# pumps.. Supply or Return



## dirk119 (Sep 20, 2012)

I am designing a new boiler system and I am kicking around the idea of running my pumps on return... the boiler is going to be ran with individual circ pumps on each loop including slab radiant. I have ran them on supply and they work like a charm but they see full 185* temp when they're running but bringing them to return would lower that temp.... the only problem i may see is the pump on the return of the radiant manifold is now pushing towards a 3-way valve ... any input?? 

Thanks

Ps I will post a photo when its drawn up


----------



## BROOKLYN\PLUMB (May 21, 2010)

dirk119 said:


> I am designing a new boiler system and I am kicking around the idea of running my pumps on return... the boiler is going to be ran with individual circ pumps on each loop including slab radiant. I have ran them on supply and they work like a charm but they see full 185* temp when they're running but bringing them to return would lower that temp.... the only problem i may see is the pump on the return of the radiant manifold is now pushing towards a 3-way valve ... any input??
> 
> Thanks
> 
> Ps I will post a photo when its drawn up


Try to find out where in the system you have little to no change of pressure, then put the pumps there!


----------



## TX MECH PLUMBER (May 27, 2011)

I don't think pushing to the 3 way valve matters. But we always put pump in supply on heating and pump on return. Our systems are engineered so it not out decision. But the boss said if you pump into boiler it can make the t&p pop off!! How true that is idk.


----------



## RealLivePlumber (Jun 22, 2008)

Put it on the return...............


If you want to have habitual, annual air problems. 

Course, then you get the service call to purge the system every year....................


----------



## OldSchool (Jan 30, 2010)

Lots has to do with the boiler itself... Is it a high mass or low mass boiler

Low mass needs pump on return to force the water through the heat exchanger

High mass boilers no big deal ... Lots of guys say on supply while lots of other guy say return...

I have never seen a pump pop the T&P unless there is another problem... Like water logged expansion tank or to small of an expansion tank or running your pressures close to the cut off point....

However you do it stay away from the boiler feed...


----------



## rjbphd (Feb 5, 2010)

OldSchool said:


> Lots has to do with the boiler itself... Is it a high mass or low mass boiler
> 
> Low mass needs pump on return to force the water through the heat exchanger
> 
> ...


 On high mass boiler pump away from PONPC, period...


----------



## dirk119 (Sep 20, 2012)

yeah this is a six pump system... not as big as you think but this eliminates the hassles or collapse of zone valves and reliability of just one pump... and the more i think of it, on the coldest day, i don't know if i want 6 pumps pushing on my return... I think pulling will be just fine... supply it is...

High mass...


----------



## rjbphd (Feb 5, 2010)

TX MECH PLUMBER said:


> I don't think pushing to the 3 way valve matters. But we always put pump in supply on heating and pump on return. Our systems are engineered so it not out decision. But the boss said if you pump into boiler it can make the t&p pop off!! How true that is idk.


 Its is very true with those GD over engineered pump on multi zones system. In fact, I have one small apt bldg doing the same thing and been telling the mr know it all property mangement of the situtaion, the answer? He keep hiring the furance company to replace the 50lbs relief valve and drain the waterlogged tank while purging more air from the system that's coming from 'nowhere'.


----------



## rjbphd (Feb 5, 2010)

dirk119 said:


> yeah this is a six pump system... not as big as you think but this eliminates the hassles or collapse of zone valves and reliability of just one pump... and the more i think of it, on the coldest day, i don't know if i want 6 pumps pushing on my return... I think pulling will be just fine... supply it is...
> 
> High mass...


 Wait a minute.... are you just replacing the boiler with new 6 pumps system??? What's the btu input on the boiler?


----------



## OldSchool (Jan 30, 2010)

rjbphd said:


> On high mass boiler pump away from PONPC, period...


How can that be period...lol ... High mass has been around for ever and back in the day and still to this date ... Pumps normally on the return


----------



## rjbphd (Feb 5, 2010)

OldSchool said:


> How can that be period...lol ... High mass has been around for ever and back in the day and still to this date ... Pumps normally on the return


 That's was before the hi velicty little pumps came out.. before that, its was low head pump and for shipping package reasons, didn't matter much.


