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08-30-2012, 04:26 PM #1
basement project: hydronic heat scavenger
This is my ongoing basement project:
It is a 3o year old Utica boiler, 80k BTU output. We have been messing around with it over the years but the latest experiment was a Hydronic heat scavenging system.
It utilizes 1 zone circulator and 1 digital timing 24v relay per heating zone. We can set the digital timing relay to literally any amount of time using the 3 switches on the relay, the circulators will then run purging any USABLE heat left in the pipes into the living space.
We set each relay for between 10-20 minutes, these relays are wired to start timing down when the thermostat satisfies and the boiler shuts off.
We are getting at least 2 more degrees off free heat from this system...not to mention the fun we had playing around with the idea.
this is just one way to maximize your heating doller with an old system like this...also since we installed this sytem, my supply and return delta T's are nearly equalized, so now I can add more register to the additions of the house without addding a new boiler or increasing BTU output.
THere are a few quirks however: because I took out the zone valves, 1 circulator will induce flow in the other zone wich tends to over heat that part of the house... its a work in progress and fun to play around with!
08-30-2012, 04:41 PM #2
You need check valves, I bet the heat I'n the boiler would gravity feed out rather than having post purge. With the check valve it will stop the gravity flow though. Do you have fin tube or cast?
08-30-2012, 04:51 PM #3Regular Guest
- Join Date
- Aug 2012
- Toronto, Canada
Was biting my tongue, holding myself back from suggesting the check valves because im not as experienced in hydronics as some on this site... But i guess i should give myself a lil more credit... Good suggestion IMO Joehvac25
08-30-2012, 05:03 PM #4
fin tube...where would the check valves go, I a not familar.
08-30-2012, 05:31 PM #5
08-30-2012, 05:32 PM #6
08-30-2012, 06:03 PM #7
Can I add......flow check valves, not standard check valves.
Also, to the OP........you are getting a 2 degree temp rise after the thermostat stratifies a call for heat? And this is being accomplished, by putting a post purge timer on the pumps? Either your boiler is way oversized for the load or your CPH on your stat is not set properly.
All that monkeying around.........the real savings is a properly sized boiler to replace that 30 year old gas hog.
08-30-2012, 06:30 PM #8
B&G makes a good flow check that you can bypass so you can drain the system. Regular checks will chatter so they need to be ok for hydronic.
08-30-2012, 06:43 PM #9
what is ...CPH?? I had to lower the aquastat after adding the circs, back down to 180, because before this boiler couldn't keep up with this drafty old house, but now its doing better.
As far as being oversized, I will be integrating a duplex utilizing the same loops just adding on, so I think this boiler will still be correctly sized.
right now I think we have 80-100 linear ft of fintube but i will be doubling that.
unfortunately for me, buying a new model is out the question, I've beeen laid off for a year now, I don't know if I'll ever catch up.