Upgrading a home AC unit questions..........

[1950ChevySuburban]

Hey guys, I have an older 1987 AC unit on one of my rental homes. It's a doublewide with a Coleman 9700 series furnace, all central.

I would like to upgrade to a more efficient unit, but unsure of what to expect?

Do I only get the outside unit - compressor and condenser? Reuse the evap in the house?

I've done automotive HVAC over the years numerous times, I can sweat copper pipe correctly, etc...... and would like to install this myself.
Vents and ducting is all tight, clean and adjusted for efficient room filling. Filter is clean.

I don't want to spend $3000 on this for marginal improvement. Existing unit cools well but costs almost $400/month (depending on tenant's usage of course).

Any thoughts on this? I call HVAC guys and they either won't call back or have conflicting info.

Many many thanks!
John

 

[deter]

Have you had anyone out to check the unit? Are both the indoor and outdoor coils clean?

 

[theoldwizard1]

Have you had anyone out to check the unit? Are both the indoor and outdoor coils clean?

+1 !! Cheap and easy to do.

As few years ago I had to have the cooling coil replaced and they used a newer, higher efficiency replacement part. The following year I inquired about upgrading the compressor. The HVAC company said I would never get my money back (but we only cool for a few months a year).

My guess is that you would have to replace the whole furnace to accomodate the new cooling coil.

 

[1991Syclone]

I know you do want to do this yourself, but check the local codes. It might be that they aren't allowed to mix and match old/new stuff so they'd have to do it on the side for cash.

I have an 88 vintage Trane in the garage that isn't cooling well. Had an A/C guy come out and charge it up, but apparently it's still not cooling very well. I will probably clean the coils this weekend and see what it does.

I'm also going to get one of them fancy no contact IR thermometers to see how cold the air is coming out of the vents. It might be that the cool air is just leaking out through old windows, poor insulation so the unit has to run longer to keep the place cold.

 

[1950ChevySuburban]

Coils are clean, system gets cold just costs a lot per month to run.
I'm not real keen on replacing the whole furnace, sounds expensive.
System's fully charged with R-22, pressures read good.

 

[1991Syclone]

If everything is running fine, I'd check the area it's heating. What's the temp set at? Digital or analog thermostat? What kind of insulation. That sort of stuff. The old units are not going to be as efficient as newer ones. You may be able to get a used take-out unit to replace it with, but it will take a while to recoup your investment.

Or start making the tenants of the rental home start paying for electricity. I'm sure the bills would drop then.

 

[Falcon67]

From what I know about asking locally - the condenser and evap coils are usually a matched set. If the inside coil can be had to fit the dimensions in your existing furnace, then it'll work. Lots of A coil sizes usually available. However - most if not all the supply houses will not sell to an individual. They sell only to the trade and you can't buy unless you have an insider do it for you. You can occasionally pry a part out of 'em, but a whole system - no. There are places online you can buy systems, but you'll need an upfront agreement from an AC guy to set it up for you if you can't DIY it start to finish. Buy a system, install and start calling HVAC companies - you will get hung up on. Guaranteed. HVAC-talk is the same attitude you will find from almost all companies and pros because they make their money on the systems. You'll need most likely have to hunt for an independent guy working out of his/her truck. Or a semi-retied old guy that likes to make extra cash and not work so hard. That's who we found when we did our last change out years ago. He bought the system at cost and I did the attic work and was general step-n-fetch. Excellent job, way cheaper. Got lucky, basically.

From HVAC-Talk:
"2. Do-It-Yourself (DIY) - not here.

This site is for industry professionals and folks seeking HVAC/R advice and knowledge. Please do not ask for step by step instructions on purchasing, installing or repairing your own equipment. This is our job and our livelihood. We are generous, but not to a fault.

Questions of this type will not be answered and may be deleted at the discretion of the Moderators. "

They will kick your **** off. NO DIY. As hard a line as PM takes on china home shop equipment.

 

[lzenglish]

Sound like you have a fully charged unit, with a clean condenser. Do you have a good split temp.? It should be around 20 degrees + or - a couple. Also, don't rule out a "Horse Blanket" on your "A" coil, and or a duct that has come loose, or eaten thru by a mouse, and you are cooling the attic.

