Cold Radiator


Old 11-25-15, 10:33 AM
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Cold Radiator

Hi. Hoping the group can be of help... I have a three story home and there is only one zone. Also it is a mixture of standard rads and baseboard. I recently had work done to my boiler and after the boiler was refilled and rads bled, all the rads are hot except one. The one stubborn rad is a cast iron baseboard on the second floor.

The rad in question has the bleed valve on the flow side (not return). I assumed it was air locked so I tried bleeding it but only got cold water (no air). There are also isolation valves for this rad only in the basement with bleed valves (I believe a past owner had done work to that room and had to isolate that rad). As a next step I shut off the return valve in the basement and opened the bleed valve. It is hard to tell if any air came out but I let it run for a while and the rad eventually got hot and the water coming from the bleed valve in the basement went from cold to hot. I thought I solved the problem and I opened the valve again. Unfortunately, once everything was opened I noticed that rad was still not getting hot.

I am stumped. Could it be a balancing issue? Should I turn off all flow valves on the rest of the rads on the house and then see what happens? Any help is appreciated.

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Old 11-27-15, 06:15 AM
Join Date: Jul 2009
Location: Toronto
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Was trying to get to this sooner, but didn't sorry>

Sometimes when people renovate they do silly things with rad piping.
I have been in the situation a few times, and it's usually when there is a mix of radiator products.

Still sounds air locked, so there is a few things that you can try.
First raise the water pressure up as high as you can, watch the boiler relief valve. 30 PSI max if you can't isolate the boiler. More pressure if you can isolate the boiler.
This will try to push the air back into solution and it may flow better to the rad, while you bleed it.
We have used fittings to adapt a hose bib to the rad bleeder, this allows higher flow rates to be used with higher water pressures. If you have a good transfer pump you can even put that on the hose and draw water out. Anything to get the fastest flow to get the water moving.

Let us know how it goes

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