New zone for cast iron sun rads

hoss50

I am zoning off a new kitchen extension that already has 1-22 section sun rad.
we are adding 1-18 section and another of an unknown size at this moment depending on where the new stairs end up.
The rest of the house is on 2-zones, 2" reverse return.
How do I size the supply & return lines for the new zone if I do reverse return?
Is a venturi system feasible with sun rads?

Paul S_3

You need to tell us your heat loss for kitchen,which will tell us the GPM using a giving delta T....then we can help you size your pipes and pump same for reverse return and direct return systems. ...I'm guessing this is a two pipe reverse return hot water system?when you say reverse return you mean first radiator supplied off the main is the last returned on the return main ?yes a venturi(diverter tee) is feasible with sunrads.....when you say zoning off you mean kitchen will be independent using its own thermostat which I would not do. ... Paul S