Wayne

 

[theoldwizard1]

Coils are clean, system gets cold just costs a lot per month to run.

My guess is you need better insulation. Pretty hard to do in a double wide.

 

[1950ChevySuburban]

All good points here.
The HVAC guys that want to keep a lid on their livelihood, I get that. I'm an auto mechanic but I share info and help a brother out. So yes, I expect that in return.

Ducting is tight, secured. Been there, done the mouse thing!

Insulation should be decent, new complete shingled roofing and entire outside stucco'd. Sure, not the greatest windows and doors, but maybe I should look towards them as a major issue.

I work at the U of Arizona, our HVAC guy here suggested that because my cooling temps are good there's not much he can improve upon. I find that hard to believe.

 

[slopecarver]

decrease the load on the a/c by turning up the thermostat
mist the condenser with water when it is on
have the condenser in a shaded cooler area
have them turn off the vents to rooms they are not in or using
implement a programmable thermostat
lock out or hide the thermostat if they keep adjusting it and have them pay the bill.

 

[BD1]

Be prepared for a shock . Your system is currently R 22. Not sure about your area BUT NOW, 22 is out. NEW is 410A . Runs at higher pressure, incorporates multiple refrigerants, and IS NOT COMPATIABLE with 22. RESULT. Complete NEW SYSTEM!!!!! Tubing, evap coil, and compressor. It *****!!! Do not reuse old components, not worth taking a chance.

 

[1950ChevySuburban]

I was afraid of R22 being done with. We went through this in the automotive world back around '93. Now R1234 is hitting us.

Everything else is as best as can be. Condensor IS actually shaded, has good airflow, not boxed in. T-stat is programmeable and I verified it as good. And the tenants do pay the bill.

 

[lzenglish]

I was afraid of R22 being done with. We went through this in the automotive world back around '93. Now R1234 is hitting us.

Everything else is as best as can be. Condensor IS actually shaded, has good airflow, not boxed in. T-stat is programmeable and I verified it as good. And the tenants do pay the bill.

I forgot to ask you, did this problem just crop up, or was it happening when you bought the place? Since your unit is charged up, your condenser is clean, your "A" coil is clean, you have no supply air duct leaks,you have a 20 degree or better split, the only conclusion I can come to is the following: Unit undersized, bad thermostat, or your renters like it real cold in the house! If your compressor was drawing excessive amps, you would see the breaker tripping.

P.S. Maybee you can find some State and or Federal tax incentives, coupled with your Local Utility rebates to help offset the cost of a new unit. And, as a past lanlord myself, write off the balance on your taxes?

Good Luck,

Wayne

 

[1950ChevySuburban]

I think it's just old and inefficient as opposed to any real problems.
I know when I converted cars to 134a from R12, we'd swap out everything except the evaporator. Flush it out well, use updated oil and off it went.

 

[1991Syclone]

I think I'm in the same boat with our new place. I haven't had a chance to do a full inspection, but we did just have the unit serviced and 1lb of R22 added to it, but she says she can't get it below 78 in the house.

 

[mpire]

A/C work is voodoo to just about anyone that isn't an A/C Pro.

Those that do know how it works don't want to explain it to you.

I am constantly afraid that my 4 ton Heat pump is going to die any day now, as I am the only one on the street with the original one still in service.

My temporary solution was to put in a mini-split in the master bedroom.

Will all the incentives, it was just about free, and the monthly savings on my power bill are about 80-100 bucks. We pretty much only run it at night, but its impressed the hell out of me. I had a faulty thermistor on it, but LG sent me a replacement overnight no questions asked. So heating didn't work well, but after replacing the thermistor it heats like a champ. So warrantly response has been excellent.

Anyways, if you are spending most of your time in one room like we do, its a dramatic change and well worth the time. I hooked everything up myself and then had my A/C guy hook it up the lineset and test the pressures, but I really didn't need him to do that either.

