Central heating inhibitor

ajohnmartin

I have a mixed-metal central heating system with copper tubulation in and from the gas-heated boiler, connected by steel tubulation to steel radiators. The original system was probably installed in the 50s or 60s, and the original boiler was replaced about six years ago. The hot water tank has a 40 gallon capacity.
About three years ago my plumber drained the system, but, on refilling he omitted to use any inhibitor such as Fernox. I have just tested the contained water by immersing a copper coin with two steel nails, both of which have shown fine surface rusting over a period of seven days.
Can you advise me as to what I should do to limit further damage to my system? For example, should I drain the system and use a phosphate anti-rust agent before introducing Fernox? Should I go for a power-flush? Or should I ask an expert heating engineer to examine the system?
Yor advice would be appreciated.

Canucklehead

Hi
If I were to look at your system I would advise a flush, with the following advice.
I would use Sentinal x400 (or similar) to remove the sludge, as the pipework is stainless and the joints (if soldered) will not be as strong as a copper to copper joint. (I have seen it done with all compression fittings, much better) It might also show up other problems with radiators such as pinholes along the bottom. Any problems arising from the flush, such as the above, would be chargeable.
There are alternatives to powerflushing including, taking off the rads and washing out with a hose or filling and running with x400 for a week or two then draining and refilling several times.
Taking off a rad might disturb one of the said joints under the floor.
Fit a Magnaclean or Boilerbuddy to the return pipework will filter out any remaining, and future, magnatite.
Fill with Sentinal x100 inhibitor (or similar)
Get a few quotes through the door.
HSS will hire the machine if you are prepared to give it a go yourself.

Corgi Guy.