Sealed CH - draining down

[Andy]

I feel incredibly dumb asking this question and yes I have looked at the FAQ. How do you drain down a Combi boiler CH system ? I want to flush my system with Sentinel cleaner - system is a couple of months old and there is some Hydrogen being produced in one of my rads.

I have a draincock which I know is where the water will come out but im not sure of the procedure. Boiler is an oil combi (Worcester Bosch). It has seperate temp controls for HW and CH and I have the ability to switch off either HW / CH or both. So what do I do ??

Thanks for any replies.

Andy

[andrewpreece]

Don't know if you can operate the HW when the CH is drained, but why bother? It won't take all that long to drain down. Procedure I use is:-

1. Switch off combi at mains.
2. Open CH drain c*ck, making sure the CH water has somewhere safe to go.
3. Crack open the upstairs radiator vents first, then as the system drains down crack open the downstairs radiator vents. This is to ensure the radiators drain fully.
4. Squirt or pour your cleaner into the system, probably via the draincock: you may need a tube and a funnel.
5. Close draincock and fill system slowly with filling loop ( fom mains ) - you will either have a built-in filling loop or need to attach one between your cold water and your CH loop.
6. The difficult bit - probably there's a better method - rush around turning your radiator vents shut, starting downstairs, before they completey fill up, else the vents shoot water everywhere.
7. When the upstairs radiators are full or nearly so close their vents too and get back to your filling loop and pressure gauge to keep an eye on the system pressure so it doesn't get too high and cause an overpressure venting.
8. Turn combi back on. NB Your combi should have an air venting device, like a little pot or bulb with a plastic knurled screw top cap on it - make sure the cap is unscrewed one or two turns during refilling of the CH or you'll get an airlock in the combi.

Andy.

[Lurch]

On Tue, 2 Mar 2004 15:33:57 -0000, in uk.d-i-y "andrewpreece" strung together this:

Nearly, each drop will need draining individually. If you drain one drop and open the vents on another you'll be draing that drop through vents.

The better way is shut them first then fill up the system to about

2-2.5 bar. Bleed a couple of rads and check the pressure. You should end up with all rads bled and the final pressure at about 1.5 bar. ..

SJW A.C.S. Ltd.

[Paul King]

Agree with both previous posters - except I prefer to

1. Open CH drain c*ck, making sure the CH water has somewhere safe to go, and drop the system pressure *JUST* to zero - before
2. Crack open the upstairs radiator vents, and then open CH drain c*ck again. I prefer to refil using Lurches method too!