# Can't figure it



## RealLivePlumber (Jun 22, 2008)

Lets say you're piping a boiler, with primary /secondary piping. 1 pump to circulate the primary zone, and 3 zones with pumps off of the primary loop. Now, the first tee in the line is a supply, and the second is a return. They are to be closely spaced. ( To allow the supply water to not run through the zone when it is not calling) The third tee in the line is a supply for the second zone, and the fourth tee is a return for the second zone. Same for the last zone. 

Doesn't the cooler return water from the first zone cool the supply for the second zone, and even more for the third zone? (with 2 returns ahead of it?)

How does it affect the temp to the other zones? Or is something else happening within the primary loop to overcome the cooler return water?


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## njoy plumbing (May 19, 2009)

RealLivePlumber said:


> Lets say you're piping a boiler, with primary /secondary piping. 1 pump to circulate the primary zone, and 3 zones with pumps off of the primary loop. Now, the first tee in the line is a supply, and the second is a return. They are to be closely spaced. ( To allow the supply water to not run through the zone when it is not calling) The third tee in the line is a supply for the second zone, and the fourth tee is a return for the second zone. Same for the last zone.
> 
> Doesn't the cooler return water from the first zone cool the supply for the second zone, and even more for the third zone? (with 2 returns ahead of it?)
> 
> How does it affect the temp to the other zones? Or is something else happening within the primary loop to overcome the cooler return water?


 Yes downstream zones will recieve that cooler water, so install your highest heat demands first, and so on. 
Usually there isn't a huge difference especially if the zones are not running at the same time.


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## OldSchool (Jan 30, 2010)

RealLivePlumber said:


> Lets say you're piping a boiler, with primary /secondary piping. 1 pump to circulate the primary zone, and 3 zones with pumps off of the primary loop. Now, the first tee in the line is a supply, and the second is a return. They are to be closely spaced. ( To allow the supply water to not run through the zone when it is not calling) The third tee in the line is a supply for the second zone, and the fourth tee is a return for the second zone. Same for the last zone.
> 
> Doesn't the cooler return water from the first zone cool the supply for the second zone, and even more for the third zone? (with 2 returns ahead of it?)
> 
> How does it affect the temp to the other zones? Or is something else happening within the primary loop to overcome the cooler return water?


You are right on......That could be the worst possible way to pipe any boiler system.

This trade is going to hell with misinformation coming from alot of manufacturers.

A proper system using a primary loop will always have the supplies first one after the other. Therefore all the loops will have the same temperature. There will be PZ member that disagree with this but that is because they are not thinking ahead.

What if you needed another loop after the fact at a later date that required a high temp. What then....if you went supply /return supply /return....

This is a good reason to do all supply first.


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## njoy plumbing (May 19, 2009)

OldSchool said:


> You are right on......That could be the worst possible way to pipe any boiler system.
> 
> This trade is going to hell with misinformation coming from alot of manufacturers.
> 
> ...


 Exactly! There are manufactures that do have it right though. I don't know about the rest of you, but I have tried many systems, some I have regreted trying and now am totally comfortable with what I use now. My heating designer at my wholsaler is really well respected and works with us from design to start up, making sure that the system is soing what it is suppose to. 
The system designs I use don't use the Op's version anymore, even though it will work in certain instances.


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