Moving rad - depressurising system?

[jeebee]

Hello,
I'm currently renewing my kitchen and need to move a radiator from one wall to another. My system is a sealed system - condesing boiler, pressure vessel, all rads on trv's and joined by 8mm microbore. I've read the other threads on this forum and understand that the following procedure will be required:

- Close all valves on all rads.
- Remove rad fitting new valves to avoid water loss.
- depressurise sytem.
- extend pipework to new rad location and connect to rad (one side at a time to avoid water loss).
- open rad valves and repressurise system using filling loop

I'm quite happy with rerouting/connecting the new pipes and valves etc but feeling like a bit of a dufus as I can't seem to work out how to depressurise the sytem, I can find the pressure relief valve but know I'm not supposed to touch this, but can't seem to find any other valves that would appear to release the pressure. Help please, it's a pain to be stuck on what I assume is one of the 'easy' bits.
thanks.

[meldrew's_mate]

Sound like you have a "regular" boiler with external pressurisation kit rather than a "system" boiler with all the bits built in.

Firstly find the draining point (hosepipe connection), usually at a system lowpoint, or a modified rad valve with hose connection built-in. This is the preferred method for draining/depressurising. As a last resort and if there isn't a drain point use the safety relief valve, this has a red knob which can be twisted by hand to test its operation, usually located close to the filling loop and expansion vessel; it discharges directly to outside so watch out if it can cause damage or nuisance when you open it.
Bleed all rads of air before shutting all flow and return valves (mark their positions for ease of balancing later). Shut all auto air bleed valves.

Next drain water to depressurise the system, probably no more than a couple of litres using the hose point, though as a last resort use the safety valve, remembering to "snap" it shut so it is less likely to leak later.

When connecting to microbore make sure the cut ends are square and clean by using a file or de-burring tool; it's easy to make a 6mm hole into a 4mm one just by leaving it "as cut", and go easy with the solder / don't swing on the spanners for the same reason.

__________________
I'm a born again virgin...does the strain show??

[jeebee]

Thanks for that, can't seem to find any sign of a hose point to release the pressure (unless it's under the floor - likely?) so I suppose will have to use the safety relief valve. Thanks for your speedy reply.