# Potable in-floor heating



## Radium (Dec 25, 2010)

I am looking at a grundfos miximizer pump for a 350' loop in the joist space of a kitchen. I want to tie into the indirect water tank (geothermal ground source) potable side and make a recirc loop from the tank to the kitchen. Any suggestions for a pump? I would think that a normal circulator pump for a recirc line has too high of flow.


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## rjbphd (Feb 5, 2010)

Radium said:


> I am looking at a grundfos miximizer pump for a 350' loop in the joist space of a kitchen. I want to tie into the indirect water tank (geothermal ground source) potable side and make a recirc loop from the tank to the kitchen. Any suggestions for a pump? I would think that a normal circulator pump for a recirc line has too high of flow.


Why it must be on the potable water side?? Can't be heat exchangered system??


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## Radium (Dec 25, 2010)

rjbphd said:


> Why it must be on the potable water side?? Can't be heat exchangered system??


I want to make a recirc loop and heat the floor.


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## rjbphd (Feb 5, 2010)

Radium said:


> I want to make a recirc loop and heat the floor.


Risk of stagent water... use a 3 speed bronze pump and set it on low speed.. however, one loop of 350 ft is still too long.. better to break it down to 3 loops,using manifold.


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## Catlin987987 (Nov 12, 2010)

Radium said:


> I am looking at a grundfos miximizer pump for a 350' loop in the joist space of a kitchen. I want to tie into the indirect water tank (geothermal ground source) potable side and make a recirc loop from the tank to the kitchen. Any suggestions for a pump? I would think that a normal circulator pump for a recirc line has too high of flow.


Canadian code says 250' Max on 1/2" infloor, min 2 zones and you wont have to have a large pump on it.


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## Plumbworker (Oct 23, 2008)

you will need to figure the heat loss from the kitchen before you can size circ pump gpm.. then will have to calculate head loss through total developed length of circuit.. then look at pump manufacturers curve charts to select correct circulator


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## wyrickmech (Mar 16, 2013)

Plumbworker said:


> you will need to figure the heat loss from the kitchen before you can size circ pump gpm.. then will have to calculate head loss through total developed length of circuit.. then look at pump manufacturers curve charts to select correct circulator


And if flow rates are a little to high still, you can put a flow control valve on for the proper gpm


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## redbeardplumber (Dec 4, 2012)

Plumbworker said:


> you will need to figure the heat loss from the kitchen before you can size circ pump gpm.. then will have to calculate head loss through total developed length of circuit.. then look at pump manufacturers curve charts to select correct circulator


I know you do way more of this type of work than me. But I think this is over kill. I'm with RJ. Even with 2 loops at 175' or 350' loop of 5/8" pipe( which in Canada is good for 400') a bronze circulator on low speed is plenty.


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## redbeardplumber (Dec 4, 2012)

Maybe you have found the loop hole Radium. In Alberta we have to use heat exchanger now, used to be, a combination system was ok if you moved the water every 24 hours.

BUT if it's a recirq line...... Perfect, just put a timer on the thing to prevent stagnant water.

Great idea


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## Plumbworker (Oct 23, 2008)

redbeardplumber said:


> I know you do way more of this type of work than me. But I think this is over kill. I'm with RJ. Even with 2 loops at 175' or 350' loop of 5/8" pipe( which in Canada is good for 400') a bronze circulator on low speed is plenty.


thats fine go ahead and make a guess.. I'm just stating how to go about properly sizing a pump for hydronic heat..

it would probably take all of what 5 min to calculate all this..?


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## Radium (Dec 25, 2010)

Thanks for the help guys, I looked at the job again. There is 1/2" copper to the kitchen sink, I am going to tee off that line. Looks like my loop will be around 250. I'm going to try a bronze pump with a switch under the sink. Cold return piping to the cold on the hwt and install a spring check valves. 
This will be strictly tile heat and is a secondary heat overall to the geothermal. 
But now I'm wondering if I need to knock down the pressure for the pump or will it be fine at house pressure. I've seen what pumps do when they shut off at high pressures (commercial). But that was a line that should have been 70 psi running at 160 psi.


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## RealLivePlumber (Jun 22, 2008)

There will be no heat at the end of that long loop. All the warmth will be extracted in the 1st 75'. So the rest of the loop will be worthless. 

Manifold it with 4 shorter loops.


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## Radium (Dec 25, 2010)

RealLivePlumber said:


> There will be no heat at the end of that long loop. All the warmth will be extracted in the 1st 75'. So the rest of the loop will be worthless.
> 
> Manifold it with 4 shorter loops.


Huh, 75 ft hey??? Right.
What book have you been reading?


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## wyrickmech (Mar 16, 2013)

Radium said:


> Thanks for the help guys, I looked at the job again. There is 1/2" copper to the kitchen sink, I am going to tee off that line. Looks like my loop will be around 250. I'm going to try a bronze pump with a switch under the sink. Cold return piping to the cold on the hwt and install a spring check valves.
> This will be strictly tile heat and is a secondary heat overall to the geothermal.
> But now I'm wondering if I need to knock down the pressure for the pump or will it be fine at house pressure. I've seen what pumps do when they shut off at high pressures (commercial). But that was a line that should have been 70 psi running at 160 psi.


Pressure is not an issue flow rate is either your friend or foe. To much and you have little heat exchange to little and you decrease your loop temp to the point that you are always running your source of heat and sending your bill threw the roof. You simply need a flow control device . Over shoot your gpm by five or ten percent and throttle it back with a circuit setter this will give you the advantage to increase the flow a little or decrease it if it is a little to high. The loop is not to long but the flow rate might vary a little at that distance because of resistance.


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## Radium (Dec 25, 2010)

wyrickmech said:


> Pressure is not an issue flow rate is either your friend or foe. To much and you have little heat exchange to little and you decrease your loop temp to the point that you are always running your source of heat and sending your bill threw the roof. You simply need a flow control device . Over shoot your gpm by five or ten percent and throttle it back with a circuit setter this will give you the advantage to increase the flow a little or decrease it if it is a little to high. The loop is not to long but the flow rate might vary a little at that distance because of resistance.


Right on, thanks.


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## Spridle (Oct 30, 2012)

What about premature wear on the 1/2 piping? How old is the house? 
Also, what about the warmer months when the loop will not be running for heat? How do you transfer 350' of water to fight the stagnation? 

I like the idea, just tossing 2¢ in the ring here.


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## mariamenounos (Jul 27, 2013)

*Better idea*



rjbphd said:


> Risk of stagent water... use a 3 speed bronze pump and set it on low speed.. however, one loop of 350 ft is still too long.. better to break it down to 3 loops,using manifold.




Hi,

That's better process to break it down to 3 loops. :thumbsup:


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## Radium (Dec 25, 2010)

Home owner is selling his house and building a new one, thumbs up! 
Thanks for all the help.


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