Sidearm Heat Exchanger

[Eric Johnson]

I don't have a check valve on mine. Maybe I should. The way I look at it, there is no flow through the sidearm on the boiler side when the wood boiler water is below 160 degrees. And since there's a flow control on that line and the water is entering the sidearm from the top and flowing down, there's no place for the boiler water to thermosiphon to. That's with a direct feed from the EKO. I haven't really thought through the implications of using it with hot water storage, but I don't think it would be much different.

As a practical matter, the boiler can shut down for hours and we don't run out of hot water.

 

[BrownianHeatingTech]

I don't have a check valve on mine. Maybe I should. The way I look at it, there is no flow through the sidearm on the boiler side when the wood boiler water is below 160 degrees. And since there's a flow control on that line and the water is entering the sidearm from the top and flowing down, there's no place for the boiler water to thermosiphon to. That's with a direct feed from the EKO. I haven't really thought through the implications of using it with hot water storage, but I don't think it would be much different.

As a practical matter, the boiler can shut down for hours and we don't run out of hot water.

It depends on the piping layout. Thermosiphoning is not exactly a forceful thing, in these sort of systems, so the piping may easily restrict the flow. Or the pump may be enough resistance.

Joe

 

[Tony H]

I don't have a check valve in my layout either should I add one? Also the setup shows water from the boiler to sidearm and the to heat exchanger in gas forced air furnace and back to boiler. Would it be better to go to the heat exchanger first or sidearm first?

 

[Eric Johnson]

Flow checks are good to have, IMO. These days many pumps come with them built in. When I did my piping layout, I realized that I needed flow controls in places to make the water go where I wanted it to go. It took some headscratching, but I finally figured it out.

As to the sequence, with heat exchangers I don't think it matters much. I piped my sidearm ahead of my zones because they're being served by a gas boiler vessel into which I'm piping water directly from the wood side. I thought it would be best to have consistently hot water running through the sidearm, instead of essentially making another zone off the main distribution system, which experiences more variable water temps. If that makes any sense. With most heat exchangers, the water coming out isn't much cooler than the water going in, so I don't think it matters from a practical standpoint.