C/H Inhibitor Recommendation?

[dwtowner]

Hi all,

I am just finishing off the installation of a new C/H system. The tank and boiler instructions recommend Fernox-brand inhibitor, but there are lots of other inhibitors on the market. Will I see a noticeable difference between a cheaper inhibitor like Triple-X

, and a more expensive inhibitor like Fernox F1 or Sentinel X100? This is for a 300l heat- bank system, so the difference in price between cheap and expensive adds up. If the expensive stuff simply comes in a better class of bottle, but contains a virtually identical liquid, then I may as well get the cheap stuff!

thanks,

dan.

[stuart noble]

I don't think any of them contain anything much other than a mild acid, like boric.

[Rod]

Suggest a look here:

Can't remember what I used, but it seems to be doing the job. It

*wasn't* Fernox!

[Andy Wade]

I'm no chemist but I think that's utter nonsense. For a start the pH of Fernox MB-1 (probably still the most common inhibitor?) is given as

8.3 - 8.8 for the concentrate [1], so it's hardly acidic. Fernox say:

"The majority of domestic central heating inhibitors are essentially anodic passivators. This type of inhibitor reacts with the metal (anode) being corroded to form a very thin film that prevents any further metal being lost. The film is only maintained by the continued presence of inhibitor in the water." [2]

So far as the OP's question is concerned, why take the risk? The cost of the approved inhibitor is surely tiny compared to what's been spent on the rest of the system. Also using non-approved products might invalidate the manufacturer's guarantee on the boiler.

[1]

[Andrew Gabriel]

I've never seen any comparison done between products (sometimes wondered myself). It's an opportunity which is wide open to fake products which are appearing too (mostly chinese).

One thing I recall Andy Hall did where he had to use the more expensive versions with anti-freeze was to design in the ability to drain down and capture the water, and use it to refill the system, thereby not losing all the inhibitor if you need to drain down to fix a leak just after installation. My be less practical with a large water content though.

I might be inclined to fill with only one bottle for a few weeks (sort of simulating situation near the end of the life of the inhibitor) so that if you do need to drain down to fix any initial leaks, the loss is limited. Then top up to full strength after some weeks of no leaks.

[YAPH]

Then you haven't been following uk.d-i-y very closely! ;-)

Rod's already posted the link to the article in our very own wiki.

[stuart noble]

Sentinel x100 has a ph of 6.4, and the main ingredient is boric acid. Hardly utter nonsense

[TheScullster]

wrote

Without a doubt go Fernox. As others have said the cost is minimal when considered alongside the capital cost of just an overhaul, let alone major works. They have a good technical department too if you are in any doubt over which product(s) to use.

From experience, I spent a lot of time trying to resolve issues with my heating system and in the course of this used both Sentinel and Fernox. I think most agree these are the most respected products - wish Andy Hall was here as I know he would certainly back this up!

I found of the two that my system ran noticably quieter with the Fernox (I'm talking boiler noise here not un-bled air).

HTH

Phil

[<me9]

I use a small hand pump to pressurise my system. It is fed from an old 5 gallon homebrew pressure barrel. It normally holds enough to part drain the system for repairs, but occasionally needs supplementing by a couple of buckets.

[Andy Wade]

COSHH data sheets are on the Screwfix website. The hazardous ingredients for X100 are listed as benzotriazole (2.5%) and sodium molybdate (2.5 - 25%). No mention of boric acid, but that might not count as hazardous. The pH is given as 6.7,

For MB-1 the only listed ingredient is triethanolamine (1 - 5%) and the stated pH is 7.2.

So with data on only two products we can conclude that they aren't all acidic and that at least two products contain ingredients other than just a mild acid. So not utter nonsense - apologies - but not correct either.

[stuart noble]

It's what happens when non-chemists discuss chemistry :-) I doubt whether triethanolamine is an "active" ingredient when it comes to corrosion, AFAIK it just maintains alkalinity. No idea why Fernox is alkaline and Sentinel is acidic though.