open vent ch?

Indeed. There are also many different types of plastic. If the OP is concerned he could have a galvanised steel header tank - if you can buy one nowadays.

If you keep putting heat into a presssurized system, the pressure will increase and the water will quite probably just boil at a higher temperature. The conseqencies of any subsequent failures will likely be that much worse. Hence the regulations regarding the boilers used in steam engines!

Reply to
Michael Chare
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Modern tank valves often won't switch off if you do that.

Well, you have to do it so much more often because the tank exposed to the air wastes all the inhibitor within a year (or much faster if it's pumping over, which is something else you have to be careful to avoid).

Using the filling loop, I can flush a sealed system using full mains water pressure/flow. The irony is that a vented system is much more likely to need flushing in the first place;-)

Reply to
Andrew Gabriel

You said that in the last post. And I then said...

Reply to
meow2222

My take is that vented systems have a large number of failure modes, some of which are quite serious, many of which are due to mis-installation but go undetected for years.

Pressurized systems have really only one common fault which is failure of the expansion vessel. This, if the user then resorts to continuous refilling is quite a serious.

The advantages of pressurised systems outweigh those of vented ones, IME, IMHO.

Reply to
Ed Sirett

An odd bubble means very little A boiling system will thunder and crash continuously until it runs out of water or someone hears it who has sufficient brain to switch off.

Could be within expected limits. the 1% per year sounds unlikely as I would expect an initial drop then a fairly stable lifetime. Your service engineer should take combustion readings and your report sheet ought to show the nominal efficiency based on the temperature differential of inlet air to flue outlet related to the CO2 content of the flue gas. Its a close approximation!

I seriously doubt your Mistral (I think its a pressure jet burner) is down to 50%, nearer to 70% if it has been kept in a reasonably well maintained condition.

If he is OFTEC registered he ought to know the basics but has he any good references from other customers? OFTEC are somewhat similar to CORGI in that they offer registration for different categories of work. Make sure your guy is ok for boiler installation and commissioning from his ticket. Or you could ask OFTEC for confirmation.

Reply to
cynic

When you heat cold water the dissolved air comes out. Look at the bottom= of a pan of cold water being heated on the cooker, it'll be covered in bubbles very soon after the heat is applied. I suspect that this releaed= air is collecting somewhere and you are hearing it glug away up the vent= pipe when you first draw of water. The vent pipe should rise straight fr= om the top of cylinder with the hot water feed T'd from it and angled very =

slightly down.

Our service engineer does and our boiler comes out at 70% or so and is about 15 years old.

40p/l in Jan is about right, 80p/l appears to be about 20p+ over the current price of around 55p/l (looks to have dropped a little recently).=

Well I'd take a pinch of salt with both of those figures. I suspect the =

makers figure is when running optimally in full condesing mode, in the real world it won't be doing that all the time. So push the makers one down 10% and yours up by maybe 20%, giving 85% and 70%. Some fuel saving= but not the best part of half...

Agreed see above, our boiler is also a Mistral.

Reply to
Dave Liquorice

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