hot water zone off a steam boiler

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Old 12-12-13, 08:33 PM
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hot water zone off a steam boiler

I would like to run 2 hot water baseboard zones off my steam boiler (2-50foot loops). I am aware that taking too much water out could be a problem therefore I would like to use a water to water flat plate heat exchanger. effectively taking only a minimal amount of water out of the boiler. and running the 2 zones on the other side of the heat exchanger. I would like to know if there is a diagram to do this with all the valves, pumps, checks, needed to complete. can anyone help me? thanks jimmy
 
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Old 12-12-13, 08:45 PM
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Moved to own thread.... Someone will help you shortly with your questions........
 
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Old 12-12-13, 09:08 PM
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I would like to know if there is a diagram to do this with all the valves, pumps, checks, needed to complete. can anyone help me?
I don't think you will find one that is exactly what you are looking for.

Look at hot water boilers. On the baseboard side of the heat exchangers, you need basically everything that a hot water boiler system has. Expansion tank, pump, air collection and venting, water fill and pressure regulator... all the same stuff... only difference is the heat source. If you look at a boiler piping diagram and scratch out the boiler and draw in a heat exchanger, that's what you will need.

Instead of running two separate heat exchangers and having to DOUBLE all that equipment for each loop, you could use one LARGE heat exchanger and treat the two loops as 'zones' off that single exchanger just as would be done on a regular boiler system.

On the boiler side, it's a little more tricky... you need to be very careful what you do there. Bell & Gossett had a 'white paper' that shows how. You need a pump of course, but what's very important is that you also need a BYPASS LINE around the boiler so that the water in the loop doesn't get TOO HOT and FLASH TO STEAM as it loses pressure around the loop. That article was quoted here on the forum several times. Either search here for it using the forum search tools, or search the internet.

I am aware that taking too much water out could be a problem
But you aren't taking water out. The loops should be FULL of water at all times. Water level should not change because you aren't filling and draining the loops, only MOVING the water that's in them.

Still, steam boilers are likely to be sized for the attached radiators reasonably closely and pulling 6000 BTU out into two 50' baseboard runs might not be a great idea. You might could set it up so that a call from the steam heat system has 'priority' and shuts down the baseboard zones for the duration of the steam call. That would be pretty easy to do with a relay or two.
 
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