Inhibitor for aluminium heating boiler?

pamela wrote in news:XnsA8989386895B6D4AM2@

CORGI - really?

By law all gas engineers must be on the Gas Safe Register. Trust the Triangle.

Gas Safe Register replaced CORGI as the gas registration body in 2009.

Some engineers have hi-jacked the Corgi brand

CORGI still exist as a trade body... just no longer responsible for maintaining the register.

Generally, yes.

Sentinel x100 claims compatibility with ali system parts:

Flushing may be worth doing (depending on how clean the system is). However make sure its done with the boiler isolated from the pipework so that you do not end up flushing anything into it.

I'm showing how hopelessly out of touch I am because I have no idea what the current qualification or trade body is for heating engineers.

When I said "Corgi", I meant he's a qualified heating engineer rather than some jack-the-lad plumber out of his depth but having a go.

Why would doing this have any impact on the amount of condensate produced? (if indeed it has any)

Much obliged.

After raising the boiler temperature to near maximum in this cold weather, I noticed a gurgling sound from the flue and the system pressure had dropped to 0.5 bar.

Maybe system water was lost in the heat exchanger.

Instead of a full trap, could all this be caused by a frozen condensate pipe?

Flushing will have no impact on the amount of condensate produced. That just depends on the amount of gas burnt, and how effectively the boiler can condense the water from the flue gasses.

Hopefully not - that would be a fairly catastrophic failure.

It would be more indicative of a failed (or partly de-pressurised) expansion vessel... The high flow temperature causing more expansion of the primary water than usual. That in turn raises the pressure more, and the pressure relief valve would operate if it exceeded the maximum.

(tie a plastic bag over the end of the pressure relief pipe - that will show you if its operating at some point in the cycle).

The trap should periodically fill, and when full automatically empty itself into the drain. (by doing it in doses like that it reduces the chance of it freezing, which would be more likely with a steady trickle of water). The only time the trap should need attention is if it gets clogged with slime or mould etc.

If the condensate drain freezes, then eventually the main heat exchange will start to collect water (since it can't now escape). That can indeed cause a gurgling sound. (usually shortly before the boiler locks out).

A quick temporary fix if you think the condensate drain is blocked is to divert it into a bucket, and then manually empty it form time to time.

Condensate pipes should be run inside prior to discharging into a larger diameter pipe before exiting the building. They should also ideally be run through a heated space. (hence installs in lofts and garages are prone to problems with freezing pipes).

Thank you for your advice. I can see a trail of ice where the water has fallen from the relief pipe and down the wall, so this seems to be as you suggest.

My condensate trap fills with what I think are aluminium (oxide?) particles from the corroding aluminium heat exchanger. They're like small granules. I asked about introducing inhibitor in order to reduce this corrosion as I believe the heat exchanger will eventually fail from this.

I thawed the outdoor condensate pipe because it was frozen and I saw a foot or two of ice slide out.

When the weather improves in a few days, I will lag it. Maybe I will get it cut shorter because it runs outdoors for 1.5 metres to a drain in the yard, although maybe acidic condensate dripping onto concrete will erode it.

In which case you need to check the expansion vessel. Its often red in colour and on many boilers is fitted at the back of the casing. It normally has a Shrader valve (i.e. like a car tyre) on it so it can be pumped up. If you give a brief push on the pin in the valve you should get a puff of air out. If water comes out then the diaphragm inside has ruptured.

Example of how to check and re-pressurise:

Also see:

Inhibitor can't help with that - its on the wrong side of the heat exchanger.

The HE is basically a heatsink inside a combustion chamber, which has a water pathway though it. The primary water (plus any included inhibitor) passes through the HE, but should never have any contact with the combustion chamber exposed parts of the HE.

The condensate drain is connected to the combustion chamber side of it, not the primary water bit. Hence it can only collect water that condenses out of the combustion gasses, and any moisture of debris that is drawn in through the flue's air intake. So any corrosion products you see in the condensate can't be coming out of the primary water in the boiler (unless the HE is actually leaking!).

What size pipe is it? Ideally it should be dumped to a drain or soak-away. While it won't dissolve the concrete on a significant scale, it may cause staining or marking on it.