[drphoto]

Last year some idiot stole my air conditioner compressor and homeowners would not cover. I was think instead of just putting compressor on roof, why not go with one of the modern self contained units? I could run duct myself and save a bit. Then I could keep existing furnace which works fine.

Any ideas on cost? building is about 2500 sq feet. Would take 5 ton unit for regular AC, but these are more efficient.

[aldcoll]

When I lived in the Mid West (Kansas) you had to get a AC rider due to hail damage.  IF you put it on the roof it will be the least efficient (last time I was looking) compared to a shaded spot.  It's also about the free flowing air around it.  I ended up with a planting and fence to shade it and keep the south west hail off it.

My $.02

Alan

[drphoto]

you have a point about unit being in sun. I'd put of shadier side of roof. The reason I say more efficient is cold air sinks. Better idea, as least in theory, than producing cold air down low an pushing up through ducting.

Insurance companies suck. I don't even want to think about what I pay for healthcare. Let's just say monthly is more than car.......With a huge deductable.

[JLM]

Where are you located?  In southern Michigan we have a 3 ton unit serving a reasonably well insulated 2200 s.f. (plus finished basement) house.  One ton = 12,000 Btu.  For most of the country the furnace is sized for roughly 3 times the central air.  Accordingly our house has a 3 ton (36,000 Btu) air conditioning unit and a 90,000 Btu furnace.

In high crime neighborhoods I've seen heavy/locked cages installed around all the roof top units.

[Scott F.]

You would be looking $1200 to $1400 per ton for an RTU (Roof Top Unit). You've got one major issue that will preclude you from doing an RTU on residential construction....weight. Your typical home's roof isn't designed to carry north of 600 pounds of live load. Next up, you'll have to rent a crane to set the curb (1st) and the unit (2nd). You'll have to get 80 to 100 amps of electrical up there along with natural gas. That 5 ton unit is only 13 SEER with a single stage of cooling. That alone will eat you out of house and home.

Your best bet is to reinstall a condensing unit and then install a chain link fence, with a chain link cover over it. You can always install a variety of chain link fence covers if you don't like that 'raw' look....or you could just install it with some good old fashion electrified cattle fencing.

[drphoto]

Thanks Scott. Yeah, I was thinking weight would be the issue. Rafter in this place are on 24" center, which makes it worse. I figured I'd have to cut out roof decking and reenforce structure.

Most of the neighbors have regular compressors on roof, and run freon line inside.

I knew I'd have to run electric line. Why gas? (for self contained) There's no heat in one's I'm thinking about.

[Scott F.]

Oops, I misread your original post. My gas reference would be if you had a total self contained air conditioning unit (including he furnace and blower sections) on the roof.

You could put the condensing unit up there but as you mentioned, you'll have to do a lot of reinforcing of the roof.

Might be best (and cheaper) if you do some kind of secured enclosure around the condensing unit on the ground. Its tough to stop thieves once they get their sights set on a target. Worst part about all of it, there can't be more than $30 bucks in copper in those coils.

[JLM]

Would be best to considering moving from such a neighborhood.  A heavy gage (or mean dog) could be a solution too.

In now infamous Flint Michigan the thieves have long ago moved from stealing wiring at of abandoned houses to stealing the aluminum siding off of occupied houses.


But seriously, have you considered using multiple mini-split systems?  By each serving one room/area of the house you can gain significant energy savings and avoid your roof load issue.  And they can be mounted on the exterior wall to make theft harder plus with less copper per unit less attractive to steal.

[Escott1377]

Would be best to considering moving from such a neighborhood.  A heavy gage (or mean dog) could be a solution too.

In now infamous Flint Michigan the thieves have long ago moved from stealing wiring at of abandoned houses to stealing the aluminum siding off of occupied houses.


But seriously, have you considered using multiple mini-split systems?  By each serving one room/area of the house you can gain significant energy savings and avoid your roof load issue.  And they can be mounted on the exterior wall to make theft harder plus with less copper per unit less attractive to steal.

I work for Mitsubishi in their commercial division.  Mini splits hit all the points that you mention, but are very expensive.  You could do the house w/ 1 outdoor unit and multiple indoor fan coils.  These are also all heat pump units so the furnace will no longer be needed.  The compressor is inverter driven so it carefully matches the load of the building, either w/ sub cooled liquid refrigerant for cooling or super heated gas for heating.

[Scott F.]

VRV/VRF rocks! I've got north of 5000 tons designed and installed in commercial buildings to date. It is my go-to for any building owner who wants to replace their HVAC system. North of 20 SEER, heats well in any climate (providing you size the system for heat as basis of design). Variable speed fans, compressors, refrigerant, no issues with dehumidifying....ever. Killer system and significantly cheaper that ground source.

[drphoto]

Yeah, I figured they got maybe $5 bucks worth of scrap. Hell, I'd just have soon paid shakedown money, like business owners in big cities do to the mob.

I guess I'l get a consult on this. I could reenforce roof my self. I have to patch some bad roof decking near the ridge line anyway, do to poor roof vent install by previous owner. It's not hard. More pain in the ass than anything. I might even re shingle it my self. Again, not hard if I can rent a conveyer to get bundles up. Really the trick is getting first course on straight.

Wouldn't be hard to run electric cable, & I might be able to put in duct too. This is an open floor plan loft type building, so open ducting is ok. Actually can look cool.

cheers.

[Escott1377]

Yeah, I figured they got maybe $5 bucks worth of scrap. Hell, I'd just have soon paid shakedown money, like business owners in big cities do to the mob.

