Vaillant ecoTEC 831 filling loops and flushing. Why 2 loops?

[Albumen]

I'd like to flush my CH system doing something like this:

//www.diynot.com/forums/viewtopic.php?t=38902

Whenever I've need to add water to the CH I've always used the 'filling loop' pictured here:

View media item 5816
I say 'filling loop' because looking at the installation manual I see no mention of it, and the soldered joints hint that the installers added it. It joins mains and CH return. So looking at the manual and at the underside of the boiler I see another one which I've never notice before, joining mains and CH flow:

View media item 5817
Why would the fitters add the other one?

Does it matter which one I use? Even though the one going into the CH return is presumably acting against any one way TRVs I've never had a problem (perhaps they're all 2 way). Fill up, run for a bit. Let out any air. Add a bit more water, has always worked.

Why would the fitter add another one?

Anyway, main point of post - I want to flush. So after draining, closing all but one TRVS etc I let water in via the low filling loop (i.e. water into CH return) and out via a hose connected to drain off (at bottom of CH Flow):

View media item 5819
that's cleaning it one way, yes?

Then to reverse the flow use other filling loop, disconnect the lower filling loop from the CH return and that gives me an outlet (with suitable hose).

I know I may not get great flow, but that should work, maybe?

Only thing I don't know is which valves to close to stop water 'short circuiting' through the boiler - any advice there.

TIA, Mike

 

[gas4you]

Looks simply like your fitter hasn't a clue about the Vaillant Ecotec Plus boiler If he can't do this basic installation bit I would doubt the boiler has been set up correctly.

There shouldn't be the extra filling loop. He certainly hasn't fitted it to let you flush the system

Why did he not flush the system properly for you, it is after all part of the commissioning process that is part of the benchmark that he should have filled in and signed for.

 

[Albumen]

I assume he flushed it. But it was fitted 2.5 years ago. Vaillant will be servicing it soon, I'll ask whoever they send if it's fitted OK.

 

[PlanetThanet]

Hi

Looks like the service guy will need to move the PRV pipe to get the condensate trap out


Thanet.

 

[Albumen]

It might be an optical illusion. Just looked at it now and I think it'll just clear that pipe. Though of course it would have been a bit less awkward if they'd run the PRV pipe straight down for a bit before exiting through the wall.

 

[Albumen]

Any suggestions on how the isolating valves work to prevent water just going straight through the boiler when I flush.

Cheers, Mike

 

[spacethegas]

shut the appropriate boiler flow & return valve/valves as necessary.