Ac not cooling shop?

[Hobby_Man22]

I'll probably have him come back out and check the charge level. Yes this is the first season for cooling. It was installed in November.

 

[Hobby_Man22]

Upon researching that suction line is supposed to be between 35 and 55 degrees. Sometime isn't right if it's 80. I measured right where it came out of the condenser where the filling poets are.

 

[Hobby_Man22]

As far as what it looks like. It uses insulated spiral ductwork like what you would see in a restaurant

 

[Terry D]

Is that line supposed to be cold? It was sweating and draining out the condensate line, but that copper line was like 80 degrees when I shot it with the temp gun. I thought it's supposed to be cold?

Small line should be warm to the touch, just not real hot. Larger line should be somewhat cold, but if it is sweating and you are removing humidity, is a good sign. But checking the charge is the only way to tell. Was this unit installed by a professional.

 

[kj_mustang]

Hobby man,

Take a look at my garage build linked in my signature for another data reference. My build is 32 X52. Half my building doesn't even have AC. It has been over 85-90 degrees for over a week here. I walked in that non ac half yesterday afternoon and it was comfortable inside, probably 74 - 75F. Insulation and air sealing is key. Also my garage doors on that side haven't been opened in a week.

 

[Hobby_Man22]

Small line should be warm to the touch, just not real hot. Larger line should be somewhat cold, but if it is sweating and you are removing humidity, is a good sign. But checking the charge is the only way to tell. Was this unit installed by a professional.

They never checked the charge level when they installed it. It came precharged with 15ft line set and they said that's about what they used. The outside temperature wasn't hot enough to get the system to show the correct pressures was the explanation inwas given when I asked if they were going to check the charge. Yes it was installed by one of the big name companies.

 

[56Mark]

Is that line supposed to be cold? It was sweating and draining out the condensate line, but that copper line was like 80 degrees when I shot it with the temp gun. I thought it's supposed to be cold?

edit: The suction line outside at the compressor should be close to the temperature of the air in the building.(edited, that is not correct, it should be colder than the air temp but not near freezing) The refrigerant evaporates inside causing the inside coil to be cold, once it is all evaporated to vapor in the top part of the coil, it starts picking up heat and warms up to nearly the same as the air from the building passing over the coil. So if your inside coil is 64 and the line is 80, you have picked up 16 degrees, that is called superheat. You would need gauges to check the actual superheat, and then need a chart of wet bulb temp inside vs outside temp to determine what the target superheat is. This will tell you the system has the correct refrigerant charge. As the heat load drops, that suction line (larger one) outside will get cooler.

edit: if you get someone to check the charge make sure they check by superheat or subcooling methods depending on what type of expansion valve/device it has. If they only check pressures, they are somewhat guessing.

 

[56Mark]

Upon researching that suction line is supposed to be between 35 and 55 degrees. Sometime isn't right if it's 80. I measured right where it came out of the condenser where the filling poets are.

I am not an HVAC tech, but have a pretty good understanding of these systems. The 35-55 range may be your saturation temperature in the evaporator, not the temperature of the suction line. When you read pressure on that line, you convert it to saturation temperature so what you are really reading is the temp of the coldest part of the inside evaporator coil. The coil inside is picking up the heat from the building, so it will be several degrees warmer than the coldest coil temperature. 35 is a little too close to freezing and most good techs won't charge a system to the point it runs that close. Low refrigerant will cause low saturation temps and that is why inside coils freeze up, that blocks air flow, and the problem gets worse because no heat is being removed. This video is better than my rambling I am sure:

 

[grounded-b]

IR temperature "guns" are terribly inaccurate. The rely on IR reflecting back off the surface you are aiming at. Bright shiny objects will emit less IR than dull dark surfaces. they need to be told what the "emissivity" of the object is. by default they usually use a value of 0.95

 

[Hobby_Man22]

IR temperature "guns" are terribly inaccurate. The rely on IR reflecting back off the surface you are aiming at. Bright shiny objects will emit less IR than dull dark surfaces. they need to be told what the "emissivity" of the object is. by default they usually use a value of 0.95

I realized that. The copper.was.far.from.bright and shiny. There was a guy on YouTube that put a piece of painters tape on the line for a more accurate reading.

