CH header tank continually overflowing?

[myedsor]

Here's my setup.
1 - Live in a bungalow, all radiators are ground level.
2 - I Have an open feed gravity fed Hot Water system, pumped CH system.
3 - CH pump was in the loft on the return side of radiators.
4 - One of the radiators was connected to the return feed from the gravity fed side and the other side of radiator to the return flow from the pumped side. (Figure that one out?)
5 - I was continually getting air in system.

Here's what I did at the weekend on advice from the boiler company. I have a Worcester Dansmoor 15/19 CF.

1 - Moved CH pump from the loft and put into CH flow pipe directly as it comes out of boiler. (Top right)
2 - Disconnected radiator that bridged systems incorrectly and put into the CH pumped side of circuit.
3 - Turned boiler thermostat on the front up to half way on advice from Worcester heat systems as boiler was cutting in and out every 3 or 4 minutes.

Here are my problems now.
1 - CH expansion tank in the loft is overflowing continually with system on.
2 - I have emptied water level out to way below minimum, I have bent ball valve float rod and the tank still fills up even though the ball valve float is under water!
3 - The water in the expansion tank is hot!
4 - This filling up seems to be happening between days (ie when the boiler is switched off at night and on again next day, if you sit and watch header tank, nothing happens when you switch off the boiler and/or pump, this filling up must happen when water cools down or something? No faulty ball valve either.)
5 - My CH pump is on No.3 although I tried on No.2 and didn't seem to make any differences.
6 - Bled all rads with CH pump off zillions of times.
7 - Still seem to get a little air in towel radiator.

Please help as I'm losing my rag, keep getting home to a dripping overflow and up and down the ladder like a yo-yo!

thanks
Mark
3 -

 

[masona]

Is the pump in the right direction? (a little arrow on the pump).Sounds like the coils in your cylinder is leaking bypassing back up to your F&E tank,see what the others think...........

 

[oilman]

Coming out of the boiler the first connection should be the safety vent pipe to the header tank. The next connection should be the feed pipe from the header tank, and should be within 6 inches of the vent connection. Then comes the pump.

It sounds like you have the pump first, and then as soon as it starts, it pumps some water into the header tank as the pressure on the flow side of the pump increases.