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Storage hot water heater (gas)

Posted by joshct (My Page) on
Mon, Jun 13, 11 at 8:22


I have a large Victorian home (1890). Our house was retrofitted with a pex plumbing system, hydronic baseboard heat, and a condensing boiler. We get our domestic hot water from a coil in the boiler. Our gas bills are very low, but our domestic hot water situation leaves much to be desired. If you are running a shower, and someone turns on the hot water anywhere else in the house, the shower pressure drops way down and/or runs much cooler. It takes FOREVER for hot water to reach some of the faucets. We are very miserly with our hot water, so turn the hot water on and off on short cycles for things like dish washing. I am thinking about having a storage gas hot water heater installed to hopefully alleviate these problems. Would it make sense to run the new hot water in series with the boiler? Or should I just cap off the boiler coil? Or maybe run the boiler hot water to one fixture and do everything else off the storage? Any advice would be greatly appreciated.

Follow-Up Postings:

RE: Storage hot water heater (gas)


Unfortunately with a condensing boiler, it runs most efficiently at lower temps (about 120 degrees) when it condenses the flue gasses it is wringing out as much heat as possible. At higher temps the flue gasses will not condense. To get 120 degree water for your shower, you should have a separate instantaneous or storage water heater. As for the wait for HW, there are recirc pumps you can get, but to be satisfied with this setup, you need to run an additional recirc line (1/2" or 3/4") from the farthest HW run back to the cold water inlet of the water heater. This will continuously (or timer model) recirculate HW through the run and back to the water heater eliminating the wait.

Hope this helps,


RE: Storage hot water heater (gas)

Thanks Dan,

Very helpful! I will look into other options. I normally need to crank up the boiler in the dead of winter as I don't have enough radiation in the house for 120 degree water to heat enough, i.e. the circulator runs 24 hours a day and the house cannot reach the setpoint.


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