Worcester 24i stops atfer start with air bubbles noise

[radio_engineer]

After many years of unreliable service I have replaced Potterton Puma 80 with Worcester 24 i. This replacement work was performed by British Gas.

Radiators are still original but system was cleaned , inhibitor was added.

Worcester was operating fine until this week when heating was turned on for the first time after summer. The result was some noise and after few minutes boiler stoped. I checked and pressure was low, I have then filled system with more water but the problem does not go away.

When turned on, boiler seems to run start up sequence. Ingition light comes on for short time. All this time noises are comming from boiler that sound as if plenty of air bubbles are released or developed. After short time boiler stops and red light comes on. Reset button does not resolve the problem.

Even if CH is turned off and only DHW mode selected same problem appears.

I suspect some form of air lock or blockage ? Any ideas and how to diagnose this ?

Thanks

 

[gigz]

Airlock in the hex probably.

 

[radio_engineer]

Airlock in the hex probably.

thanks, what is the Hex and how to clear this airlock ?

 

[radio_engineer]

Hi

If anyone has any idea on this Hex airlock and how to clear this , thanks

 

[gigz]

If you look in the manual, you have to take the cover off and there's a bleed tube on top of the hex (heat exchanger) while your in there check the pump is spinning.

 

[denso13]

This replacement work was performed by British Gas.

In Bosnia? Blimey.

 

[radio_engineer]

If you look in the manual, you have to take the cover off and there's a bleed tube on top of the hex (heat exchanger) while your in there check the pump is spinning.

I have taken cover off the boiler and inspected what I can see.

All i have done was to clean sump for condensate ( this seemed to be full of what looked like sand ). Returned all back to it's position. I have opened screw at the front of the circulating pump , to let some water out. I have then opened and closed plastic cap on the top of the air bleed valve that sits behind the pump. I could not identify any bleed pipe on HEX ? . There are some rubber hoses , at the top of the boiler. One of those is transparent rubber tube , only connected on one end and just dangling inside the boiler. I mean the other end is just not connected ?

When I have put all back, I have turned boiler on and all was working fine. CH and DHW all OK and only difference was higher pressure in the system . This was building up on its own as boiler had wormed up, but was still under red area. Pump is working fine as the water is circulating to radiators and boiler burner turns ON and OFF as water temperature in CH reaches set temperature, even when thermostat is calling for heat

This morning, the water pressure had dropped again very low, to red area. I have filled some water in, to push pressure back to green, but the same problem occurs as boiler now cuts out after 10 minutes .

There seems to be loss of water in the system , but once I fill the system the problem does not go away.

any ideas please

 

[cjl123]

You mentioned opening and closing the air vent behind the pump. This is the Automatic Air Vent and should not be 'closed'. It needs to remains loose/open'. That may explain the rising pressure and subsequent loss of pressure.

 

[kidgreen61]

You mentioned opening and closing the air vent behind the pump. This is the Automatic Air Vent and should not be 'closed'. It needs to remains loose/open'. That may explain the rising pressure and subsequent loss of pressure.

Errr, I think not

 

[cjl123]

You are correct about the clear tube that was hanging from the top of the Heat Exchanger, it is the bleed point for the hex. The little lever/tap it is attached to spins around and will release air/water from the heat exchanger.

Be very careful if you are to operate the tap, ensure you have a suitable container to catch the water and ensure you don't drip any water onto the fan electrical connections or the PCB below.

 

[cjl123]

kidgreen

'I have then opened and closed plastic cap on the top of the air bleed valve that sits behind the pump'

The grey cap situated behind the pump it the AAV is it not?

 

[radio_engineer]

I have resolved the problem so just here to explain the detail.

I have used the transparent tube and air vent to blead air from HEX. This was not problem.

I have then identified that sump for the condensate is full again and after taking sump out I have noticed that plastic pipe under the biouler is blocked. This pipe is not part of the boiler it is one fitted as part of the drain.

The blockage was at the point where white plastic pipe connects to grey soil pipe , under sink. It seems that fat deposit was pushed inside the pipe from the soil pipe, probably as the sink was cleaned and water released etc.

As soon as I have cleared the pipe , bubbles noise in the boiler had gone out and all sorted now.

Note for others : you need to be very carefull when taking out condensate sump if it is blocked as condensate is inside the black rubber cap / hose connecting the boiler and plastic sump body. As you remove the cap to take sumb out water spills all over the boiler and in my case over the main board. I was fortunate not to damage it with water. It is probably best to cover well with cloth and plastic bag . Do not risk spilage ![/b]

 

[radio_engineer]

I am still not happy with pressure changes in the system , when hot it does rise for 0.7 bar, from 0.7 to around 1.4 .

Is this within expected changes?

the system is only small for 2 bed flat so not huge amount of water i guess.

I need to check expansion cylinder perhaps ?