Aluminium Radiators

[rog]

 

I am  presently helping a friend renovate a villa that he has purchased in the Gers.On attempting to refill the Central heating system we find that several of the radiators are leaking; not just dripping but pouring out.They are made of Aluminium panels some 100mm wide of differing heights which are then connected to give the required length, they therefore have a join at both the top and the bottom of each panel.It is my suspicion that they were left filled during the several years that the property was left empty and as all the pipe grid is the standard braised thick wall copper pipe they were the weakest link when a freeze-up came. My questions are these:

How are the panels joined and can these joins be repaired?  

[Gluestick]

If the property has been left unused and the CH system not drained for "Several years.........", I would be very concerned about corrosion.

The effectiveness of any original anti-corrosion additive would have vanished some years ago. Further, you then have the probem of tri-metal corrosion; salts of copper and brass and aluminium would create various electrolytic processes as the anti-corrosion additive failed. Pinholes tend to appear in the aluminium as it becomes increasingly crystalline in structure.

Any joining gaskets are replacable; as in traditional cast iron modular rads. Persauding the separate modules apart to change the gaskets, without damaging the corroded ally, however, might be a wholly different matter!

If you do decide to re-condition the rads, personally, I would cobble together some form of pressure testing kit. Can be a 'bike pump, car footpump, whatever; simply solder or braze a spare schrader valve into a spare appropriately threaded fitting; seal any other junctions with plugs and pump up!

Washing up liquid in water, whisked to foam, placed around the joints will bubble nicely if there are air leaks. (Normally pressure testing is carried out in a deep water trough; and streams of air bubbles coming to the surface tell their own tale!).

Bonne Chance !

 

[rog]

Thanks for your input Gluestick.The rads generally seem in very good condition and I do not think they are that old.It is their form of connnection that interests me as I have never seen their like before and I gather from your post they are push fitted together with some sort of sealing gasket for water integrity.The leaks appear to be coming only from the joints and it is very easy to non-pressure test by just standing rad on its side and pouring water in!When it hits the duff level it just streams out.I also take your point that if the Ali surrounding the joint is also suspect then the whole process is mute and its off to the scrapper with them!!

[Gluestick]

Rog; remember that French CH system pressure is same as the water main! Mega high!

I've had quite a few dramas with ally cylinder heads and manifolds, in my time and these tend to be pressure cast in much better alloy than heating rads. Pinholes due to corrosion are the very devil to spot with the naked eye as the metallic salts tend to seem to be sound ally! Pressurised automotive cooling systems run at circa 12 -14 PSI (when hot).

In any case, if the system has been left static for any length of time, I'd de-scale 'em as a matter of course. Improves the heat dissapation.

 

[Aly (used to be Charlotte3)]

Rog,

If you contact a local central heating and plumbing firm they will repair them for you.

We've come across this problem often in work and have never had a problem getting them fixed for clients.

Aly

 

[Aly (used to be Charlotte3)]

Rog,

If you contact a local central heating and plumbing firm they will repair them for you.

We've come across this problem often in work (we have to dismount them to paint and on moving they mysteriously spring leaks) and have never had a problem getting them fixed for clients.

Aly (one of our apprentces managed to drop one, breaking it literally in half and it was fixed no problem)[:)]

 

[rog]

Thanks Aly, I'll certainly look into that.I fear I might have a bigger problem though as some 20 rads have been de-mounted and moved around the house by multi tradesmen for the last 5 months.Oh dear![Www]

[Gyn_Paul]

GS,

I don't know that I would call a French sealed Ch system , Megga-high

pressure: it's at whatever pressure you set it to. Mine is just over 1

bar when cold and expands to 2.7 when hot.  though higher, I grant

you, than a UK header-tank-in-the-loft pressure of about 7 metres

standing head.

p

[Gluestick]

GP.

14.5 PSI (1 bar) to 39.16 PSI (2.7 bar) is high: relative to older UK gravity systems where the primary circuit is open to atmosphere!

Far higher than most automotive sealed cooling systems: and any one here with experience of aluminium car rads, heater matrix and manifold leaks will know instantly what I mean. Which is why I used the example.

And since the top up tank is usually two rooms (7.6 feet X 2 = 15 feet = 4.6 metres) plus the loft joists and floor, above the boiler and pipework, let's say 5 metres of head.

My core point was that such sealed-system pressures will seek out any pinhole caused by corrosion.

In fact, same thing often happens when converting a standard gravity fed system to combi: existing pipework and rads, which operated quite happily before, suddenly spring big leaks!

Happened to me a couple of years ago: a rad,which looked absolutely fine, burst immediately the system was pressured up.

 

[jc]

One Bar is roughly equivalent to 34ft. head of water.

[Michael]

Rule of thumb,for every 3ft in height its 1pound Psi head pressure.If the old aluminium rads are over 15 years scrap them, they have gone well past the sale by date. The price of alloy is at an all time high.20 alloy rads scrap value would probably pay for half the new ones!!. If the pressure is set 1or under1.5 bar on the guage and when hot it goes right up to the pressure of 2.7 bar normal working ,that system seems a little high. considering most combi or pressure systems safety valves blow at 3 bar.Sometimes that shows maybe that  the expansion vessel is not large enough for the system.On very large systems if you are useing what they call a System Boiler with integral pump/vessel etc sometimes you have to install an extra expansion vessel in line.Michael.

[Gyn_Paul]

[quote user="Michael"]Rule of thumb,for every 3ft in height its

1pound Psi head pressure.If the old aluminium rads are over 15

years scrap them, they have gone well past the sale by

date. The price of alloy is at an all time high.20 alloy rads

scrap value would probably pay for half the new ones!!. If

the pressure is set 1or under1.5 bar on the guage and

when hot it goes right up to the pressure of 2.7 bar normal

working ,that system seems a little high. considering most combi

or pressure systems safety valves blow at 3 bar.Sometimes that shows

maybe that  the expansion vessel is not large enough for the

system.On very large systems if you are useing what they call a

System Boiler with integral pump/vessel etc sometimes you

have to install an extra expansion vessel in

line.Michael.[/quote]

Yes, I've thought it a little high too... When I get round to the next

phase - which involves adding more rads and 3 under floor zones, I will

be adding another expansion vessel.

p

[maude]

Could be dangerous if using air as the test medium.The release of energy if failed is frightenning to say the least.fill with water and use hudraulic pressure only.    Maude

[Gluestick]

Perhaps you are thinking of (e.g.) compressor tanks, gas bottles et al, Maude........................

Yes, these are normally hydraulically tested: but at around 450 psi, which is the pressure I use to test mine, or double the working pressure, althought I do take mine well above the expected working pressure range. Call me careful!

10 PSI will show up any leaks and the rupture damage risk is then quite low.

Of course heating radiators (and of course automotive rads and heater matrices) are usually tested using a water tank - which cushions any explosion, since water being a liquid is basically non-compressable: first rule of hyraulics. The string of air bubbles demonstrates the leak/s location/s.

Few amateur building restorers have access to a large enough water tank, however.