Re: Hot Water Tank
I agree with John.
Anyone who has had an indirect hwh installed knows the value of not having to run out of hw; typical size is 40 gallons, but the sizing chart below will be a better guide---these units last for years without any service (especially if you have soft water); basically, the hot boiler water is piped thru the center of the indirect hwh and the heat from the hot boiler water is transferred (heat exchanger) to the domestic hot water (DHW) that supplies the showers, faucets, dishwasher, clothes washer, etc.---the upfront cost of the indirects is initially high, but it's a one-shot expense that should last you at least a decade, and you won't be burning any additional oil to heat up an oil-fired HWH, or any elec. to heat up an electric HWH.
Indirect 40 gallon hot water heaters made by Triangle Tube Phase 3 (stainless steel innards), HTP Superstor, Weil-MvcLain G0ld Plus, Lochinvar Squire, or TFI Everhot and others, have a stainless steel tank inside a stainless steel tank to prevent corrosion, especially if you have hard water (lots of minerals)---the stainless steel versions also are more efficient in making hot water because there is more surface area involved in the heat exchanging process---the stainless steel versions generally run $500 to $800 more than the "copper coil inside the tank" models (Amtrol Boiler Mate & others)---if you have soft water in your area (low in calcium & minerals) you may be able to get away with using the lower priced 40 gallon Amtrol, but since you will be running hw water thru from a steam boiler, which is not as clean as a hot water boiler, you probably will be better off with a stainless steel model.
Since you have a steam heat boiler, the installation is a little more involved to include an in-line strainer in the pipe supply from the boiler to the indirect hwh, and a quad check valve from the indirect return to the boiler; drain valves also have to be installed in both supply & return lines to prevent boiler water crud from clogging up the piping.
If you don't have a service contract now with your current boiler service co., by all means get at least 2 more estimates for this job; the stainless steel indirects go for approx $1200 plus installation, and the Amtrol non-stainless steel go for approx $800 plus installation.
Calculate your PEAK HOURLY HOT WATER DEMAND, following the 2nd site below---this is the time of day (usually the morning rush hour) when everyone in the household is trying to shower, wash, shave, etc., roughly at the same time, so you need something like a 30 gal or 40 gal indirect to not only have enough HW ready, but to have a QUICK RECOVERY RATE during that one or two hours when DHW demand is at its highest.
Last edited by Pelton; 03-12-2013 at 12:05 AM.