Sidearm or brazed plate hx?

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lmholmes11

Member
Jul 27, 2014
77
Northern Michigan
I have a Ridgewood 7500 outdoor wood boiler heating domestic hotwater. Right now I have a side arm heat exchanger on the water heater. It gets it hot, BUT takes a long time to recover. Family of 5 doing dishes daily and multiple loads of laundry a day. I have heard a brazed plate heat exchanger acts like a on demand heater in a way and recovers quicker because it heats the cold incoming water and stores it in the water heater. Should I switch?
 
Part of the trick of getting satisfactory performance out of a sidearm is having a big DHW tank. So you have a big reserve, and it can heat up in periods of low use. (Like over night). So maybe a bigger DHW tank?

I started with a sidearm, but it wasn't the answer for heating DHW from storage. So I added a 20 plate FP. Just left the sidearm there, so they're in series. The FP generates a lot more hot water, no question. But you'll need to pump the DHW side, whereas a sidearm can work by convection on the DHW side. Not sure what you mean by 'heats the cold incoming water and stores it in the water heater' - they would typically both work the same, just that one by convection & the other by pumping. Which might mean adding some controls to control the pumping - don't know much about your existing setup. So you'd have to make the call on whether you should or not.

Do you use it to heat DHW in the summer too? I have the past 2 summers with my IWB and storage. But am not this summer. It's a toss-up for me between heating with wood in the summer or electric, even with the pretty efficient wood setup I have. But I don't think I would do it if I had an OWB.
 
I have a boiler outside with a pump on it. Pumps water from boiler through the sidearm and then to the house furnace and then back out to the stove. No I don't burn wood during the summer.
 
And the dhw side circulates by convection?

I likely would stick with the sidearm. But make sure it is situated for best possible convection. Then after that maybe consider a bigger tank. You could likely increase performance by adding a FP, in series with your sidearm on the boiler water side but before the tank and outside the sidearm dhw circuit. That would heat your incoming cold supply water before it gets to your tank, whenever a hot tap is on, without using another pump. But not sure it would be worth it? Maybe?
 
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