Adding A/C to my old Victorian house

Jamie Hall

Oh? I hate to be firm, but... none of those options are good for an older Victorian house which has an existing operating steam system which works -- which the OP's house has.

I'll go back to what I said before -- in this situation, the best bet is a Unico system. Much less intrusive, and does the job which is needed.

As an additional point -- in century plus old houses (and other older buildings), if they haven't been destroyed internally by misguided "renovations" (all too common, unfortunately, by the ham-handed), avoiding damaging the existing walls, floors, and ceilings is step 1. Repairs to them, if they are done properly, can be hideously expensive.

SHS111

Proceeding with Unico installation, first floor. Work began today. Good to have made the decision and very pleased with the professionalism of the team. Thanks everyone for your helpful comments and suggestions. Will update once it’s done.

HVACNUT

Does Unico offer 2 stage cooling?
Manual J, heat gain, solar gain...
an old home needs a little more TLC in sizing and application.
I would go with one correctly sized 2 stage system per finished level. Try to get returns throughout for even distribution. A whole house dehumidifier piped through the 1st floor A/C return. and account for future insulation, windows, siding upgrades, etc. as long as those projects are priority and will get done.

Tinman

@HVACNUT Unico can be used with a stage condensing unit. Typically, a single common return is used although I've done them both ways. No need for further dehumidification as it removes up to 25-30% more humidity than a conventional system.

mikeg2015

With a house that large, I'd seriously be looking at chilled water. Will have a lot better ability to zone bedrooms, control humidity and keep it comfortable in mild weather (most of the time). A smaller cooling tower and a pair of 5 ton water to water heat pumps might cost less than you think and have a smaller footprint. In mild weather you can use AC upstairs and heat downstairs at a very low cost (which may happen more than you think in a tall house).

Best thing about chilled water is that if you have a large kitchen with a big vent hood, you can bring in a lot of outside air.

mikeg2015

SHS111 said:

Proceeding with Unico installation, first floor. Work began today. Good to have made the decision and very pleased with the professionalism of the team. Thanks everyone for your helpful comments and suggestions. Will update once it’s done.

Make sure the contractor follows the manual, Unico signed off on the layout and they seal the s*** out of the system.

I've had a nightmare install on my Unico. Noisy, drafty and an energy hog with tons of leaks in the attic. Took them forever to install. Ordered wrong AHU, then the TXV failed out of the box. Mid range Lennox 3 ton condenser is the loudest unit I've ever owned. They were supposed to put a sound blanket on it. Installed it on the wrong AC condenser... seriously. I can't make this up. Unico has tried to help. But there's been a lot of hurdles. Aparently they claim I can't select different heating speeds vs. cooling speeds on the Smart ECM motor even though it's an option in the software. "O" input apparently does nothing. YOU CANNOT RUN <250cfm/ton with heating especially with a long lineset. A lot less air leaks, quieter and better humidity control at 225/ton.

In hindsight I would have just installed a conventional 2 ton system and spent $1000 on materials for full attic insulation. May still need to insulate the attic to get it all working well.

Probably have to call the Unico rep myself this week and have a long discussion. Sometimes I think ignorance is bliss.