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[martyinmi]

Early this summer I accidentally stumbled across what is probably the biggest source for wasted BTU's in my application - namely the earth leaching heat from the continuous running of my pump. I found that by reducing my pump run time from 24/7 to just 8 hours/day, my wood consumption was reduced by just about exactly half when just heating my hot water. I put the pump on a timer so that it would come on from 3:30 - 6:30 am and also 5:30 - 10:30pm. I have a sidearm exchanger on a 52 gallon water heater and my tank temp would usually be in the 165* range. My wife has Mondays off, so I would leave the circulator on all day so she could catch up on laundry.

My plan is to move my pump to my basement and somehow hook it up so that when my tank temperature falls to a certain point (maybe 125*)my circulator would kick on. I would also want the pump to activate when my house calls for heat, but there needs to be about a 25 second delay so that in the event it hadn't ran in a while(the pump), I wouldn't have 25 seconds of ambient plenum air, or colder (think 40* line water going through the water to air exchanger) circulating through my house. I realize I'd need two controls, but I thought I'd see if you guys had done something similar to this in the past.

I believe that we all lose A LOT of heat to the ground by means of our underground lines. I think we can reduce our fuel consumption considerably by only running the pumps when necessary. I realize it wouldn't be the 50% I realized in the summer months just heating my DHW, but would a 10 - 20% reduction be unrealistic when heating both home and water? BTW, my underground line is from CB. I used to believe it was the best insulated line out there. I'm not so sure anymore.

Yoder, RSI, Scott, what do you all think? 

[willieG]

marty, you can so some figuring (if you have the info) and determine your wood usage with running your pump all the time or even how much you may save y not.

if you know your water temp leaving yoru stove and the water temp when it reaches the house (and i guess the same situation on teh return line)

lets say you are losing 1 degree between boiler and the house and you know your pump is pumping say...10 gpm that is about 100 pounds of water and we know it takes 1 btu to raise 1 pound of water 1 degree so you would be losing 100 btu per min to the ground in your feed line. x that by 60 (1 hour) and you would be losing 6000 btu per hour x 24 would be 144,000 btu per day devide that by 7400 (btu in one pound of 10percent moisture wood) works out to about 19.5 pounds of wood
that looks like if you cut your pump run time in half you could save almost 10 pounds of wood a day..but you also would have much cooler water to heat up in your lines that were not moving as they would cool down a lot more so your saving would be less. (you would also have to figure out the heat loss in your return line as well..then there is the thought of some of the heat you lost in your feed line would actually be going back into the return line so your actual heat loss may not be all be lost as some would be returning to your owb...boy this it getting confusing!

[kj5036]

Why not just leave your pump at the stove and run a line right after the pump from supply to return(bypassing everything). Have an automatic valve that opens when you call for heat. That way your pump is always runnin but not goin underground. Only when it has to. I thought about doin this with my plate exchanger. Why have it circin through all the time but I havent even fired it up yet so maybe at a later date.

[martyinmi]

Why not just leave your pump at the stove and run a line right after the pump from supply to return(bypassing everything).

Hindsight is 20/20, and looking back I suppose I should have ran some wires along with my thermopex when I buried it- but I didn't. My boiler is 95' from my house, and moving the pump will be much easier than than burying new wire.

[kj5036]

Hmmmm...I guess im not following you. Where is your pump now? And you should have power out there.
All im saying is recirc the water right back to the boiler before it goes underground until it calls for heat then the auto valve on supply opens and recirc valve shuts. Once your furnace shuts off, the supply valve shuts and recirc opens

[martyinmi]

My pump is outside mounted on the back of my boiler. Left in that location, and for what I want to achieve, I will need to have a means to communicate with the pump (or even an auto valve) when either the house calls for heat or the water heater needs warming up. Maybe there is something wireless out there that could accomplish what I want, but I'm guessing that it would be cost prohibitive. Remember, my sidearm exchanger works by thermo siphoning- not on demand like your plate exchanger will be.

 I can use an aqua stat to monitor my tank temperature and set it to trigger the pump in a given range-say 125*-165* for my hot water. That will be easy. 

When my home calls for heat, the pump would come on, but I'll need a 25 second delay that would postpone when the furnace fan kicks on. This is where I need the help. I'm sure it can be done and has been done, but I don't know where to get the parts (some type of a delay timer?) necessary to accomplish it.

