System pumping over

[onlyfitidealboilers]

that is why its called a feed & EXPANSION tank! that is where the hot water will go as the oxygen in the system expands.

It's the water expanding which causes the level in the tank to rise, not the oxygen.

the water level in the tank should not rise too much only very little.

The expansion is approximately 4% of the volume of the water in the complete system when cold. So if you have 75 litres, it will expand by 3 litres

also check the level of the water in the tank when cold, isn't more than say 4 inches

Make sure that the float valve in the F/E tank opens before the water level reaches the outlet at the bottom of the tank.

its the oxygen in the water that expandes not the water. how can water expand

 

[joe-90]

The molecules are further apart. That is why hot water rises. It is less dense.

 

[neiln]

Swap the pump round
swap the 2 port valves round
swap the flow and return on the cylinder
and change the boiler pipework as per drawing

i will be a lot less work just to move the pump.

Guess an expansion vessel kit would be even less work.

 

[iep]

Expansion vessel, PRV, gauge and filling loop are all on the list for next year when we replace the boiler. For now though we just want to prevent the system from becoming airated by the pump over.

In a sign from the plumbing gods, the existing pump packed in last night so it is defintely time for a change.

Out of curiosity, what are the signs of a failed grundfos pump? Ours still moves water arpound the system but makes a nasty buzzing/grinding noise on speeds 2 and 3. For now I have set the boiler stat low and am running it on speed 1. New pump ordered this morning.

Cheers

iep

 

[D_Hailsham]

its the oxygen in the water that expands not the water. how can water expand

In the same way that a piece of metal expands when you heat it.

You really should have paid more attention in the Science classes at school.