Timer for oil-fired domestic hot water?

[stheem]

Like everyone, I'm trying to cut down on my heating oil use. My home has a three-year-old Weil McLain WGO-4 boiler, which also produces my domestic hot water. That hot water is stored in a Weil McMain Gold Plus 40 storage tank, which has a thermostat that signals the boiler to kick on when the tank temp drops. So, the boiler kicks on and off throughout the day and night keeping the tank of water warm. It is pretty efficient, actually, but what I want to know if I can do is this:

I used to have an electric hot water heater on a timer that basically warmed up the water in morning and evening, but was otherwise off. Saved lots of bucks doing this, but could only have hot water those times of the day, which was no biggie, really. What I want to do with my oil-fired system is wire some kind of timer between the thermostat on the water tank and the boiler. This way, I could control when the signal was sent from the tank to the boiler, with the idea that I'd set the timer for morning and evening, when I need hot water, but otherwise the boiler would remain off.

There is obviously the question of whether heating the colder water up after it has been off all day would cost me more than having the boiler maintain the right temp all day, but it seems to me I am paying $4 -something a gallon for heating oil to keep a tank of hot water hot all day when I really only use it an hour or two in the morning and to do the dishes at night.

Thoughts? Can this be done? Should it be done?

[Noel Murdough]

A lot of people do it that way. It might save a little, if the boiler doesn't maintain IT'S temperature all day. Some boilers are cold start, some maintain temperature.

Noel

[inhoth2o]

a tank with-in a tank is an efficient water heater with a stand by loss of less then 1* an hour it does sound as if the aquastat is maintaining boiler temp

[firecontrol]

A good indirect (with no domestic water draw on it) should loose only about 1/2° per hour. If you're using your water like most people in the mornings and night that will coincide usually with the tank needing to be reheated anyhow. What I'm trying to say is if your tank is calling for heat, with no hot water use, more than 2 times a day I suspect there's a plumbing problem or control problem and should be checked by a professional.

To get an automatic timer to control when it can fire up the boiler you are again going to need a professional so that nothing is done that may make the operation after modification dangerous.