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[cajoneric]

I plumbed my CB OWB into my Hot Water Heater using a plate heat exchanger. I am using a circulation pump to keep the water continuously mixed. My question is what will happen with the water in the HWH if my boiler overheats? will it also boil? will it blow the pressure relief valve? What is the worst case, and how can I mitigate it. Thank you for any input.

[buckgrunt]

I have a CB 2300, which is equipped with a blow that blows air into the fire box when the house calls for heat or hot water.  When the house does not call for any heat, your CB should not be blowing air thus fanning the fire.   

[yoderheating]

If you are using a flat plate to preheat the water going into the hot water heater you have nothing to worry about.

[cajoneric]

Thank you for your replies. I am using a flat plate heat exchanger however I believe it is doing more than pre-heating the water.  The way I Plumbed it is from the drain port on the HWH the line runs to the circulation pump to a check valve through the heat exchanger and to an extra port on top of the HWH. the circulation pump runs constantly. Is there any danger in "boiling" with this set up? Thanks

[Scott7m]

Yea you installed a plate exchanger how your supposed to install a side arm exchanger.  I wouldn't want mine like that personally, it's not as safe and no reason for it really

[cajoneric]

Thanks for the reply Scott. Because my detached garage heater, the house furnace, and the domestic water are all heated from my Hot water heater, and the week of -40 degree weather in the winter I didn't think the plate heat exchanger set up as hot water on demand would work. I figured if we weren't using water for showers, clothes, etc.... the water in the tank would cool from circulating to the different heaters? I looked at a side arm but from reading this forum was afraid that it wouldn't be able to handle the load? I found the attached schematic on this or another forum, and decided to try it. What do you think?

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[Scott7m]

Yes it can work like that, I take it that you have your hot water circulating at all times through the house or not?

If so....   That does cause a bit of heat loss and ur thinking could be correct in that it could lose heat constantly if not in use...

If its not circulating constantly you'd be fine on demand because I've installed them for folks to wash equipment with and they can stand there and spray super hot water all day

Sooo could it cause u problems if your stove overheated, yes it could match the temp of the stove.

If its truly relying on the pump to cause circulation you could set the pump on the hear exchanger up on a strap on aqua stat so that once it got so hot the pump would kick off and not allow that water to get any hotter

[slimjim]

Great answers Scott, I just got back from a show at Shelburne farms in northern VT. man you would not believe the view of lake Champlain and the Adirondack mountains in the background that they enjoy every day. Any way the one thing I would suggest the homeowner to do is install a mixing valve on the hot water tank supply to the house so that nobody gets scalded from the hot water. headed out to another show in Acton, Me. for the weekend, talk to you soon, any more thought on selling for us?

[Scott7m]

I haven't had time to think about much lately haha

10-4 on the view

I def wanna visit those areas, seems like we always go south though haha

[slimjim]

We are going to try to post some of the film I took on PM's website soon, I'll let you know when it's up