Old House Air Conditioning

Project updates and progress reports
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Jeepnstein
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Old House Air Conditioning

Post by Jeepnstein »

It's that time at last. A couple years back I was looking at having traditional duct work and a four ton A/C air handler setup installed in the downstairs half of the Big Pile O' Bricks. We have hot water heat and want to keep the radiators so A/C only was the order of the day. We have a four ton unit with air handler cooling the upstairs already. The best quote we got at the time was around $15K. Then the roof started to show some signs of failure and we shelved the project.

In the mean time the technology has moved ahead quite a bit. And local acceptance of new technology has improved. A very dear friend put a system of mini-splits in his historic hotel that has been converted to corporate apartments. When he was over for Christmas he sold me on doing the same in our downstairs. The savings on install labor and energy efficiency seemed too good to be true. After spending some time crawling around in the guts of the system he installed I decided to give it a go.

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It's a great house. Lots of room and huge windows with lots of natural light. But it can get a wee bit on the hot and stuffy side in the summer. We did use window shakers downstairs but they are noisy, don't really cool all that well, cost a fortune to run, and leak water down the walls. The guys down at my dojo are really going to enjoy the hand me down AC.

Now as we all know mini-splits have those hideous wall mounted air handlers. That just wasn't acceptable at all to the Building Inspector also known as the Countess Von Jeepnstein. Fortunately for me I had already kicked the tires on a mini-split system that is hidden and utilizes very short runs of conventional duct work for the one return and several supplies. After letting my HVAC contractor kick it around he concurred that I was on to something. He proposed a system with two concealed duct work mini-splits and two two-ton outside units. We won't get maximum efficiency in this configuration but life is full of compromises. The lower half of the house will be divided East and West with each having their own thermostat zone. The cost? Around $8,000 with the good buddy discount.

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The units we're installing are also heat pumps which should eliminate the energy wasting oil filled electric space heaters the Countess Von Jeepnstein is so fond of in the winter. We will keep the boiler for our main heat source

So this is Day One. The day I hand a monster check over to my HVAC pro so he can order the equipment. He'll have a couple of days of bending duct work for either end of the units before the install. I am assuming I'll have to so some site prep and will probably be the one cutting the three inch holes for the line sets and power to pass through to the outside units.

The goal of this exercise is to keep the house cool while not wrecking it's appearance. The fact that it is roughly half the cost of our original conventional install estimate is also a big factor.

phil
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Re: Old House Air Conditioning

Post by phil »

I took a 12000 Btu window unit and stuck it in a big plywood box. covered the plywood with tin, made a drip tray and hose. baffles separate the incoming and outgoing air. the temp control is via a window I made in front of the box so the remote works. I use a couple of blowers, one sucks outside air, puts it through the cooling section and into the bedroom. the other collects all the hot attic air and blows through the back of the box then outside. that cools the attic space and the unit and even looks after getting rid of almost all the water from the drip tray.
I ran a hose out from the drip tray and I have seen water come out but usually it just evaporates. If I lift the lid to check it seems fine in there. I have little doors to access storage under the low part of the attic so I just open one so I can point the remote. It' s way quieter than a window unit, not the best system one could buy , but the best I could afford on a shoestring ;-)

total cost was $200 including the scrap plywood and re-used blowers. it works. it's quiet, it was cheap but it wouldn't compare to the stuff you are doing in efficiency or the amount of cooling. I added a relay to switch the blowers on and off with the internal fans. it had a heat sensor in the grille so I relocated that so it can control room temp.

I got the idea from looking at the portable units. they are twice the price of the window units so I made my own basically ;-)

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Jeepnstein
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Re: Old House Air Conditioning

Post by Jeepnstein »

I've done that cooler box trick before to do some "expedient" cooling of a server room. Some times you just have to do what you have to do. It would be a better setup than sticking one in a window as far as I can tell. It's a very low tech version of what we're doing as a matter of fact. Our humidity is very high here and it made a horrific mess but that's just another lesson learned. Your setup would limit that mess quite a bit.

We did the pre-construction meeting last night. Decided on vent locations, return locations, and where the outside units will be located. The goal is to keep the line sets very short to help offset the loss in efficiency we'll see from using some duct work. I think our longest supply will be in the neighborhood of ten feet.

