shortage. Generally, you need a 1/2 ton for every 1,000 sq. feet. You're a ton short, and even a larger unit may not overcome the lack of insulation. Are you cooling your stock room?? Could you disconnect and seal off the duct to it and redirect the flow to your shopping area and offices????? Could you use large fans in the place of A/C in the stock room? How about blowing some insulation over the top of your drop ceiling (I assume that's the kind you have). Just some thoughts.

[Pianoman]

Not a cooling authority - but work in a brick & metal office that experienced similar problems.

First - regardless of whether it's the entire cause or not - I would certainly invest in insulation. It's not going to hurt - and I would think the savings in utilities alone would allow it to pay for itself.

These were some of the problems we had in our office - it's brown & the roof is brown (heat magnet) - lots of cheap windows (increases the toaster oven effect) - one central air return for the entire office (since each room does not have it's own return - very poor circulation. If you close an office door especially at night - no circulation at all) - vents in the celing (big pet peeve for me - not so much for A/C - but great cause of discomfort in winter - heat stays at the celing & your feet are always cold).
Lastly - we're in a flat, open industrial park with no trees, shade, wind block, etc. of any kind.

Our office had cheap windows that were poorly installed & you could literally feel a warm draft around them when someone opened an outside door.

Our A/C unit was alleged to have been large enough to cool our offices under optimum condition - but the combination of the above problems said otherwise. A/C guy told us we could get a larger unit - but we'd basically just be spending more money trying to compensate for all the problems.

Every building is different in situations like these & a bigger unit is not always the entire answer!

[pastorables]

Gee whiz, PA, coming from a family of A/C people and electricians, I think you've answered your own questions. I'm sure some insulation in the ceiling would help, but you still have a capacity shortage. Generally, you need a 1/2 ton for every 1,000 sq. feet. You're a ton short, and even a larger unit may not overcome the lack of insulation. Are you cooling your stock room?? Could you disconnect and seal off the duct to it and redirect the flow to your shopping area and offices????? Could you use large fans in the place of A/C in the stock room? How about blowing some insulation over the top of your drop ceiling (I assume that's the kind you have). Just some thoughts.

The building is rented, so I really hesitate to put money in both insulation and a new air unit or second unit. I need to be able to solve the problem with one or the other. The stock room is not sealed off from the shopping area, it's only separated by shelving and curtains. There are only 6 air duct/vents in the building and they come from the ceiling through the drop tiles.

The blown insulation is one idea, or adding a second air unit, but no one has been able to instruct me in the wisest direction for the problem.

[dolfan]

And, you'll probably get answers depending on if you ask an insulation salesman or an A/C salesman!

I don't know the layout of your store, but I do know that lumber costs are down somewhat. It may be (this is just food for thought) cheaper and effective to build a partition wall for your stockroom and cut off any air vents that cool it, pushing all the cold air into the store area. That may save you enough money that you could insulate the ceiling. How many square feet could you seal off that way? And, how old is the unit???

[pastorables]

And, you'll probably get answers depending on if you ask an insulation salesman or an A/C salesman!

I don't know the layout of your store, but I do know that lumber costs are down somewhat. It may be (this is just food for thought) cheaper and effective to build a partition wall for your stockroom and cut off any air vents that cool it, pushing all the cold air into the store area. That may save you enough money that you could insulate the ceiling. How many square feet could you seal off that way? And, how old is the unit???

There are no air vents in the stock area, which is only about 1/4 of the entire area. There are 4 vents in the main shopping area, one small vent in the office, and one small vent in the bathroom. The stock area used to have a meat cooler/freezer which could explain for lack of vents. The back area was relatively cool at one time, I'm sure.

The drop ceiling covers the entire building ( around 3,000 feet give or take) and as I understand contains no insulation in the 4 foot space between it and the metal roof.

