Worcester 350 Highflow problem

[chaoswill]

Hi,
Can anyone help with my Central Heating problem?

I've recently moved into a late 70's house fitted with a Worcester 350 Highflow Combi boiler / 8mm microbore pipework. The house has laid empty for upto 2 years.

Following a replacement timer being fitted, the Central Heating functions (all rads heat well), but there is a servere sound of air flowing in the pipes in the upstairs rooms. I've bled all the rads with no air being released. From reading things of the Net, it seems that Combi systems are sealed water systems, but I've got a small water tank in the loft and I can't see a pressure gauge!

Also, water flow rates from the taps are very poor (especially the hot water upstairs). The water flow rates in the bathroom vary relative to the hot / cold taps being turned.

If anyone has any comments I would be most grateful. Are flow rates normally poor with Combi systems? Is the Header Tank normal?

Chaoswill.

 

[COG]

First off to avoid confusion ,you cant get a 350 highflow but you can get a 3.5 highflow, this model is available open vented as you have. check that the tank in the loft is full to around 50mil below the overflow, vent rads with the boiler off and vent the manual air vent ontop of the boiler at the right hand side, the flow rate at all taps should be around 17 lt per min,you can work it out with a jug and a watch.

 

[chaoswill]

COG

Thanks for the swift reply.

Yes the Boiler is a 3.5 Highflow!

I'll look at the manual vent over the w/end. The tank in the loft is full as described.

Chaoswill

 

[chaoswill]

COG

I checked the internal bleed valve and the rads over the W/end and all seems OK (no air).

Also, the flow rates from either / both taps never exceeded 5 L/min. The cold tap even STOPPED for a period of 20 seconds, and the hot tap 'sucked' air back into the system when it was switched off.

With a combi, is the cold water side directly connected to the hot water side?

Chaoswill