Replacing radiators (Unvented system)

phoenix__

Hi all,

I have removed a couple of radiators whilst decorating 2 rooms in our house; almost ready to put them back on and I have a couple of queries.

Firstly, is there a recommendation to top up any inhibitor? About a year ago we had TRVs installed on all the radiators and were told that inhibitor was added then. When we took the radiators off, the water was clear until the very last bit which then came out a darker colour.

Secondly, when refitting I was going to open the TRV, bleed the radiators to get all the air out and then open the return pipe (whatever the technical terms are) however looking around I now wonder if there might be something different needed as our system is unvented. Does anyone know if I can do as I was originally thinking or if I need to do something different (and if so, what)?

Any advice gratefully received.

-Jeff

southcoastrgi

adding some more inhibitor is never a bad thing, you can get the ones that pump into the rad before you turn the valves back on or if you are using one of the pressure cans this can just be screwed on the heating side of the filling loop, it doesn't matter which valve you turn on first just refit the rads turn on the valves (both of them) & bleed the rads (without the boiler switched on), do you remember how many turns it took to switch off the locksheild valves ? i bet you didn't lol, if you didn't a good place to start is downstairs rads fully open & upstairs rads 1.5 turns, to balance the system all the rads should heat up at roughly the same time so start with those figures then adjust as necessary.

phoenix__

Thanks for the reply.

The lockshield valves were 1 turn (front room) and 1.5 turns (back room)

So I don't need to do anything different to re-fit the radiators for an unvented heating system?

Cheers,
-Jeff

southcoastrgi

nope but you will lose pressure when you bleed so you will need to use the filling loop to add more water, gauge should read around 1 bar without the boiler working.

phoenix__

southcoastrgi wrote: »

nope but you will lose pressure when you bleed so you will need to use the filling loop to add more water, gauge should read around 1 bar without the boiler working.

Right ... Any guidance on how to do that?

Looking at the system, there is a mains water supply that goes into the cold inlet for the water tank (as you would expect). This also goes into the sealed red tank (with a pressure gauge) directly on top of the boiler.

Cheers,
-Jeff

southcoastrgi

you are looking for something like this or it could be built into the bottom of the boiler

phoenix__

That is exactly what is on top of the boiler ... I'll look at it in more detail tonight.

Thanks!

phoenix__

So I looked at this in more detail last night, between the mains cold water inlet and the red tank there is a valve (which I had never noticed before) just like the picture in the previous post.

Currently the gauge shows ~1.5, I presume this will go down when I fill the rads so once the radiators have been re-filled I guess it's just as simple as opening this valve until the pressure increases then closing it again?

cheers,
-Jeff

southcoastrgi

you got it, 1 bar without the boiler operating

phoenix__

Great - many thanks for the advise ... much appreciated.

-Jeff