 

[PoorUB]

Sorry, but I have no clue why you are concerned about the ability of your air conditioning to cool your shop when you haven't properly insulated and weather stripped it. You are seriously putting the cart before the horse! It is like wondering why your car can't do 60 MPH on four flat tires. Or "What should I do? My air conditioning in my house won't keep it cool. Do you think I should close the doors?

Also you comment that it will be expensive to run the AC if it runs all the time. Well you can put in more air conditioning so it doesn't run as much, but it will cost even more to run.

Finish the insulation and weather strip and then worry about it.

"Is that line supposed to be cold? It was sweating and draining out the condensate line, but that copper line was like 80 degrees when I shot it with the temp gun. I thought it's supposed to be cold?"

It should be cool, but also, shooting it with a infrared temperature gun will give you weird readings. You can not use an IR them gun on bare copper pipe, or any shiny surface. I seriously doubt it was 80 degrees.

 

[PoorUB]

Another thing. I have a 24x38 shop with 9 foot ceilings, (8,200 cubic feet) I air condition easily with 1-1/2 tons. It was 105F here the other day when I turned on the AC and it cooled it down to 72 degrees in a reasonable time. I am not sure how long as I wasn't paying attention, but certainly less than an hour.

You have a 30x50 x12 or 18,000 cubic feet that you can not cool to your satisfaction with 5 tons. Your cubic feet is 2-1/4 times the size of mine, so 1-1/2 tons x 2-1/4 = 3.375 tons. Four tons should cool it easily.

FIX YOUR INSULATION!!!

 

[American Locomotive]

Put. the. temperature. gun. down.

Install the door seals, hang some plastic in front of the doors to isolate them from the shop, and let the system run for several days to get your slab temp down. Just leave it running - even overnight. Who cares if it runs constantly for a few days - it won't be a big deal deal. If your slab is staying at 80 degrees, you'll never get the shop cold.

Like others mentioned, 75-80 degrees is a typical slab temp for radiant heat. You're fighting a heat-soaked slab (and honestly, I'm really not sure HOW the slab could get that warm...) and leaky doors radiating a ton of heat.

 

[PoorUB]

I realized that. The copper.was.far.from.bright and shiny. There was a guy on YouTube that put a piece of painters tape on the line for a more accurate reading.

If you want a accurate temp with an IR gun, spray paint the object, in this case the copper line, with flat black paint. Also, how close we you to the line wit the IR gun, you need to be pretty much touching it or it will rear the temp of what ever is behind the line. Hard to get a temp with an IR gun on a small object lie a 7/8" copper line.

 

[metlmunchr]

Any even half competent a/c tech will tell you that it's impossible to get useful refrigerant line temps using an ir temp gun. Past that, the suction line temp alone doesn't really tell you anything. Probably the most reliable conclusion that can be drawn from observation alone is that, in fairly humid areas, if the suction line isn't sweating then the system is likely undercharged.

But, to accurately determine the charge level on a fixed orifice system, you have to measure the indoor wet bulb temp, the outdoor dry bulb temp, the suction line temp, and the suction line pressure.

The tools required are a manifold gauge set, a psychrometer, and an electronic thermometer with a contact type probe that can be attached to the suction line and wrapped with insulation.

Once the above readings are collected, they can be plugged into a free app from Emerson Electric, the mfgr of Copeland compressors. If anyone cares to download the app, it is CheckCharge. It covers the standard refrigerants used for a/c as well as all the common alternative and replacement gases, and works for charging via both superheat and subcooling. The superheat calculation can of course be done manually, but this app is so handy and easy to use that doing manual calcs just doesn't make sense.

 

[Hobby_Man22]

I kind of thought that was bs that they just left me with whatever Freon it came with in the system. Didn't bother to hook anything up to it to check the charge. I know they said it was charged enough for 15ft of line set, but what happens if it's actually 18ft. How critical is this?

 

[PoorUB]

A good tech will hook up gauges and test subcooling and superheat. I did HVAC service for years. New units would came charged, most were not charged like the factory claimed the were. I always ran tests on a new unit and most of the time had to adjust the refrigerant charge.

