Replacing central air components to increase effeciency

[bushmechanic]

I live in a 2500 square foot warehouse, at 50X50X15 feet.

It is divided into three interior zones.

1: A roughly 850 square foot heated and cooled area, with eight foot high drop ceilings.

2: A roughly 400 square foot shop that is not heated or cooled. Given the nature of the building, the ceiling height reaches close to the top of the structure, and airspace extends over the other two areas.

3: The last area is heated and cooled, and makes up the remaining space with again eight foot high drop ceilings.

So, two zones of my "house" are heated and cooled. They are isolated from one another, and use separate ducts, separate air handlers, and separate condensers. They must be separated for various reasons.

That means I've got two spinny boxes outside; one for each zone.

Now, this building was constructed in 2002. The little boxes outside were likely installed at that time. The labels are worn off, so I don't know what they are. I'm fairly certain they are... What's the technical term again?

Oh yeah. Cheap ****. There was never even so much as a badge or label on the things beyond the spec stickers on the tops, which have faded away. They are also rather small, but I suppose each isn't handling much volume.

Now... Here are some points:

1: I run the fan on the 850 square foot space 24/7, so long as I am home. Living in such a building has it's drawbacks. The windows don't open, and the air stagnates unless it's moved constantly.

2: I like the temperature of that 850 square foot space to remain at 66 degrees Fahrenheit all year long, again, so long as I am home.

3: The other climate controlled zone is usually set to around 80 in the summer, and 60 in the winter. The fan turns on and off as required.

Now, a single month of me being at home rakes in a $450 electric bill. I realize I'm a bit of a hog, but aside from the HVAC and a powerful (but very efficient) computer, I'm actually rather miserly.

I require very little light (as in, very, very little), I have a refrigerator that is no bigger than I need, and one person can only do so much damage to a 50 gallon water heater.

I have some bad *** electronics, but most of them are off most of the time. I do almost all of my cooking on my outdoor grill or in the microwave. Most of the food I eat isn't cooked, actually... I'm lazy like that.

That being the case, I'll have to contend that the nasty factor on that bill is directly related to those two systems controlling the climate in this tin can.

I have a few questions:

1: What efficiency level would the cheapest **** available in 2002 reach? Just how bad can it be?

2: If I were to buy two of the newest, most highly efficient systems available today, what sort of drop might I expect in the bill?

3: What would be my most efficient purchase if I am indeed to buy new systems? I'm not considering brands, at the moment.

There are a number of different ways to arrange a system, after all. What capacity does this building require in order to meet my requirements in as efficient a manner as possible?

I post this thread, because I just dropped $300 to fix an air handler, and I'm about to have to replace one of the outdoor cooling fans tomorrow, at an unknown cost. Let's assume another $300. Why not?

That would mean that, in but a single month, I've managed to spend $1,050 to remain in my desired level of comfort and luxury.

 

[CWO4GUNNER]

Too many unknowns, you'd have to be on sight to look at all the variables you listed. While getting the outside unit fan replaced as you mentioned, why not just ask the tech to clean the condenser coil while at it and ask if he could clean the evap coil as well, that should help. As far as your bill, it is a warehouse after all with allot of empty space. Fill up that warehouse and your efficiency will go up, less empty space.

 

[bushmechanic]

Too many unknowns, you'd have to be on sight to look at all the variables you listed. While getting the outside unit fan replaced as you mentioned, why not just ask the tech to clean the condenser coil while at it and ask if he could clean the evap coil as well, that should help. As far as your bill, it is a warehouse after all with allot of empty space. Fill up that warehouse and your efficiency will go up, less empty space.

It's pretty darn full in the front, actually. I've got much to sell right now. I bought too large of a lot. I'll be happy when the place is much more empty, actually. I can hardly get a thing done up there now.

I fully intend to have the man maintain the system as required and as he suggests while he is here, and I will obviously ask his opinions on the matter, and note them carefully.

His contentions and recommendations will more accurately describe my situation than my own notes. He's pretty darn good, in my opinion, and owns a very high class operation.

I just want to explore efficiency with a number of people here. I expect I will have much more information to share after he visits.

He won't lose any job as a result of discussion. If I buy something, he'll source it and install it. I believe in information and discussion, but I also believe in supporting good service.

 

[LS6 Tommy]

Not to sound preachy, but you have expectations that fall pretty far outside "normal" design considerations. If you've been running that one zone at 66* since 2002, I'm surprised the compressor didn't crash. Especially if it's "cheap ****" equipment. Running that cool is also not the most efficient method of operation. Get your set point up to say, 70* and I can all but guarantee a decrease in energy usage.

