Replacing rads, no drains or pressurisation loop

Merch

As per the title,
I'm replacing a few rads,

There are a few problems, which I was already aware of, but wanted to bring this up to get opinions on, in the original instal was it right?
I'm intend rectifying it, but want to see am I thinking along the right lines.

Basically, there is no drain anywhere in the system, not under the boiler, not at the lowest point in the system,ok I can disconnect a rad and drain it that way (after isolating the fill supply), but its a bit inconvenient, thinking of putting one in.

that leads me to the next issue, the fill connection was always open, but also it seems to be the only means to pressurise the system. There is no other connection anywhere to do that.
I've done a quick calculation and it doesn't look like it will be possible (even though I'm in a standard semi-d) to pressurise the system adequetly, the height of the water tank even being in the attic is really only a difference from the top of the system of a max of 5m from the top of the tank to the bottom of the lowest point of the heating system, Im not even sure if it should be a head of highest point in system to heighest/mid point of the boiler but either way it could only develop a max pressure of about .5 of a bar?

Another issue which was highlighted to me here previously was that the safety valve which was leaking but stopped vents directly to the outside and not to a drain.

The heating has generally worked fine for years (fingers crossed) but it makes me think as all the houses in the area are the same that all the installations are the same, and possibly not 100% correct.

Is a pressurisation loop necessary? without it I cannot see how the system could be pressurised, without some additional means with the current set-up.There is no easy way to install one at the boiler but it would be possible at the hot press, I'm unsure how much the volume of water is in the system, the expansion vessel is 8 litres.

DGOBS

Yes a drain point is 'handy' but how often do you intend draining your system?

The 'semi-sealed' or open vented Yates you have can be sealed, cut and blank the feed from tank (drain first...lol) then take a feed just before the tank inlet (mains) and connect to the old CH feed via a 1/2inch filling loop and gauge. Once you have pressurized the system to 1-1.5 bar then remove a blank the filling loop until required again.

Before embarking on ths, make sure you expansion vessel is present and correctly sized for you installation.

Merch

thanks for the reply

re the draining, I agree not much use maybe but it is handy to have, if either I have to drain it for some reason, I'm thinking just stick one in as it will be drained anyway.
The expansion vessel is there (on top of the boiler) I had a look to see if a label or plate of some kind was on it, says 8 litres.
While i dont know the volume in my system, I can assume the expansion vessel size is correct, as its always been there and appears functional without issues, but again while the system is drained I'll just check the pressure to ensure it is ok (I say that I assume all is correct but there seems to be other things which, while they may not be wrong seem not to be the best idea, ie like no drain or pressurisation connection?) and edit, no seperate header tank for the CH. This all as fitted at the time of build, more than a decade ago in a large estate.

Its only dawning on me recently,as I just looked online and found a manual for my boiler type and it says the boiler system pressure can be between 0.5-1.5 bar, by my calculation at the height involved 0.5bar is barely achievable without additional pressurisation, just wonder why they did this??
It would have been so much easier if this was fitted at the time of install at the boiler, I think I'll put a pressure gauge in the hot press too as the one at the boiler is too far and a double NRV.
Re the gauge in the hotpress,my other half understands kPa but is only aware of usage in the order of a couple of Pascals! bars is too much (for her to understand ), I taught her to pump the tyres on the car but I tell her, just go to a specific number and i know it will end in an argument if i have to get her to shout up to me what the gauge is at on the boiler.

I'm already viewing the possibility of saving for a new boiler, so if this one holds out for a few more years and we have the money, I'll probably upgrade to a more efficient condensing one, hopefully I will be able to get one that has the longevity and reliability of my current one.

I am curious and almost concerned to ask, what is the limit, technically or accurately where I am legally allowed to work on my system, I have no intention of touching the gas side (obviously) but I am replacing rads to save me money and installing a few features for convenience like the above mentioned loop and drain.
In brief I'm not doing anything at the boiler, im not taking the covers off even if Im looking at the expansion vessel.

edit, excuse the long replies, it just seems to happen, any opinions from anyone, great