I guess I'l get a consult on this. I could reenforce roof my self. I have to patch some bad roof decking near the ridge line anyway, do to poor roof vent install by previous owner. It's not hard. More pain in the ass than anything. I might even re shingle it my self. Again, not hard if I can rent a conveyer to get bundles up. Really the trick is getting first course on straight.

Wouldn't be hard to run electric cable, & I might be able to put in duct too. This is an open floor plan loft type building, so open ducting is ok. Actually can look cool.

cheers.

Don't want to be a Debbie Downer here, but anytime you deal w/ refrigerant you need an EPA license.  Where would you deal w/ refrigerant in your scenario?  Anytime you may need to adjust your charge.  Just an FYI - everybody have a great weekend -

[Escott1377]

VRV/VRF rocks! I've got north of 5000 tons designed and installed in commercial buildings to date. It is my go-to for any building owner who wants to replace their HVAC system. North of 20 SEER, heats well in any climate (providing you size the system for heat as basis of design). Variable speed fans, compressors, refrigerant, no issues with dehumidifying....ever. Killer system and significantly cheaper that ground source.

VRF is the future of HVAC for North America.  I left a 14 year with Carrier selling chillers and their associated equipment and controls 3 years ago for Mitsubishi.

Since I entered the VRF industry, total market share of the commercial HVAC market has increased from 4% - 6% which is incredible growth!

[Scott F.]

Here's a thought. Remember the chain link fence I mentioned? Here are the basic parts for one...bare with me, I'm headed somewhere...promise



So, take and install four fence posts in concrete (five actually as you'll need a gate but forget about the gate for this concept). Now, rather than installing the actual fence with the Tension Bands, take and install a series of horizontal bars using more fence post piping (Rails). You would install the Brace Band and Rail Ends. Space them at about 12" on center horizontally on all sides and across the top. This effectively creates a jail cell for your condensing unit. It also gives plenty of room for it to breathe and it needs breathing room.

After you get it installed, I'd purposely gum up the threads on the bolts so the theavin' little turds can't just disassemble the cage. Also, you'll have to cut the rail piping a bit long so they can't slide it one way or the other in the sockets of the Rail End and then just force the pipe out of the socket. A through bolt would work too. Those Rail Ends are pot metal, otherwise you could weld it.

Getting back to the fifth post, you'll need a gate. You could construct it the same way.

As I think about this, you'll need access to it at some point as it will fail, or the service guy will need to do a deep clean rather than just a simple wash down of the coils with a hose and coil cleaner. That means you'll need some way to disassemble the cage. IDK, maybe have a shop weld up panels using welded wire fabric or something?

Taking it up on the roof is pretty drastic...and expensive. Bet you could come up with some secure ground solution for half the 'roof move' cost.

Good luck.

[drphoto]

Scott, I figure the thevin turds as you call them, would just cut the fencing and or cut the lock on a gate. If I go 'ground', I may put it up on stilts or cantilever a platform 10' off the ground. I may seriously wrap the sucker with razor wire!

And for those of us who are not versed in HVAC speak.....what is VRV/ VRF?

And escott. No refrigerant to deal with. They took the compressor, and the line. No recharging here!

Yeah, maybe I could run duct, but I know I need a pro to install the system.  I'm not really bright, but I know you need licensed contractor for certain things, like water heaters, etc. And HVAC.

[drphoto]

Oh, and I'm not going anywhere soon, but the hot chick next door wants to buy the place to expand here booming B&B business. However, maybe that's what I should do. She rents that place for $950 a night. And it's always booked. In Louisville! unreal!

[Doublej]

Oh, and I'm not going anywhere soon, but the hot chick next door wants to buy the place to expand here booming B&B business. However, maybe that's what I should do. She rents that place for $950 a night. And it's always booked. In Louisville! unreal!

WTF  $950 a night for a room or is it a suite?... in a neighborhood where people steal AC compressors?

[JLM]

VRV: Variable Refrigerant Volume
VRF: Variable Refrigerant Flow

Both terms are used interchangeably and refer to one large outdoor condenser (heat exchanger) and multiple indoor units to serve individual rooms/areas of the house.  Each individual unit can be controlled separately.  As mentioned can do cooling or both heating/cooling.  Efficiency comes from adjusting settings to match each room (occupied/not, basement colder, 2nd floor hotter, individual tastes, etc.) and that the equipment operates at variable speeds to serve the exact demand.

[JLM]

WTF  $950 a night for a room or is it a suite?... in a neighborhood where people steal AC compressors?

+1

Yeah, wondering what the attractive neighbor includes for $950/night?   

[drphoto]

She rent's whole house, which is 6 bedrooms and 6 full baths + 2 half. Plus kitchen and entertainment room. Plus rooms all have a self contained 'record player'. Doubt if real hi fi, but cool she's into analog. Another reason to regret selling my wonderful Rega/Denon setup.

& I dunno if she throws in in extras, so to speak.  Don't think so, as I never see her car when I see guest cars.

JLM, can that heat exchanger go on roof? I think for conventional unit I was told I need 5 ton.

I appreciate all the advice guys. It's been one long hot summer, but with a dehumidifier and a couple of big fans, I've endured. Hey, at least my electric bill is low! (honestly, I never ran air all that much when I had. I'd turn it on, let the place cool, then shut off, and just use fans)

Getting the humidity out helps a lot, as that's big problem here on eastern seaboard. I dunno how the people in deep south function. I had to go to south FL in July once. Jeezus it was miserable. I also had to go to way south Texas (McAllen) to shoot cotton farming for Monsanto, and it was like April. It was 90 and about 100% humidity, and the rep from the company said (with a big Texas accent) Son, you ought to be glad you got here when it's still cool!