Oil to gas, steam to water conversion

fastcat

I am planning a conversion from oil to

gas. I have bids from three contractors with three different boilers and three

different heat load calculations. They are all experienced and the price difference

among them is very small.



The house has two stories, about 2000 sq.

ft., 2/3 of it is 170 years old (assumed uninsulated) and 1/3 is 35 years old

and insulated. It has a rubble foundation and dirt floor where the boiler will

be installed.



The old part of the house is heated by

steam, the newer part by FHW through baseboards. A Burnham V8 series oil fired

boiler services both zones as well as the indirect water heater. The baseboard

loop is fed from a tankless coil in the boiler, so it is clean. As with many of

its ilk, the boiler is leaking water, but I have managed to limp though most

of our northeast winter with it.



I am planning to replace the

8 single pipe steam radiators (in 7 rooms) with Ecostyle panel radiators and replace the

boiler with a high efficiency gas condensing boiler. The three proposed boilers

are Viessmann Vitodens 100-W, Lochinvar Knight 155K btu and Weil-McLain WM97.

All three contractors did heat load calculations, but the results show as much

as a 50% variation in some rooms.



Are there some criteria I can use to

evaluate the bids?

Is there a clear preference among the

three proposed boilers?

Is it important that the installer

also service the boiler in future years?



Thanks for any guidance you can

provide.