Externally mounted replacement expansion vessel on heating boiler?

[Jethro_uk]

The usual outcome was they'd carry on bodging until the car was unrecoverable, and then get upset when we charged them a premium for a flatbed.

[RJH]

That would take some doing. Water was coming from the inside of my boiler a while back. Turned out it was unusual weather - a few hours of rain driving directly onto the flue, found its way past the gasket.

[Pamela]

Thank you for the very useful explanation. It took a while to digest but now makes a lot of sense. There's more going on than I realised and the online videos I saw were too superificial to account for the things you describe.

If this boiler makes it through winter, I'll get it replaced in the spring. What would be good make to get? People say Worcester Bosch are good but others point out their aluminium heat exchangers (like the Ideal Isar) are inherently troublesome.

[newshound]

Then go for Vaillant. Although them in the know generally seem to rate Vaillant and WB equally highly. Certainly my latest Vaillant is very trouble-free.

[John Rumm]

So was mine until I had to replace the main HX :-)

(to be fair, its well made, I would replace it with another Vaillant if I need to)

[John Rumm]

I get the impression its usually the electronics that kills Isars... (I did fit one of those to my previous house (they were new, so had not acquired a reputation at that point, and it was small enough to fit the available space!)

In reality it never caused me much problem - but then again I moved not that long after fitting it, so it did not get much chance!

WB and Vaillant are usually pretty well rated, but of course that does not mean your particular example will be faultless. Conversely you may find a poor one lasts better than expected. (previous neighbours of mine had a low end Biasi fitted 12 years ago, and its still going strong).

Vaillants are nicely made and easy to work on. Their documentation could use some improvement (its very good at describing all the bits in detail (if a little Germanic), but not good at covering the big picture "system level" stuff.

[Pamela]

[Detailed information above is included for context.]

An external expansion vessel was fitted into the nearby pipework and the pressure gauge is much more steady.

If it's relevant, the heating engineer didn't disconnect the internal expansion vessel.

The external steam I used to see billowing outside when the boiler started up in the morning is very much reduced. Out of interest, why would this be?

[John Rumm]

There is no need - it might not work, but it won't do any harm being there.

You mean the visible vapour you see in the flue exhaust? That will be partly influenced by by return temperature and external temperature. So if the flow temp was set a bit higher by the person fixing the boiler, you may see less visible vapour at the flue. (ideally it want to be set as low as you can get away with and still get the house warm enough - that promotes maximum condensing efficiency in the boiler)

[Pamela]

A clicking sound every few seconds in the pipework stopped after the external expansion tank was fitted. I could never worked out its source. Could it have been the damaged diaphram in the expansion vessel rising and falling?

Thanks for the info. So it's it just a coincidence that the steam vapour is much reduced after fitting the expnasion vessel.

[newshound]

I'd go with John's explanation. On my Vaillant flow temperature is something you can easily check from the LCD display, and adjust yourself if you want to. I do wind mine up and down a little, depending on the external temperature.