On Tue, 04 Nov 2003 14:23:28 +0000, PoP
wrote:

On Tue, 04 Nov 2003 09:37:19 +0000, Andy Hall
wrote:

I doubt whether there would be any reaction between different brands
of chemical, but personally I would flush the lot and start again,
simply to have a known situation.

I have the same thoughts on this.

I know there is a recommended minimum level of inhibitor for a CH
system, but is it feasible that there might be a maximum level? So if
you've got inhibitor in there already and don't flush it out the
system could overdose on inhibitor?

Might sound implausible I suppose, but I expect heat transfer
constants in water and in inhibitor to be different, so if you get the
mix wrong.....

PoP

I'm not sure that overdosing (like double) with products like MB-1 is
a particular problem - Fernox recommend a 4% dosing but don't warn
about higher levels.

I did use some of their Alphi-11 product, which is a combined
antifreeze and inhibitor for my garage workshop circuit, which is
separate to the main house. While the pipework is well insulated, I
thought that there could be circumstances such as pump or other
failure where freezing could occur. With this product, there is a
maximum dosing level of 40%, which is good to -22 degrees, although I
used 30% which is good to -15 so a pretty safe bet.
ALphi-11 is glycol based and distinctly more viscous than water.

The circuit in question is sealed, and since this is a liquid product
rather than gel, it was necessary to come up with a means of delivery.
Fernox sells an injector product, which is, in effect, a modified
pumped garden sprayer. I bought a cheap sprayer from a DIY shed and
modified it with suitable pipework to have an adaptor to fit onto a
filling connection point. I was able to add the inhibitor (4
containers of it) quite easily this way and then added water to fill
and pressurise it in the same way. To begin with, the two liquids
didn't mix very well and there were circulation problems through the
radiators - one getting hot, the rest not. Judicious operating of
valves forced flow and mixing in the end, but it illustrates that
additives can have an effect. I've kept the injection machine in
case I have to do any work on the circuit. Since Alphi-11 is fairly
expensive, I can part drain the circuit into a large container and the
re-use the liquid. With some hard pumping, I can get 2 bar out of
the sprayer to pressurise the system.



..andy

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