hvac1, I'm not knocking tankless heaters. Tank type and tankless have there plusses and minuses in different applications. I have a 50 gal electric without the elements wired up. It is heated by a pump circulating water through a heat exchanger and the 50 gal tank. The other side of the heat exchanger is water-glycol mixture heated by ground sourced heat pump. The heat pump's regular job is to satisfy the thermostat of a 30 gal electric water heater whose elements are not wired up. (Serves as insulated pressure vessel to store hot water for hydronic heat.) I do have a water heater that is hooked up in normal fashion. It is propane fired and gets its "cold" water from the 50 gal tank.

After installing the 50 gal tank and filling it I discovered that it had no thermostats. Not conventional ones anyway. It has electronic sensors connected to a circuit card (probably thermistors in a bridge circuit) so I had to wire up some relays to adapt it to work with my system.

I don't know how long you could run a shower before you'd run out of hot enough water but two lengthly showers while a load of dishes and a load of clothes are running had no noticible effect. I'm sure if you ran the water long enough it would not meet the demand but so far with 4 couples in the house (family get together) it has kept up just fine.

If I had a house full of kids, especially teenagers, I'd probably be installing a propane fired tankless for a truely endless supply.

The good thing is that the water heating by geothermal is about 1/4 to 1/3 the cost of standard electric water heater and the propane requirement is way reduced by preheating its cold supply.

Pat [img]/forums/images/icons/smile.gif[/img] [img]/forums/images/icons/smile.gif[/img]