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Posted (edited)

What ho.  

 

I am hoping to soon be at a point when I can fill my Webasto central heating system for the first time.   Grateful for a sense-check from members... and probably further follow up questions to come.  

 

 

My volume calculations require around 80lts (rads, piperuns, coil, expansion tank plus a bit extra).   Pre-mixed 25% anti-freeze to water ratio, so 20litres of AF should do to 60litres water. 

 

1)   Webasto recommend IAT ethylene glycol (non-methanol based) AF  -  are there any recommendations on brand, 10year versus 2yr etc?  

 

2)   Is it worth using distilled water (it's a hard water area) in the final mix? 

 

I think I will do a plain tap water fill first in case of plumbing leaks and also to get a sense of the whole process, without worrying about salvaging the mix.  

 

 

 

Re. the Webasto itself: 

 

3)  Presume I am going to need to be running the Webasto to get the circulation pump working, to get the liquid moving through the system and dispel the air - I can't just fill up from the expansion tank and expect to get the system filled and air expelled? 

 

 

I don't have the fancy diagnostic kit for the Webasto - it's just installed as per the manual.

 

4)   Is there anything I can/should do with the Webasto at this first point of use - or, just fire it up via the controller and see what happens? 

 

I approach with trepidation... both for my general plumbing disasters and the first use of the Webasto, so appreciate any advice. 

 

 

 

 

TIA 

 

 

Edit - for brevity - i've not really described the system, but it's as per the Webasto installation guide, including "summer/winter" valves to isolate the radiators from the towel rail/calorifier.  The cally has isolation valves, one of which will act as a balance valve.  I have bypass valve in the return as per Webasto manual which when closed will force the return flow through the header tank to disperse air bubbles. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Edited by TandC
Posted
1 hour ago, TandC said:

 

I think I will do a plain tap water fill first in case of plumbing leaks and also to get a sense of the whole process, without worrying about salvaging the mix.

Not only as a leak check, but also to flush out any debris within the pipework and radiators.

 

1 hour ago, TandC said:

Webasto recommend IAT ethylene glycol (non-methanol based) AF  -  are there any recommendations on brand, 10year versus 2yr etc?  

https://www.screwfix.com/p/flomasta-concentrated-central-heating-inhibited-antifreeze-5ltr/4409r has been recommended on the forum before, as a combined inhibitor and antifreeze.

Posted
1 hour ago, TandC said:

What ho.  

 

I am hoping to soon be at a point when I can fill my Webasto central heating system for the first time.   Grateful for a sense-check from members... and probably further follow up questions to come.  

 

 

My volume calculations require around 80lts (rads, piperuns, coil, expansion tank plus a bit extra).   Pre-mixed 25% anti-freeze to water ratio, so 20litres of AF should do to 60litres water. 

 

1)   Webasto recommend IAT ethylene glycol (non-methanol based) AF  -  are there any recommendations on brand, 10year versus 2yr etc?  

 

2)   Is it worth using distilled water (it's a hard water area) in the final mix? 

 

I think I will do a plain tap water fill first in case of plumbing leaks and also to get a sense of the whole process, without worrying about salvaging the mix.  

 

 

 

Re. the Webasto itself: 

 

3)  Presume I am going to need to be running the Webasto to get the circulation pump working, to get the liquid moving through the system and dispel the air - I can't just fill up from the expansion tank and expect to get the system filled and air expelled? 

 

 

I don't have the fancy diagnostic kit for the Webasto - it's just installed as per the manual.

 

4)   Is there anything I can/should do with the Webasto at this first point of use - or, just fire it up via the controller and see what happens? 

 

I approach with trepidation... both for my general plumbing disasters and the first use of the Webasto, so appreciate any advice. 

 

 

 

 

TIA 

 

 

Edit - for brevity - i've not really described the system, but it's as per the Webasto installation guide, including "summer/winter" valves to isolate the radiators from the towel rail/calorifier.  The cally has isolation valves, one of which will act as a balance valve.  I have bypass valve in the return as per Webasto manual which when closed will force the return flow through the header tank to disperse air bubbles. 

 

 

As far as I am aware only the Ford Longlife and Prestone make 10 year life antifreeze.

 

https://shop.ford.co.uk/products/coolant-anti-freeze-5-litres-premium-long-life#:~:text=Longlife%2C silicate and nitrite free,corrosion up to 10 years.

 

https://prestone.com/product/prestone-all-vehicles-antifreezecoolant-ready-to-use/#:~:text=While ordinary antifreeze%2Bcoolant only,Protection handles the complete job.&text=Designed to last and protect,for 10 years%2F300%2C000 miles.

