Boiler making big noises when central heating drained and trying to use for hot water only.

[macfarpe]

I accidentally put a hole through one of the central heating pipes earlier so I turned the boiler off and drained the central heating. I should still be able to switch the boiler to hot water only but when I did that just now it started making a really horrible noise. I'm assuming (hoping) it's because there is no water to heat and that somehow the central heating being empty is stopping the hot water being heated.

The two should not be linked but it's too much of a coincidence that when the central heating is drained the boiler is making noiises all of a sudden.

Could it be that my 3 point mid position valve is not doing it's job so the boiler is not able to heat the hot water independantly of the central heating?

[eltelioni]

The systems are connected. The boiler heats water which is pumped either through the radiators, or through a coil in the hot water tank, or both. The 3 position valve controls where the water goes. If you have drained the heating system, then you have drained water from the boiler, the radiators and from the coil in the hot water tank, so neither system will work.

[alan1967]

Hi macfarpe

eltelioni is correct

1. You will have 2 Tanks in the loft
2. large tank fills the cylinder for the hot water
3. Small tank will fill the coil within the cylinder and the radiators, it circulates from the boiler through the coil and heats the surrounding water

4 Rpair the damaged pipe

5.Close all bleed valves on your radiators
6.Fill system ( which will be by the Small Tank)
7.Release the air from the radiators starting from downstairs
8.Turn on Boiler let the system heat up
9.let system cool Check repair for leaks (exspansion & Contraction)
10.If ok run system as normal you may need to clear air from radiators always turn off boiler before bleeding

[carver99]

You might find that running the system with no water in it has damaged the pump too, once you've refilled the system turn the boiler thermostat right down and run both hot water and central heating, listen carefully to the pump and any unusal noise might mean an early pump bearing failure in the same way a car fails when you dn't put oil in it.