[RSI]

I wonder if all your wood saving are from not losing heat into the ground or if it is because the water isn't mixing in the boiler and is getting cold at the bottom. If that is the case then you are losing it into the air outside. Also, how much uninsulated pipe do you have in the house? A lot of it could be going there too.

If you are really saving that much wood from just not running the pump, I would replace that sidearm with a plate and also put a recirc pump on the DHW. They you can have both pumps start at the same time and heat the water in the tank up to 170+ in a few minutes and then shut down.

As far as the blower for the furnace, just set it up to have the thermostat turn on the pump too and put an aquastat or snap switch on the pipe so the blower will only run when the pipe is hot.

[Scott7m]

Marty, I'd have to say if your losing that much heat to the ground something is up, do you have a lot of line inside that is uninsulated?   I agree that a lot of heat is wasted to the ground but for it to reduce wood usage in winter would be a lot.  How deep is your lines?  Are they down to the watery muck in the ground?  Any chance it's been punctured?

[martyinmi]

RSI,
   You might be on to something. My friend has a recirc pump on his sidearm that he plumbed to heat both of his 50 gallon heaters and it works very well. I'll bet my water would stay hot enough if the pump just ran when the house needs heat if I had a recirc pump installed. Have you ever tried a recirc pump with a sidearm?
   I'm sure the water is mixing well. I pull from the top right and return to the bottom left. I've never noticed any spikes in temperatures one way or the other. The secondary  burn chamber is surrounded by water and it gets pretty hot down there.
   All of my pipe in the basement is insulated, but it will still get up to 80+ with the pump on in the summer. I have it insulated with those cheap noodles you get from Lowes or Menards, and they do radiate a lot of heat. I'm not a fan of those at all.

Scott,
   I don't think I have an issue with my insulated pipe. It has functioned the same way for 6 years now. It's buried 18" through my yard and 24" under my driveway. I've only noticed a little bit of snow melting once. It's made by CB, so it has to be right, right?

   I think what I will try is what you suggested RSI- recirc pump on water heater and a snap switch for furnace fan.

I have valves before my heat exchangers in my basement that I can open and close to loop the boiler water right back where it came from. I've played with them on a couple weekends when my wife was gone early this summer, and that's the reason I know that I'm losing a bit of heat to the ground.

The amount of extra wood in the summer months really isn't a lot - maybe between 10 and 15 lbs/day, but that amount probably doubles in the winter months. An extra 25 lbs of wood/day for a 200 day heating season would equate to over a cord of wood. I'd like to try to cut that amount in half, and I think it's possible.

Dean186 did heat loss calculations from his insulated pex and I think he figured he lost over 90,000 btu's/day for every 1 degree of heat loss between his boiler and his house. I have that study bookmarked, but I don't know how to paste(if that is the right term?) it over here. If you search "Calculations for BTU Loss in OWF Water Line" on the FF you'll see his study. He's a pretty smart cookie.

And Willie,
   You've met me. You know my feeble little brain can't absorb all those numbers

Thanks for all the replies guys!!

[RSI]

I am talking about the water in the boiler not mixing when the pump is not running. It will be much hotter at the top. I used to have a 275 gallon tank that I used for heat storage and would start out with it cold. There was a line you could feel on the tank where the water temp changed about 100 degrees. It slowly moved down as more water was heated till it hit the bottom.

I am thinking that might be happening when your pump is not running.

I have put a pump on a sidearm before. You will get a lot more heat storage with one because the water at the bottom of the tank is never as hot when they thermo siphon. It is still slow recovery though. It took around 3 hours to go from cold water to hot enough to use with the pump running.

A 20 plate would probably take maybe 10 or 15 minutes.

Anyway, if you are going to go ahead and do this, I would get a fan center relay to control the pump and connect the the thermostat to it to turn it on. You could leave the wire going to the furnace the way it is now but add the snap switch is series after the fan center.

For the water heater pump, you could would need to add a thermostat and run it to also control the fan center. I don't think it would screw anything up if you just connect in parallel with the house thermostat. If you use a 2 pole thermostat / aquastat on the water heater you can run the recirc pump off that too. You might want to put another snap switch on the recirc pump circuit so that won't run when the line is cold either. I would try finding a thermostat that can go with a real high differential so the main pump can cycle as little as possible.

[Scott7m]

If I turn my boiler off and pump, let's say the water is 190, end of the day it will be that or maybe more cause of the smoldering, but I turn the pump on and within minutes it's down to 155 or so and running, I think it's partially cause of the water coming out of the lines, "only a few gallons" but mostly from the hot water raising yo the top I think