A way to heat DHW

[fishman]

Has anyone ever heard of taking main loop and run it down through the pressure relief opening (obviously with a tee) and out the drain on DHW tank back to zone

 

[stee6043]

Are you talking about sending it "through" the DHW tank? Are you running a pressurized system or open OWB? With any open system I don't think this would work due to domestic water pressure. You'll also likley have corrosion issues. Any reason you don't want to run the traditional side-arm setup?

EDIT: Not to mention the obvious which has been brought up already - but you can't mix boiler water and domestic water. That would be a problem regardless of whether or not it "could" be done...

 

[rkusek]

You don't mean mixing your boiler water with your DHW do you? That would be a big no-no since you could contaminate your drinking water. An indirect heater (like SuperStor) with electric element backup would be ideal for those of us that don't have existing oil boilers but I don't even think they exist. I have been reading that a sidearm can't keep up with a lot of hot water usage so I have been wondering what would work best with my 80 gal electic heater. A sidearm is definitely the simplest way to go I would think. Since I will have a secondary loop feeding my sidearm DHW (not yet installed) I was wondering about the possibility of having a second small circ, bronze or stainless, that would be cleared for use with potable water circulating the water thru the sidearm. Circ would activate only when the tank temp dropped and possibly thermosiphon (no integral check valve in pump) when DHW demand was light working just like an ordinary sidearm. I'm guessing the limitation with sidearms is not tranferring the heat from the boiler but instead the slow response of thermosiphoning it from the sidearm throughout the tank. I haven't read the specs on my water heater but I'm not sure how much you can overheat the water like the folks with the superstors are doing. I have never heard anyone discuss this setup in the Boiler Room so there is probably a good reason why it won't work. A mixing valve out the output side would be necessary no matter what setup was used in my view for safety's sake.

 

[700renegade]

Huskers, this is a bit off topic but could you put in a tee at the bottom drain fitting where you pull off your cold water and install a Honeywell aquastat? When the temp hits say 140* it shuts off your pump. At that point presumably the whole tank would be at 140* or so ( not sure you'd have much stratification with 10 or 15 gpm blowing into the top of the tank while the pump is running ). You'd have to insulate the area well to avoid a bunch of short-cycling of the pump due to heat loss at that external fitting.

You'd still probably need the tempering valve on the domestic output in case you get thermosiphoning.

 

[Tarmsolo60]

What are you using to keep your boiler water and DHW separated? Do you have a heat exchanger in the circuit somewhere?

 

[Tony H]

Has anyone ever heard of taking main loop and run it down through the pressure relief opening (obviously with a tee) and out the drain on DHW tank back to zone

Those would be the exact places to connect in your sidearm for heating hot water. Boiler water runs thru one section of the sidearm and water heater water runs thru the other section (no mixing) and the heat is transferred by convection. Works great for my system.