Hot water trickles into F+E tank when 3 port valve is in Mid position.

[KevinD]

Went into the loft to put some stuff away and noticed that there was water trickling into the F+E tank via the expansion pipe.
I drained the system down and added Sentinel cleaner which I left for a few days to work its magic.
I drained down again and added Sentinel inhibitor but the problem persists and I thought to investigate further.

So This morning after the system had been running for 20 minutes or so I went into the loft and hot water was trickling into the F+E tank via the expansion pipe.


With the 3 Port valve on MID position - water trickle into F+E via expansion pipe

I turned the room stat down and waited until the 3 port valve moved to HW only - trickle stopped

I turned the room stat back up and waited until the 3 port valve moved back to MID - trickle resumed

I turned the tank stat down and waited until the 3 port valve moved to HEATING position - trickle stopped

I turned the tank stat back up and waited until the 3 port valve moved back to MID position - trickle resumed

With the 3 port valve still in MID position I switched the CH pump control from middle to lowest speed - trickle stopped

Moving the pump speed control back to its middle position resulted in the trickle resuming


The pump has previously been set on middle speed without issue
I thought that lowering the pump speed to its lowest setting had solved the problem but this morning there was no hot water, the pump on its lowest setting is not powerful enough to pump the water from the boiler up into the loft and down to the HW tank in the airing cupboard.

It is a Y plan system, about 12 years old, with indirect cylinder and Glow worm boiler. The 3 port valve was changed a couple of years ago and appears to be functioning as it should so I am mystified as to what is going on.

I'll call in the people who do the annual service to take a look but meanwhile I'm mystified as to what's going on.

 

[gassafe]

Probably an issue with the cold feed & vent pipework.

 

[Unregistered]

It's 20 years since I was a central heating installer but I used to fit an air separator, which is basically a special tee which you connect the cold feed and vent into before the pump and 3 way valve and used to fit a by pass with a 15mm gate valve,

hope this solves the problem.

 

[chris watkins]

It's 20 years since I was a central heating installer but I used to fit an air separator, which is basically a special tee which you connect the cold feed and vent into before the pump and 3 way valve and used to fit a by pass with a 15mm gate valve,

hope this solves the problem.

No manual by-passes (15mm gate valve) allowed any more must be an auto I am afraid.

Why not register Mr Guest & post some more, it is alway good to have fresh input.

 

[chris watkins]

Welcome KevinD
Sounds like a clogged up system to me & just putting some cleaner in will not shift it.

Trouble is you don't no how long it has been pumping over for & each time it has been doing it water which has been oxygenated has been drawn into the system & more oxides have been formed restricting the pipes.

Don't think that a power flush will do much good either, my advice is to get the pipework cut out & inspected / replaced around the Cold feed / SOP Vent connections to the system & check around the pump to confirm that pipes are not restricted, only then think about cleaning the rest of the system.

 

[PlumbBobBob]

as said Mr unregistered guest please register with us you will be most welcome :smile5: