fernox Ds-40 cleaning results

[sknight]

I have a bad kettling boiler.
I have tried both Sentinal X200 and fernox HEAVY DUTY CENTRAL HEATING RESTORER.
These chemicals are both form of (EDTA) ethylene diamine tetraacetic acid. I belive that they somehow remove the limescale ion's in the water.
These chemicals do not change pH of the water.

My question is:- How effective are these chemical compared with DS-40 which is a true acidic cleaner.

Will DS-40 sort out my noisy boiler?

There is no air in the system and the boiler is only 8yrs old. Potterton Kinnfisher2.

Also tried all pump speeds with no luck so can not be low flow.

Water is clean as I have cleaned out with the above EDTA chemicals several times.


Thanks

 

[Bahco]

Kettling can be caused by an incorrectly set bypass, or could be you do not have one.
Have a plumber check this for you.

 

[sknight]

You are correct I do not have a by-pass.
I have two rads that do not have TRV's. These rads have the valve wide open.
I assume this will give sufficient flow back to the boiler?

 

[ChrisR]

Look up chelating agents. EDTA is only a small part of above named.
That fernox elixir won't touch boiler scale, DS40 (malic + acetic acids) will, to a point. Hydrochloric is better but more difficult - don't try it. Even HCl won't dissolve rust.
Phosphoric acid based chems are available too, also sulphamic acid. You pays your money...
8 years is old. Some boilers kettle after 6 months given a chance.

All the more aggressive chems are more likely to test the joints to leaking point.

 

[sknight]

Added ds-40 tonight afet a long period of draining and flushing to get rid of the black water.
I have changed my controller settings to a pumped system rather than gravity, to allow me to keep the pump running to circulate the system for a few days with out the heating or hot water. This is gravity fed, so normally the boiler would stike up if the pump was running.
Also changed pump speed to max.
Have notioced a slight differnce even after a few hours of circulating hot.

Packaging says circulate for 7 days.

Any ideas if this is too long or long enough? or is it a case of wait untill the banging goes hopeing not for a leak first!!!

 

[croydoncorgi]

Chances are the boiler has a layer of black sludge at tyhe bottom of the heat exchanger. Burner heats up metalwork and the small amount of water at the bottom of the sludge. Temperature rises and water flashes to steam, steam creates bubble which disturbs sludge layer and allows cooler water to get onto the hot metal and cools it below 100C. Sludge layer settles back down. Cycle repeats all over the bottom of the HX, creating knocking, banging and kettling noises.

If you're up for it, best way to remove it is to completely drain the system, undo top and bottom connections on the HX, connect a hose to the bottom one and flush it through with another hose. It's very hard work trying to mobilise the sludge so that it flows UP out of the boiler and then around to the drain-off point. It's a messy job, especially if access is tight.