cold radiators on ground floor/noise in open-vent/hot pipe work

[bushymusic]

Hi all,

I have a conventional close-coupled open-vented heating system comprising of wall mounted boiler in kitchen a Potterton profile 80,
Thermostat in the hall,
Airing cupboard on landing with the following:
Hot water tank
Honeywell 3 port valve V4073A
Potterton EP2000 programmer set to so that you can only have two options –
HW or HW + Ch (no CH only)
So 3 port valve moves between A-HW and AB-mid position and not B –CH only.
close-coupled configuration of open-vented and cold feed pipe work set 150mm apart that both go straight up to the loft & expansion tank above.
grundfos 15-60 pump place below and after the cold feed, pointing down.
I have 10 radiators, 5 standard size on upper floor, 3 5ft tall rads on ground with the last two in the run standard size again.

My problems are:
1. Within 20 minute of calling for hot water and central heating cavitation or kettling starts noisily in open vent pipe work in airing cupboard then continues for duration.
It did use to pump over into expansion tank but I raised the pipe work to stop this in the short term to stop it steaming.
2. Last three radiators on ground floor are a BIG PROBLEM as they take 1 hour to partially warm in the morning, if at all.
Pump is set to maximum (3).
3 port valve in mid position so flow is split.
I can work around this if I Water then travels around CH only and all radiators are very hot.
All pipe work and pump/3 port valve very hot to the touch in airing cupboard.
Air constantly in highest radiator so needs bleeding every few days.

Had an engineer look at it:
He recommended and carried out following:
Changed pump
Power flushed system
balanced rads/ showed me trick of close off valve on the coil of the hot water tank.

No change all problems remain.

Any recommendations?

Cheers,

David.

 

[helpsy]

AB is incoming port from boiler

A is outlet to rads
B is outlet to Hot water

 

[helpsy]

Is the feed behind the pump and then the vent the other side of the feed?
The height above the water level in the F&E that the pipe should be is 450mm.
Place a magnet by the feed/vent connections and see if its attracted to the pipe.
Check water level in F&E and float operational.

 

[bushymusic]

I was using the AB as an example of mid position (apologies).
With the vent at 450mm the water is hot and over pumps into the expansion tank creating steam in loft. (I’ve extended to 3ft temporarily to stop this).
Magnet shows no sign of slug/rust.
IS it possible the mid point favours WH rather than CH creating a bigger flow on one side?
Could my boiler be over heater- ever though it switches off regularly it seems to ignite correctly but I’m guessing. Feed in and out warm up correctly. Thermostat seems to switch on and off but I’ve no knowledge.

 

[bushymusic]

P.s FE water level 1inch over outlet so thats fine, float OK too.

 

[bushymusic]

heres the airing cupboard with close coupled pipe work, pump, 3 port valve, side of tank and valve on coil used to increae flow on CH.