A/C for 4 rooms

[mike93lx]

We have a 2 ton Friedrich mini split that covers the kitchen/living room/dining room, but still use window units in the 3 bedrooms plus office/nursery. two bedrooms are 10x11, the nursery/office is 7x11, the master is 13x16 plus the en suite. I want something quieter, more efficient, better looking and more effective.

I think another 2-3 tons would be plenty for the four rooms. Insulation is pretty good with R30ish in the ceiling and R12 plus an inch of polyiso on the walls.

Heat really isn't a concern as I have a 96%= nat gas furnace and hydronic hydronic baseboard.

I do not want to go through the expense of installing central A/C as I don't have any ducting already and have no desire to switch over for heating due to the high initial cost.

I do have attic and basement access and everything is on one floor (split entry ranch, above the garage.

I'm thinking either a single compressor with four heads, around 3 ton or a pair of 1.5 ton units with two heads each.

From as aesthetics perspective, a single would certainly be preferable, but I don't know how much more complex the setup would be. Two bedrooms would be a ~35' run, the other two would be >25'

what would you do?

 

[99LeCouch]

First, figure out heat gain for the area. Total that up, and size your unit/units that way. If two rooms face south with no shade while two other rooms are shaded, that'll make the cooling load different for those spaces.

I'd probably go with two smaller units since that will be better able to match loads for the occupied rooms. Mini splits are also more efficient with fewer heads.

 

[ChevyEFI]

I would take time to do ducting to exterior wall / floor / ceiling locations and go central. You said you have access.

A central unit would be so nice, and add value to the house.

Background of my opinion: Different climate here, but the ducting installed in many older homes here is central, with vents going to the interior wall of the rooms, which is intended for evap. coolers, used until refrigerated became more common. It works, but isn't ideal. Also, I did HVAC a few years earlier in my life. Most recently, evap. to refrigerated conversions. Maybe a guy currently in the trade can suggest a plan to fit things in for refrigerated and get the heat built in later when it's furnace time.

/ignoring what you said. Sorry.

 

[Bigblue&Goldie]

Go with a 2 ton mini split with 2 heads. My 3 car garage with no insulation is handled by a 2 ton. You can do the whole install yourself (might have to hire out electric) and pay someone a couple of hundred bucks for the startup. I have a few good friends in the HVAC industry and they all say if they were to do a new build they would go with all mini splits. I've personally installed a couple and they are no big deal.

 

[mike93lx]

First, figure out heat gain for the area. Total that up, and size your unit/units that way. If two rooms face south with no shade while two other rooms are shaded, that'll make the cooling load different for those spaces.

I'd probably go with two smaller units since that will be better able to match loads for the occupied rooms. Mini splits are also more efficient with fewer heads.

i get that a heat gain calc might be ideal, but the window shakers work fine and have done so for the several years we have been here. what do i have to gain, especially with switching to an inverter unit that will throttle as needed?

 

[mike93lx]

I would take time to do ducting to exterior wall / floor / ceiling locations and go central. You said you have access.

A central unit would be so nice, and add value to the house.

Background of my opinion: Different climate here, but the ducting installed in many older homes here is central, with vents going to the interior wall of the rooms, which is intended for evap. coolers, used until refrigerated became more common. It works, but isn't ideal. Also, I did HVAC a few years earlier in my life. Most recently, evap. to refrigerated conversions. Maybe a guy currently in the trade can suggest a plan to fit things in for refrigerated and get the heat built in later when it's furnace time.

/ignoring what you said. Sorry.

adding value really isn't a concern as we intend to be here long term.

my current furnace is 8 years old and I find it hard to believe that I would abandon the hydronic system. uninstalling everything and patching up would be a ton of work and a lot of money, for what? I spend $1200/year with the current system for heat and hot water. no chance that could ever be reduced by enough to justify the expense.

I'm open to other opinions, that's why I posted here.

My main point of reference is a friend nearby that had central air with a heat pump installed in a similarly sized house that has oil-fired hydronic heat. He had justification for the heat pump as oil was over $3k/year. his system, including duct work was nearly $20k. I can buy two 2-ton, 2-head minisplits for under $4k, run the linesets and electrical myself, and have an HVAC tech hook it up. I just don't see the value in spending over $10k more for central.

 

[mike93lx]

Go with a 2 ton mini split with 2 heads. My 3 car garage with no insulation is handled by a 2 ton. You can do the whole install yourself (might have to hire out electric) and pay someone a couple of hundred bucks for the startup. I have a few good friends in the HVAC industry and they all say if they were to do a new build they would go with all mini splits. I've personally installed a couple and they are no big deal.

i installed my freidrich breeze system, but that was precharged, so i did everything end to end, including electrical. my intention is to run linesets, drains, electrical and mount up the compressors, then have someone hookup the linesets.