 

[Hobby_Man22]

A good tech will hook up gauges and test subcooling and superheat. I did HVAC service for years. New units would came charged, most were not charged like the factory claimed the were. I always ran tests on a new unit and most of the time had to adjust the refrigerant charge.

Is it true that the pressures won't read correctly if the outside temp isn't warm enough? It was like 65-70 degrees at the time of install. That's why they didn't check. They just said to call them up in the winter time if it's not heating.

 

[acmikee]

air conditioning does not cool a room it removers heat
insulate your garage as other have said
what is your supply and return temps

 

[metlmunchr]

Is it true that the pressures won't read correctly if the outside temp isn't warm enough? It was like 65-70 degrees at the time of install. That's why they didn't check. They just said to call them up in the winter time if it's not heating.

With that sort of outside temperatures the charge definitely can be checked and adjusted accurately IF a competent tech is doing the start up. The truth is, whoever told you that line of ******** likely doesn't have a clue about where to even begin to do a proper system start up.

While you've gotten a lot of advice and criticism in all of your threads concerning the necessity of insulation and air sealing prior to being able to judge the proper functioning of your system, I view a lot of that as johnny come lately "internet expertise". The fact is, you have 300 sq ft per ton and with a properly functioning system that's enough capacity to cool a building from 50-60 years ago when minimal insulation was the norm, heating oil was 13¢/gallon, and most new residential and light commercial buildings weren't air conditioned.

Using the house where I grew up as an example of typical construction in the south in the 60's. 1800 sq ft, built in 1961. 3.5" batts in the walls and between the ceiling joists. Black fiberboard on the exterior underneath brick veneer. No under floor insulation between the living area and full daylight basement. And jalousie windows, which were close equivalents to having holes in the walls as none of them ever sealed well regardless of brand. By today's standards, a black hole for energy. Yet, for that house, which wasn't insulated nearly as well as your building even though you may have some finishing up work to do, the 3 ton a/c system installed during construction had no problem maintaining 72° in the house when outside temps were in the upper 80's or low 90's. That's 600 sq ft per ton, or half the cooling capacity you have per square foot. 5 tons, working as it should, ought to keep your building comfortable even if you left one of the doors raised a couple feet.

I'd recommend you set the thermostat at whatever temp you want to maintain and let it run untouched for at least 3 days and see how it's performing once it's had time to overcome the heat soaked condition of the slab and the steel in the building. Then, if you're not satisfied, call the installer and request they send a tech to go over the system since that wasn't done initially.

Once you're satisfied with the system's operation, it's much better to set the temp up when unoccupied than to just cut it off, both to prevent heat soak and to keep humidity under control. Uncontrolled humidity affects not only the air but also everything else that's capable of absorbing moisture like the insulation, floor slab, etc. Then when you start it back up, all this humidity creates a latent load which combines with the sensible heat soak load to cause extended pulldown times even if the system is working perfectly and doing everything it can do.

 

[Hobby_Man22]

I'm going to call them out regardless. I spent a lot of money on this system so it needs to run correctly.

 

[Hobby_Man22]

There is a guy on here that has a 40x60x16 steel building and he says his system inthink it's a 5 ton that it cools his building fine.

 

[Hobby_Man22]

I put R30 on both the ceiling and the walls. Of course since it's a metal building that's all it has, but that's supposed to be above code for my area I believe. R30 on walls was overkill, but it fit inside the red purlons without anything holding it up, so I went with that. Only cost me $4k

 

[PoorUB]

Is it true that the pressures won't read correctly if the outside temp isn't warm enough? It was like 65-70 degrees at the time of install. That's why they didn't check. They just said to call them up in the winter time if it's not heating.

If you know what you are doing you can test the charge on an air conditioner in most any temps. I have done it multiple times with snow on the ground. 65-70 degrees is a piece of cake! There are things you need to do to account for the temps, but certainly way easier that trying to do it in the winter.