Now on to tracking down my concrete guy about the pad for the outdoor kitchen. I'll probably just post pictures of that one when it's done.

phil
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Re: Old House Air Conditioning

Post by phil »

sounds like an interesting project. figuring out air flow and size of ductwork always seems complicated and I would assume many systems out there are based on guesswork. Many of our houses are fitted with ductwok that was done as an upgrade to central heat.

with fluids, the size needed is pretty much a factor of pressure and flow needed but with air you have this extra factor as hot air takes up more space than cool air and after you move it and then return it the size changes. It must make for some pretty complex math, or educated guesswork to tune a system like that.

I keep wondering if I could reduce the size of my air returns for basement clearance, and things like how big do those air return vents really have to be? I have a hole in my living room wall where the air return was. i have a heat vent that is pretty vintage but a bit smaller than the duct or the grate that was there, which is just painted tin. and I am trying to design a cover for it but it's pretty much guesswork for me at this point. I'm sure a lot of us have weird sizes of ductwork that are way too large or too small for the application. maybe they have some gizmos they can put in the vents to measure pressure and flow. It must be quite a science.

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Jeepnstein
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Re: Old House Air Conditioning

Post by Jeepnstein »

The equipment finally made it here! My HVAC guy works pretty slow. So for now I've got lots of really nice equipment sitting on the lawn.

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So for now we've got a bunch of thumping and banging in the basement. No worries because I have to go to a training session on the range tonight and my lovely wife gets to deal with all this for a while.

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OurPhillyRow
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Re: Old House Air Conditioning

Post by OurPhillyRow »

I am looking forward to your experience with this. Our 1852 brick rowhouse has little in the way of decent options for conventional AC even though we have forced air heat (the ducts are all on the floor and in the fireboxes). I am thinking about setting up a three zone system using a combination of hidden mini-splits (living room, and adjacent space) as well as a few of the ugly wall mounted ones in bedrooms (compromises on cost and flexibility in that there is no need to cool the guest suite and bath if we have no guests).

Keep posting updates!
Devyn - Old House Lover
1852 Brick Rowhouse - Philadelphia

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Jeepnstein
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Re: Old House Air Conditioning

Post by Jeepnstein »

We're on Day Five of a "two day install". This is typical of HVAC contractors and I'd be lying if I said I was surprised. They worked 14 hours on it yesterday and are trying desperately to finish it today because they've got some angry service calls backed up in queue.

The system is really nice so far. I've gotten quite and education on mini splits in general and ducted ones in particular. My only concern at this point is the fact the outdoor units are very light and I would say easily stolen. Looks like I'm heading to the metal shop later for some angle and flat stock to make cages. This is one time I can say I'm really glad I can weld because custom enclosures like this aren't cheap.

The highlights so far. The outdoor units require a 20 amp 240 volt line. The indoor units are run off of 12 volt from the outdoor unit. Wiring these things is dead simple. Line set length is a bit of an issue and the goal is to keep them as short as possible. We have one line set about six feet long and one about 15, very good for us. They're connected with flared fittings and no brazing is required. We don't have to add any coolant. They're extremely quiet.

I can't say anything about how they work beyond that because we don't have any duct work actually connected to the units yet. That's where I'm really glad I hired this out because they're really particular about their ducting.

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I'll lose head room over my workbench but it's a small price to pay.

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Jeepnstein
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Re: Old House Air Conditioning

Post by Jeepnstein »

It's done.

The loss of headroom is minimal in my shop area and well worth it. Installation was fairly straight forward even though we did bring in a sheet metal worker on the last day to get it done fast. The system is totally silent. As luck would have it the weather has turned cold and we're running the heat pump now instead of the AC. Sure beats baking the house with the boiler on these Spring in Ohio days. I'll update on the energy savings, if any, in a few months.

Two two ton units, one on the east and one of the west side of the house. Each has it's own thermostat and runs independently. The ducting runs are pretty short and we're looking for fairly good efficiency.


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mkiehn20
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Re: Old House Air Conditioning

Post by mkiehn20 »

I'm watching your project with interest! We are looking into mini splits within the next few years. Are you at all trying to cool your upstairs?

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Jeepnstein
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Re: Old House Air Conditioning

Post by Jeepnstein »

Downstairs only. We have a conventional 4 ton unit upstairs.

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