Webasto Thermo Top C - 15mm or 22mm pipes?

[canals are us?]

Glad they are sorting it out.

 

James.

[Mattiph]

Hi All. Sorry to hijack this old thread, but I'm interested in hearing how you are getting on with your new Webasto? I've read the discussion and your issue seems relatively similar to one I've been having over the years - corroding heat exchangers. I think someone in the thread hit the nail on the head there (although it may well not have been your only issue). Basically nothing else answers why your unit twice failed previously - the system worked, if inefficient.

What I think happened to your prior units is that some sort of corrosion occurred in the heat exchanger. I'm guessing some sort of direct galvanic corrosion, or copper particles from the calorifier coil settled in the Webasto heat exchanger beginning the corrosion process. Overtime the aluminium in the Webasto corroded through, at which point you have a "coolant dump", whereby all the coolant in the system above the burner (i.e. header tank and pipes) drains down through the pinhole in the heat exchanger created by the corrosion and out the exhaust (or through the condensate drain hole in the silencer and into the engineroom, or both). This explains the smoke (burning antifreeze) and the draining. It also explains the smoke on start-up of the new unit as that's the rest of the antifreeze still in the exhaust pipe slowly burning off. On your second unit, same thing happened. We're now a year later - has it happened again?

It's an issue I've been suffering from as well over past few years, albeit I now know the tell-tale signs before the heat exchanger starts to leak. Air gets into the heating system, generally storing up in the closest radiators, which need regular bleeding. Webasto begins cycling more frequently (probably due to air build up in the heat exchanger so poor dissipation of the heat through the system). Takes much longer to heat up water and rads, and not to same temperature as before for the same reason. Cycling then leads to carbonification of the burner, and start-up takes longer. At about that point my contained frustration bursts, I buy a new heat exchanger, switch the units and begin the predictable pattern once again... Sometimes I get a year out of it, usually less as I buy hit-and-miss second-hand units from scrapyards. 😬😅

It's my fourth heat exchanger now, so pretty sure of my general analysis (although not the chemistry - can't be sure where the corrosion comes from!!), and am searching for a durable solution. I've been thinking trying to work a way of fixing a magnesium anode to the heat exchanger, but doesn't seem feasible for reasons of size, flow, practicality, etc. So, I'm pretty sure I'm just going to drain the AF, clean the system again (hate this part of the job as I like to do things "properly" taking all rads off, flushing through etc) and put in some different AF, with additional inhibitors. LOTS of additional inhibitors. Saw on a separate thread Flomasta at screwfix could be an idea as you can get the AF and separate top-up inhibitors, which I will likely bulk-buy 🤣.

Really hope this resolves the issue as is getting exceedingly frustrating, despite now having all the isolating valves needed to easily isolate, replace and bleed with minimal fuss. I might then even splash out on a proper new heat exchanger unit if I feel it'll last a long time.

Wanted to write this reply for 2 reasons:

1. sounds like a similar issue to you, so good to check your current position (and what AF you used if your system is still sound!), and

2. despite lots of searching online, nothing clearly comes up as explaining what we've suffered, so thought it worth sharing my thoughts in case it can help others in their search for clues.

 

[Grassman]

Nearly 12 months on from them coming back and changing the main circuit of pipes from 15mm to 22mm, and re-routing some of the pipework, the Webasto has worked fine (I hope I'm not tempting fate here). The general opinion was that the Webasto units kept failing due to the strain of having to pump the coolant through 15mm pipes instead of 22m, and to a lesser extent due to the general poor quality installation, and not because of heat exchanger corrosion.

 

On a cautionary note, 2 of the others lasted for around 12 months before failing, so on that basis I won't know for sure whether the problem has been cured until a few months time.

[Tracy D'arth]

The corrosion of cast aluminium heat exchangers is a well known problem in domestic boilers too.  The corrosion inhibitor has to be aluminium friendly, like most car antifreeze is. Most manufacturers now use stainless steel for heat exchangers. I would never fit a gas boiler that had an aluminium heat exchanger having seen some Italian made units that fell apart in short order.

