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Author Topic: Glycol vs...  (Read 566 times)
julian
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« on: November 05, 2019, 10:16:20 PM »

So, I understand that car antifreeze will kill you etc. you drink it.

...and that is the reason glycol is used.


But...


My system is a vented thermal store.  The body of the water will be filthy old stuff.  The dhw runs through a coil and is heated in demand.

Say if I filled my solar coil with deadly stuff, and the coil failed - it would make the body of the thermal store slightly more toxic to drink than it probably alreaddy is.

Say if the solar coil failed, I did not notice, and then the dhw coil failed?  Well the dhw coil runs at 3.5 bar anyway, so there is no chance of anything getting in there from the body of the store.  If the coil failed the store would overflow.

Which, sure, would release the antifreeze into the environment, which wouldn't be good.  But I'm imagining that there's a car somewhere right now overheating and doing the same.


I'm not really trying to reinvent the wheel.  Basically I've forgotten to order the glycol stuff and I have a load of car antifreeze here.  And I really can't understand why I can't use that?

So that's why I'm asking here!

Thank you.
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ecogeorge
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« Reply #1 on: November 05, 2019, 10:47:27 PM »

Assume (always a mistake) that you wish to protect against freezing ?
My controller (resoll 12v version) has a function to run pump when collector temp <5c -stops freezing.
Never had a problem in 11 yrs.
saves expensive antifreeze....
George
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oliver90owner
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« Reply #2 on: November 05, 2019, 10:55:52 PM »

Not sure of the question but assume you want to know why you should not use car type antifreeze in a domestic scenario?

Use the proper stuff and be done with it.  Simple reason is safety.

BTW both are glycols.  Car antifreeze is ethylene glycol - which is extremely toxic - and the proper stuff is dipropylene glycol, which, if of suitable purity, can be used in foodstuffs - so not toxic.  At least I think it is not monopropylene glycol (not toxic like ethylene glycol but not used in foods).
« Last Edit: November 05, 2019, 10:57:23 PM by oliver90owner » Logged
julian
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« Reply #3 on: November 05, 2019, 11:27:05 PM »

I'm honestly not looking for a confrontation, but how is the "proper" stuff any more safe in the setup I tried to explain in detail?

Again, the dhw coil is pressurised.  If *both* coils managed to fail at the same time, there would still be no way for the solar coolant to get into the potable water.  The tank would pressurise and the contents vent out of the overflow, at 3.5 bar.  It would be gushing out!
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oliver90owner
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« Reply #4 on: November 06, 2019, 07:51:36 AM »

Please yourself.  If any small leak from your system could accumulate, it could kill anything that drinks it - it is sweet and apparently attractive as a beverage.  Note the large numbers of people killed by unscrupulous(?) idiots who have used it to sweeten wine in the past, for instance.
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Countrypaul
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« Reply #5 on: November 06, 2019, 09:26:02 AM »

I'm honestly not looking for a confrontation, but how is the "proper" stuff any more safe in the setup I tried to explain in detail?

Again, the dhw coil is pressurised.  If *both* coils managed to fail at the same time, there would still be no way for the solar coolant to get into the potable water.  The tank would pressurise and the contents vent out of the overflow, at 3.5 bar.  It would be gushing out!

The main cause of problems with the wromg glycol is when things go wrong and it does not work as intended. For example when there is a cut in water supply and the tank leaks into the internal coil as there is no pressure in the coil that normally keeps the leak sealed. Or when someone else works on the system (say for example because you are ill in hospital) and they don't know that the glycol used is not the normal one).

It is your decision, just like wiring a house with no earth would be your decision, only you can decide if the saving is worth the risk to live with if someone gets seriously poinsoned b it.
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dimengineer
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« Reply #6 on: November 10, 2019, 09:55:18 PM »

I'm honestly not looking for a confrontation, but how is the "proper" stuff any more safe in the setup I tried to explain in detail?

Again, the dhw coil is pressurised.  If *both* coils managed to fail at the same time, there would still be no way for the solar coolant to get into the potable water.  The tank would pressurise and the contents vent out of the overflow, at 3.5 bar.  It would be gushing out!

The main cause of problems with the wromg glycol is when things go wrong and it does not work as intended. For example when there is a cut in water supply and the tank leaks into the internal coil as there is no pressure in the coil that normally keeps the leak sealed. Or when someone else works on the system (say for example because you are ill in hospital) and they don't know that the glycol used is not the normal one).

It is your decision, just like wiring a house with no earth would be your decision, only you can decide if the saving is worth the risk to live with if someone gets seriously poinsoned b it.

Agreed. That is exactly the sort of scenario that often happens. Everyone thinks of the normal operating situation and thinks "A is at higher pressure than B, so its OK" But you have to consider the "what ifs"
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Philip R
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« Reply #7 on: November 10, 2019, 11:04:26 PM »

Does your 3.5 bar coil have a suitable backflow prevention device fitted to it, to prevent Category 4 or 5 non potable water backflowing into the water main, (Category 1 Water) should it depressurize, say when a water main bursts? If you are found out to have poisoned the water undertakings water supply by using monoethylene glycol or methanol antifreeze, you could find yourself in Crown Court facing an unlimited punishment!

Philip R
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oliver90owner
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« Reply #8 on: November 10, 2019, 11:42:20 PM »

Never mind poisoning, the simple fact of contaminating the mains with non-potable water is bad enough to certainly land up in court.
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