Tommy

 

[zmaxmotorsports]

Is there any kind of insulation in the place?

 

[Jackfre]

2002 efficiency would be in the 8-10 seer range. Where are you? Minot or Miami? With single stage equipment you have to look at the sizing and cycle count of the equipment to see how it is doing. Pulling in a compressor all the time really bump that start-up amperage draw and you pay for it. It is one of the things I like about the mini splits. One way they achieve their efficiency is they unload the compressor so you get easy starts not having to pump against the system head. That saves operating costs and is easier on the equipment.
Your seer ratings on most newer equipment will be in the 13-16 range.

I would suggest that you insulate the ceiling and seal off the "attic" area that you are not using. Ventilate that area. As I understand it you are not using that space. If the air is stagnant you might want to consider an Energy Recovery Ventilator. No sense stewing in your own juices.

I would get your top tech out there to evaluate the operation of each system. You might want to consider a data logger to capture the information. So in sequence, insulate, evaluate, and then do the worst system and see how the bill goes.

Your equipment alternative would be mini-splits. Variable speed, high seer and hspf numbers. Mine are 25 and 21.5 and the dual is 16.5 seer. As long as you are considering new equipment look at these. How would the space be if you could eliminate the duct work. I gained a lot of space when I did it.

 

[theoldwizard1]

Insulation is usually the cheapest way to lower your heating and cooling bill.

 

[bushmechanic]

Every wall, both indoor and out, as well as the roof and all ceilings are insulated and sealed. It's the one thing in here that was done properly. This place is insulated to hell and back.

I only run the fan all the time. The air conditioner fires up as needed.

Even held at 70 for a few days, it feels like it's running overly often. In general, the building wants to level off at ambient temperature if left alone, but on really hot days it becomes an oven. There's a tipping point somewhere.

Mind you, it's a giant tan metal cube, including the roof. It's all metal, and only one side is shaded.

It's 89 right now outside, and with two fans blowing out two ceiling tiles, It's been 83 all night.

I just found a sticker with a model number:

Goodman CPLJ24-1

I was a bit surprised. Not a lot of information is out there about this one. There's a black one with the same designation and a badge, but this one has neither color nor badge.

Looking about on the net, I found a specification sheet somewhere:

I'm not sure from at which point on that chart I should pull a "ton" rating. Many numbers are quoted in different scenarios. I expected as much.

It looks like it's supposed to be a "2 ton" unit, however.

 

[bushmechanic]

I'm going to call the average of all those SEER numbers 11. I don't know what air handler I have at the moment; I'll have to remove several ceiling tiles, and I don't want to heat up.

So, if it can be assumed that I'm at 11 now, would these new SEER 20 units make a difference, if I don't change my daily practices?

As well, given the spaces I indicated, what "ton" unit would be a good idea?

The air man isn't here yet, so I'm just killing time.

 

[Jackfre]

I guess I'd say you could leave everything in place and add a mini-split or two. As I understand it you have the areas split so try a system in one area or another. Operate the high efficiency mini-split and have a two stage stat that will bring in the Goodman at a certain set-point. Depending upon where you are (minot or miami?) your sq ft/ton will vary. Commercial sizings on ac usually run in the 400 sq ft/ton area. Your building may require that higher tonnage. In New England on a residence I had no trouble going 650-750 sq ft/ton unless there was a lot of late afternoon direct gain. Equipment that runs constantly when the system is at capacity is ok and actually desirable, as long as everything is right, filters and coils are clean so you are getting rated operation. When you think of it, it is starts and stops that kill equipment.

 

[CWO4GUNNER]

Personal opinion, but if you do decide to add AC to an already working, albeit weak AC, I would make sure whatever you add on is load ccalculated to support that space independent of the old system. And I would only use the old system as a separate indepenent backup only. Not 2 systems interdependent mixed matched types/age.

 

[bushmechanic]

If I'm going to do it, I'm just going to replace it all. It's not hard to do the work in here.

The owner of the repair operation will evaluate the system within the next few days sometime to determine whether or not he thinks the units I've got are properly sized given the conditions and my operational demands.

The first move I'm going to make will be replacing my current windows with windows that open. In the living space, you're pretty much stuffed in a box. The air doesn't move. Two windows are present, but they don't open.