 

However changing the antifreeze on a boat is often a difficult and messy job, as you have to drain it into the bilge to pump it out. My engine holds 45 litres and my central heating system holds 25 litres. Don't use a solution greater than 25% antifreeze for a central heating system or it won't heat up and circulate properly. 

 

I changed mine for Ford 10 year antifreeze 11 years ago. The antifreeze component lasts indefinitely (as long it is not over diluted) but the anti corrosion component only lasts 2-10 years depending on the manufacturer. I have recently added Morris Ankorsol to my 11 year old antifreeze, as this tops up the anti corrosion component for 2 years, which is much easier to do than draining and refilling the system with fresh antifreeze.

 

https://www.morrislubricantsonline.co.uk/ankorsol-anti-corrosion-fluid.html

Posted

thanks - David, good point re. debris - there'll be sawdust and all sorts, despite sealing off open pipe ends etc wherever I could.

 

 

Cuthound - your central heating holds 25litres...  does mine seem ridiculously big at 80lts???  It's four double rads (of various sizes) and towel rail which have 5,000w output total.  I got the capacity from the radiator specifications so I think I'm correct... but yours seems very small in comparison with my working out, that's the same as just one of my radiators - which makes me think im doing something wrong?

 

 

With that Ford stuff - it's a straight concentrate to be mixed 25% - so 20 litres in 80 litres total should be more than enough.  And while that's £125, that should last 10years...  which indeed, considering the faff of draining 80 litres, flushing etc seems worth going for. 

 

 

 

 

 

Posted (edited)
23 minutes ago, TandC said:

thanks - David, good point re. debris - there'll be sawdust and all sorts, despite sealing off open pipe ends etc wherever I could.

 

 

Cuthound - your central heating holds 25litres...  does mine seem ridiculously big at 80lts???  It's four double rads (of various sizes) and towel rail which have 5,000w output total.  I got the capacity from the radiator specifications so I think I'm correct... but yours seems very small in comparison with my working out, that's the same as just one of my radiators - which makes me think im doing something wrong?

 

 

With that Ford stuff - it's a straight concentrate to be mixed 25% - so 20 litres in 80 litres total should be more than enough.  And while that's £125, that should last 10years...  which indeed, considering the faff of draining 80 litres, flushing etc seems worth going for. 

 

 

 

 

 

 

My central heating system comprises one large double radiator, and two smaller doubles (one half width and one half height) plus a heated towel rail in a 60 foot boat. I measured what I put in (one litre of de-ionised water followed by one litre of concentrated Ford antifreeze until each system was full).

 

Having been through the pain of draining and refilling once is what made me try using the Akorsol after the Ford antifreeze had been in for 10 years.

 

I was initially sceptical of the Ford antifreeze actually lasting 10 years, so each year I take a small sample of antifreeze from each system and drop a nail, an offcut of copper pipe and a snippet of aluminium in it. If after a month they haven't shown any signs of corrosion I consider the antifreeze still to have anti corrosion properties. The Ford antifreeze was still OK after 10 years, but I decided not to chance it further and after consulting with Morris Lubricants, started to use the Ankersol.

Edited by cuthound
Clarification
  • Greenie 1
Posted

I generally fill as much as possible before starting Webasto up, as if you get an airlock in the unit itself, it will fault out, 3 of those and you need it unlocking with a Webasto controller program.

So, fill header, keep pouring until as full as you can, then bleed radiators along system, one by one, topping up header tank as you go. Start with the rad last in the system, and work back to first. 

Once you think it's as full as you can get it, shut bypass valve and start system. This may take 2 goes unless you have drawn fuel right through to the heater unit as well as the pump.

Let it run, bleeding radiators again, topping to fill line as necessary.

  • Greenie 1
Posted

The whole "3 times and then you're buggered" situation doesn't fill me with joy... patience required.    But thanks - all good advice. 

Posted (edited)
1 hour ago, GUMPY said:

Distilled/deionised water every time. It's cheap enough on eBay.

 

Great - 75lts ordered... still seems like a hell of a lot of liquid...  

 

 

And found a 20lt drum of the Ford Super Plus in Leighton Buzzard which is easy enough to collect

Edited by TandC
Posted
On 21/01/2025 at 14:29, TandC said:

Cuthound - your central heating holds 25litres...  does mine seem ridiculously big at 80lts???

 

Yes! A three-bed semi with 8 rads usually holds about 100 litres....

 

 

Posted

this is crazy... this is what i've been thinking all along that surely this can't be right....  

