Central Heating Maintenance

[Keith Dunbar]

This is the second of what will probably be many questions for the newsgroup. We have just moved into a new to us, but very old, house - 1650 or so. This question is about what we should do to service the central heating system.

The house is quite large. It has modern-ish central heating - oil boiler (relatively new), copper pipework, panel radiators, a few thermostats. It seems to be working OK, but bleeding a radiator recently let out a lot of black water. I'm wondering what we might need to do in the way of flushing it out, fitting thermostats, balancing, and perhaps fitting more controls - at present there is no separate control of the hot water circuit.

Any thoughts? I'm certainly planning to do a good wash out and fit thermostats everywhere. Are new radiators more efficient? Should they be replaced? Should be wait a year and see how well we feel the system works next winter?

All comments gratefully received.

Keith

[Dave Plowman (News)]

Sounds like no inhibitor has been used. By far the best value maintance is to add this.

[TheScullster]

"Keith Dunbar" wrote

Faced with a similar dilemma, I flushed my system numerous times with cleaning additives and included a magna-clean filter. Probably best to do this after adopting Andy Hall's method. ie take all rads off at same time and flush manually. Then connect mains water to pipe work and blast through every conceivable rad valve/connection until clear. More work this, but a lot more likely to achieve the desired effect.

Phil

[Keith Dunbar]

Previous owner claims inhibitor has been used meticulously! Do radiators deteriorate with age anyway, or is it always simply a matter of corrosion? If they're 20, 30, 40 years old a) can one tell? and b) are they likely to need replacing because of corrosion? Are more modern radiators any more efficient?

Keith

[Keith Dunbar]

Any particular recommendation for cleaning additive? What is a magna-clean filter?

Any particular preferences for new thermostats - are they all much of a muchness?

Keith

[Andrew Mawson]

radiators

corrosion?

I have a pair of (very large) radiators that were scrounged from a skip 22 years ago, and one already had a pin hole. I gave them a very thorough flushing to remove the black gunge, brazed up the hole (which was on the rear face), and fitted them to my then new system which was well dosed with Fernox inhibitor. No problems with them whatsoever over the last 22 years. I wouldn't have chosen to use known faulty s/h rads, but fiscal necessity forced the issue ! (and they were exactly the long low shapes I needed for under a window!)

AWEM

[Andy Hall]

Yeah right.

To be fair, he may have dosed the system regularly, but there could be an issue where the pump is not correctly located. This can cause pumping over or sucking down of air at the header tank. This introduces oxygen into the system and the inhibiting effect is eventually used up. If a system is working OK,inhibitor at the correct dose level should last a year. A fault like this uses it up more quickly.

There is no real reason that they should as long as the system is not introducing air and inhibitor concentration is maintained. I have some aged now > 20 years and they are as clean as a whistle.

Age should not be a significant factor. If they have already corroded then you may be on borrowed time before pinhole leaks appear.

This depends on your definition of efficient. Emission from radiators is mainly convection, some radiation and depends on the total surface area. Over the last 25 years or so there have been design changes to incorporate find on the back to do this and there are two panel radiators.

If your question is really whether you can obtain more heat from a given size by wall area then the answer is probably yes. This isn't really a definition of efficiency, however.

[Andy Hall]

Cleaning additives really only make a minor effect. They can be used to mop up small amounts of sludge and crud and generally clean after a thorough mechanical cleaning. However, if the system is heavily sludged to the point where a lot of crud comes out when you drain or there are cool spots at the bottom of radiators, chemical cleaners are not going to do too much. They should be used after the system is predominantly clean.

A Magnaclean filter is something which will magnetically attract magnetic materials in the circulating water. It may be interesting to do this but is rather like sticking a Band Aid on the end of an amputated limb. It doesn't deal with the cause of the problem. If that is fixed, then there is no point in having a Magnaclean. It can be used to help prevent sludge reaching a boiler but does nothing to prevent the demise of radiators.

For thermostatic radiator valves, purchase a good brand. Invensys TRV4s have been around for many years, are a good and reliable product. Pegler products are good as well. It isn't worth giving DIY supermarket brands the house room.

[Dave Plowman (News)]

If the water was truly black it indicates corrosion of steel somewhere (rads) and this can't happen if the inhibitor is kept at the correct strength. Of course if it's an open system and is pumping over I'm not sure how long inhibitor remains effective.

It's rather how long is a piece of string. Good quality rads - made out of decent steel - would corrode reasonably evenly, if they corrode. Cheap steel will have impurities and will pinhole. Decent rads with inhibitor will never need replacing.

All rads are of the same efficiency in that they themselves can't waste any energy. But well designed ones with a low water content and high surface area may make the system more efficient overall.

[Andrew Mawson]

somewhere

inhibitor

IMHO most pinholes occur where the black gunge build up sits against the inner wall of the rad, so bottom edges towards the middle where the flow rate is slowest ae most vunerable

AWEM

[TheScullster]

"Keith Dunbar" wrote

I'd go with Fernox products every time for both cleaning and (don't forget the) inhibitor. This is based on experience of the noise reduction experienced when using Fernox vs Sentinel (argueably Fernox's main competitor). Also their tech support is good, so once you have a clear idea of the state of your system give them a call and see what is recommended.

As Andy Hall has noted, the Magna Clean filter collects the magnetite (black sludge) which can circulate in the system. The sludge is a sign of other issues - no inhibitor used in the first place or air entering the system. In an ideal world, whatever cleaning method you use should be aimed at removing all crud from the system. However, if you are not completely successful, there's a chance that the Magna Clean (or its Fernox equivalent the Boiler Buddy) will catch the stuff for easy removal. I preferred the Magna Clean for ease of crud removal.

Andy's comment on Invensys (formerly Drayton) TRV4s is seconded - never fitted anything else and haven't had any issues to date. Probably one of the most expensive TRVs on the market though ~£17 IIRC :(. Watch out for compatibility of bodies - they are now sold through the sheds and I have ended up with two different heads which look the same but are not interchangeable.

HTH

Phil

[Keith Dunbar]

Many thanks everyone for a great deal of very helpful and useful information.

Keith

[Keith Dunbar]

I have a horrible question that this is a silly question - so apologies in advance.

Further investigation of my set up (following a major leak after turning off one radiator - when water poured from the radiator valve) revealed on drain down that the water coming out looked pretty clear - so perhaps the previous occupant had been using inhibitor and air isn't getting into the system.

BUT I definitely got dirty black water I got when I bled the bathroom radiator. That radiator is plumbed into the hot water heating segment of the conventional central heating system rather than the radiator segment. What I was going to ask was how is the hot water segment supplied with water and how does one add inhibitor to that water - but now I realise that presumably it is fed from the same header tank as the radiator segment.

So why should the bathroom radiator contain such black water when the rest of the system seems OK. It is a pretty manky old radiator though - but I assumed that was just because it has been affected by condensation in the bathroom.

Keith