Handyman on call: some a/c advice, minus the tech-speak
Q. We own a three-family house and occupy the first-floor apartment, which has its own forced hot air furnace; a separate furnace serves tenants on the second and third floors. Last fall our plumber replaced our 28-year-old gas furnace with an American Standard Freedom 95 gas furnace. He asked if we wanted him to install a coil that would allow for us later to obtain air conditioning. We agreed.
This spring we were attracted by the National Grid offer of a 20 percent rebate, plus a utility rebate, plus a tax credit on installation of air conditioning this year. We have since spoken with National Grid and a private contractor. It turns out that the coil our plumber installed has to be used with the previous generation’s system. We now face the dilemma of whether to use the existing coil and install an R22 coolant system with a SEER 13 condenser (or possibly a SEER 15 condenser with the addition of an American Standard valve) or replace the coil (and our existing main trunk duct work - which we understand is not adequate for the “state of the art’’ system) for a SEER 16 condenser (which uses a next generation coolant). We hope you can help us decide.
If we receive all the rebates and discounts, the SEER 16 system will cost about $6,900 ($9,000, if we do not receive any rebate, discount, or tax credit). If we use our existing coil, and install the R22 system, the cost would be about $5,200.
ALICE & AUBREY, Jamaica Plain
A. Never in the field of heating and cooling has so much tech-speak been foisted on so few innocent people. I have a feeling you don’t understand it any more than I do. What you need is a compressor and to charge the system to get it going. A typical central a/c installation is about $5,000, so take the R22 system at $5,200. With 1,200 square feet of living space, that current coil should be adequate. If you feel this is not a good idea, then get the people to speak to you in English, not tech-speak. As for your duct system not being adequate for any system, I think that is baloney. Any hot air system can be adapted to a central a/c. I have an ancient house with a good hot air system, and the a/c (added on later) works very well, thank you.
Q. In New England, how many inches thick should a base be for patio pavers?
FRED, in Hotton’s chat room
A. Two inches of sand or stone dust is adequate for concrete patio pavers, stone pavers, or bricks. The pavers are installed as tightly against each other as possible without mortar, with fine sand sprinkled in the joints.
Globe Handyman on Call also appears in the Sunday Real Estate section. He’s available 1-6 p.m. Tuesdays to answer questions on house repair. Call 617-929-2930. Hotton (photton@globe.com) also chats online about house matters 2-3 p.m. Thursdays. Go to www.boston.com. 
