I have an old arcoliner. gas fired tankless boiler and water heater. it was originally oil fired and i was told maybe coal before that. it has been well maintained, has a new burner, and low water cutoff. The aquastat needs replacing but isnt affecting anything the way it is now. I currently have endless hot water on demand(and it is really on demand, immediately hot except in the summer when it takes about a minute to heat up.) It heats the house very well despite there being no wall insulation(old stucco house), heats the basement, and two extra rooms that dont have radiators in them.

Ive had a bid to replace it and am concerned that what is proposed is not sufficient, and have read bad reviews about the proposed boiler. Any info/suggestions/comments would be greatly appreciated.

I was told that what would be installed is a Dunkirk 124/4steam boiler with an 82% effeciency rating with a burner and an indirect fired Burnham 30 gallon water tank. I was told the water tank supplied 6 gallons per minute of 125 degree water and had a recovery rate of 100 per hour and that i would have endless 125 degree water.

My concerns are these, I have read horrible reviews about the Dunkirk boilers, and cannot find any info about the burnham indirect fire water heater. i also have a 120 gallon bath tub(to the overflow), and we are tub people and sometimes take back to back baths while other appliances are running in the house(washer, dishwasher, sink, etc). Im also thinking the basement will no longer be heated with a new boiler which would mean cold floors as they are not insulated either, and i was told that a vent would need to be cut into the side of the house to vent it instead of using the chimney which would increase the effeciency.

Any thoughts?

Thank you!