AC advice please - newbie

[geocade]

Hello:

I'd appreciate using you as a sounding board. I have a two storey house with full basement. It has hot water baseboard heat and I would like (need) AC.

As I see it the two options are a ductless split or a high velocity unit.

The guy spec'ing the ductless split is suggesting only two air exchangers (and compressors) one for the top floor and one for the ground floor. He is suggesting 12,000 btu Mr. Slims. The top floor is 4 bedrooms making 850 square feet. The first floor is 5 rooms making 1300 square feet. The basement is another 1300 square feet (reference only - no AC needed in the basement - although humidity control is). It is not open concept and was built in the 60's and has no upgrades with respect to insulation or windows.

My concern is that the two exchangers are not adequate and I would have far too great a temperature difference between rooms - if not some rooms completely 'unconditioned'. Of course all doors would need to be kept open.

Despite my concerns this guy is firm in that they will do the trick.

Any thoughts or pearls of wisdom are greatly appreciated. Any other options are also appreciated.

Geocade

[beenthere]

I would prefer a HV system.

Not know your location 2 tons sounds light for your home, but i didn't a the load calc, did he?

[geocade]

Thanks for the reply.

I'm in Southern Ontario (thought my profile would show - oh well). I'm not aware of him doing any calc's which I guess adds to my doubt.

Geocade

[Irascible]

As the beenthere just said, two tons seems smallish and you really need that calc.

I don't deal with either mini-splits or HV much. But just so you know there are multi-zone mini-splits. You can get up to three zones per unit. So you could theoretically get up to six zones with two outdoor units.

But in my mind having six units hanging from various areas of the house would not be esthetically pleasing. If there's room to run HV hoses to different parts of the house then I think you'll be much happier with the result both in terms of performance and esthetics.

[geocade]

My heart is with the HV system, but the ductless splits have a very tangible incentive ($$$$). They are quite a bit cheaper.

I thought of the option of more air exchangers but, again, was concerned that one room would be over air conditioned while others would be under. Having a very small amount of knowledge on these matters, I wouldn't expect the cool air to 'radiate' around that easily - unless there is actual air movement. Should I expect that the cool air from the air exchanger would travel 30 some feet, making 90 degree turns to get to another room?

I can certainly push for a calc, but would that not just show how much tonnage I would need - not how the cool air is going to make it around the house??? Having said that I agree a calc is required.

I certainly appreciate the advice.

Geocade

[beenthere]

Your right that the air won't travel around corners on its own.

Thats why I prefer the HV over mini's.

They have their place though.

The HV will be more costly to install, but will have at least 1 outlet in each room. So you know it will deliver the air where you need it.


Sorry about not checking your profile, so many HO's don't fill them out, I didn't check it.

The load calc, will help you not waste money on an oversized, or undersized system.

[Black Adder]

Ductless split is only going to cool the room that the unit is in, I don't care what your contractor says. They are no different than a window shaker, just a lot quieter. They definetly have their place but not if you are trying to cool a whole house. HV is going to be your only viable option. As far as your "$$$$" incentive, you can acheive the same thing with a couple of window units for a whole lot less money than ductless split.

[Irascible]

Heat always moves from hot to cold no matter how many 90 degree turns you give it. But the real question is will it do so well enough to make you happy. There's no way to know that for certain. Your happiness is too subjective. And I know of no easy formulas to project temperature differences between areas next to the air handler and areas far away from it. You'd probably have to have some genius egghead type run a computer model of the house.

But... My highly subjective guess is that the mini-split would not make me happy. Thirty feet and several turns is a bit much. It could make you happy, especially if you're prone to denial. Once someone has spent thousands on one solution to save thousands on another, they have a powerful incentive to convince themselves they've made a good decision even when they didn't. No one wants to admit a very expensive mistake.

Plus, once you start adding more evaporators to a mini-split to really make it effective I would assume the price incentive goes away for the most part.

[tinknocker service tech]

your concerns are correct. the room with the unit or units will be cool and the others will suffer. if the doors are open maybe they will cool to some extent but not enough to be comfortable. hv systen thow it is costly would be your best bet. with 3in outlets and pipe it will not take away a lot of room it closets and it also will be out of site. you inteire house will be cool and you will in the long run be happier
good luck

[geocade]

Thanks for the responses, everyone has pretty much confirmed what I was thinking. I just needed impartial professional advice. I'm never sure you get that from someone trying to sell you something.

I'll make sure I follow up here when I get more info/quotes regarding the HV systems.

I have made the assumption that HV and ductless splits are my only two choices (other than window units). Am I missing something??

Thanks all!

Geocade

[Irascible]

Missing something? I assume this is a space issue where you don't have room in the house to run conventional ducts. So the answer is: Yes! An exposed rooftop system. You get yerself a package unit and set it on the roof just like they do at the strip mall. Then you run a bunch of metal ducts to various points and penetrate the roof wherever you want vents.

Sure it'll look like crap. But just a few decades ago AC was considered a status symbol in Hicksville, USA. People proudly looked upon their rooftop monstrosities as a sign that their household was doing well. You can join them in their garish display of conspicuous consumption.

[geocade]

Irascible:
I thought of that solution, but the rest of the residents in the neighbourhood would have kittens. Besides, I have to look at re-sale value - I don't want my house to be worth 300g's less than Frank next door.

I wondered about such a system inside the attic but worried about noise / vibration and the interior bulk head work (read lots of hardwood flooring, chair rail, crown and other and special molding on the walls).

Actually, I thought of two 'conventional' systems. One in the attic as described above with vents from the attic through the ceilings serving the top floor and one in the basement serving the ground floor with vents coming through the floor.

I wasn't sure how that would all come together though.

I called more HVAC companies in the area today and all seem to be very limited in their level of competency in retro fit situations.

Geocade

[Freezeking2000]

put the system in the attic and duct down. Maybe you could find some closet space to make a few runs to the first floor cieling from the attic.

[johnl45]

Originally posted by geocade
My heart is with the HV system, but the ductless splits have a very tangible incentive ($$$$). They are quite a bit cheaper.


Geocade

Comfort cost money! there is no way around it.

[Irascible]

So you do have room for a conventional system? Noise is a concern. But if that's you're only concern then conventional systems can be engineered for quiet. I sort of assumed that you were checking into ductless and HV because there was no room for conventional ducts.

As far as the nice finish goes, have them put in the contract that any damage will be repaired by a third party of your choosing at the HVAC contractor's expense. That'll keep them on their toes.

[Black Adder]

If it is possible go with a conventional system, costs should be considerably lower for what you will gain. As far as possible damage, the contractor will be liable for it unless he specifically mentions it in your contract. We do retrofits like that all the time with very little or no damage whatsoever. For the drywall ceiling outlets I use a 6" hole saw in a cordless drill to turn the bit very slowly. Makes a clean hole and if you hold a shop vac beside it there is virtualy no dust. Getting the equipment into the attic and running the refrig lines are the only difficult thing. As far as a systim in the basement, as long as they are careful cutting the outlet holes there should be no problem.