Can I drain Valliant system and keep HW on?

[thornton_chris]

Hi,

I am going to install a rad and re-locate a towel rail heater and so need to dain down the central heating system. The trouble is I don't want to rush!

Can I drain it down and then leave just the hot water bit running so that all the hot taps still work? Then I can spend a couple of hours a day over the next week moving the relevant pipe work.

The boiler is a combi - Valliant Eco tec plus.

I did hear that running the hot water when the central heating is drained can destroy the boiler.

Many thanks in advance.

Chris

 

[seco services]

answer no you can't run dhw with boiler drained.

 

[mickyg]

turn the heating isos off on the boiler with "a correctly sized allen key" . then drain away, should be fine.

 

[thornton_chris]

Conflicting answers here guys! Which one is correct?

Chris

 

[onlyfitidealboilers]

the later one

 

[kevindgas]

both are technically correct! the thing is that you need around 1 bar pressure on the pressure switch within the boiler so draining will remove the pressure. the 2nd answer tells you how to keep the pressure in the boiler whilst draining the pipework!

personally i would do all the work by using temporary caps.

drain the pressure cut the pipes, cap

do the work up to the point where you are ready to reconnect

then drain the pressure again and do the final reconnections

 

[thornton_chris]

both are technically correct! the thing is that you need around 1 bar pressure on the pressure switch within the boiler so draining will remove the pressure. the 2nd answer tells you how to keep the pressure in the boiler whilst draining the pipework!

personally i would do all the work by using temporary caps.

drain the pressure cut the pipes, cap

do the work up to the point where you are ready to reconnect

then drain the pressure again and do the final reconnections

Ok. Ideally I still want to drain it for a few days and carry on running the hot water. Are we sure I can do this as long as I turn off these ISOS? I don't want to kill my boiler!

Chris

 

[mickyg]

the boiler has an internal bypass, no harm can be done, just make sure the heating is definately off and isolate the valves with an allen key not a flat screwdriver.

 

[Happyplumber]

I totally agree with micky.thats what i would do.The built in bypass gets rid of any excess heat so whats the problem.The reason he is asking you to use an allen key to close the isloation valves is because most people mullerize them flat screwdriver!

 

[Bunnyman]

Mickg is correct that's the way to do it no problem

Untitled

• Bunnyman
• 26 Mar 2010
• 499

 

[thornton_chris]

Right, all pipe work finished now!

In what order to I fill the system?

Do I open the ISO valves first and then top up in the normal way or fill the system up with water and then open the ISO valves last?

Thanks again,

Chris

 

[The831Bunny]

Turn the boiler off.

Open the isolation valves (pressure gauge will drop).

Fill system and vent air from radiators. Fill so needle on pressure gauge is about 'ten to' as relating to a clock face. ie. in the centre of the grey section.

Turn on boiler, run heating with all rads open for 5 minutes, then run some hot water, then heating again. This should help to move any air out through the auto air vent in the boiler.

Finally vent the rads once more for any remaining air and re-check system pressure is in the centre of the grey section. Pressing the '-' minus button below the LCD display will give you a digital pressure read out. Anything from 1.2 to 1.5 bar is fine (unless you live in a 3 story house).

Don't forget you may have diluted any inhibitor that was in the system

Bunny