manifold first in first out question

PeteA

Is the first in first out connections to a manifold based on the distance of the radiatior, the size of the radiator or the type of radiator (baseboard cast iron etc..) I'm thinking distance from the manifold since it is probably one of the steps to aid in balancing the heat delivery but I figured I'd ask.
I assume the longer distances produce the most heat loss so sending the hottest water through first should get the furthest away radiator warmed at around the same as the last one out which would be closer. Or do I have this practice reversed in my head?

Ironman

First out, last back is how you do reverse return for balanced flow.

If you have a good pre-fab manifold with flow setters, it’s not that critical 

PeteA

OK awesome thanks
So it's about the flow not the delivery of the heat. Thank You very much.

Ironman

PeteA said:

OK awesome thanks So it's about the flow not the delivery of the heat. Thank You very much.

Well, you can’t separate them since it’s the flow that delivers the heat.

PeteA

OK thanks ironman
But @Ironman I have to go back to my original question then. Is the "first one out last one in" based on the distance from the mainfold? I am assembling my own manifold so I don't have any fancy flow setters but I will have full port 1/2 ball valves on both the supply and return side of each pex al pex home run. My furthest runs are not very long in my particular case so I am just thinking that my second floor radiators should get the 1,2,3 positions since they are "furthest away" from the manifold (approx 16 additional feet of pipe for each radiator since each supply and return is 8ft longer on each leg compared to the 1st floor) and then the 4 thru 7 positions would get the 1st floor radiatiors since they are the closest to the basement ceiling and therefore they are the closest to the manifold. I was mainly concerned about heating up the 2nd floor bedrooms too fast and just wanted to connect the manifold up the right way and then use the ball valves to do minor adjustments.

Ironman

What what type of radiators do you have?

PeteA

5 cast iron radiators not too larger approx 22" tall but various lengths. 2 pipe circuits are 8' baseboards. for a total of 7 home runs I'll be running to and from the manifold.

hot_rod

If the runs to all the radiators are different lengths, the only way to balance is at the manifold or at the radiator with a valve or TRV.

The shortest loop will get the most flow regardless of how you connect to the manifold.

A Delta P circulator will be a nice option for zoned radiators

Ironman

If all the radiators are similar and the piping is the same size, I don’t see where it’s gonna be a problem. If your radiator valves are functional, you should be able to throttle them somewhat.

Old timers (the dead men) put orifice plates in the upstairs valves when the systems were gravity flow. They should have been moved to the downstairs valves when the system was converted to forced flow.

PeteA

OK thanks @ironman I will verify if orifices were installed or not. I converted the system several years ago from gravity to forced flow and I know that I did not look for or relocate any orifice plates. So i will make the effort to check for them when I do the piping replacement. I did not plan on touching the valves at the radiators but now I will at least check for these plates.

PeteA

AS always thanks for the details and graphics @hot_rod

EBEBRATT-Ed

@PeteA

The purpose of a manifold is to get all the radiation fed with the same supply temps and to mix the return temps so the boiler sees a constant mixed return temp. You always have to balance each piece of radiation at the manifold. Where each manifold connects to each piece of radiation is not that critical.

PeteA

thanks @EBEBRATT-Ed i appreciate the info. i will be watching the first couple of startups once i get the piping done to monitor how quickly or slowly things warm up