Uneven heating in radiator

danitheplumber

Hydronic heating system 1 zone top floor has radiator pipe in top and gets heat across top but not the bottom. Originally pipe in bottom but had issue same issue bottom hot top cold. Any suggestions? Auto vent?

Fred

Is this a one pipe Steam system? If so, you have a vent on that radiator that is venting too fast and steam races across the radiator to the vent and closes it, trapping air in the radiator. Put a slower vent on that radiator and the problem will likely disappear.

danitheplumber

Hydronic not steam

JUGHNE

Picture of rad showing both valve ends and its air vent??

danitheplumber

No pic just 3 risers coming up 3 floors first 2 floors the supply and return are connected in the bottom and on the 3rd floor they're connected into the top of the radiator. Previously on the 3rd floor the radiators were connected at the bottom but only the bottom would heat and the top was cold now the reverse is happing top hot bottom cold. It seems it's going straight across in either scenario. Fully bleed the radiators. Put an auto vent to see id it helps. Never seen this issue hoping someone has.

JohnNY

Sounds like the system is over pumped. Slowing the water will allow the heat to diffuse in the radiator.

danitheplumber

Ya but why then do the radiator on the 1st and 2nd floor heat evenly?

JohnNY

Maybe because they're in different locations and subject to different flow rates. I don't know for sure.
If you want me to come by with my thermal imaging camera, we can look at it, and learn, together. No charge.
Do you happen to know a Mr. Stein, Dani? He's a guy I know from the Mechanic's Institute that also oversees maintenance of many Broadway theatre houses in the city.

Harvey Ramer

Is the rad return top or bottom of the rad?

danitheplumber

They try bottom and had issue and now that its pipe in top same issue you can clearly feel it get colder as you move your hand toward the bottom but hot on top... I'll look him up jobs in Brownsville old brownstone use to be force air oil change to gas hydronic with baseboard and then change to cast iron radiators.

danitheplumber

Oh sorry no supply and return on top taps right now before was on bottom taps like the rest of the house

danitheplumber

Can't get a hold of customer for update but I suggested closing valve slightly on return to restrict flow to allow radiator to heat before it goes out the return side...

Harvey Ramer

The return pipe has to connect to the bottom of the rad, always. Most always anyway. It works best that way.

If the supply pipe is connected to the bottom, the flow has to be slow enough to permit gravity circulation within the rad itself. The first couple sections on the supply side should get hot as the rad starts warming up. Then it heats across the top of the rad, and begins warming up the remaining sections as the water on the top cools off and drops toward the return pipe.

If the supply pipe enter's the top and the return off the bottom on the other side, it can handle more flow and should heat evenly across the top tapering off in temp towards the bottom.

It sounds to me like you may not be getting any forced circulation. Just some gravity flow. Have you checked the pump or zone valve for proper operation?

JohnNY

I confused Dani with misterheat, the theatre heating guy.

Carry on.