It's that time of year...Q about CH inhibitor

[Terry Fields]

Recently moved into a house with a thermal store system, a Gledhill Boilermate 2000. The system is 7 years old, and I have the commissioning engineer's report, which includes a reference to the inhibitor being Furnox.

AIUI in this system primary water is shared between the boiler, heat store, and radiators. As the system is vented, there is a jockey tank in the loft.

According to the previous owner, the system was serviced by British Gas, but I have no details of what was meant by this term.

The water in the jockey tank has a greenish cast to it, but having previously been a user of Sentinel products, wouldn't know whether this indicated the presence of Furnox.

In my old system, I used to clean out the jockey tank once a year, refill and add Sentinel inhibitor. It never gave any trouble in the 30 years we used it.

My Q is this: would a similar approach be suitable for this new system, obviously using the appropriate Furnox product?

Although a recent examination revealed that all the lockshield valves were fully open, and the system obviously unbalanced, there are no 'cold spots' on any of the radiators. A first-guess balancing exercise has evened up the radiator flow, and I'm awaiting the arrival of an IR thermometer before completing the exercise.

TF

[A.Lee]

It probably means they cleaned the combustion chamber, twiddled a few knobs, then said they had serviced it.

I fell into that trap a few years ago, I was told the boiler was serviced regularly, I refitted a rad, then blocked up the boiler with a lot of gunk from the header tank. There was 2" of crap at the bottom of the tank, it had never been cleaned out, or emptied, so when i filled up the rad, all the sludge made its way in the boiler, and blocked it. Never trust a previous owners claims that the boiler is serviced, unless you have a list of what has been done.

I'd be tempted to drain off and refill with fresh solution - at least that way you know the system has been flushed and filled with the correct fluid. Alan.

[JohnW]

I have a British Gas contract and they have never been near my loft tank except when they changed the Hot Water Cylinder and I made sure they added inhibitor. I had a boiler change over a year ago and the plumber used Plumb Center inhibitor when refilling. I have always used Fernox, so emailed them about mixing it with what was there. Even though, allegedly, Fernox make Plumb Center inhibitor, they said I should drain down and refill when adding their, or any other dissimilar inhibitor. I cleaned out the header tank a few years ago, but when I came to look during the drain down, it was full of black gunge again. So bailed it all out and cleaned round before refilling. I agree with Alan, drain, leave the water running for a while to "flush" and refill with Fernox, leaving a bit in the bottle to add to the header tank when it is up to level.

John

[Vortex7]

You can buy fernox test strips, for example from:

for the rpice you may as well buy some inhibitor and put it straight in.

What is the volume of the tehrmal store? You will probably need an extra large dose to be sure of manufacturers recommended dilution.

D

[Mathew Newton]

Presumably the LSVs should be opened fully prior to draining to minimise clogging from disrupted crud? I'm mindful that having just balanced my system some of the LSVs are virtually completely closed off and could easily get blocked my the smallest amount of debris.

Mathew

[A.Lee]

After my problem with a blocked boiler, if I ever get a radiator change, I always check the header tank before draining off any water. If the tank is full of gunge, then you can be pretty certain it is also in the pipe going to the boiler. The usual place for a blockage is in the air separation pipework, where the header tank pipe meets the boiler/radiator pipework. To make sure it doesnt go further than this joint, you need to cut the pipe just above the separator, fit a valve there, then you can safely isolate and drain down from there if needed, with little fear of the muck getting into the system (apart from the small amount that is in the pipes below the cut.) It sounds difficult, but can be done quite easily, with little loss of water - stick a cork or suitable plug into the header tank outlet, then it should stop any water coming from the header tank, as well as slowing down the release of the water that is in the pipe leading to the boiler.

Alan.

[Mathew Newton]

I've got a sealed sytem so I was more wondering about drain downs in general terms of system flushing?

I'm due to make some modifications to our heating circuit shortly (in a recently purchased house) and will be adding inhibitor at the end but have no idea what the current contents are like. I figured I might as well renew the whole lot as it'd be a good opportunity to give it all a flush through to gauge what condition it's in.

Mathew

[A.Lee]

I've never had a problem with a sealed system. You do get the small pieces of rust/debris in systems that have no inhibitor, but otherwise it is usually pretty clean when drained off. Alan.

[Mike Buckley]

I've got a MagnaClean, had it fitted when we had the combi fitted in Summer. It's great, no messing with draining etc, and dead easy to clean.