 

[Bert_]

I put R30 on both the ceiling and the walls. Of course since it's a metal building that's all it has, but that's supposed to be above code for my area I believe. R30 on walls was overkill, but it fit inside the red purlons without anything holding it up, so I went with that. Only cost me $4k

What did you do for air sealing?

Most buildings like that leak air like a seive without some sort of barrier

 

[Hobby_Man22]

What did you do for air sealing?

Most buildings like that leak air like a seive without some sort of barrier

I went around with spray foam cans and filled in all the gaps. That made a difference for sure.

 

[American Locomotive]

"Above code" doesn't mean anything.

You still have unsealed and uninsulated steel doors. You have a giant air leak letting humid air in - which takes away from cooling efficiency, and giant radiators (uninsulated doors) radiating heat.

Install your door seals and hang a plastic barrier in front of the doors. If you really want to use your temp gun, put a bunch of black tape on your garage door during peak sun and measure the door surface temp right against the tape.

 

[Hobby_Man22]

I'm going to work on installing the seals this weekend

 

[Hobby_Man22]

Okay I've left it on a few days the lowest she will do is 77. It was 95 outside though. Set at 77 it ran continuously. So I either need more insulation than the R30 or a bigger a.c.

 

[Hobby_Man22]

R30 is the minimum code btw. I'm not sure who on here said it was above code.

 

[Hobby_Man22]

R30 to R60 is the range for zone 1

 

[PoorUB]

Now that you have all the building issues taken care of, (I assuming you do!), now get the HVAC contractor back over and let him know it isn't cooling the shop. Perhaps the refrigerant charge is off.

 

[nadogail]

Have you measured the air temp moving through the evaporator coil. the difference between those two temps is called Delta T.

I have seen many tons of ship move fast through the water with a Delta T of only something like 2 or 3 degrees. No Delta T, means no cooling or heating. It's all about getting a Delta T.

 

[American Locomotive]

Okay I've left it on a few days the lowest she will do is 77. It was 95 outside though. Set at 77 it ran continuously. So I either need more insulation than the R30 or a bigger a.c.

In general, your AC should be sized so it runs just about continuously on the hottest day.

Were you able to get the door seals installed? Have you done anything yet to block the heat being radiated by your uninsulated metal doors? Have you measured the temperature of the doors during peak sun times? You'll have to attach black tape to the door and put your temp gun right up to the tape to get an accurate temperature.

R30 is the minimum code btw. I'm not sure who on here said it was above code.

... you said it was above code.

 

[Hobby_Man22]

The insulation on the ceiling was about 83 and the steel doors were about 95 although I didn't put tape on them when I checked.

 

[930dreamer]

So if the slab isn't insulated is it a losing battle?

 

[Hobby_Man22]

So if the slab isn't insulated is it a losing battle?

How do you insulate the slab?

 

[930dreamer]

It's done before the concrete is poured. I have a 1950's shop that needes wall /ceiling insulation but i know doesn't have a insulated slab, so wondering if I can ever make the building as I want/need it?

 

[PoorUB]

Have you measured the air temp moving through the evaporator coil. the difference between those two temps is called Delta T.

I have seen many tons of ship move fast through the water with a Delta T of only something like 2 or 3 degrees. No Delta T, means no cooling or heating. It's all about getting a Delta T.

The Delta T means nothing without measuring subcooling and superheat, humidity. The humidity could be 95% and you would get a poor Delta T and the system is working fine.

He needs a GOOD tech to come out and check it over. Not the same hacks that installed it, turned it on and walked away.

 

[Hobby_Man22]

Another thing. I have a 24x38 shop with 9 foot ceilings, (8,200 cubic feet) I air condition easily with 1-1/2 tons. It was 105F here the other day when I turned on the AC and it cooled it down to 72 degrees in a reasonable time. I am not sure how long as I wasn't paying attention, but certainly less than an hour.

You have a 30x50 x12 or 18,000 cubic feet that you can not cool to your satisfaction with 5 tons. Your cubic feet is 2-1/4 times the size of mine, so 1-1/2 tons x 2-1/4 = 3.375 tons. Four tons should cool it easily.

FIX YOUR INSULATION!!!

It's finished. I have the door seals on too. I think I need to have the charge checked on the unit. Or I need more insulation.