This is the one I put in the bedroom, now its $300 cheaper! Its probably paid for itself two times over since last may.

http://www.acwholesalers.com/Ductless_air_conditioner_LG_mini_split_p/70222.htm

 

[lzenglish]

I think I'm in the same boat with our new place. I haven't had a chance to do a full inspection, but we did just have the unit serviced and 1lb of R22 added to it, but she says she can't get it below 78 in the house.

Anytime you need to add Refrigerent to a Hemetic system, it means you have leak, which needs to be repaired. If your new house is still in the warrenty stage, you should have the seller fix it at no cost to you.

Wayne

 

[brewchief]

To upgrade you need to replace the entire system, new evap coil will in almost every case be designed for higher efficiency by be larger, having more layers of tube, closer fin spacing, TXV or some or all of the above.

The oils are not compatible so the lineset should be replaced as well, if you have a lineset buried in a wall or ceiling that cannot be changed there are flush kits that will remove the oil, we use these as a last resort only when there is no other option.

The lines do not get sweated together, they get brazed with a brazing rod that contains 6% to 15% silver, during brazing it is recommended that nitrogen is flowing though the lines to minimize oxide buildup in the lines(this is skipped by a lot of guys in the business, there is some debate on how well it works but it is in every manufacturers instructions I've looked though).

After brazing you need a nitrogen tank and regulator to do a pressure test and a vacuum pump capable of drawing the system below 500 microns(and you need a vacuum gauge to determine if you are down that low).

Since the average guy does not have the equipment it is pretty tough to do a proper install as a DIY.

However since it is a mobile home you may be able to buy a condenser/coil/lineset package with fittings that are presealed and screw together, I'm not sure if they still make them but they did as of a few years ago, this eliminates the brazing/pressure test/vacuum part of the job ands makes it more DIYable.

 

[mpire]

I would seriously look into augmenting your current system with mini-splits. They are just so cheap and efficient that its hard not to consider them. You can get multi-zone mini-splits as well so it can cool multiple zones with one compressor unit.

Also, check with the power company, city, and state to see what incentives they have for upgrading your A/C unit. My mini split was literally FREE after all the incentives and credits. ($1100)

They are offering up to $1275 in energy credits for high efficiency A/C systems depending on tonnage for 2012.

Free money is hard to turn down.

 

[mpire]

The oils are not compatible so the lineset should be replaced as well, if you have a lineset buried in a wall or ceiling that cannot be changed there are flush kits that will remove the oil, we use these as a last resort only when there is no other option.

Neighbors got burned on this. Cost them another $1000 after the $6500 install because the installer used the original linesets. They ended up putting in new linesets for the A/C. Cost for the new lineset is under $200 for every 25', and its not rocket science to run, so I would plan on replacing everything if you are going to put in a new compressor. When new equipment is cheaper than the labor to diagnose the old equipment, I say just buy the new stuff.

The lines do not get sweated together, they get brazed with a brazing rod that contains 6% to 15% silver, during brazing it is recommended that nitrogen is flowing though the lines to minimize oxide buildup in the lines(this is skipped by a lot of guys in the business, there is some debate on how well it works but it is in every manufacturers instructions I've looked though).

They make glue for a/c lines, not sure if it is any good, but I was told by my A/C guy that its not bad.

Honestly though, you are going to need a receipt from a professional in order to have a warranty on the unit, so you might as well plan to pay a pro $100 to hook up the lines and do the charge. You can do the grunt work and set all the stuff in place, just don't connect it yourself.

Since the average guy does not have the equipment it is pretty tough to do a proper install as a DIY.

I agree mostly, but you can buy the unit, set it in place, and run the power and lineset and just have a pro hook it up and set the levels. Thats 90% DIY.

 

[1991Syclone]

Anytime you need to add Refrigerent to a Hemetic system, it means you have leak, which needs to be repaired. If your new house is still in the warrenty stage, you should have the seller fix it at no cost to you.

Wayne

No warranty with this house. System is an 88 vintage Trane unit. Took temperatures today and the air coming out of the vents was between 69 and 74 degrees. Basically the system needs to be replaced. I cleaned the coils and cleaned out the outside unit, but at this point we're planning on replacing it soon.

