indirect DHW off existing steam boiler

Jerry_15

That's why I asked. A flash (tankless) won't work for you. Al probably has the right stuff on the set-up, I'll check it out and advise in the unlikely event that I could add anything productive.

Bart_5

Can anyone

guide me in the right direction to find piping and wiring schematics for installing an indirect domestic hot water storage tank off of a steam boiler.

Jerry_15

There are ways to do it and I've done em very successfully for DHW and radiant off existint steam, but remember the boiler needs to be fired on stand-by 24/7. A simple dedicated flash heater will cost far less in equipment and installation costs, not to mention fuel. What is your application, though?

Bart_5

not sure what you

mean by "flash heater". The application I'm looking at is a customer that would like to have a better volume of domestic hot water than he now has from his tankless coil. He has steam heat fueled by oil. No natural gas available in the house. He was quoted a pretty hefty amount by the gas supplier to bring the gas in. He's not interested in propane and feels electricity will be too expensive.

Al Letellier_9

indirect on steam boiler

Look at any boiler manufacturer's installation guide and get the piping diagram. We use Weil exclusively for steam and you can find wiring and piping diagrams on their web site. Have done it many times and have two going in this month, so it does work. Pay close attention to the piping and do it as draw.

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Jerry_15

Whoops - missed the part that you already had a tankless coil, so your controls are already set up. Way simple. Put in a 30/40 gal electric and pipe the coil as if it was a recirc line, with a small circ pump and check valve. Use the two legs coming out of the tank as a switch for hot on the pump. Built in aquastat. Done deal. I'd add a tempering valve for safety, and maybe use a flow check or spring check to avoid thermo-siphoning. Oh Yeah, put the pump on the return to boiler so it doesn't lock out from high heat, or use a coupled pump. Good luck.

Guy_6

indirect

Actually, the boiler will not need to maintain a constant temp, it can be called on with a demand from the indirect. What I usually do for wiring is the standard relay configuration, with the end switch first going through an aquastat (to break TT before steaming) to the TT terminals.
Piping- I usually pump off the bottom of the boiler and return as close to the water line as possible. A Y strainer is recommended to protect the circ.

Jerry_15

You fire the boiler from a cold start when the tank puts in a call, on a steam boiler? How bigga tanka you gotta? Some customers look good in goose-bumps, but alas, I only hear about it on the phone.

Jerry_15

Did my suggestion make sense, or just confuse you. Too simple? Curious to hear some feed-back.

Bart_5

Thank you Jerry,

The only part I was unsure of is do you still wire the water heater so that the elements heat or are you using the water heater just as a storage tank?