 

 

The specifications of the radiators - which were sized to match the Webasto 5kw output - 

 

These are the online specifications for the one largest radiator - which has a stated volume of 21.59lts - that's nearly as much as Cuthound's entire system in one radiator! 

 

 

image.png.942d6ae6412d8440fec5753b892762aa.png
 
The total size of the system - in a 45ft widebeam - is:
 
Large radiator on starboard side in living room = 634mm x 1180mm = 21.59litres - 1470 watts at Delta T50
Medium radiator on port side in hall = 635 x 1000mm = 18.35litres - 1249 watts 
Small radiator on port side in living room = 635 x 826mm = 15.11litres - 1029 watts
Small radiator on starboard side in bedroom 635 x 826mm = 15.11litres - 1029 watts
Towel Rail = 3.63litres - 295 watts
 
Total litres in radiators: 73.79lts
Total Watts: 5,072watts 
 
 
Posted (edited)

You may find that as the Webasto runs at 80deg using the Delta T65 rating will give you a better approximation of the radiator wattage. @MtB can confirm or ridicule this.

 

Edited by GUMPY
Posted (edited)
39 minutes ago, GUMPY said:

You may find that as the Webasto runs at 80deg using the Delta T65 rating will give you a better approximation of the radiator wattage. @MtB can confirm or ridicule this.

 

This was some poor system design on my behalf if that's the case - and now I am really worried I've made a massive cock up.

 

I had been advised to use T50 as the basis of calculating the total radiator output wattage...  and then Webasto advise sizing radiators to the 10% over the boiler rated output, which would be 5,500w.  

 

If I use the published rad specifications of T65 (they don't use T70) - the wattage per radiator is as follows:

 

2068

1758

1447

1447

250 - (the specs are only given as T50, so it'd be a bit more!) 

 

This would give a total radiator output wattage as near to 7,000w!   That's well over the top...    we'll be boiled alive and the Webasto will be working its nuts off. 

 

Bollocks.  Have I made a huge error here....?

 

What are my options...    these rads are not cheap, plus all the plumbing has been done to their sizings.

 

Can I just turn them down on their valves (simple non-thermostatic ones)?  

 

Or, am I looking at having to replace radiators to get the output down? 

 

 

I could potentially swap the largest two radiators - which are both doubles - to singles - as I think the plumbing can stay the same then.   It would bring the total rad output at T65 to 5,591w total radiator output which would be bob on.    That would cost me £400 in two new radiators....  (and coming back to the original thread discussion which was about volume of liquid required would mean around 20litres less in total fluid in the system!)

 

Edited by TandC
Posted

It shouldn't be a problem having the Webasto running hard. In the days of HS diesel one always had more rads than needed to keep the heater on high so it didn't coke up. I don't see it as a problem to be honest it just means you will be warm 🤔

Posted (edited)
8 minutes ago, GUMPY said:

It shouldn't be a problem having the Webasto running hard. In the days of HS diesel one always had more rads than needed to keep the heater on high so it didn't coke up. I don't see it as a problem to be honest it just means you will be warm 🤔

hmm..... but, there's running hard - and then there's running short.

 

Will it not mean that it is so insanely warm inside that it needs turning off after a (too short) short period....? 

 

Which leads me to ask - what's the optimum run-time for a Webasto... whats the ideal kind of length of a programmed burst....   Thinking I'd have a programmed schedule (say, come on at 5am in the morning to provide a warm boat til 8am) -  come on at 5pm etc.  

 

 

Edited by TandC
Posted

My Eber used to run for 2hrs  until just before it switched down to low power.

We didn't rely on it as a primary source in winter as although it took the chill off nicely in the mornings it was also noisy.

On a boat I much prefer a stove for general heating as it can run 24/7 in winter with a diesel boiler as backup.

Posted
1 minute ago, GUMPY said:

My Eber used to run for 2hrs  until just before it switched down to low power.

We didn't rely on it as a primary source in winter as although it took the chill off nicely in the mornings it was also noisy.

On a boat I much prefer a stove for general heating as it can run 24/7 in winter with a diesel boiler as backup.

Yep - this is what I was planning too.  Stove for the majority (I get free seasoned wood, and so I let it go out overnight) - but the Webasto for those short programmed bursts before we leave for work, and in the evenings when required, or if coming home late etc.   

 

It's tricky as if I get the system running this weekend, it still isn't  a representative test as the boat is still awaiting paint and therefore windows.  So, I can't really tell whether the current system (with it;s potentially hugely over-sized/powered radiators) are going to a) cook us in our beds and b) require turning off in short order.

