Hello Everyone!
Here's my situation. I've just installed an outdoor wood boiler and it's delivering 175ºF water to a stainless steel, double-walled sidearm heat exchanger installed immediately alongside my electric water heater. The bottom of the sidearm is plumbed into the drain outlet of the water heater, while the top end of the sidearm connects to the pressure relief outlet on the side of the water tank. The hookup is just what's needed for proper thermosiphon action, but to boost water circulation through the inner part of the sidearm I have a Grundfos 15-58 circulator on top of the sidearm, drawing water from the bottom of the tank and moving it up to the top connection. A Grundfos 26-99 circulates boiler water through the outer passage of the sidearm. Water flows are opposite to each other – downward flow of the 175ºF boiler water, and upward flow of the DHW from the the bottom of the tank to the top.
The sidearm gets hot to the touch on the outside, but it doesn't transfer heat to the water flowing through the inner pipe. I know for sure that water is flowing through the inner part of the sidearm (I can hear it flowing if I partially close a shut-off valve at the bottom of the sidearm), but even with the system running all night, and no DHW being used, the tank only gets to about 100ºF with the electric elements turned off.
I thought at first that the problem might be too much mixing of the DHW in the tank because of the 15-58 circulator, but that's not the case. The tank heats up fine with the circulator running and the electric elements turned on. The more I look at things, the more it seems like that sidearm simply isn't transferring heat. I had originally planned to go with a flat plate heat exchanger in a similar set up to what I have, but opted for a pump-assisted sidearm because of the hard water I've got.
The sidearm I've got is double-walled, and perhaps theres a design flaw in this approach. If "double-walled" means there's some kind of an air space between the inner water passage and the outer one, that sounds like the problem to me.
I'm at a loss on how to proceed. Can anyone offer some insights? I know sidearms work because I've seen them work. Mine is plumbed for thermosiphon action, but it's simply not heating the water flowing through it, even when pump-assisted. Is there anything I can do other than scrap a brand new, $250 sidearm heat exchanger and plumb in a flat plate exchanger?
Thanks a million!
Steve
Here's my situation. I've just installed an outdoor wood boiler and it's delivering 175ºF water to a stainless steel, double-walled sidearm heat exchanger installed immediately alongside my electric water heater. The bottom of the sidearm is plumbed into the drain outlet of the water heater, while the top end of the sidearm connects to the pressure relief outlet on the side of the water tank. The hookup is just what's needed for proper thermosiphon action, but to boost water circulation through the inner part of the sidearm I have a Grundfos 15-58 circulator on top of the sidearm, drawing water from the bottom of the tank and moving it up to the top connection. A Grundfos 26-99 circulates boiler water through the outer passage of the sidearm. Water flows are opposite to each other – downward flow of the 175ºF boiler water, and upward flow of the DHW from the the bottom of the tank to the top.
The sidearm gets hot to the touch on the outside, but it doesn't transfer heat to the water flowing through the inner pipe. I know for sure that water is flowing through the inner part of the sidearm (I can hear it flowing if I partially close a shut-off valve at the bottom of the sidearm), but even with the system running all night, and no DHW being used, the tank only gets to about 100ºF with the electric elements turned off.
I thought at first that the problem might be too much mixing of the DHW in the tank because of the 15-58 circulator, but that's not the case. The tank heats up fine with the circulator running and the electric elements turned on. The more I look at things, the more it seems like that sidearm simply isn't transferring heat. I had originally planned to go with a flat plate heat exchanger in a similar set up to what I have, but opted for a pump-assisted sidearm because of the hard water I've got.
The sidearm I've got is double-walled, and perhaps theres a design flaw in this approach. If "double-walled" means there's some kind of an air space between the inner water passage and the outer one, that sounds like the problem to me.
I'm at a loss on how to proceed. Can anyone offer some insights? I know sidearms work because I've seen them work. Mine is plumbed for thermosiphon action, but it's simply not heating the water flowing through it, even when pump-assisted. Is there anything I can do other than scrap a brand new, $250 sidearm heat exchanger and plumb in a flat plate exchanger?
Thanks a million!
Steve