Code doesn't permit mixing and matching old and used units here so it would be a completely new system inside and out. Since this will be a long term dwelling we're fine with a new system instead of patching.

I do need to look into rebates on replacements though.

 

[1950ChevySuburban]

I've never heard of mini-splits before. Got a referral for a reputable company, gonna send them over there and see what they have to say.
I have a time crunch with this, tenant's moving out 4-1-12, and I have a surgery 4-10-12, so I want to at least be coherent for the diagnosis and replacement estimate. (Brain surgery for possible reoccurrant tumor)

 

[mpire]

You can put in a mini split in an afternoon if you have the power run to the spot already.

 

[SmokinFletch]

If it's a double wide home like the ones I have worked on:
You got to get an entire system, it's a double wide, you will not be able to fit a new coil in the existing space, have you seen a 13 seer coil, in a word, "huge". So you need a new downflow furnace, coil, lineset,class B vent, and a condensing unit, maybe a disconnect and a pad also. May have to enlarge the mechanical room to get all the parts in, I have had to disconnect and drain water heaters to swap out equipment in some DW's. Sometimes they can be a chore.
About the electrical usage, it is what it is, the older units for the 70's, 80's used lots of power to get the job done. high amps usage, power was cheap. Now days the amp draw on equipment is much lower.
The mimi split is an awesome alternative, BUT it's,
Made in China,
your results may vary.

 

[1950ChevySuburban]

I'm just going to let this project ride for now. Going to assess the situation Sunday and focus on sealing up any leaks. Doors, windows.....

Thanks to all! Very much appreciated!

 

[Jackfre]

I would seriously look into augmenting your current system with mini-splits. They are just so cheap and efficient that its hard not to consider them. You can get multi-zone mini-splits as well so it can cool multiple zones with one compressor unit.

Also, check with the power company, city, and state to see what incentives they have for upgrading your A/C unit. My mini split was literally FREE after all the incentives and credits. ($1100)

They are offering up to $1275 in energy credits for high efficiency A/C systems depending on tonnage for 2012.

Free money is hard to turn down.

What he said!! In spades. Anything you do to the old 22 system is throwing good money after bad. The mini-splits are inverter technology and likely more than double the efficiency of your current system. Clear everything out of the old furnace room and make a closet

 

[1950ChevySuburban]

Now THAT sounds fun! These mini-splits make heat as well? House heats on propane now, hard to beat gas with electric for heat I believe.

 

[mpire]

Now THAT sounds fun! These mini-splits make heat as well? House heats on propane now, hard to beat gas with electric for heat I believe.

Yes, Mini splits are heat pumps, so the only difference between them and the system you have now is that they don't have ducting running thought the attic to waste energy.

Its not hard to beat the efficiency of your gas heat when you are only heating one room. When you are only in one room, there really isn't much point in heating the whole house.

The lack of ducting alone makes a big difference in the efficiency of the units.

If its a heat pump, it can pump the heat either way, if its an a/c it can only pump the heat outside. Same difference really. My little 3/4 ton unit in my master bedroom has saved me enough money to buy one to put one in the garage!

 

[Robleticia]

Check out Daikin VRV systems. No, Im not a rep or promoting them, we have been installing alot of them lately in the Houston area, nice equipment! Only downside in a residential installation is the lack of conditioned outside/make up air.

 

[Falcon67]

Originally Posted by mpire
I would seriously look into augmenting your current system with mini-splits. They are just so cheap and efficient that its hard not to consider them. You can get multi-zone mini-splits as well so it can cool multiple zones with one compressor unit.

Also, check with the power company, city, and state to see what incentives they have for upgrading your A/C unit. My mini split was literally FREE after all the incentives and credits. ($1100)

They are offering up to $1275 in energy credits for high efficiency A/C systems depending on tonnage for 2012.

Free money is hard to turn down.

Glad to know someone gets some free money - we got jack here in energy rebates/programs/etc.

 

[mpire]

Not sure where Merkel is, but here are the Austin rebates.

http://www.austinenergy.com/Energy .../Residential/Air Conditioner/rebateLevels.htm

I would assume its a state program. Off they don't have it on the website, call then on the phone and ask.