I am tempted to try the blown insulation, but I don't want to eat the investment either.

pa

[dolfan]

I think you should insulate, for sure, but without sealing that stock area off from the air flow, I think you're going to be disappointed. Cool air sinks. Most of your loss from lack of insulation is at the ceiling by the time the air hits the vent. If the capacity for cooling is sufficient (enough A/C for the space, that is), then insulation may be the difference. But, if you've got 750 square feet to be cooled by an aging unit (I assume it isn't less than 3 years old) that is already big enough to cool only 2,000 feet ---- you're still going to have more space to cool (2,250 ft) than you'll have A/C to cool it. On August's dog days, I don't know that the investment in insulation will actually get you where you want to be.

[pastorables]

But, if you've got 750 square feet to be cooled by an aging unit (I assume it isn't less than 3 years old) that is already big enough to cool only 2,000 feet ---- you're still going to have more space to cool (2,250 ft) than you'll have A/C to cool it. On August's dog days, I don't know that the investment in insulation will actually get you where you want to be.

The unit is actually only about 3 years old. I have no clue why they replaced a 5 ton unit with a 4 ton unit, unless they thought they were saving money. We do so much work in the stock area, I probably couldn't seal it off from the general air flow. Also, you must factor that our doors open about 100 times per day allowing the cool air to escape the building quickly.

A second air unit might be the way to go first? That would give me 9 tons cooling 3,000 feet. If I go with insulation, I could find that I still need more air flow. Of course, what would the power bill look like with two units running?

pa

[dalebert]

i thought it was for ever 600sq ft is one ton of cooling. So if u have 3,000 sq ft u would need a 5 ton condenser. If u do upgrade u need to make sure that the blower is the right size to blow the air...if it is too small it will freeze the a- coil...and if u upgrade u might have to upgrade the a-coil from a 4 ton to a 5 ton a-coil.

[Poimen]

The cheaper investment will most likely be the insulation. It may not be a perfect resolution. But it could be quite workable (especially if you put it in extra thick). You want know for sure until you try.

The price for buying and installing the second unit, plus the cost to run it, will be significantly more than installing blown insulation.

Have you ever blown any? It's not hard at all. Messy, but not hard.

I encourage you to try the insulation first.

[Poimen]

Just asked my dad (who owns a licensed construction company, and does a little of it all) he said it doesn't really matter if you have two units or not, if there is absolutely no insulation in the building it's still not going to cool.

He says you ideally need two 5 tons units for a commercial space that size.

But he says do insulation first. However, unless you have 2 by 2 tiles he suggests NOT blowing. Even then he advices you to get R30 4 foot roll insulation instead.

[Poimen]

Until you can get a second unit, he further suggests you taking a few blocks out and putting in a ventilation/fan system (similar to an attic fan). That will help draw off the heat when it is exceptionally hot. You could cycle it every 20 minutes or so as needed. Just a thought to help in the mean time.

BTW, with the insulation suggested you should get your inside temps down about 15 degrees since you are getting about 5 degrees without anything.

Of course, once you add a second unit you shouldn't have any issues, if you have already insulated.

[Poimen]

Errr, uhhh,

Dad misunderstood something. He thought you owned the property.

Having realized you are leasing, he says forget all that and just blow it!

He says you should be able to blow it for about $500.00

Just be sure to leave a few tiles without any so you can get in to them for wiring access if/when needed

[oletimer]

He says you should be able to blow it for about $500.00

Just be sure to leave a few tiles without any so you can get in to them for wiring access if/when needed

I would not recommand blowing, not that it wouldn't be cheap, but because the tile want hold up to the weight aand having to get back into the atic area. Regular roll insulation can work out OK, may require a little more work, but no real later problems. The fan will help a lot more then you will ever realize. Just remember that if you push it out then you will have to have a replacment air source.

My two cents

[MacUser]

Go to the Pawn shop and buy some cheaper large A/C window units and install those if the blown insulation doesn't work.

Some of the newer ones even come with remotes to turn them and adjust from a distance.