gas boiler conversion

The forever home may need to have a replacement boiler in 17 to 22 years if you go with a Mod-Con Combi.  and they are more expensive that a conventional CI boiler.  I would recommend that you stay with Oil Heat if there was no [problem with the current system.  When you try to justify the cost of a new boiler system just to convert to Gas from Oil there really is no break even point in the foreseeable future.  The savings you will realize from that conversion will not be enough to pay for itself within the lifetime of a ModCon, Combi.  For example using hypothetical numbers (because we are not supposed to talk about prices on this site)

Let's say that a complete new system will be about $15,000.00 for the most efficient boiler. (These numbers are older than today’s) and you spend $2,000.00 per year on fuel oil.

The 15,000.00 job will end up with a gas bill of 1500.00 per year.

 That is a $500.00 per year savings

How many years of saving $500.00 will it take to equal $15,000.00? 

Without considering inflation… that would be 30 years.   

The ModCon Combi has a life expectancy of 20 years.  So if you keep your old oil burner, in 20 years you would have saved $5000.00 by not purchasing a new ModCon Combi.  

On the other hand, If you have a broken oil boiler or one that is from the 1930’s that used to burn coal, and is operating at only 45% overall efficiency then that is a different story.  You need to at least replace it with a $10,000.00 replacement oil boiler.  When comparing that to a $15,000.00 Gas boiler that will save you 500.00 per year over that of the replacement oil boiler, then you have a payback that makes sense.   Since you need to spend $10,000 anyway the you only need to decide between the oil or the Gas for an additional $5,000.00, that is an easy decision.  Your payback on the additional $5000.00 is only 10 years and you will have another 10 years of savings to put in your pocket. 

See my edit above:

I have had customers with the original WM GV boiler.  It is cast iron and it lasts longer than the other ModCon boilers.   The GV90 is the original GV, CI boiler that has an additional secondary Heat Exchanger that increases the efficiency from the high 80% to over 90%.  That additional HX may not last as long as the CI sections but as long as the secondary HX is available to replace when there is a failure in 17 to 22 years, I would select that one.   But if your existing oil fired boiler is less than 25 years old and is operating without problems, you may want to consider keeping it and having a good tuneup and maintenance performed.   That will last a lot longer that any of the new stuff available today.   

Yeah, it might make sense to switch to gas — but you won't save anything on fuel.

Agree with the reason to convert for your situation. The new WM GV90 would be my choice of those you were offered. There will be some savings from the $3000.00 per year. You may be pleasantly surprise with a $2000.00 per year gas bill, but I would not bet on that. I would be satisfied with a 2500.00 Gas bill and be pleasantly surprised with anything more. It all depends on the existing oil heater overall efficiency.

Not a fan of the ModCon/Combi for a forever home! Use a separate water heater or an indirect. If I were in your shoes, the GV90 and a indirect for DHW. I like that the best because the 90+% efficient burners will be heating you home and your hot water. A very efficient design IMO

The rationale for switching to gas seems obvious in your situation.

The gas boiler you choose is often much less important than the installer you choose.

I focus on much older houses (18th and 19th century) located in the northeast. Finding good boiler installers who can service your equipment year after year are becoming harder to find (even in areas where boiler heat still rules the day).

I strongly suggest that you put the majority of your effort into working with a plumber you can trust for the install and maintenance of your new boiler.

In terms of the equipment, newer modcon boilers are becoming the norm in the markets I have worked and currently work in, so it remains to be seen if the more tried and true cast iron boilers will soon require “specialized” techs to maintain them, or owners who are willing to maintain their own equipment.

That boiler, a Weil-McLain 62 series, is built like a tank. If it were mine, I'd probably retrofit it with a Carlin EZ-Gas or Midco EC-200 gas burner.

The coil gasket has been leaking. That may or may not be fixable, but if it is………….

I'd get a licensed chimney contractor to look at it.

If the chimney is as old as the house, then of course you would want it inspected by a chimney pro. Didn't you see "The Money Pit"?

The boiler may be in great shape or maybe not. Although a gas burner conversion is a good idea even if it were mine and I could do the conversion myself I couldn't justify the expense with a boiler that age. But it's not a yes or now answer other may look at it differently

I would run it as is and save for a new boiler. JMHO

There are no crystal balls for boiler integrity.  I was saying that if I had the chance to be in your position, I would do it as an experiment, just to see the cost of heating for the year, adjusted for actual degree day in each winter season.  Also to convert back to oil after 2 years and see if a newer oil burner might save on fuel. 

That's just me.  And for the experiment, I would not put in the liner. (but you should if this was to be forever heater) That is because I know that there will be a new boiler in the near future, and it will be direct vented like the GV-90. You are not in the position to do experiments like that.  There is nothing in the game for you to learn what might be the best way to go.  And of course the equipment would be at wholesale cost or even second hand, removed from a customer’s home, that purchased new equipment. (there must be 15 second hand oil burners on a shelf somewhere that I was saving for parts or to rebuild and have ready for an emergency.)  The labor would also be my own time that I would chalk up to R&D.  You can do that when you own the company.

As far as @Ghynes440 is concerned, I would still pick the GV-90 as the forever boiler for that home.