----------



## OldSchool (Jan 30, 2010)

rjbphd said:


> That's was before the hi velicty little pumps came out.. before that, its was low head pump and for shipping package reasons, didn't matter much.


How about guys learn to size pumps and then they won't be over sized little suckers


----------



## rjbphd (Feb 5, 2010)

OldSchool said:


> How about guys learn to size pumps and then they won't be over sized little suckers


 True.... but those little sucker are high velicity to begin with, therefore, supply side at the PONPC..


----------



## luv2plum (May 16, 2012)

Anyone read "Pumping Away" by Dan Hoolihan? I found it very eye-opening as far as circulator and expansion tank placement in hydronic systems. 

Basically, the theory presented in it states that you always want to pump away from the expansion tank connection, since that is the one point in the system that is not vulnerable to pressure changes. Therefore, you can only add to the pre-charge pressure with the circs, not taking away from it. 
Eg 30psi pre-charge in the ET = 30 psi static pressure. If you have a circ with a 31 psi differential, pushing away from the ET connection, the pressure downstream of the circ would be 61 psi. But if the circ is pushing into the ET connection, the pressure upstream of the circ would now be -1 psi. Mucho problemo.


----------



## rjbphd (Feb 5, 2010)

luv2plum said:


> Anyone read "Pumping Away" by Dan Hoolihan? I found it very eye-opening as far as circulator and expansion tank placement in hydronic systems.
> 
> Basically, the theory presented in it states that you always want to pump away from the expansion tank connection, since that is the one point in the system that is not vulnerable to pressure changes. Therefore, you can only add to the pre-charge pressure with the circs, not taking away from it.
> Eg 30psi pre-charge in the ET = 30 psi static pressure. If you have a circ with a 31 psi differential, pushing away from the ET connection, the pressure downstream of the circ would be 61 psi. But if the circ is pushing into the ET connection, the pressure upstream of the circ would now be -1 psi. Mucho problemo.


Yes,yes,yes,yes,yes, all of his books are better than those over engineered code books


----------



## RealLivePlumber (Jun 22, 2008)

He is quite the author.  However. 

I call bs on the 61 psi part. With that theory, every residential boiler ever installed would pop the relief valve every time there was a call for heat. 

And, the only loss you get through the system is a bit of friction loss. You are, technically, still pumping toward the expansion tank, no matter where the pump is. The pump has no idea where the boiler is, only the expansion tank.


----------



## theplumbinator (Sep 6, 2012)

Ever since I read pumping away and I understood what point of no pressure change meant, I've always installed pump on supply, never had any issues. Dan H. Is the man! Todays pumps no longer have rawhide seals so hotter water temp is no issue. Its way easier to push than to pull so less work on the pump in he long run. Think about why most race cars are rear wheel drive not front wheel same theory.


----------



## Catlin987987 (Nov 12, 2010)

Look in the boiler manual and it will tell you where they want the primary pump.


----------



## Gettinit (May 9, 2012)

Catlin987987 said:


> Look in the boiler manual and it will tell you where they want the primary pump.


Burnham wants there pumps on the supply. They put them on the return "for shipment" taped, tightened with a wrench, and wired but not long enough to relocate. :whistling2::laughing:


----------



## plumbcrazy81 (Jun 17, 2012)

Dan Holohan actually mentioned that in his book, the reason the manufacturers put the pumps on the return was for shipping costs, they could stack and ship more boilers that way. Pump Away!:thumbup:


----------



## Gettinit (May 9, 2012)

plumbcrazy81 said:


> Dan Holohan actually mentioned that in his book, the reason the manufacturers put the pumps on the return was for shipping costs, they could stack and ship more boilers that way. Pump Away!:thumbup:


I don't know about Dan but that is what Burnham says. Seems like they could make more money not installing the pump and just toss it in the fire box with the other junk.


----------

