Viessmann boiler failure

[Radio Fixer]

Do you have the outside temperature device fitted to the Viessman boiler? Good or just save the money and use as conventional indoor stat?

thanks Gary

[ppppenguin]

I don't have the outdoor sensor but Mark H does and swears by it. I'm running temperature control entirely on TRVs now.

[Mark Hennessy]

Correct. I try not to mention it too much because I've harangued Jeffrey far too much about it already. But yeah - you'd be mad not to go for it.

Jeffrey does have a reasonable excuse, BTW

[ppppenguin]

Got the stainblock paint on the kitchen ceiling. Actually solvent based undercoat which I had in stock and works perfectly well. The neat way is an aerosol can of Zinsser BIN123. It works like a charm on all sorts of nasty surfaces and dries quickly. But I didn't have one and I did have the undercoat.

I'll get the white emulsion on tomorrow or Wednesday.

I've also topped up the inhibitor Will think about best way to clean out system. An acid clean like DS9 will give a lovely clean system but some of the rads are old and might suffer. I've seen what can happen with just a powerflush and old rads. Rust held together by paint = flood. About a year after the powerflush as it happens. Acid can only make it worse. I wonder if Sentinel X400 or X800 would do a decent job?

[boater sam]

Rads are cheap in relation to boilers, if they are so bad, change them. Acid clean is not so vicious, at the working pressure the paint won't hold the water anyway! Its the early part of their lives that has rotted them, not the fact that they are cleaned.
 Take them out one at a time and flush with a hose both ways and upside down, pressure test to 5 bar and if you can re-fit them upside down for a bit more life and peace of mind.

[ppppenguin]

The problem with rads is not knowing if they're bad. I fitted most of them myself when I moved here in 1998. They are all the Barlo or similar round top types which can't be fitted upside down. The system has always had inhibitor in it since I've been here. There are 3 older rads that I kept. One is a custom curved thing in a bay window.

I don't have a pressure tester. Any simple way of improvising this, perhaps with a car tyre inflator?

[boater sam]

Easy, remove and flush with a hose through both ends, invert and fill with water. fit 2 bungs where the valves were. stand the right way up, remove bleed screw.
Get a snap in rubber tyre valve from a tyre depot, use that in your tyre pump holding it against the bleed hole and pump it up.

You will soon find any pin holes!

[ppppenguin]

Presumably if I turn off the boiler isolation valves I could pressure test the whole system that way.

Products like X400 don't actually dissolve black sludge, just flocculate (i think that's the word) it for easier flushing. Whereas DS40 actually dissolves the muck.

So to get the system clean...

1: Pressure test to see if there are any imminent points of failure
2: Use DS40 in accordance with manufacturer' instructions. WIll probably need to fit a couple of T's to the system to couple the hoses for a good flush.
3: Refill with fresh inhibitor

PS: Would it be worth hiring a powerflush machine or just use mains pressure?

[Radio Fixer]

If all the rads get hot and the house is warm why bother? Certainly wait for summer anyway when you don't need the system. Did you keep the cylinder and immersion heater for hot water?

Changed all of ours about 4 years ago that were massively thick steel and ugly things. None had leaks and the house was warm enough but decided after more than 30 years it was time for them to go whilst I was still strong enough to do it myself.

Gary

[ppppenguin]

The reason for cleaning the system is to avoid another similar hose failure and ultimately premature failure of the heat exchanger in the boiler. It can definitely wait until summer. The black muck isn't significantly impairing efficiency or effectiveness.

Fortunately I still have a conventional vented hot water system with cylinder. The immersion works OK. i have pumps on both showers to get decent flow and pressure.