I'm putting a radiator in my conservatory so I can use it on the odd day in the winter so I'm going to add Fernox alphi11 antifreeze to the system. How much do I need to add? They reommend a 25% mix, is there a quick way to calculate the ammount of water in the system so I don't have to drain the whole thing down.
Before anyone asks part of the system has stop valves so I don't have to drain down to fit the new rad. Thanks
The hard way. I needed to do this for a separate circuit that I have heating my workshop.
Find the radiator types or one close to it on a radiator manufacturer's web site. Obviously there are various types with one or two panels. Normally the data sheets give a water capacity in litres per section for a given height of radiator. Count the sections on each radiator in question and multiply out. This will be the largest amount.
For the pipework, guesstimate and treat it as a set of cylinders. Add up the 15mm runs and the 22mm (and other sizes) in terms of length (two legs remember). Multiply diameter by pi and by length to determine the volume, remembering to get the decimal point in the right place to determine litres.
The HW cylinder and boiler together you can count as 10 litres. Add another 5 for the header tank or pressure vessel.
As a sanity check in a typical house you will be between 50 and
150litres.Work out the Alphi-11 on that basis. It doesn't matter too much if you go to higher concentration than 25%. I have mine at about 35%.
.andy
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Volume of a cylinder = pi * radius^2 * length (not; pi * diam * length).
At last I've managed to contribute something to this group, instead of always asking!
You're absolutely right pi x d provides the circumference.
This was the deliberate mistake to make sure that people were paying attention.
Well that's my story and I'm sticking to it. :-)
.andy
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Also provides the area for circles where d = r^2 - so your original formula would work fine for pipes of 2cm diameter :-)
Err........... don't you mean 4cm diameter? Thus radius = 2 and radius squared = 4 = diameter (numerically, that is)
David
Yes! That's exactly what I mean. Or rather, I meant to say "would work for pipes of 2cm /radius/".
The radius squared multiplied by pi gives the area of a circle. Two times Pi multiplied by the diameter give the circumference. Pi multiplied by 4 then multiplied by the radius squared gives you the surface area of a sphere.
Or to put it another way:-
15mm tube = 7.57 metres/litre 22mm tube = 3.18 metres/litre;-) Dave
OK, so we're all arithmetically challenged today. :-)
.andy
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2 x pi x radius = circumference
.andy
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That would make more sense - the circumference is Pi x Diameter which is the same as Pi x Diameter x radius, the Diameter being twice that radius.
Why not drain off a rough 25% - say 25L if Andy is right - add this amount of antifreeze to the header tank and run the system for a few months until it's thoroughly mixed. (It's not going to freeze over the summer...).
Then take a small sample from the drain point and put it in the fridge ice-box or freezer.It shouldn't freeze at all in the former, and should stay liquid or at worst slushy in the latter.
If this antifreeze is glycol- based you might also get a good idea of its freezing point using a hygrometer designed for car radiators.
True, although it is worth getting it reasonably right because Alphi-11 (which is an antifreeze and inhibitor is around £17 per
5 litres..andy
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Is the conservatory on its own zone with a programmable room thermostat?
Mine will be, so won't require antifreeze, as the programmable thermostat has frost protection. It's pretty hard to freeze burst plastic pipe, too, so it might be an idea to plumb in that, rather than copper.
Christian.
What stops the antifreeze from evaporating in an open system? Have I missed something?
Regards Capitol
I don't think that the OP has said whether his is open anyway.
I used Alphi-11 in a sealed system.
I can't find anything on the container or the Fernox web site saying that it is not suitable for open vented systems.
.andy
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It's an open vented system and the rad will be on the same circuit as all the rest of the rads. I could put a frost stat in the conservatory but her indoors doesn't like the central heating to come on in the middle of the night hence adding anti freeze. I will drain it down over the summer then add the anti freeze. Thanks
Fair enough. I'd still use plastic pipe in a conservatory, though.
Christian.
Two points you should be aware of.
1) Anti-freeze contains glycols (ethylene or propylene). Ethylene glycol is cheaper, but it is toxic. In the US there are plumbing codes that specify the use of proylene glycol where there is any risk of the anti-freeze contaminating the domestic water supply, i.e., an indirect DHWS cylinder.2) The hot glycols in the anti-freeze will combine with any dissolved oxygen and will form acidic compounds; I can't recall the formulae. The solution will start off with a pH of 10 or 11 (alkaline). Once it becomes acidic (pH < 7), it becomes very corrosive, causing rapid galvanic corrosion. You need to monitor the pH and change the solution, or replenish the corrosion inhibitors to maintain the pH.
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