Noisy System

[RP61973]

I drew this from memory (at office at mo), so some config of some of the pipes where they go in and out of tanks, cisterns etc. may be iffy, but the principle of the layout is correct.

Vent from cylinder does go over cold water tank (although shown over expansion in error)

Not sure, but pretty certain there is a vent from primary side to feed/expansion

2 pipes drawn from f/e tank in error - only 1

This is a rough schematic so the boiler return pipe won't be higher than the tank, but shows the principle of what is there.

Any ideas??

 

[spacethegas]

the two bleed points could do with replacing with aavs.

the system needs a bypass.

are trvs fitted ?

a lot depends on exactly where the cf & ov are on the system.

is the noise constant, now & again, only when ch on ?

 

[RP61973]

Spacethegas, many thanks.

I will visit the local plumbing shop and see if they have any suitable aav's

No trv's on the rads, just standard Myson valves

Not sure what cf and ov's are?

Noise is not constant, seems to build to a crescendo every few minutes.

Where do you think the bypass is needed?

 

[RP61973]

Spacethegas - re the noise. It occurs when the CH is on or the HW is on or both are on. Also seems worse when the boiler starts from cold.

 

[D_Hailsham]

The Grundfos Selectric pumps need a minimum static head which depends on the water temperature.

85°C - 0.5m
90°C - 2.8m
110°C - 11.0m

This is the vertical height from inlet port to the water level in the F/E tank.

Your diagram shows the pump in a horizontal configuration; ideally it should be vertical, pumping upwards. If this is not possible then Grundfos advise:

Where pumps can only be installed in horizontal pipework, it is imperative that the pump shaft is horizontal, or slightly higher at the vent plug end.
The shaft must not fall below the horizontal plane, even by a few degrees, as this causes premature wear of the top bearing and shaft.

The vent plug is the large chrome screw in the front.

 

[RP61973]

Many thanks. I will check how the pump sits (it definitely is in horizontal plane) and whether it is higher at the vent plug end. I have not bled the pump itself as I thought the bleed ports directly next to it would have taken care of any air, but I will give it a bleed!

 

[JohnD]

Noise is not constant, seems to build to a crescendo every few minutes.

I know what you mean, my latest exwife does that.

 

[RP61973]

John D, I trust you are not likening your latest ex-wife to a noisy, troublesome old boiler?

 

[spacethegas]

the cold feed (cf) you have drawn from your feed & expansion (f&e) tank down to your boiler.

i would guess the open vent (ov) comes from the bend (on the diagram) just before the pump & terminates over the f&e tank ?

DH asked for the static head distance ?

as you have no trvs a bypass is not really necessary.

 

[RP61973]

I will need to take a look at the connectivity/routeing of the open vent and get back to you.

Not sure about static head. I would guess from the configuration that this would be around 1.5m or a little less, but I would need to check (pump sits just above loft joists and F/E tank is around shoulder height).