side arm

The benefit in using the T & P outlet is that the heated water is forced back into the tank where the cold water inlet connection would be above the tank into a tee.

I always hook mine up to the t/p connection on the top and the drain on the bottom. With tees. Here's a diagram, in case you haven't seen it.

Several things bug me about this Eric

One -- you now need to remove the T&P;as you call it and upon reinstall the probe is slightly divorced from the tank - maybe its still ok -- but maybe??

Two -- lets not forget that an anti scald valve or an aquastat and a zone valve should be added for some sort of control - Pink parts burn too fast in hot water - something - ANYTHING needs to be done to ensure liquid is never delivered to tap above code of 120 degrees

I might rather leave the safety valve ported as it was designed and use the supply port out for a return with a anti siphon valve above it - chances are that enough water will not be drawn out the bottom of the tank to bring too much new cold water into the supply but this isn't the perfect design -- its just really cheep

Also lets not forget the isolation couplings on the new pipe connections to earth.

Kind Regards
Sting

That diagram doesn't address the tempering valve which, as you point out, is important. But you put a tempering valve on the hot water line, not on the sidearm hookup, so it wouldn't be part of what this diagram is trying to show.

The temperature probe can be a problem with any supplementary heat source for a hot water heater, because you don't temper the water going into the tank--only the water going out. So the tank is going to have 190+ degree water in most wood-fired heat exchanger systems. These days I try to keep my system water temp above 190 and I've never had the valve open because of high temp. But in the past with another boiler that I routinely ran over 200 degrees, it would let go from time to time. I got around that by installing the valve out at the end of a pipe that was about 12 inches away from the water heater tank.

The pressure relief part is not affected by a remote or semi-remote location, but it does have an impact on the heat sensor.

To my way of thinking, the temp sensor in a t/p valve exists as one more safety mechanism on an electric- or gas-fired water heater in case the thermostat goes haywire and doesn't shut off the heat source. Then you can have your tank blow up under certain conditions if the temps get too high. Since I shut my electric elements off when the wood boiler is running, I don't think it's as important. I still have it installed; I just don't think it's necessary.

That's right. And it works really well

Thermal syphon definitely works, and works very well when set up properly. Heat transfer will be less efficient than using a brazed plate with a circulator, but for most households, a thermosyphon sidearm setup generally meets the DHW load requirements. Nice thing about the sidearms... you can pipe in a cleanout at either end to remove mineral buildup that accumulates in the exchange area. If you have hard water, these things can plug up after a few years... and if you are using a brazed plate, you'll be replacing it every couple years.

cheers

I've seen them plug up solid with mineral deposits. That happened to my dad. He solved the problem by putting a Taco 007 on the domestic water side to keep it moving. That was about 10 years ago and it's still working well. I find that if I don't drain a few gallons off through the water heater drain about once a month, the thermosiphoning will slow and eventually stop altogether. No biggie, but you gotta remember to do it, lest you hear those bone-chilling words: "Honey, there's no hot water." I have hard water, but I also have a water softener. Apparently that's not enough.