Hydronic heat, I broke it.

[DerbyRunner]

I recall years ago, someone commented to me - "How hard can plumbing be? Water always flows downhill right?"

Very appropriate. So to ask, in a closed pipe system, why would water flow uphill to the first radiator? Unless there is some other source of energy, it would not. Water would just flow through the main line without going "up" then "down" to/from the radiators.

I believe the source of energy at the 3/4 line is heat rise. In the section you created with the modification, you caused a second need to flow water upward, except this doesn't have any tap to the main line so no "heat rise" on that section. I believe that is where your problem is.

I'm confused why your diagram shows two radiators before the changes, and 3 radiators after the changes? I would bet if you plumbed the line out of the 2nd radiator over to the 1/2 inch return to the main line those two connected radiators would work fine. Of course the 3rd one would be orphaned at that point.

 

[CalG]

Very appropriate. So to ask, in a closed pipe system, why would water flow uphill to the first radiator? Unless there is some other source of energy, it would not. Water would just flow through the main line without going "up" then "down" to/from the radiators.

I believe the source of energy at the 3/4 line is heat rise. In the section you created with the modification, you caused a second need to flow water upward, except this doesn't have any tap to the main line so no "heat rise" on that section. I believe that is where your problem is.

I'm confused why your diagram shows two radiators before the changes, and 3 radiators after the changes? I would bet if you plumbed the line out of the 2nd radiator over to the 1/2 inch return to the main line those two connected radiators would work fine. Of course the 3rd one would be orphaned at that point.

Why would water flow through the radiators? Pressure differential due to resistance of the mono flow tees (If fitted)
If there are no mono-flow tees, you have a gravity system. with a bit of Bernoulli effect.

 

[DerbyRunner]

Why would water flow through the radiators? Pressure differential due to resistance of the mono flow tees (If fitted)
If there are no mono-flow tees, you have a gravity system. with a bit of Bernoulli effect.

Perhaps you are right. I didn't see any mono flow tees in his diagram, maybe I missed those.

 

[CalG]

Perhaps you are right. I didn't see any mono flow tees in his diagram, maybe I missed those.

I didn't note any either, hence the " (if fitted) " comment.

 

[DerbyRunner]

OK. So we need to learn if those Tees exist, and where the 3rd radiator came from?

 

[widefat]

OK. So we need to learn if those Tees exist, and where the 3rd radiator came from?

I'll check the TEEs and see if they are mono-flo. I am not sure if I will be able to tell - they are older than dirt.

The third radiator - depends on which pic you are looking at . I updated and attached.

Originally, it was radiator 2.
I split radiator 2 into radiator 2a and radiator 2b.

The other pic is of the entire zone. What you see now labeled as radiator 3 is in another room, has always been there, and still works.

 

[mike48130]

I think to do it right you need to eliminate the added U. Bring the output back to the main and the main directly to the other radiator. More work but the right way.

 

[CalG]

I think to do it right you need to eliminate the added U. Bring the output back to the main and the main directly to the other radiator. More work but the right way.

That would be "the right way".

 

[LouNY]

Yes it would be the right way but it would require disassembling that main loop of old 1 1/2"pipe cutting and threading it adding two flow tee's.
With luck adding an air vent to the new #3 or 2b possibly on both sides may get flow established again.

 

[mike48130]

Can do a saddle tee.

Smith-Blair Saddle Clamp, Double Bale, 3/4 Outlet 3136 | Zoro.com