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Author Topic: heat exchanger problem  (Read 8664 times)

Scratch

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Re: heat exchanger problem
« Reply #15 on: February 03, 2009, 05:42:12 PM »

So you run your two HX's in series huh?  Don't you get so much heat loss that by the time it gets to your floor lines, it's pretty cool?
Or do you not have any floor lines.

Does anybody here have 2 HX's and floor lines?  If so can you draw up what you did.



Here's another thought...I could easily pull everything off the system but the 2nd HX.  So it would run in from the OWB on 1" PEX, then reduce down to 3/4" PEX go through the smaller HX, then back, go back up to 1" PEX and out to the OWB.

That would shouldn't lose much temp with the furnace fan on right?  I'm just trying to figure out a way to use all that 3/4" PEX I got ran through my basement now....
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Hudson, WI

willieG

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Re: heat exchanger problem
« Reply #16 on: February 03, 2009, 06:46:11 PM »

Humor me  i think that when you had only nuimber one furnace hooked up, when it was running the return water was cool enough to go right through your mixing valve and that let the house warm perfectly and when the house did not call for heat the mixing valve worked as it should and let the water only trickle through as needed but when you added the line to the second furnace you now have (when one furnace is not calling for heat) at leas one line at the mixing valve delivering water hot enough to shut the mixing valve and only let it trickle through

also when you said you shut all you could off to test the shop furnace you didnt say it you shut the first furnace off and you did say you shut part of your radiant heat off..again this caused the mixing valve to choke the system down

you need to take number one furnace off the mixing valve and go directly to the boiler return..then take number 2 furnace and tee it at the mixing valve with one line entering the mixing valve and one line to the boiler return..this way your return water goes full speed to your boiler and when the mixing valve calls for water it opens and let the water mix by adding a little hot and if the hot has to go in then some cold has to come out of the radiant lines...this cold will travel up the mixing valve and thus..mix with the hot and everything will work as it should and have NO effect on choking the two furnaces down

as long as the pump is of sufficeant size the problem is solved

Take the mixing valve out of the loop for testing purposes and see what happens
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home made OWB (2012)
Ontario Canada

willieG

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Re: heat exchanger problem
« Reply #17 on: February 03, 2009, 06:51:31 PM »

just a note scratch...in the drawing you posted form CB if you look close you will see the  mixing valve has nothing to do with the return water from the furnace to the boiler..as it should be
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home made OWB (2012)
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CL-Ohio

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Re: heat exchanger problem
« Reply #18 on: February 06, 2009, 08:15:09 AM »

Scratch- I don't have floor heat but would have plenty left to do so. The reason for in series you're pushing water not pressurized so when you wyed the line, the water split it's energy and because the first line is shorter it'll have more push when the two return lines meet back up and that might put back pressure on the second line slowing the flow more.  I'm thinking if you shut everything else down and the 2nd still blowing cold air you probably need a bigger pump for faster recovery.
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Scratch

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Re: heat exchanger problem
« Reply #19 on: February 15, 2009, 06:39:35 PM »

Re did the plumbing layout today...  I went from the OWB inside on 1" PEX to the pump, then to the water heater, then to 3/4" PEX and to the main HX, then to the second HX, and back to the OWB.  Right before it goes back out to the OWB... it T's off to go to a second pump where it pulls the water through my floor lines manifold.  Then that water T's back into the main return line back outside to the OWB.

So far it seems to work great.  The fans from both furnaces does cool it down some but not much and not nearly as much as it did before.  I think this solved the problem.

The only thing I think I would improve upon would be using 1" PEX for the furnace lines instead of 3/4".  But I already had the 3/4" ran so I figured I'd try it anyways.  Would it even help though... because both HX's are 3/4" so there would be restriction there anyways wouldn't there be?

As long as my house stays warm and I don't gotta pay for LP...
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willieG

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Re: heat exchanger problem
« Reply #20 on: February 15, 2009, 06:52:06 PM »

scratch, i'm not entirely sure what you did but even if it is wrong and it is working...it is  right

happy heads in the hair shop now!
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home made OWB (2012)
Ontario Canada

Scratch

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Re: heat exchanger problem
« Reply #21 on: February 16, 2009, 01:44:06 PM »

Here's my new layout.  Obviously not all the valves are closed...

 I forgot to draw the zone valves for the floor lines but they and the second pump are controlled by thermostats.  Also there's a mixing valve right after the second pump  there too.
« Last Edit: February 16, 2009, 01:46:46 PM by Scratch »
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willieG

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Re: heat exchanger problem
« Reply #22 on: February 16, 2009, 03:42:23 PM »

Here's my new layout.  Obviously not all the valves are closed...

 I forgot to draw the zone valves for the floor lines but they and the second pump are controlled by thermostats.  Also there's a mixing valve right after the second pump  there too.
scratch, i see you have added a bunch of valves that let you isolate your "appliances" from the system at will..good idea i think you should maybe include another set on the radiant heat, one on the inlet side of the pump and one on the return side of the mixing vavle..this will lwt you isolate the radiant system without shutting down the entire system should you need to replace the pump for your radiant heating or the mixing valve (if you can put the valve on the feed line so it also isolates your zone valve)
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home made OWB (2012)
Ontario Canada
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