I do the same with my electric water heater. I heat the water in the
morning, then the timer shuts it off until the next morning.

So I have hot water for a shower in the morning, then warm water the rest of
the day.

This saves a lot of money on my electric bill (which was $45 last month.)
When I had my water heater on all the time, my bill was always $75. (Just me
living in house.)

With your setup, I wonder how much heat is going up the flue, how much heat
is needed to heat the boiler to then heat the water heater, etc. Seems to me
a direct separate water heater where you are only heating the water in the
water heater would be more efficient? (Since you are not using the boiler to
heat the house.) Then also have this on a timer.

If I could re-design my house, I would have small electric water heaters
under each sink which would provide slightly warm water (always on). Then a
separate large hot water heater for the shower which would only heat the
water to hot in the early morning for a shower, then turn off. Also this
could be set to turn on every other day to take a shower every other day.
And of course a by-pass switch for those summer days where you need a shower
everyday or sometimes twice in one day.

"roperman" wrote in message
Here's my setup: a 12 year old forced hot water oil boiler, with a gas
conversion burner, and connected to that is a 40 gallon indirect fired
water heater. We've been heating our house with a wood stove for the
last two years, so all the boiler does is heat our hot water and serve
as a backup for our wood stove.

When the plumber installed the water heater, he turned the low point
on the boiler all the way down. The boiler kicks on when the water in
the boiler goes below around 65 F degrees. High point is 160. Water
heater is set at 127 degrees F, which gives us 120 degree water at the
faucet. The heat loss for the water heater is 1/2 degree per hour.

The water heater calls for heat when the temp goes 10 degrees below
the set point. So the boiler may sit for hours without calling for
heat, so the boiler temp goes down to room temperature again. So for
our hot water, the boiler is heating its own 6 to 8 gallons of
"boiler" water to 160 degrees in order to heat the water in the water
heater. That seems like a lot of energy going in to heat the boiler
up every time we draw hot water.

To remedy this, I installed a timer that turns on the water heater
once a day for an hour. The 40 gallons of hot water gets us through
the day (so far, but I just installed the timer last weekend). My
friend says this won't save any energy, because warming up the hot
water tank from a low temperature will take more energy than heating
it up throughout the day, where the temp differential is lower.

A drawback is that the hot water controls will be turned on daily
instead of being left on constantly, which may reduce its life
somewhat. It's got a solid state control unit with a LED control
panel.

I could get a device that measures the amount of time my boiler kicks
on to find out which way is more efficient, but before I shell out for
that, I thought I'd see if anyone had any ideas. Anyone have any
guesses which way is better? Thanks!

Jay