Central heating antifreeze and injection point

[Tim Watts]

I have UFH and an air blower in the conservatory... It's a good idea for comfort but it comes with a punishment: it's vulnerable to freezing.

So I'm going to stick some CH antifreeze in. Probably about 40l which would give about 30% dilution (I have the rad volumes from data sheets, but I need to measure out the pipes and estimate the UFH loops).

Because passive solutions are better than active solutions :)

This will protect to -11C which is lower than the lowest temperature I can find in SE England historic data so far. Not to mention, effectively we should be good for a lower temperature still due to thermal lag and averaging. Dunno - maybe -5C is good enough?

Anyway, tangible questions:

Q1) I need an injection point to use a standard "garden sprayer" type injector that's designed for a filling loop (that I don't have - WB

42CDi has a built in filling lever).

So I'd like to stick a ball valve in a rad leg with an appropriate thread on the end that is like a filling loop. So anyone know what that is? 3/4" washing machine, 1/2" or what???

Q2: It's a lot of antifreeze. So I'm going to DIY this after the system is fully debugged for air locks. So far I have Sentinel X500 as a candidate which is combined inhibitor - available online cheaper than B&M stores. The idea is we do this once and that's it for at least a few years. Which makes the cost fairly by the by.

But does anyone know of any cheaper products (but still decent - as in won't invalidate a Worcester warranty kid of decent)?

[Bob Minchin]

Never needed to fit antifreeze to my CH so can't help there but can you not inject at the boiler drain c*ck. If you have a magnaclean or similar (why not?) then they can be used to inject/add to the system I use a garden sprayer with a modified hose fitting on my solar thermal system for filling and can easily achieve 1.5 bar to overcome the system pressure if needed. There the connection is to a 1/4 valve and takes washing machine hose ends. just cut a hose in half.

I don't see why you can't use the solar glycol heat transfer fluid as that is happy up to 100C and more and down to what ever you would find on the roof in deepest winter. In solar applications it does not need any inhibitor but apart from the pump it is all brass/copper no iron

[David]

Is the conservatory system on separate piping from the rest of the house?

I thought the standard way to add treatment wasn't to inject, but to de- pressurise the system, drain some water off, then top up a radiator then re-pressurise.

Easiest is a towel rail if you have one.

You will presumably need to bleed some water off anyway to make space for the anti freeze that you are proposing to inject.

AFAICR that is what I did to add inhibitor to our system.

Cheers

Dave R

[Tim Watts]

That's behind a washing machine (or will be :) - but I have rad tails in the "plumbing" under/nextto stairs cupboard which would be a very nice location. Accessible would be nice as charging 40l of antifreeze is 8 refills of an injector :)

I do - but same, it's behind the machine. But just out of interest, how do you inject into those? There's a thingy on the top - there?

Ah - thank you :) And I did not assume a garden sprayer would produce that sort of pressure - but I suppose 1 - 1.5 bar is not that much :)

For 40l I'd have to drain down anyway - it's 30% of the system volume. So I'd probably combine it with a chemical flush.

Worth a try as the Sentinel injector (which looks suspiciously like a garden sprayer) is £100 !!!

Yeah - it's more about it being "compatible" on paper - new boiler, don't want to give WB any excuses :)

[Tim Watts]

Yes and no. Yes it is, back to a blender (to drop the temperature) then of course it mixes with the primary circulation water.

I just had a genius idea. That won't work...

I thought for one moment: what if we shove a plate exchanger in and make it a secondary system. But that does not solve the other pair of pipes that feed a Myson air blower in there. So I guess we're going to be charging the whole system with antifreeze.

It's more belt and braces if we went away over winter. In practise the heat from the house will keep it from freezing (and the fact it is protected from the wind unlike garden taps). And the UFH in the screed has a large amount of thermal lag so will probably see the daily average temperature, not the night minimum.

It's *just* if we're away, it's either isolate and drain, or stuff the system with -11C protection. For £230 once every few years, it's not worth not doing.

Yes - it will be a partial drain down. So I'd combine it with a flush and full drain/refill. Keeps everything shiny.

[Alan]

Or, do what most people do, and fit a Frost Stat in the coldest area. That will ensure you dont have any frozen CH pipes, and will be far easier and cheaper than putting anti freeze into the system. Your boiler already has frost protection (or should do, I havent fitted a WB for ages), and many stats/programmers also have a OFF/Frost setting, so you may be OK with what you've got already - just put the stat in the coldest place when you go away.

And dont worry about gas bills, they will invariably be smaller than the cost of 40 litres of antifeeze.

[Bob Minchin]

Maybe ask WB what the spec of the a/f should be?

I'm sure my filter has a injection device - not looked at it for a while. The sprayer I bought is a Silverline. Surprisingly good product compared to some things from that label.

[Tim Watts]

That's an active solution that depends on everything working, electricity being available (ie RCBO not tripped) etc.

I want a passive solution.

But not as reliable.

[Tim Watts]

Yes - might be worth a call - they do have a very helpful tech line. I've rung it before about the electrics.

Interesting - thanks. Silverline is normally a label I read as "do not buy!"

[tabbypurr]

If your Ch heats hot water for taps, as I assume it does, then you'll need the nontoxic antifreeze, and IIRC it's not cheap. I presume it's too late to fit an exchanger to isolate the conservatory ufh.

NT

[charles]

Surely the hot water for taps will be isolated from the boiler _ usually at the hot water storage cylynder.

[rmlaws54]

Is that in case the heat-exhanger springs a leak?

Robert

[Rob Morley]

You'd hope it would remain that way, if there was a toxin circulating in the heating circuit.

[Max Demian]

Like vodka .

[tabbypurr]

of course, assuming it's not an obsolete primatic. When pinholes develop you don't want toxic antifreeze in your mixer taps.

NT

[tabbypurr]

yes, you don't want toxic antifreeze in your mixer taps

NT

[charles]

wouln't that also apply to any anti-corrosion addative?

[Vir Campestris]

My header tank is lower than the top of my cold water tank - and I think it's always like that. Which means a pinhole leaks the other way.

I guess it will be different on a sealed system.

Andy