piping rads

Brad White_185

There is piping and there is <i>piping</i>. Your call. :)

Here are some thoughts:

Assuming standing cast iron, I have piped them all different ways, for largely logistic reasons such as to match available piping. I cannot say that I have seen a difference but then, my radiators tend to be over-sized so I can run cooler water temperatures.

That said, my technical preference is to supply high on one side and return low on the opposite side. This does two things: Gives nearly even water flow through all tubes and gives a little "boost" to the leaving air. By that I mean that the air just before it leaves the radiator is nearly as warm as it will get. That it sees the hottest water before the send-off increases heat transfer.

This is also known as counter-flow. Picture if reversed, with the coolest water leaving the radiator where nearly the hottest air wants to be... a drag, albeit slight.

With fin-tube, I <b>always</b> pipe "supply in the top tier, return via lower tiers" for the same principle.

(This supposes multiple tier installations which is what I use for condensing boiler applications, usually three tiers piped from the same end, not that you asked.)

I also pipe in series to maximize velocity at the lower flow rates my designs prefer.

I have piped standing CI radiators across the bottom without any noticeable problems, very even heat. These were "original gravity piping connections" left largely undisturbed except for TRV's. The flow rate is so low that I surmise that the initial burst of hot water hits a wall of cool water and rises into the tubes, setting up convection. Then again, it is a constant circulation system so it all evens out. But there was never a noticeable "scooting along the bottom tube" direct to the return. Water enters at one temperature and leaves as cool as any spot on the radiator.

Those are my observations anyway...

DD_3

piping rads

I have piped many systems hot water systems. My partner claims that the right way to pipe a system is the supply at the top and return at the bottom. any comments?