I am hoping to make a smart choice to complete an oil to gas conversion before the end of the year and could use some help. Because of the high rebates, I thought the best way to go was a high-efficiency boiler and water heating unit with an AFUE rating greater or equal to 90 percent and domestic hot water storage of 2 gallons or less, so a combi unit would be the perfect choice.
I've received quotes from two companies which came out and took pictures, etc. and also read all of the threads here that seem to do with this subject and my head is now spinning trying to figure out the terminology and what option(s) are going to provide reliable and cost-effective heating and hot water for years to come. Here are some questions I could use help with:
What are the advantages of going with a high efficiency tank less boiler if it will likely need more repairs because of the aluminum heat exchanger? Would changing that to a stainless steel one reduce the potential for maintenance?
Is the lower maintenance of a cast iron boiler worth sacrificing the higher efficiency rating?
These are the systems that have I been quoted. Are there questions I should ask or anything I should know about these?
Baxi Luna HT 380 Wallhung Condensing Boiler. This fully modulates up to 112,601 Btu’s and is up to 99% efficient. The Baxi Luna HT 380 is a combination central heating and on-demand domestic hot water boiler (with DHW flow rate of 3.9 US gpm @ (T80 F).
Navien Combo Gas Boiler vented with 3" pvc pipe model #CH240ASME
Lockinvar WHN155 Heating Gas Boiler rated at 96% with a 40-gallon indirect hot water tank.
Buderus G124X4-32 rated at 96,000 net BTUs aand 85% AFUE with a 40-gallon Heat-Flo stainless steel indirect hot water tank. An optional Buderus Logamatic Weather Sensing Control is also offered.
Are there other models I should consider?
Currently I have an oil burner that's about 25 years old with a tank less hot water, and there's plenty of hot water to go around. I have two zones in a 1800 sf slab ranch with 1.5 bathrooms. I know it has a bad mixing valve but my repair guys tell me I don't need to replace it - it just means the hot water is a little higher than code but since it's just adults here, it isn't all that important. I suppose I could just keep it but the cost savings of gas compared to oil are pretty attractive and I'd like to get a gas stove at some point.
One last question, I had a new oil tank installed about 6 months ago (and then got a free gas line installation offer from NStar), so I'm wondering whether I can sell my oil tank or if I just need to junk it (well, the installing company would take it away for me).
Many thanks in advance, this was a very interesting forum to read and I'm glad there are pros like you to help people like me figure these things out.