Myson marathon 4000???

[macka09]

Hi all. I'm changing 2 rads tomorrow and this boiler is fitted which is worrying me. Do I just turn it off and drain down or not?

 

[lame plumber]

turn off the valves either end of the rads and then drain the rad and swap, easy peasy

 

[macka09]

I know that but unfortunately the valves have gotta be changed too lol

 

[lame plumber]

freeze it all then

 

[macka09]

No freezer kit

 

[Gray0689]

Jump it

 

[macka09]

Huh? How the hell do you refill the system without a pressure gauge?

 

[Best]

Change the valves live then.
Turn the old valves off & remove old rads first. Change one rad valve at a time.
Sealed systems dead easy after pressure is dropped. Open systems you could try plugging vent & feed fully & turn off any auto vents & after a little water drained from a valve, the flow should stop.

 

[macka09]

I assume I still just open a drain off and let the water drain down?

 

[Best]

I assume I still just open a drain off and let the water drain down?

Not if you are going to do it the quick way by keeping the water in system.
Just open a rad valve into trays or fit a hose onto it after you remove the rad.
Plenty towels & it can be done, but it is risky if you have nice clean cream carpet.

 

[macka09]

I'd rather drain down to be fair. Just in case. Do I just isolate the water going to the feed and expansion tank to drain down and then let the f&e refill to fill back up?

 

[macka09]

??????

 

[Best]

Yes. Sometimes it is the safest way, even for a plumber to do, especially if loads of valves to replace & nice new carpets everywhere.
As you say, just isolate the expansion/feed tank, if that's what you have & drain at some point below your rad valves level. Open all rad vents to let air in to let the water out of them starting with the highest rads.
Don't forget you will need to replace inhibitor into system when letting the tank refill the system.

 

[macka09]

Ok thanks. I think the system is a indirect double feed system. The boiler is ancient. I've only ever done work on combi systems. So if I isolate the f&e tank and drain down. When I let the tank refill I assume it just shuts off when the whole heating system has refilled? No need for a pressure gauge? Should I turn the boiler off when I drain.

 

[Best]

If it has a separate feed/expansion tank, solely for the heating system then it will refill right up to that tank ballvalves level. No need to worry about pressure gauge.
Do turn boiler totally off, as you don't want it starting with no water in it.

 

[macka09]

If it hasn't got a smaller f&e tank what should I be looking for? I couldn't see In her cupboard earlier due to all the towels. Just trying to make sure I know what I'm looking for when I'm there?

 

[macka09]

If it's a prismatic cylinder do I just isolate the cold feed cistern?

 

[Best]

I believe so. I rarely have came across them & think of them as a thing of the past.
All you can do is check for an expansion/feed tank & if you discover it is a prismatic cylinder, then isolate cylinder & drain heating as normal from whatever low part of heating - draincock or rad valve.
To refill system just turn tank feed valve back on & also open a hot tap.

 

[happyflyer]

Why all of a sudden changing two radiators is such a pain, it never was when I was a lad, think about this is changing two radiators creates 12 posts to the experts when a novice comes on the site what the hell do they think, better go on the electrician site, hell just drain the dam thing down, might then see what crap is in the system South of Watford, only joking, about the last bit.:bomb:

If you start this job a 0900 hrs I would expect it to be filled and vented by 1100 hrs and in the pub by 1200hrs

 

[happyflyer]

If it's a prismatic cylinder do I just isolate the cold feed cistern?

If its a prismatic cylinder, I could see right through that without draining it. :50:

 

[macka09]

If its a prismatic cylinder, I could see right through that without draining it. :50:

job done. It was just a double feed cylinder. All went fine thanks for the advice.

 

[happyflyer]

There you see, another happy customer, I don't know how we do it.

 

[Ermintrude]

If it's prismatic the optics don't like inhibitor. Also as said above snatch the valves. If on ground floor roll back carpet and lift a board, auto sump . Draining is best. Get system hot before u drain and then refill venting ground floor first