 

 

Posted
1 hour ago, TandC said:

Large radiator on starboard side in living room = 634mm x 1180mm = 21.59litres 

Doesn't look right to me. The overall area of that radiator is 0.748 square metres. Dividing 21.59 litres (0.02159 cubic metres) by that area gives an average water jacket thickness of 29mm!  Since a typical pressed steel radiator is about 50% water channels and 50% with the two sheets in contact, there's no way that can be right.

 

52 minutes ago, TandC said:

 

I had been advised to use T50 as the basis of calculating the total radiator output wattage...  and then Webasto advise sizing radiators to the 10% over the boiler rated output, which would be 5,500w.  

 

If I use the published rad specifications of T65 (they don't use T70) - the wattage per radiator is as follows:

 

2068

1758

1447

1447

250 - (the specs are only given as T50, so it'd be a bit more!) 

 

This would give a total radiator output wattage as near to 7,000w!   That's well over the top...    we'll be boiled alive and the Webasto will be working its nuts off.

If the webasto is rated at 5kW then that's all it can produce, so you won't boil alive. All that will happen is that with only 5kW to output the radiators will only be able to cool the circulating water by 50 degrees, so you will end up in the T50 position you have designed for.

Posted
4 minutes ago, David Mack said:

Doesn't look right to me. The overall area of that radiator is 0.748 square metres. Dividing 21.59 litres (0.02159 cubic metres) by that area gives an average water jacket thickness of 29mm!  Since a typical pressed steel radiator is about 50% water channels and 50% with the two sheets in contact, there's no way that can be right.

 

The depth is listed as 78mm though, which suggests Type 21 or 22  (effectively 2 radiators back to back). That would imply channels around 29mm deep (or a bit less, because the top and bottom rails will have greater volume).  That's more than any radiator I've fitted recently, but not totally implausible.

  • Greenie 1
Posted (edited)
11 minutes ago, David Mack said:

Doesn't look right to me. The overall area of that radiator is 0.748 square metres. Dividing 21.59 litres (0.02159 cubic metres) by that area gives an average water jacket thickness of 29mm!  Since a typical pressed steel radiator is about 50% water channels and 50% with the two sheets in contact, there's no way that can be right.

 

If the webasto is rated at 5kW then that's all it can produce, so you won't boil alive. All that will happen is that with only 5kW to output the radiators will only be able to cool the circulating water by 50 degrees, so you will end up in the T50 position you have designed for.

Thanks David.

 

They're all double-finned radiators - and these posh looking (to the eye of the beholder!) ones if this makes any difference to your calculation? 

 

https://www.bestheating.com/milano-aruba-anthracite-horizontal-designer-radiator-choice-of-size-78654

 

Quote:  If the webasto is rated at 5kW then that's all it can produce, so you won't boil alive. All that will happen is that with only 5kW to output the radiators will only be able to cool the circulating water by 50 degrees, so you will end up in the T50 position you have designed for.

 

 

I'm a dunce on the science behind this.... (as you can probably tell by now)...   I don't fully understand this statement (although I hope it can be true!)

 

 

Edited by TandC
Posted

We have Milano Alpha tall rads in the kitchen here as well as a "normal" radiator.

The Alphas take a lot longer to get hot than the "normal" rad, despite being fully open and right next to the manifold. I suspect this is due to the fact that they seem to be made of thicker steel than the "normal" rad.

 

Posted (edited)

I used the red 5 year antifreeze mixed with tap water in my Webasto CH system. Do household CH systems generally get filled with distilled or deionised water? Maybe some do but that would surprise me.

 

I take the view that unlike a freshwater system which accumulates scale and furrs up because it's constantly being refilled, any closed loop cooling system can only contain a finite amount of minerals. So it's not worth worrying about deionised or distilled water whether that's for an engine or a heater. Yes occasionally you'll add more cooling water but the quantities of minerals are tiny.

 

The only airlocks I found were at the top of the rads which were easy to bleed and at the pump of the Webasto itself which I bled by carefully opening a tiny gap between the car heater hose and the spigot on the unit. 

 

 

Edited by blackrose
Posted
28 minutes ago, blackrose said:

I take the view that unlike a freshwater system which accumulates scale and furrs up because it's constantly being refilled, any closed loop cooling system can only contain a finite amount of minerals. So it's not worth worrying about deionised or distilled water whether that's for an engine or a heater. Yes occasionally you'll add more cooling water but the quantities of minerals are tiny.

I've never seen a household system that wasn't filled from the mains; you add a corrosion inhibitor, most of which claim to prevent limescale (presumably by neutralising the calcium ions). No need for antifreeze though.

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