boiler banging

[brettmac70]

please could anyone help? we have a Glowworm 45/2 back boiler on an open system hot water and heating.
a honeywell 3 direction flow valve and a pump with a black twist knob on up is hard pump, middle no noise, botton is low noise levels.
the cystern has a thermastat attached to the outside.
we have heating but if we turn the hot water tempreture thermostat up that is attached to the outside of the boiler the hot water does not get hot but the overflow pipe spits out boiling water int an small expansion tank?
we have fitted a new thermostat to the outside of the tank.

please can anyone help.

 

[Agile]

Have you checked the pump according to the FAQ on this site?

Tony

 

[brettmac70]

wow.

quick reply
yes the pump is wired and working.
top is pump in one direction,bottom in the other middle is gravity fed. i think....i am looking for the instructions in the loft now.

 

[dal5band]

IF all the rads are heating up then the pump is probably ok. If only the upstairs rads are getting hot slowly, may be the pump.

Sounds like the flow through the HW side is not working properly :

Check the diverter (3way) valve - has it got a manual lever that you can move. Can you feel the pipes either side of the valve to see if the one to the HW cylinder is getting hot.

The other thing we had was air in the HW part of the circuit. Check to see if there is any kind of air bleed in the HW circuit near the cylinder.

 

[brettmac70]

all rads are hot and heating ok in line with thermostat and valve settings.

the one pipe to the HW cylinder is not getting hot.

i have opend the air blead and water came straight out

sundyle 3 way splitter has a leaver on the front? is that what you mean?

or the pump that has 1,2,3 possitions on it?

thanks

 

[brettmac70]

wife (who knows best) had turned the hot water down so low due to the banging,i have turned the heat of water up,pipes now getting hot...the overflow pipe will shortly start to rumble and hot boiling water will overflow even though we will not have any hot water.

 

[brettmac70]

there you go five minutes,banging pipes and water into overflow tank.hot water in pipes but tank has hardly got warm.

 

[daveaf]

Have you checked the 3 way valve to see if it has opened to the hot water side, the pipe coming out of it should be hot?

 

[brettmac70]

pipe on boiler side is hot,the tank is now heating up.but the overflow bubbles and all the pipes rattle adly.only way to stop this is to turn the water temp down so low that it is better to boil a kettle to wash with.

 

[bengasman]

banging noise = overheating = lack of flow.
lack of flow = naf pump or blockage

 

[namsag]

2 Problems first one sounds is your boiler stat has gone as even with no circulation your water should not get that hot that it boils over . When the rads are on are they hotter than they used to be with stat turned up.

second . Is there a valve on the bottom pipe that comes out of the cylinder and has it been turned off try opening it if there is one