Do I need a heat exchanger

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woodywoodchucker

New Member
Jan 8, 2012
36
western maine
I have an cb 5036 and a Baxi luna boiler that is used for DHW but is also plumbed up to be used as a furnace for the house.I never do use the baxi for heat. My heat guy hooked up the system so the owb heats water and pumps is to a heat exchanger and back to the boiler. Im not sure I need this HX and feel it may be causing my OWB to be less efficant. Im not sure if he did that incase I wanted to use Glycol in the OWB or what.
I have radiant heat in the basement and the first floor and a loop of base board upstairs. So I guess I have a closed loop. If I remove the HX then it would be an open system.
I wonder if the HX is to keep the system from getting air in it.
Any ideas?
 
A heat exchanger is often required to connect an open system OWB with a pressurized closed system. In addition to reducing/eliminating corrosion potential on the pressurized side of the system, pressure is usually needed to lift the water to the highest point of the heat emitters and to eliminate cavitation caused by insufficient NPSH. The use of glycol in an open system also is a good reason to use a heat exchanger. I assume you have a heating transfer coil in the Baxi for the DHW. That too is a heat exchanger. In effect you may have a double wall heat exchanger which is often code required when a glycol system and potable water system interface. If you have glycol, I trust that the automotive type was not used, as it is extremely poisonous.

A heat exchanger will reduce the efficiency of any boiler due to the temp drop between the two sides of the heat exchanger, but a properly sized heat exchanger with proper flow can make this efficiency loss very small. The CB 5036 seems to be a traditional water jacket OWB. A boiler of this design typically is about 30% efficient, as compared to a gasification boiler like a Tarm, Econo, Wood Gun, Froling etc., which are in the 80-90% efficiency range. If efficiency is your concern, I think a focus on the heat exchanger may be in the wrong place.
 
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Im not running glycol in the system. Just water. The water going to the Baxi is not heated in anyway by the wood boiler. Im not too sure how the 30% and 80% are figured out.I burn 10 cord and was told that I would burn 7 to 8 cord with a gasser.Seems like fuzzy math to me.Either the Gasser is more like 50% or the classic is more like 60% with the wood useage I have experienced and been quoted by the dealer. I figure the dealed is shaving some off his estimate. Just seems like an other chance to bash the old smoker to me.
 
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