3 port valve isolate radiators?

[zerokelvin]

I have an old fashioned boiler with a vented hot water cylinder. There's a 3 port valve next to the hot water tank in the airing cupboard, where the circulation pump is also located.

I want to do some work on the central heating side while the weather's warm and ideally continue to use the boiler to supply hot water. To save me endlessly draining and refilling the system (as I won't get the job done in a day and would rather take my time), can I just use the valve to isolate the radiator loop?

I was thinking of disconnecting the outlet to the heating system and fitting a stop end and also disconnecting the power supply to the 3 port valve (as insurance against someone turning the central heating on by accident). I'd then drain down all of the radiators to allow me to replace some of them and some of the (nasty microbore) pipework.

Will this work?
Is it a really bad idea?
Are there any additional gotchas I should be aware of?

Thanks in advance.

 

[motorbiking]

This should be fine as long as the boiler can push water around your hot tank. Personally, it sounds like more of a ball ache than draining and re-filling. Can you. not use your electric emersion heater for the few days you need hot water?

 

[oldbuffer]

It is normally the three port valve moving which fires the boiler. If you disconnect it it won't fire the boiler. Why not just fit the stop end to the CH output from the valve, and turn the CH thermostat down to zero?

 

[ianmcd]

No you cant do that, the water will just run through the return

 

[zerokelvin]

No you cant do that, the water will just run through the return

That makes sense - I thought I was missing something as I couldn't visualise the whole loop closing.

This should be fine as long as the boiler can push water around your hot tank. Personally, it sounds like more of a ball ache than draining and re-filling. Can you. not use your electric emersion heater for the few days you need hot water?

Emersion heater it is. People will have to go without baths and everyone having a shower within 10 minutes of each other - not the worst problem in the world!