gravity hot water pump heating all vented bleeds weirdly!!!

[Viper Gas]

Hello All,

I have a weird problem that has caught me off balance.
About 2 years ago I power flushed an 8 rad system
Customer call me a couple of weeks ago complaining that one tad is not warm
I checked bottom of rad and found it warm so I opened bleed valve nothing came out.
I suggested to put in system cleaner
I returned flushed out water and started to fill again. All down stairs rads bled as they should but all top rads bled really slowly. And some top rads would only bleed when one side of the rad is closed.
If I open both valves the rad won't bleed.
So I closed down the locks holed as much as possible while still getting flow of water through rad.
Has anyone come across this kind of situation before.
The rads are mostly very old.

Cheers for any advice anyone can offer.

 

[ShaunCorbs]

are they 2 pipe valve? (both pipes on one valve)

 

[Best]

An open vent system should bleed no bother whether 1 or 2 pipe or whatever type of rad valves are fitted. Some can be very slow - especially if feed pipe is partly blocked and might fill the higher rads slower. Depends also where the f&e tank is situated.
Only time I find a problem bleeding an open vent system is if the pump is running as some systems will draw air into the rad.

 

[ShaunCorbs]

An open vent system should bleed no bother whether 1 or 2 pipe or whatever type of rad valves are fitted. Some can be very slow - especially if feed pipe is partly blocked and might fill the higher rads slower. Depends also where the f&e tank is situated.
Only time I find a problem bleeding an open vent system is if the pump is running as some systems will draw air into the rad.

not with these esp if the pipe is missing

 

[Leo21]

As above, is pump pff. Is the f&e tank high enough? Don't assume it has ever worked before either, customers can be crafty buggers.

 

[Best]

not with these esp if the pipe is missing

Why? I have worked on those dual pipe valves for years that were all fitted on gravity systems.
Often the internal pipe wasn't connected. I never have found any bother with them, apart from slow to fill being microbore & also air locks in the microbore. Gravity should just fill from any pipe if rad air vent open.
Different story if pump is running while trying to bleed air or f&e tank is too low.
I always hated microbore & dual valves & never fitted it though, except small alterations.

 

[jonnyswamp]

not with these esp if the pipe is missing

Always assumed that the flow and return were opposite to this sketch
Oh well everyday's a school day

 

[rpm]

Don't assume it has ever worked before either, customers can be crafty buggers.

Amen to that.

 

[ShaunCorbs]

Why? I have worked on those dual pipe valves for years that were all fitted on gravity systems.
Often the internal pipe wasn't connected. I never have found any bother with them, apart from slow to fill being microbore & also air locks in the microbore. Gravity should just fill from any pipe if rad air vent open.
Different story if pump is running while trying to bleed air or f&e tank is too low.
I always hated microbore & dual valves & never fitted it though, except small alterations.

if no internal pipe is fitted it can bypass the rad and flow down the return (short cycling)

 

[Best]

if no internal pipe is fitted it can bypass the rad and flow down the return (short cycling)

Oh, yes, I know that can happen. I was thinking more on the point the OP said about the top rads not filling if both valves on. Very strange unless pump is running while attempting bleeding rads

 

[ShaunCorbs]

Oh, yes, I know that can happen. I was thinking more on the point the OP said about the top rads not filling if both valves on. Very strange unless pump is running while attempting bleeding rads

esp when hes cleaned the system so next step is valves

 

[gizmolang]

partialy blocked cold feed ? , you could try back filling the system through drain off