Mind you, this wasn't built to be a house. I'm just now making it convenient.

There is a door, but that's where the television has to be. That will change once I build a swiveling mount strong enough to hold it (140 pound television on a 5 foot lever requires welding and big bolts).

I'll be able to use the door then.

So, getting airflow in here will be the first step toward somewhat efficient living. Leaving the fan on all the time is certainly hitting the bill, but I've just lived with it.

That's the biggest thing for me, by a long-shot.

I like AIRFLOW, and I like FRESH AIR. Everything needs to be circulating. The more, the merrier. This system doesn't even do that properly.

The closest you guys will get to truly feeling my pain here is locating a rarely used closet and locking yourself in there for a few hours. That's what the air is like here with the fan off.

It's DEAD.

 

[brewchief]

Where is the ductwork located? Is it in unconditioned space? Is it properly sealed? Is it properly insulated?

The most efficient system you can buy connected to a crappy duct system will turn out to be pretty inefficient.

If you like to run the fan all the time and end up replacing the system look at using a furnace or air handler with a variable speed fan, it will be much cheaper to run on a continuous basis. A good media filter is a must as well to protect the variable motor and to keep the system as clean(and efficient) as possible.

Some pics of the current duct system and units might help.

 

[DEnd]

I suspect you have air-sealing and insulation issues as the majority of your problems. that and you are running the system at 66°.

The first thing I would do is have a blower door test done (specifically looking for where your air leaks are). my bet is due to the dropped ceiling that you don't have adequate air-sealing at the ceiling plane. If you feel like being handy you can do the look for air-leaks part of the test yourself by building your own blower door. http://www.builditsolar.com/Projects/Conservation/BlowerDoor/BlowerDoor.htm

Even if you have well sealed duct work if it is in the unconditioned space you are losing a lot of your conditioned air and energy into the unconditioned space.

 

[pseudorealityx]

You still haven't provided a location.

Also, attempting to keep temperatures at 66 is not realistic with standard DX equipment, which is what you have.

 

[bazar01]

Hey pseudorealityx. I sent you a private message. Could you please check your PM and let me know.
Thanks.

 

[bushmechanic]

You still haven't provided a location.

Also, attempting to keep temperatures at 66 is not realistic with standard DX equipment, which is what you have.

The location is NC.

69 is the highest I'll go currently. I prefer 66, but 69 is okay during the day. It's got to be lower at night.

 

[CWO4GUNNER]

I prefer 66, but 69 is okay during the day. It's got to be lower at night.

With those desired target temperatures and the fact that your system has been under the load to support that for 12 years, Its fair to say your going to need a whole new system. As well as calling in an AC teach to load calculate what you need installed, you may want to consider calling in a refrigeration company that builds, retrofits, and installs refrigeration systems. That way you'll be sure to easily maintain those low temperatures rather than put a constant strain on an AC system.

 

[pseudorealityx]

The location is NC.

69 is the highest I'll go currently. I prefer 66, but 69 is okay during the day. It's got to be lower at night.

Well, do whatever you want. But you're going to waste of ton of money, and have high humidity issues. Good luck.

 

[sourdough]

69 is the highest I'll go currently. I prefer 66, but 69 is okay during the day. It's got to be lower at night.

I lived in Alaska for 35 years with no A/C. You prefer 66* indoor temp at night??

Buy and install a 15K window unit in your bedroom with the t-stat at the coldest setting, place a chair directly in front of it, grab a small cooler with ice and a 12 rack of beer, turn on the bedroom TV set, and take a seat.

By the time you've finished, it will be time for bed and the room will be less than 66*.

;-) Sarcasm Font Is On!

 

[Onewolf]

Ceiling fan. I find the AC can be set 4 degrees warmer if there's a ceiling fan running with the same level of comfort.

 

[bushmechanic]

I lived in Alaska for 35 years with no A/C. You prefer 66* indoor temp at night??

Buy and install a 15K window unit in your bedroom with the t-stat at the coldest setting, place a chair directly in front of it, grab a small cooler with ice and a 12 rack of beer, turn on the bedroom TV set, and take a seat.

By the time you've finished, it will be time for bed and the room will be less than 66*.

;-) Sarcasm Font Is On!

LOL

Is 66 degrees really considered all that cold?

The building holds it just fine so long as you let the gear keep on top of it.

I've endured a lot of hot weather in my time (many times in excess of 120 degrees), but for some reason a while back I began to overheat when I sleep.

