Print

[woodman]

I need some advice on how to plumb a second water-air hx in a air handler. It is a long story so I will spare the details but, we are getting ready to finish off the rest of our upstairs addition and add heat runs/cold air returns to the current upstairs bedrooms. We currently just leave the doors open and let the heat radiate upstairs. This works fine but there is always a draft coming down the stairway. Anyway, the house is fairly large and I don't have enough cfm's in my current furnace blower to evenly heat the entire house when I add another 8 registers. The easiest way I can come up with is a dedicated air handler to take care of the second floor. The air handler will also sit in the basement with the current furnace so they will be at the same level.

Should I just run them in a series or should I run them parallel off a single manifold? I have no idea the what the gpm is now. My pump is a bell and gosset pl30 I think??? The delta t off my current hx is 20 degrees. If I split my water to each of them I would assume the gpm would be cut in half to each furnace, so would I expect the delta t to double also? Would this be a problem? As it is now I can heat my house to 74 all winter long with my water between 140-165. If I ran them in a series I could just bump my water to 185 and it would still be 165 at the second hx even if the first blower was running. The thing is, I know I save some wood by keeping my water temps lower. The other thing is I am not really adding that much to my heat load. Both blowers should not be running at the same time very often.

       

[muffin]

I have 3 systems all in series and it seems to work fine.  Each has its own zone valve and thermosat.  I would put it after your first one as being upstairs it will be aided by the first one and should run much less.

[ptt811]

 I also have 2 furnaces in the house. When the 2 pex lines come in it Ts' up to the first Heat exchange. Then continues on to the water heater Plate exchanger then to the last furnace. At the T... I have a Valve in Both Supply line and return, but really only One is needed in the Return. I have the Valve closed about half way to limit the water flow. The excess is then forced on down the line. This is my first year but it is working fine, and I am very happy with the set up.

Pat

[woodman]

I also have 2 furnaces in the house. When the 2 pex lines come in it Ts' up to the first Heat exchange. Then continues on to the water heater Plate exchanger then to the last furnace. At the T... I have a Valve in Both Supply line and return, but really only One is needed in the Return. I have the Valve closed about half way to limit the water flow. The excess is then forced on down the line. This is my first year but it is working fine, and I am very happy with the set up.

Pat

I guess I am not following your design? You say when the pex line comes in it t's. Where does the other side of the supply t go? 

[ptt811]

the T goes up to the First heat exchanger....the straight part of the T goes on to the next Furnace. You are Sharing the water but the next heat exchanger still get the benifit of all the heat in the line. If you run it in series then the second heat exchanger only gets the return water from the fist which is alot cooler.  I can supply a drawing if you need me to....I know I dont explain stuff well .....LOL