Domestic Hot water conversion

 
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lsayre
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Post by lsayre » Thu. Mar. 29, 2018 10:22 am

t185 wrote:
Thu. Mar. 29, 2018 10:08 am
An indirect storage tank would not require an additional circulator, correct?
If your current circulator runs 24/7, then a plate heat exchanger for 'on demand' DHW would not require an additional circulator.

 
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Post by McGiever » Thu. Mar. 29, 2018 10:31 am

About the indirect...That depends...you would still need to do a zone control to cycle on and off to maintain tank set-point temp.

That can be by a pump zone or a valve zone other wise tank temp will always want to match boiler temp.

Since you likely will run underground loop pump constant the plate HX makes better sense.

The domestic side of plate HX is 'on demand' and replaces what HW is drawn from propane tank.

If boiler service is ever interrupted the propane is there ready to take over.

 
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Post by Rob R. » Thu. Mar. 29, 2018 10:59 am

No, but you would not want to continuously circulate through it either. A pair of zone valves would be a way to control the indirect and the plenenum exchanger.


 
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Post by t185 » Thu. Mar. 29, 2018 1:35 pm

McGiever wrote:
Thu. Mar. 29, 2018 10:31 am
About the indirect...That depends...you would still need to do a zone control to cycle on and off to maintain tank set-point temp.

That can be by a pump zone or a valve zone other wise tank temp will always want to match boiler temp.

Since you likely will run underground loop pump constant the plate HX makes better sense.

The domestic side of plate HX is 'on demand' and replaces what HW is drawn from propane tank.

If boiler service is ever interrupted the propane is there ready to take over.
Currently I have a relay at the furnace that is activated when the thermostat calls for heat. The relay turns on the circulator out at the boiler. I have a separate aqua state at the boiler that if the temp drops below 120(most likely no fire) the furnace changes over to propane.

So my plan for the DHW was to have a control wire to the circulator at the boiler when there was a call for hot water. In other words. The circulator will not be running 24/7 only when there is a demand.

I was under the impression that a plate exchanger would require a separate circulator to move the water though out the house. Which seems odd since I have a pressure tank...

Again I am a shade tree "plumber" among other things so my understanding maybe wrong.

 
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Post by Rob R. » Thu. Mar. 29, 2018 1:46 pm

You are one of the few that actually took the time to install some controls when doing a remote install - that's a good thing.

A pair of zone valves would work well if you want to add an indirect. Or, you could put a zone valve on the plenum HX and add a branch for a plate exchanger - this would require running the circulator continuously.

If your underground lines are well insulated, running the circulator continuously should not have a big impact on your coal consumption. An indirect is more efficient in the sense that you don't have to keep the underground lines hot, and you could save 15 cents per day in electric, but if your boiler gets too warm from the timer cycles in the summer you will wish you could shed some btu's into the ground.

 
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Post by McGiever » Thu. Mar. 29, 2018 3:38 pm

t185 wrote:
Thu. Mar. 29, 2018 1:35 pm
I was under the impression that a plate exchanger would require a separate circulator to move the water though out the house. Which seems odd since I have a pressure tank...
Going with what RobR has already said about circulation 24/7...my post above was stating that domestic HW could be "on demand". This is accomplished by using just the well water pressure tank to move the boiler heat away from plate HX's DHW side and over into the propane HW tank anytime a HW outlet is opened for use...hence the term "on Demand"

Need to do some piping mods, add the plate HX and set remote boiler circulation to continuous. And you'll still have propane 100% ready for back-up service. :)
And as you mentioned, need to be able to "valve off/bypass" the plenum HX for A/C season too. There are a couple different ways to do that. ;)


 
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Post by hotblast1357 » Thu. Mar. 29, 2018 5:00 pm

Plate exchangers are awesome! Just run your pump 24/7 through your water plate exchanger, and put a zone valve on the air exchanger.

 
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Post by t185 » Fri. Mar. 30, 2018 5:53 am

Thanks for all the advice gentlemen.

Enjoy the weekend!

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