Girard on-demand hot water heater?

Golden_HVAC wrote:
Hi,

On demand might work fine in a home, where water pressure is stable all the time, and they are not using a 1/8 HP pump that changes pressure often.

Also some home units have 100,000 Btu+ heat input required to heat 2 GPM from 45F (in some locations) to 120F needed in the water system.

If your flow changes quickly, it can overheat the tankless water heater for a couple of seconds, and then trip the high temp limit (say 120 or 130F) and then instantly shut off the gas valve, so scald then freeze!

So many have tried some tankless units and returned them to the supplier, buying a normal 6 gallon water heater. Much less expensive, smaller area in the sidewall, and works great when the water input temp is above 55F. For a even longer shower, the fresh water tank at 80F really increases the time you can take a shower.

I found that out while living in Lakeside CA, and the input water got as cold at 45F in the winter. Warm as 75F in the summer. So I purchased a very in-expensive tankless L-10 water heater from Amazon.com It is $129 and has only 37,000 Btu's input gas, so it can heat 5 liters per minute from 55F to 110F. You control the output temperature by speeding up or slowing the water flow through the water heater. There is a dial to control the gas flow, you can increase it or reduce it a little.

What I was doing is fill the fresh water tank with 80F water in the winter, then use the water pump to take my showers.

I had considered a electric heater, but the heat output of even a $350 9 KW electric heater is not enough to change the 55F water up by more than about 8 degrees at 2 GPM flow. With the hot (or warm) water in the tank, I could increase my shower time from about 5 minutes to well over 20 minutes!!!!

Fred.

Get about fifteen using a standard dual fuel Suburban 10 gallon in my fifth wheel without preheating the water during the winter, I am rather impressed with the results you got out of a six gallon after preheating.

I also discovered with my 6 gallon in my camper that with the manual thermostat models, cranking it up to about as hot as it would go, also extended the amount of shower time I got out of it as I would end up using less hot water to mix with the cold to get the temperature I wanted.