# Supply/Return Side of a Cast Iron Radiator



## WireNut (Oct 16, 2013)

I'm piping in my new heating system, removing a single zone system and zoning out the rooms.  There are multiple cast iron radiators (the old fin type, hot water, but have the top and bottom fittings on them).  While looking at my piping, I realized that if I can reverse the flow in some of the radiators, I can eliminate having to cross my supply/return lines as often as I was thinking.

Is there a "supply/return" side on this type of radiator, or can either side act as supply/return?  Does the location of the air vent on the radiator make a difference?


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## OldStoneHouse (Oct 16, 2013)

I have some rads that have both supply and return on the same side of the rad, on the bottom.  Others are on either side and I plumbed them so that the supply fitting was the lower with the return coming out the top (former steam rads).  The last page of this document outlines how Burnham does it with their new CI rads: http://cdn.usboiler.net/products/baseboard/slenderized/assets/literature.pdf

I think the vent typically goes on the return side.  




WireNut said:


> I'm piping in my new heating system, removing a single zone system and zoning out the rooms.  There are multiple cast iron radiators (the old fin type, hot water, but have the top and bottom fittings on them).  While looking at my piping, I realized that if I can reverse the flow in some of the radiators, I can eliminate having to cross my supply/return lines as often as I was thinking.
> 
> Is there a "supply/return" side on this type of radiator, or can either side act as supply/return?  Does the location of the air vent on the radiator make a difference?


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## WireNut (Oct 16, 2013)

OldStoneHouse said:


> I think the vent typically goes on the return side.



That is how they are currently set up, air vent on return side.  Mine are supply and return on the bottom, opposite sides of the radiator.  Is it bad to have the air vent on the supply side of the radiator, or just not typical?  I'm not opposed to being non-typical with my setup, but if there's a reason the air vent is up on the return side I'll just have to work around it....but it sure would be easier if I could just flip the pipes to have less crossing in the basement.  I suppose I *COULD* move the air vent on the radiator, but with their age I'd rather not mess with the radiators until I'm ready to get them powder coated next year....or the year after...or as money permits.


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## OldStoneHouse (Oct 16, 2013)

I don't think it really matters where the air vent is (apart from as high as possible|) - the purpose is to get the air out of the rad so I believe air will come out either end.


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## WireNut (Oct 16, 2013)

Cool, that's what I was thinking and what random internet searches were telling me....I'm going to go for it and see what happens.


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## heaterman (Oct 20, 2013)

I have one in my office plumbed bottom to bottom with the air vent on the supply side. The trick there is to keep the flow through the rad very low so the rise hot water can rise to the top of the rad and fall back down. I can "see" this happening with our infrared thermometer as I move is across and up/down the rad. It would be cool to have an infra-red picture of it at full trot.


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