Magnaclean or power flush?

itm2

Our 17-year-old Worcester Bosch combi boiler has broken down (both fan and pump need replacing), so we're looking at getting a new boiler installed. My question is: how important is it that we get a power flush done before installing the new boiler?

The rads were last power flushed 17 years ago when the current boiler was installed, and there is no filter on the return pipe.

GlowGreen offer attractive prices on new boiler installs with Magnaclean Magnetic Filter & Chemical Flush included. I know that the Magnaclean would not be as effective as a full power flush, but am struggling to decide whether the disruption of a full powerflush would be worth it?

Also, what would be the typical cost of power flushing 12 radiators (in the Greater London area)?

WIAWSNB

Your old combi is on an unvented system - no wee tank in t'loft - so is generally less prone to corrosion and sludge. And you've had no sludge issues during its life - eg, the P2P exchanger hasn't blocked at any time?

In which case, the chances are that any sludge will be relatively minimal. So if you wish to avoid the cost and disruption of a full PF, then that's 'likely' to be ok.

In addition, all new installations are required to perform a system clean to a BS. This is not only to preserve the boiler, but to comply with its warranty requirements. So, if you go for a boiler with a typical ~10-year warranty, and comply with it in all respects, then you should be fine. And a magnetic filter is also a warranty requirement for most, if not all, new boilers. 

Once installed, the annual check of the fitted magnetic filter will soon tell you what condition your system is in. 

Something you may wish to try is to catch a third-of-a-glassful of radiator 'bleed' water to check its colour. Bear in mind, tho', that your CH system is unlikely to have been used for a looong time, so it may be more clear than normal. But it could be a guide. 

FreeBear

WIAWSNB said:

Your old combi is on an unvented system - no wee tank in t'loft - so is generally less prone to corrosion and sludge. And you've had no sludge issues during its life - eg, the P2P exchanger hasn't blocked at any time?

In which case, the chances are that any sludge will be relatively minimal. So if you wish to avoid the cost and disruption of a full PF, then that's 'likely' to be ok.

Operating temperature can also have an impact on how much sludge is produced. If you can run at (say) a 50°C flow temperature, not only is efficiency significantly increased, but corrosion within the system is reduced.

Reducing the temperature of the DHW will cut the amount of scale clogging up the system - Only really a concern if you are in a hard water area.

If you are having a new boiler installed, it is worth looking at current radiator sizes and replacing some/all of them with higher output versions. This would enable you to run at lower flow temperatures. But if you have micro-bore pipes, there will be limits on how big a radiator can be fitted.

Also worth looking at heat pumps - When I had a new gas boiler installed, an ASHP was only a few hundred more (from Octopus). But at the time, there was a requirement to increase insulation levels as recommended by the EPC, putting the total cost out of reach - That requirement has since been dropped.