CH inhibitor life and sealed vs. unsealed systems

[Fred]

Hi,

Please can anyone tell me how often the CH should be drained down and the inhibitor replaced? I've got two years in my head but I might be thinking of car antifreeze (the blue rather than red version)!

I've been using fernox but their web site is a bit vague on the issue and says to buy a tester. Inhibitor is readily available but I don't see anyone selling tests and I wonder if I did, whether the test would cost more than the inhibitor!

I can't remember whether I used F1 or MB1 last time, if that make a difference, I have used both in the past; buying whichever was the best price in the past at the time.

It is a vented system. Would the interval be longer in a sealed system? I imagine the F&E tank constantly allows oxygen into the system whereas a sealed system contains only a finite amount?

Is it worth me converting the system to a sealed type? What is involved in this? I know many here like sealed systems and say that there is only a finite volume of water so leaks are limited, but what other advantages are there? Some would say no need for a loft tank but to be fair, that hardly takes up any room.

Regarding the drain down, is it worth using a cleaner beforehand like Fernox F3? I know I used one when we first moved in and didn't know the condition of the system but since then we have changed a lot of the radiators as we have redecorated the rooms, so I am quite confident that the system is in good shape now. Is cleaner only needed in bad / dirty systems? Fernox say to use it but they have an interest in generating sales!

TIA

[polly filler]

If I remember right MB1 is for use on boilers with a cast iron heat exchanger, F1 for copper. If you put the right ammount in should last for years with out changing. I personally wouldn't go down the combi road unless my old baxi packed up, fingers crossed

[Andy Cap]

From the Fernox site...

"What is the difference "between Fernox MB-1 and F1? The Protector MB-1 4 litre and Protector F1 500ml are both Buildcert approved inhibitors and are equally as effective in protecting the system from the effects of corrosion and limescale. Both products treat

100 litre systems or 10 single radiators.

The MB-1 is a heritage product and its formulation requires a larger unit pack size but it has a loyal customer base and as such has a place in the market. The Protector F1 500ml is a concentrated product which is favoured by installers and homeowners who prefer to use smaller packaged products, which are easier to handle and transport.

The efficacy of both products is the same. Another example might be washing powders, which are available as loose powder, gels, liquids and tablet form in varying pack sizes.

It is a matter of personal choice which product to buy. "

[Mark]

On the whole I prefer a sealed system but getting in inhibitor is slightly harder since you have no header tank. A failure in a vented system could mean unlimited amounts of water in your house but this should be unlikely if you look after it.

In your situation I wouldn't bother converting it but, for a completely new system, it's definitely worth considering. I converted mine to sealed because I wanted to lose the header tank and the hot water cylinder.

[Onetap]

You don't drain it, just top it up. You need to drain car anti-freeze becau= se the ethylene glycol degrades with age and turn into an acidic compound w= hich starts rapid corrosion.=20

Domestic CH inhibitors are usually sodium molybdate, so you can't overdos= e it SFAIK.=20

If you're considering changing to a sealed system, I'd suggest you shut o= ff the fill valve and monior the water level. An open vented system can top= up a leaking systems for years without being noticed; it causes corrosion = problems. The same leak on a sealed system will require regular topping up.

You need to check your boiler is suitable, the manual will tell you. It = needs a manual- reset overheat thermostat; not all have them.

[Fred]

Thanks. I was only thinking of switching to a sealed CH; I would keep the vented HW for now.

[Fred]

Thanks. I hadn't realised the difference. I had wrongly assumed you flushed out the "spent" inhibitor; it seems I have been making extra work for myself!