I'll wake up with a splitting headache, covered in sweat, and all manner of dehydrated. I tried the fan thing, and it didn't work out.

66 degrees is the sweet spot. If I keep it that cold, I won't overheat. It's bad enough snapping a popping out of bed every morning, without needing to drink half my shower too.

I'll stand in there like a turkey with my mouth open, I **** you not.

 

[DEnd]

I've endured a lot of hot weather in my time (many times in excess of 120 degrees), but for some reason a while back I began to overheat when I sleep.

I'll wake up with a splitting headache, covered in sweat, and all manner of dehydrated. I tried the fan thing, and it didn't work out.

Have you seen a doctor about that? As a RN there are several possible causes that pop into my mind. I'm not going to try to diagnose you, but it is something you should talk to your doctor about if you haven't already.

 

[bushmechanic]

Well, do whatever you want. But you're going to waste of ton of money, and have high humidity issues. Good luck.

You speak as if we've spoken. You only pointed out that I hadn't given a location.

All I wanted to know is if a more modern, more efficient, and potentially higher capacity equivalent system would better serve my needs.

I got a few nice suggestions upon which to follow up later, and I will indeed do so.

The building is insulated; roof, walls and all. The drop ceiling is insulated. The duct work is insulated. The interior walls are insulated. I'm in a big, fluffy pile of insulation.

The very nature of my request supposes that I have no intention of changing my habits; though I am indeed doing so out of curiosity. What is it you meant for me to do?

You certainly didn't make a suggestion.

Here's how this thread went:

Me: I have System X calibrated a certain way. I would like to know if System Z will be more efficient within those parameters.

GJ: Under what conditions do those parameters apply?

Me: They apply in (insert manner here)

GJ: Perhaps your system is incompatible with those parameters. Consider exploring Systems J, R and Q.

Me: My plans will not be served by Q.

You: Your System X is not compatible with the parameters you specify.

Me, silent: ...Clearly it is; it's been compatible for neigh on 12 years now. It simply might not be as efficient as System J or System R.

Me: The parameters will not change.

You: I authorize your previous behavior. Be wasteful and wet.

You know, I've learned a lot from the other posters here, and have been encouraged to investigate a few things. In the end, however, there is you.

You ask where I live, and indicate that my dry system isn't "realistic". How-so? It works. It works, and it's small, and it's cheap. That indicates potential.

If what I've got can keep this building in check, that tells me, logically, that a more powerful system will have an easier time of it.

I want to know how that more powerful, and even more clever system might integrate into this building, and whether or not it will change things.

Incidentally, I bumped the temperature up to 69 just to see if I can tolerate it for a while.

Current interior humidity: 52%

Seems fine to me.

 

[bushmechanic]

Have you seen a doctor about that? As a RN there are several possible causes that pop into my mind. I'm not going to try to diagnose you, but it is something you should talk to your doctor about if you haven't already.

A decent handle is had on the origins of the issue, if not the specifics.

I got nailed by something in Africa a while back. I'd go for a week, with temperatures pushing 106. Hallucinations, fits; the works.

When I got back, blood samples were sent to the CDC, because it wasn't malaria, but could well have been something like it.

The could not identify the organism. It hadn't been reported before, so there's no telling what it was.

Every year, after that, I'd be struck down by horrible, brain-addling fevers, but they began to fade over time. Now, I'll deal with 101-102 for about a week and a half every year.

My natural body temperature is 97.2, so you can imagine what that kind of jack in the numbers might feel like. An average human would feel an increase of 7.4 degrees, where I experience a rise of 8.8 degrees at 106.

Now, I've also had my head knocked a few times, and that's where the thermostat is kept. Lost my perception of time in one event, so there's certainly been some damage.

That being the case, it's not pushing supposition to suggest that my thermostat might just be processing faulty information. That's the only answer I've got to the question of why I overheat at night now.

The immediate effects of the contamination and their associated dangers may be gone, but the lasting damage may still linger here.

I'm also in constant pain, which can be handled so long as I'm awake, but when you sleep, you give up a bit of the control you've been using all day.

I'm also not a very pleasant dreamer.

I sleep, and the furnace fires right up. That's just the way it is.

 

[DEnd]

A decent handle is had on the origins of the issue, if not the specifics.

I sleep, and the furnace fires right up. That's just the way it is.

Just wanted to make sure. Too many of the people I see in the hospital are there because they ignored stuff they should have seen a doc about.

