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[nrford]

 Hello folks!  I'm am considering an OWB. I have some questions I would like you to consider.

          1. My system now is a NG boiler that runs part of the home on HW heat and also runs into a forced air HX to heat the balance of
              home. It also is heating our DHW. I asked my OEM installer if I could just install a W/W HX for the whole system. He says it
              would be be difficult to do because of heat loss at the W/W HX he claims you loss 15 degrees with these things. He also says it
              would be difficult to keep system automatic, meaning hard to keep the systems seperate yet have the NG system start up on its
              own if need be. Any thoughts on this??

           2. I'm heating home and pole building for about $2400 per year. Figuring to operate system from Oct-April  Figuring on saving about
               80% of this as NG bill is about $30/mon. rest of year. Seem logical?

           3. I will have to run lines under a paved road(about 30') I can have a 4" pipe installed for about $1500 and then run lines thru this
               either wrapped or foam pipe after lines are threaded thru, recommendations please.

       I'm located in northern lower Michigan and frostline is 42" so I'm a little concerned about the road crossing over the lines driving frost
      down to the lines.
   


n.

[dirtryder]

Hello,
Can't help with the technical questions but if it cost me $2400 a "year" to heat my home with gas I would never had installed my OWB in the first place. I burn about 10 cord (4x4x8) a year. Heating my home and pole barn with propane cost me about $6000 a year.......yes that's thousand.... Dec thru March.....$1,000 to $1,200 a MONTH.....

Welcome, and you will get all your answers here from some very knowledgable folks.

[juddspaintballs]

What temperature does your NG boiler heat the water to, and what are the low/high water temps that it normally runs? 

A W/W heat exchanger may lose a little heat, but I doubt it will lose 15 degrees.  If you're concerned about it, you can wrap it in insulation or keep it in a conditioned space.  Anything is possible with for controlling the two systems separately but to work together in case the OWB fails to heat the water.  Lots of people run a OWB in conjunction with a boiler (NG, propane, oil).  It's nothing a couple aquastats, zone valves, and relays can't control. 

What kind of 4" line under the road?  You might want to step up to 6" so you have more options for sliding your favorite type of insulated pipe through it.   

[nrford]

 I'm told the boiler heats to 182 degrees. If I jump to 6" it will cost $3-4000 just to put pipe in. I was talking about a 4"steel pipe and then running triple wrapped pex thru that, or else filling pipe with srayed foam. Rest of the run would probably triple wrapped in the flexibe 4" tube style I see most people using around here.

[juddspaintballs]

I would reconsider using the triple wrapped pipe in drain tubing.  That is the worst way of running underground lines because it will eventually leak water into the drain tile and the triple wrap insulation absorbs the water.  Spray foaming the entire run would be the best route to go, and if you can fill the entire 30' void under the road inside the 4" pipe with spray foam, then that would be awesome. 
Food for thought:
http://www.hearth.com/econtent/index.php/forums/viewthread/55730/


182 degree NG boiler temps are perfect.  That's right in the range of a OWB, so there's no conflict there. 

[yoderheating]

 I doubt you will be able to get 182 water from a w/w heat exchanger unless you are running the outdoor furnace near 200. The 15 degree drop is consistent with what I have seen and I've installed a number of them. Try dropping your NG Boiler down to 160 and see if it still heats your home. If it does you will be able to heat your home running your outdoor furnace at 180.
  You shouldn't have any trouble making everything run aromatically. If they guy you talked to doesn't know how to do that he must not have any experience in installing these furnaces.

[nrford]

 Dirt,

  I didn't tell you that I supplement with about 2 1/2 full cords of wood heat, and am beginning to suspect that at least 3 members of household may have allergies of some sort associated with the wood heat.

[RSI]

To keep the system fully automatic, just put a strap on aquastat on the line coming from the OWB that disables the gas boiler over a set temp.

[mikenc]

I have a 60 plate heat exchanger piped into my existing system, probably similar to yours. My boiler is oil fired. I keep my owb set at 155 during winter. Have Ahu with hotwater coil and tankless heater in boiler for dhw. Run owb pump 24/7 to keep temp up on oil fired boiler. This way i kept my existing system fully operational.