Uneven heating in some Cast Iron Radiators

hal1000 · January 2018

I have an old 2 story home with a boiler and cast iron radiators. I only have 1 zone, but the supply splits up into two loops. I believe that the loops are not divided by floor, but by North half/South half. 3 of the radiators are not as hot as the others. I think that colder radiators are at the tail end of the loops. Curiously, the return pipe is slightly hotter than the 3 lukewarm radiators....

I have 1 circulator pump.

Any ideas?

Brewbeer · January 2018

Is this a monoflow system? Can you post photos?

JohnNY · January 2018

Can you use the shutoff valves on the hottest radiators to dial back some flow and allow more heat to travel to the farther radiators?

hal1000 · January 2018

I believe it is a 2 pipe system.

hal1000 · January 2018

@JohnNY
Yes, I will try turning down the valves to the hottest radiator. This could possibly even out the radiators within that loop.

How do I control the flow if one loop is colder than the 2nd loop? There is one circulator with 0 zone valves. However, there are some shutoff valves for each loop.

flat_twin · January 2018

Did the system work fine before and this is a new problem?

You think it's a two pipe system. Can you trace the piping in and out of each radiator and tell us if it's direct return or reverse return?
Direct return diagram...
https://insulation.org/io/wp-content/uploads/sites/3/2016/10/IO150205_01.jpg

Reverse return diagram...
https://insulation.org/io/wp-content/uploads/sites/3/2016/10/IO150205_02.jpg

What size are the main supply and return pipes? How many radiators on each loop? What is the length out and back for the furthest radiator in each loop?

Per your other thread about circulator pumps, what circulator is there now?

Uneven heating in some Cast Iron Radiators

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