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Old 05-10-2011, 09:57 PM   #1
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new radiant zone


hi all
I am adding a new zone for a radiant heat floor to my existing hw system
the current systen has three zones controlled by zone valves and one circulator.
I know that i need to add a mixing valve.Does the new radiant zone need its own circulator?

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Old 05-11-2011, 05:49 PM   #2
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Hi All
I had found an old thread about radiant heat

A fellow member Beenthere Had posted this drawing and I had a couple questions on it.
If anyone can answer or knows Beenthere maybe you can help

It looks pretty simple to do but the layout looks a bit confusing to me

1) should the loop(thicker green line) between the supply and return be broken at the point between the new radiant zone

any help would be appreciated
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File Type: pdf High and Low temp Boiler 2A .pdf (5.5 KB, 142 views)

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Old 05-11-2011, 08:07 PM   #3
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The thicker pipe is a loop in itself, and is not broken at any point. The circ of the radiant loop pulls water from it in varying amounts as the radiant loop warms up. But the flow through the thicker green line must remain some what constant no matter how much water the radiant loop is or isn't pulling..
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Old 05-12-2011, 06:33 AM   #4
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Quote:
Originally Posted by beenthere View Post
The thicker pipe is a loop in itself, and is not broken at any point. The circ of the radiant loop pulls water from it in varying amounts as the radiant loop warms up. But the flow through the thicker green line must remain some what constant no matter how much water the radiant loop is or isn't pulling..
agree. maybe it's a good idea to put a balancing valve on the loop, i.e. the thick green line.
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Old 05-12-2011, 07:30 AM   #5
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Bump for Dave. Anyone?
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Old 05-12-2011, 08:56 AM   #6
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What might be confusing is the temperatures of the different loops. The black and green lines are at standard boiler temp ~180F. The radiant loop is much less so as heat is pulled out of that loop the mixing valve blends it back up ~120F
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Old 05-12-2011, 11:21 AM   #7
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Ok I understand all.
I am not sure why I would want to set up the new radiant loop this way. Please tell me if my thinking is incorrect.
I have on the supply side a zone valve(Taco 570)
the tt calls for heat, opens the zone valve, the water flows thru the loop and goes to the return.
This is of course being pumped by a circulator
In this design arent two circulators running at the same time?
I am pretty sure that i need a circulator on the radiant loop after the mixing valve to control flow for the radiant zone.
Is there a reason why I would want to do it this way as opposed to tee'ing off the 1 1/4 supply line coming out of the boiler , adding mixing valve then circulator(with built in flow check to conserve space, its tight) and back to the return?
I am still working on the electrical but want to get the plumbing fixtures worked out first
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Old 05-12-2011, 05:18 PM   #8
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Originally Posted by mechth View Post
agree. maybe it's a good idea to put a balancing valve on the loop, i.e. the thick green line.
Nope, it needs to be free flowing, no balancing valve, as the amount of return water from the radiant loop will vary. So the boiler circ will respond to the head pressure as needed without a balancing valve. And a balancing valve could hurt flow rate.
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Old 05-12-2011, 08:33 PM   #9
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I think the reason it was piped that way in that drawing is because he already had the taps and a zone valve in his existing manifold. Don't remember for sure anymore.

Yes it can be tapped off the risers of the boiler.
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Old 05-14-2011, 01:45 PM   #10
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Do you think my fixtures are correct or did i leave anything out?
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Old 05-14-2011, 03:50 PM   #11
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Looks like you covered the piping devices.
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Old 05-16-2011, 11:59 AM   #12
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Thanks Beenthere. I thought I did but just wanted another opinion.
I will have some questions on wiring as soon as I get the plubing installed this weekend. But I have another somewhat related question on my aquastat
I had my oil company add an indirect hot water heater a few months back as my independent hw heater started leaking
Originally the boiler was set up as a cold start. They changed the auastat to a Honewell L8124a
As I understand it if I set the high limit to 180 and the low limit temp at 140 and the diff at 25 them the boiler will not fire unit it hits a low limit of 115 This is all fine and seems to be working fine. No problem with hot water

but my question is shouldnt the boiler fire until it hits the high limit of 180
It shuts down when it hits the low limit of 140.00
Any advice would be appreciated

Dave
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Old 05-16-2011, 04:45 PM   #13
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Its working as it should. The low limit is to maintain a min temp. Which is what it is doing. The low limit's off setting is over ridden when a heat call comes in, thats when the high limit does its job if the water temp reaches 190.
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Old 05-16-2011, 05:01 PM   #14
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Thanks Beenthere
I just want to be sure that the diff control has no relation to the high limit
The high limit has a fixed diff of 10 degrees correct?

and the low limit will increase to 180 only when the call for heat by a tt?
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Old 05-16-2011, 05:06 PM   #15
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Correct, high limit is fixed 10. And the low limit won't shut the burner off when the control receives a call on the TT terminals,

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