There is a school of thought that copper filings in the water will increase the corrosion. This is certainly true of steel domestic radiators which will rust through pin holes in 12 months if there is copper swarf in the bottom. For this reason it is advisable to cut all copper pipe on installation with pipe cutters rather than hacksaws.

I think that with a boat using plastic pipe the causes of corrosion would be the poor corrosion inhibitor and the action of localised boiling due to lack of circulation which would seem to be the cause in this case.

 

[Mattiph]

Thanks for this. Glad to note the new unit is still holding up! Also good to see that my self-diagnosis might not be far off, although it would have been even better if the corrosion didn't happen in the first place... I'll make sure to put in plenty of inhibitor next time and keep on dosing a bit every year to try to ensure continued protection.

[cuthound]

12 hours ago, Mattiph said:

Thanks for this. Glad to note the new unit is still holding up! Also good to see that my self-diagnosis might not be far off, although it would have been even better if the corrosion didn't happen in the first place... I'll make sure to put in plenty of inhibitor next time and keep on dosing a bit every year to try to ensure continued protection.

 

If the antifreeze content is too high, then the radiators will not get hot as the antifreeze can no longer circulate properly. 25% works well but anything stringer is a risk.

[Opener]

On 20/02/2022 at 22:43, Mattiph said:

Hi All. Sorry to hijack this old thread, but I'm interested in hearing how you are getting on with your new Webasto? I've read the discussion and your issue seems relatively similar to one I've been having over the years - corroding heat exchangers. I think someone in the thread hit the nail on the head there (although it may well not have been your only issue). Basically nothing else answers why your unit twice failed previously - the system worked, if inefficient.

What I think happened to your prior units is that some sort of corrosion occurred in the heat exchanger. I'm guessing some sort of direct galvanic corrosion, or copper particles from the calorifier coil settled in the Webasto heat exchanger beginning the corrosion process. Overtime the aluminium in the Webasto corroded through, at which point you have a "coolant dump", whereby all the coolant in the system above the burner (i.e. header tank and pipes) drains down through the pinhole in the heat exchanger created by the corrosion and out the exhaust (or through the condensate drain hole in the silencer and into the engineroom, or both). This explains the smoke (burning antifreeze) and the draining. It also explains the smoke on start-up of the new unit as that's the rest of the antifreeze still in the exhaust pipe slowly burning off. On your second unit, same thing happened. We're now a year later - has it happened again?

It's an issue I've been suffering from as well over past few years, albeit I now know the tell-tale signs before the heat exchanger starts to leak. Air gets into the heating system, generally storing up in the closest radiators, which need regular bleeding. Webasto begins cycling more frequently (probably due to air build up in the heat exchanger so poor dissipation of the heat through the system). Takes much longer to heat up water and rads, and not to same temperature as before for the same reason. Cycling then leads to carbonification of the burner, and start-up takes longer. At about that point my contained frustration bursts, I buy a new heat exchanger, switch the units and begin the predictable pattern once again... Sometimes I get a year out of it, usually less as I buy hit-and-miss second-hand units from scrapyards. 😬😅

It's my fourth heat exchanger now, so pretty sure of my general analysis (although not the chemistry - can't be sure where the corrosion comes from!!), and am searching for a durable solution. I've been thinking trying to work a way of fixing a magnesium anode to the heat exchanger, but doesn't seem feasible for reasons of size, flow, practicality, etc. So, I'm pretty sure I'm just going to drain the AF, clean the system again (hate this part of the job as I like to do things "properly" taking all rads off, flushing through etc) and put in some different AF, with additional inhibitors. LOTS of additional inhibitors. Saw on a separate thread Flomasta at screwfix could be an idea as you can get the AF and separate top-up inhibitors, which I will likely bulk-buy 🤣.

