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Discussion Starter #1 (Edited)
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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Discussion Starter #2
radiant heat layout

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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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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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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What might be confusing is the temperatures of the different loops. The black and green lines are at standard boiler temp ~180°F. The radiant loop is much less so as heat is pulled out of that loop the mixing valve blends it back up ~120°F
 

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Discussion Starter #7
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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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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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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Looks like you covered the piping devices.
 

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Discussion Starter #12
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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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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Discussion Starter #14
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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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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Discussion Starter #16
thank you very much
i think i may have the electrical correct and will check my notes over the next week/weekend
if you dont mind i would like to confirm my thoughts with you

thanks again
dave
 

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Your welcome.
Just post any questions you have, and I'll answer them if I can.


I still haven't figured out the meaning of life, so don't ask that one. :laughing:
 

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Discussion Starter #18
Hi Beenthere
i had originally planned on using baseboard for this project and had changed my mind and am instqlling the radiant floor. I had originally run a 3/4 copper pipe(type-m) for the supply to the room. it is approx 75 feet from the boiler
Would you think i can attach the 1/2 pex to that supply and run the pex return back to the boiler or should i make a new run with the pex for the supply side
 

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If the return is going to be 75' long also. then you should run the return out to that room in copper, and then connect the 1/2" pex to those 3/4" copper lines. How long will the radiant loop itself be.
 

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Discussion Starter #20
The room is appr 17 x8. Taking off the floor space for the shower, toilet, and under the tub I figured about 170 feet.
I do have in the crawl space under this bathroom a common return from two other rooms and when I was originally thinking of baseboard I was going to pipe the return for this bathroom into this common return.
Am I correct in thinking that the radiant zone needs its own designated return or can I tap into this return for this bathroom also?

If not then your advise is to use the copper supply, connect the pex to it,run the loop for the radiant, then to a 3/4 copper return for the run back to the boiler.
 
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