 

[Bigblue&Goldie]

i installed my freidrich breeze system, but that was precharged, so i did everything end to end, including electrical. my intention is to run linesets, drains, electrical and mount up the compressors, then have someone hookup the linesets.

Did you pull a vacuum on the system before charging it? A good friend of mine is a regional rep for Friedrich (coincidentally talked to him today). I've never done anything with their mini splits, so I'll have to ask him about those. I actually used to work for their distributor here in AZ, so I spec'd a lot of their window units and through wall units for military and data center applications. Good quality stuff, but they didn't even do mini splits back then.

 

[mike93lx]

Did you pull a vacuum on the system before charging it?

no. it uses a quick connect that didn't require that. plug and play.

system has been installed and working great since June 2014

 

[Bigblue&Goldie]

no. it uses a quick connect that didn't require that. plug and play.

system has been installed and working great since June 2014

I texted him and he called me. He said they used to use precharged line sets (in addition to the charged unit) which is why the vacuum wasn't required. He said they no longer do that, they now use a conventional line set.

 

[mike93lx]

I texted him and he called me. He said they used to use precharged line sets (in addition to the charged unit) which is why the vacuum wasn't required. He said they no longer do that, they now use a conventional line set.

yeah, this system has been off the market for a couple years. it was perfect at the time. 2 tons for 2 grand. just ran a 20 amp 240 circuit to the interior unit, very simple. only challenge was the fixed 25' lineset, but it ended up working really well where I put it in.

 

[MattT]

i get that a heat gain calc might be ideal, but the window shakers work fine and have done so for the several years we have been here. what do i have to gain, especially with switching to an inverter unit that will throttle as needed?

They'll throttle down to a point and I believe the multi-head units don't htrottle down as well as single heads.

You'd gain up front by buying smaller less expensive equipment. Then get the ongoing benefit of better humidity control which'll definitely improve comfort and may also allow you to run a higher thermostat setting to reduce running costs.

 

[kaffine]

My preference is for single units. This way if one unit fails it only affects one room. For me the line sets are the ugliest part so I would rather short runs for the line set and more compressors. Of course if the line sets are concealed it looks nicer but need to consider what happens if you need to replace the lines if a unit fails.

I have had better luck with Mitsubishi than LG. Have had 2 LG fail recently. One the 4 way valve started leaking the other was a controller. The Mitsubishi units I have installed have been fairly quiet. Although the first one I installed ~12 years ago is starting to make a bit of noise I looked at replacing the bearing and decided to live with the noise for now.

I took out the central system from my house and am replacing it with mini-splits and have thought about doing the same at my parents house. The issue with ducted systems is I haven't seen many that are done correctly. This leads to some rooms not getting the right amount of heating or cooling. The up side is they can have better filtering.

I have only used wall mounted indoor units. I keep looking at the ceiling cassettes but haven't had a case yet that I thought it was worth the extra costs.

 

[fitter30]

If there is duct work from the furnace why not central air added. Mini splits would be more expensive all units would have to be piped and wired. Mini split heat pumps when in defrost do not have back up heat. Find a company that will do a heat load.

 

[Worsedog]

If there is duct work from the furnace why not central air added. Mini splits would be more expensive all units would have to be piped and wired. Mini split heat pumps when in defrost do not have back up heat. Find a company that will do a heat load.

In the OP: Heat really isn't a concern as I have a 96%= nat gas furnace and hydronic baseboard.

 

[mike93lx]

If there is duct work from the furnace why not central air added. Mini splits would be more expensive all units would have to be piped and wired. Mini split heat pumps when in defrost do not have back up heat. Find a company that will do a heat load.

Curious where you saw anything about duct work in my post...

 

[MikeinNorthWales]

I have been considering mini-splits for a while, but I can't wrap my head around one problem on my second floor. The floor has 4 bedrooms and a bath. The hallway is really a large landing situated between all of the rooms. Figuring 2 bedrooms per unit, total of 2 outdoor units, what does everyone do with the bathroom and hall?


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[mike93lx]

I have been considering mini-splits for a while, but I can't wrap my head around one problem on my second floor. The floor has 4 bedrooms and a bath. The hallway is really a large landing situated between all of the rooms. Figuring 2 bedrooms per unit, total of 2 outdoor units, what does everyone do with the bathroom and hall?


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I don't think a hall or bathroom are really critical places to air condition