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Webasto central heating antifreeze amount


Bazza954

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hi all,

just serviced the boiler and decided to drain down the system and change the water as it's not been changed for a while, I have been advised by a Webasto dealer that the antifreeze level in the system should be 50%, this does seem to be rather a strong mix.

Any advice from the collective  before I go ahead and do this ?

The system holds 30 litres, so that would be 15 litres of antifreeze in total, is this too much ?

 

bazza

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50% ethylene glycol is rated to protect down to -37 degrees C.

It will also raise the boiling point of water to 129 degrees C. at sea level.

 

There is a chart https://www.fcsdchemicalsandlubricants.com/main/quickref/ethylene.pdf if it helps.

 

I usually go for 33% 'cos I'm a cheapskate and the boat is not in the Arctic.

 

There is a lot to be said for using the red stuff, propylene glycol, its kinder on pumps and the environment and is not toxic.

Edited by Boater Sam
added more
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12 minutes ago, David Mack said:

NMEA recommended Screwfix inhibitor at 25%.

 

Beat me to it. An advantage here is, as NMEA says,  that you can add inhibitor periodically to maintain the anti corrosive element which is what deteriorates with time. This might also be possible with automotive antifreeze, but with the Flomaster stuff you know that it is compatible.

Edited by Sea Dog
Compatibility
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2 hours ago, Sea Dog said:

Beat me to it. An advantage here is, as NMEA says,  that you can add inhibitor periodically to maintain the anti corrosive element which is what deteriorates with time. This might also be possible with automotive antifreeze, but with the Flomaster stuff you know that it is compatible.

But what are its anti freeze properties if you are not a live aboard?

 

If I was using automobile antifreeze I would buy ready mixed rather than putting tap water into the system

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42 minutes ago, Detling said:

Most ready mix is 10%   remember to pre mix before you add as otherwise you may get layering which is a pig to get rid of, much easier to mix in a jug and then add.

Very true, it will layer out in the radiators so you will get hot and cold bits

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1 hour ago, ditchcrawler said:

But what are its anti freeze properties if you are not a live aboard?

 

If I was using automobile antifreeze I would buy ready mixed rather than putting tap water into the system

Their recommended 25% mix protects down to -11c.  It's not the ordinary central heating additive, it's the antifreeze one.

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3 hours ago, ditchcrawler said:

 

 

If I was using automobile antifreeze I would buy ready mixed rather than putting tap water into the system

I'm going to use deionised water to dilute the antifreeze, not tap water as ours is from a borehole and goes through a softener which adds brine to alter the ph, so don't get salty water in the mix.

3 hours ago, Detling said:

Most ready mix is 10%   remember to pre mix before you add as otherwise you may get layering which is a pig to get rid of, much easier to mix in a jug and then add.

Thanks for the reminder to pre mix, I did know about that though.

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3 minutes ago, Bazza954 said:

I'm going to use deionised water to dilute the antifreeze, not tap water as ours is from a borehole and goes through a softener which adds brine to alter the ph, so don't get salty water in the mix.

Any idea what the difference is between deionised,distilled and rainwater?

 

It all baffles me

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1 hour ago, cuthound said:

I filled up my Webasto CH system with a 50% mix, as per instructions, only to find the radiators wouldnt get hot.

 

 

On the advice of NMEA and others on here, I diluted it to 25% and it has worked fine ever since.

 

 

That's interesting, maybe start off at 25%, I'm live aboard, so heating gets used most days during winter, not too worried about freezing up.

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2 minutes ago, rusty69 said:

Any idea what the difference is between deionised,distilled and rainwater?

 

It all baffles me

Nope, I'm not sure either, but it's got to be better than the tap water, I'm sure somebody will explain !

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25 minutes ago, rusty69 said:

Any idea what the difference is between deionised,distilled and rainwater?

 

It all baffles me

Deionised has had the ions (salts) removed. 

Distilled is boiled (evaporated) and re condensed, which removes almost everything. 

Rain water is like distilled mixed up with all the muck in the air. 

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1 minute ago, WotEver said:

Deionised has had the ions (salts) removed. 

Distilled is boiled (evaporated) and re condensed, which removes almost everything. 

Rain water is like distilled mixed up with all the muck in the air. 

Thankyou. 

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9 minutes ago, WotEver said:

Deionised has had the ions (salts) removed. 

Distilled is boiled (evaporated) and re condensed, which removes almost everything. 

Rain water is like distilled mixed up with all the muck in the air. 

Which in some cases is quite acid

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Increasing the percentage of antifreeze reduces the heat carrying capacity of the fluid as it is the water that does the work. Use 25% as recommended in the manual, where it is all explained. As always, as a last resort, RTFM! Oops, must remember the emoji - :D

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I would be wary of using de-ionised water. When I sold valves, in a previous existence, we had to avoid brass bodies, and nitrile seals, as the soft water degraded these materials.

Where you are uncertain of what materials are used in pumps etc., you never know what effect it could have. I would use distilled, unless you live in Birmingham, where you used to be able to use tap water to top up batteries.

Edited by Ex Brummie
Itchy finger before finishing post
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