Really hope this resolves the issue as is getting exceedingly frustrating, despite now having all the isolating valves needed to easily isolate, replace and bleed with minimal fuss. I might then even splash out on a proper new heat exchanger unit if I feel it'll last a long time.

Wanted to write this reply for 2 reasons:

1. sounds like a similar issue to you, so good to check your current position (and what AF you used if your system is still sound!), and

2. despite lots of searching online, nothing clearly comes up as explaining what we've suffered, so thought it worth sharing my thoughts in case it can help others in their search for clues.

 

I'm NOT a user/owner - I have NO direct experience but one comment you make got me twitched. I watch reports about Webs and similar and I thought the big no-no was the use of an exhaust with a condensate drain down hole. Is that not a road vehicle option - CO poisoning an option!

Or have I misunderstood?

[Alan de Enfield]

1 hour ago, Opener said:

I'm NOT a user/owner - I have NO direct experience but one comment you make got me twitched. I watch reports about Webs and similar and I thought the big no-no was the use of an exhaust with a condensate drain down hole. Is that not a road vehicle option - CO poisoning an option!

Or have I misunderstood?

 

 

Absolutely correct - the automotive ones that folks buy off ebay (because they are cheap) are death-traps.

They are designed to run off higher voltages than boat batteries tend be at, AND as you say, they need a marine exhaust (which pushes the price well above buying the correct one in the first place.

 

A correct Marine exhaust :

 

 

Edited February 23, 2022 by Alan de Enfield

[Tony Brooks]

1 hour ago, Opener said:

I'm NOT a user/owner - I have NO direct experience but one comment you make got me twitched. I watch reports about Webs and similar and I thought the big no-no was the use of an exhaust with a condensate drain down hole. Is that not a road vehicle option - CO poisoning an option!

Or have I misunderstood?

 

You will see the image Alan has posted shows a U bend that forms a water trap so CO can't exit from the drain and the condensate keeps the water level topped up.

[system 4-50]

10 hours ago, cuthound said:

If the antifreeze content is too high, then the radiators will not get hot as the antifreeze can no longer circulate properly. 25% works well but anything stringer is a risk.

It won't circulate properly if some parts of the system have significantly different concentrations of antifreeze from other parts, a bit like air-locks, but even if the AF is evenly mixed and it does circulate, the heat carrying power is reduced as antifreeze has a lower capability than plain water.  I think 33% is the max recommended concentration.

[cuthound]

13 hours ago, system 4-50 said:

It won't circulate properly if some parts of the system have significantly different concentrations of antifreeze from other parts, a bit like air-locks, but even if the AF is evenly mixed and it does circulate, the heat carrying power is reduced as antifreeze has a lower capability than plain water.  I think 33% is the max recommended concentration.

 

Indeed, when I changed the central heating system antifreeze in mine I initially used a 50% mix, that I had left over from the engine., And the radiators wouldn't get hot. I dluted it to 25% and everything then worked normally.

[Mattiph]

Thanks All, insightful as always. Quite right re antifreeze concentration. My concern is to keep the corrosion inhibitor level topped up, not increasing the glycol (antifreeze) concentration. Hence why I will be using a AF for which I can buy compatible inhibitor. I'm thinking either Screwfix Flomasta or Sentinel 400 + 100 inhibitor top ups. I know about the silencer and circuitry issues too. I think marine ones are designed not to cut out until voltage drops lower than car batts (possibly 11.5V or something), but I never wish for my batts to get that low anyway. Can be a pain on cold winter mornings without full charge though. Someone once told me that marine ones also keep operating past a certain time, whereas car versions stop automatically, but I have no idea - mine appears to struggle to light below 12V, but doesn't auto cut out. As to silencer, it's in the ventilated engine room and there's no obvious way it would vent into the cabin space through the bulkhead. What minor levels of CO there may be that vent through the pin-hole drain rather than the main exhaust don't worry me much. My CO alarm registers CO concentrations and has never suggested an issue. But, quite right, ideally a marine silencer could be fitted.