 

[DEnd]

If what I've got can keep this building in check, that tells me, logically, that a more powerful system will have an easier time of it.

I want to know how that more powerful, and even more clever system might integrate into this building, and whether or not it will change things.

Incidentally, I bumped the temperature up to 69 just to see if I can tolerate it for a while.

Current interior humidity: 52%

Seems fine to me.

Maybe an easier time of it but that won't mean it will save you any money.

If you are looking to save money then you need to first address the efficiency of the building and the efficiency of the ductwork location (meaning making sure it is inside the conditioned space), then address the sizing and efficiency of the mechanicals. While a more efficient system will likely save you money it may not be sized right if you go about things the opposite way (mechanical system first then addressing building efficiency). Ideally the most energy efficient system is one that runs 100% of the time, as that eliminates cycling losses. Granted that's not possible even with Variable Refrigerant Flow systems (generally the most efficient). The more oversized your system is the more it will cycle, so it spends more energy just to get things going. If you are going to go about things backwards (replacing the A/C first) then you should look into Variable Refrigerant Flow (VRF) air conditioners. This technology basically allows your A/C to throttle its output reducing the amount it cycles. This throttling allows you to have a bit of oversize built into the mechanicals and not lose much efficiency if you improve your building envelope. For residential sized systems VRF technology is generally only available in "Mini-Split" type systems.

 

[pseudorealityx]

You speak as if we've spoken. You only pointed out that I hadn't given a location.

All I wanted to know is if a more modern, more efficient, and potentially higher capacity equivalent system would better serve my needs.

I got a few nice suggestions upon which to follow up later, and I will indeed do so.

The building is insulated; roof, walls and all. The drop ceiling is insulated. The duct work is insulated. The interior walls are insulated. I'm in a big, fluffy pile of insulation.

The very nature of my request supposes that I have no intention of changing my habits; though I am indeed doing so out of curiosity. What is it you meant for me to do?

You certainly didn't make a suggestion.

Here's how this thread went:

Me: I have System X calibrated a certain way. I would like to know if System Z will be more efficient within those parameters.

GJ: Under what conditions do those parameters apply?

Me: They apply in (insert manner here)

GJ: Perhaps your system is incompatible with those parameters. Consider exploring Systems J, R and Q.

Me: My plans will not be served by Q.

You: Your System X is not compatible with the parameters you specify.

Me, silent: ...Clearly it is; it's been compatible for neigh on 12 years now. It simply might not be as efficient as System J or System R.

Me: The parameters will not change.

You: I authorize your previous behavior. Be wasteful and wet.

You know, I've learned a lot from the other posters here, and have been encouraged to investigate a few things. In the end, however, there is you.

You ask where I live, and indicate that my dry system isn't "realistic". How-so? It works. It works, and it's small, and it's cheap. That indicates potential.

If what I've got can keep this building in check, that tells me, logically, that a more powerful system will have an easier time of it.

I want to know how that more powerful, and even more clever system might integrate into this building, and whether or not it will change things.

Incidentally, I bumped the temperature up to 69 just to see if I can tolerate it for a while.

Current interior humidity: 52%

Seems fine to me.

Standard DX equipment cools air down to ~55 degrees saturated leaving the unit. If you heat up that air to 66, without adding ANY moisture, you've got 68% RH. There is NO way to bring that down more.

That's what's actually happening in your system.

 

[bushmechanic]

Maybe an easier time of it but that won't mean it will save you any money.

If you are looking to save money then you need to first address the efficiency of the building and the efficiency of the ductwork location (meaning making sure it is inside the conditioned space), then address the sizing and efficiency of the mechanicals. While a more efficient system will likely save you money it may not be sized right if you go about things the opposite way (mechanical system first then addressing building efficiency). Ideally the most energy efficient system is one that runs 100% of the time, as that eliminates cycling losses. Granted that's not possible even with Variable Refrigerant Flow systems (generally the most efficient). The more oversized your system is the more it will cycle, so it spends more energy just to get things going. If you are going to go about things backwards (replacing the A/C first) then you should look into Variable Refrigerant Flow (VRF) air conditioners. This technology basically allows your A/C to throttle its output reducing the amount it cycles. This throttling allows you to have a bit of oversize built into the mechanicals and not lose much efficiency if you improve your building envelope. For residential sized systems VRF technology is generally only available in "Mini-Split" type systems.

That makes sense.

It's been raining quite a bit, so the system and building haven't been entirely evaluated, but this is certainly first on the list.