domestic hot water coil

[jdurant]

Hey Eric or anybody else,

I want to add a domestic hot water coil to my logwood (wood coal boiler). This is unit is hooked in parallel to my burnham oil boiler. I want to heat my hotwater tank during the heating season. I want the electric to be standby and used only in the summer. How do I set this up with out getting the water tank to hot and causing the electric element thermostat to keep tripping off. I know I have to use a tempering valve and an anti scold valve. How do I make this all work together? I do not want to cause problems with the hotwater delivery (wife will kill me).

 

[Nofossil]

There are a few sidearm threads, some with pretty good plumbing diagrams.

The anti-scald needs to go on the hot water tank outlet, supplied by the outlet and by cold water. I don't think the electric controls will care if the tank gets too hot.

 

[Eric Johnson]

There's a heat-activated circuit breaker in the water heater's top heating element that trips when the water temp gets pretty high--probably about 200 degrees, I'm guessing. Over the course of a heating season, your tank might see temps that high. All it takes is once. Then, when you go to turn the water heater back on in the spring, it doesn't work, resulting in a negative WAF and a lot of apologizing and head scratching on your part.

A long time ago I gave up trying to comingle my electric and wood hot water sources. When the boiler is running, I shut off the water heater. If I ever turn it back on, I'll just remember to reset the little breaker on the thermostat and go about my business. And yes, I've replaced my share of perfectly good elements because I forgot to do it.

If you want to keep your tank temps down, then like I said in your previous thread, wire the circulator through the water heater's thermostat so that it shuts off at whatever setpoint you dial it to.