Need help completing Webasto water based heating system

[Lomax]

Hi all,

I've got a second-hand Webasto Thermo Top C which is fully working but lacks all external components (except the wiring, which thankfully is still attached). Using this I would like to get a basic heating system up & running as quickly (and cheaply) as possible, while not skimping on safety. I would like to have two fan matrix radiators in the cabin, and connect these to the heater using PEX. I also know I need a skin fitting for the exhaust (I have a steel hull, so don't need anything elaborate), an air-tight muffler and some exhaust tubing. Dosing pump, filter and fuel connection also needed. For the time being I'm happy to run the heater with a simple on/off switch, so not looking for a dedicated controller.

• Is it ok to use PEX for the heating?
• Anything I need to think of when running the pipes?
• Will I need a separate circulation pump for 6m pipe (one way)?
• What size/power do the matrix heaters need to be?
• Any suggestions for a cheap matrix option?
• Will I need an expansion vessel, and if so how big does it need to be?
• What should I use to fill the system, glycol/antifreeze?
• Can I use any dosing pump, or does it need to be a specific model/size?
• Have I missed anything?

Grateful for input!

 

[rotrax]

I used two heated towel rails, one in the heads and one on the end of the galley unit. A long narrow radiator was used under the setee berth. They were joined by 'speedfit' plastic pipe. From club members and reports on here I discounted fan matrix type as overcomplication. Their only advantage appeared to be smaller size.

Not only did we get hot water for showers and washing, within twenty minutes it was down to tee shirts inside our Gibsea 96.

Fabulous bit of kit the thermo top.

 

[Lomax]

I used two heated towel rails, one in the heads and one on the end of the galley unit. A long narrow radiator was used under the setee berth. They were joined by 'speedfit' plastic pipe. From club members and reports on here I discounted fan matrix type as overcomplication. Their only advantage appeared to be smaller size.

Not only did we get hot water for showers and washing, within twenty minutes it was down to tee shirts inside our Gibsea 96.

Fabulous bit of kit the thermo top.

Thanks, I hear you on the towel rails; I had planned to fit one in the (yet to be built) heads, but having a second one in the galley sounds like a great idea. I'm thinking of using matrix heaters for now since their small size makes them easier to fit, but long term I want to have slim/low radiators along the port side of the cabin (like the ones found on old buses). I have not been able to locate a source for these, so if anyone has any suggestions... TBH I just want to get warm - it was 8°C on board this morning

 

[rotrax]

An impecunios chap scrounged some copper tube and had it made into three long lengths with a 'U' at each end plus connectors for the 'Speedfit' pipe. He fitted it under his long settee berth. Worked as good as my long radiator and cost very little.

 

[Lomax]

An impecunios chap scrounged some copper tube and had it made into three long lengths with a 'U' at each end plus connectors for the 'Speedfit' pipe. He fitted it under his long settee berth. Worked as good as my long radiator and cost very little.

Another great idea, thanks! But what about galvanic corrosion, won't that be a potential problem if using copper tube? I'm assuming that the Webasto heating surface inside the unit is made from some aluminium alloy?

 

[PaulRainbow]

Another great idea, thanks! But what about galvanic corrosion, won't that be a potential problem if using copper tube? I'm assuming that the Webasto heating surface inside the unit is made from some aluminium alloy?

Common practice to use copper, chances are the heater matrix would also be copper. I would avoid the heater matrix option.

 

[Lomax]

Common practice to use copper, chances are the heater matrix would also be copper. I would avoid the heater matrix option.

Ok, thanks! Why not use matrix heaters, is it the noise?

 

[PaulRainbow]

Ok, thanks! Why not use matrix heaters, is it the noise?

Boats i've been on with matrix heaters haven't seemed that efficient and then you have fans running, so added noise. The copper tube option sounds good.

I would look up the fitting instructions ref a circulation pump. Also, check the part number for the dosing pump to see if it's the same as other systems, i very much doubt they will all be the same.

This site should be helpful : Technical Manuals, PDFs & Guides for Webasto & Eberspacher

 

[CrikeyChris]

I have two Kalori Silencio 2 5.5kw matrix heaters connected to a Thermo Top C. The heater will run for a short (20minutes) with coolant flow directed to just one matrix, with fan on full but sooner or later the thermo top will turn itself off. I think matrix heaters are rated on the basis of a 100degree C difference between coolant and air flowing over the matrix.So if the coolant was 90 degree C the air would need to be minus 10 degrees C. Even so I have been surprised at how little heat they produce. The thermo top c needs to run out at least half power - if at that level the coolant temperature continues to rise it will switch off. Not so much a problem if you plan to always run both matrices at once. The silencio range purports to be low noise and perhaps they are compared to the ones with more poweful fans (needed to push the air through ducting) but they can still be a bit obtrusive. They use significantly less power though. The matrix material appears to me as aluminium.
When setting mine up I measured the output voltage from a proper Webasto controller and was surprised it was 10.5 V.
The manual will say what the maximum pipe run is - MellorOnline - Technical help- Downloads will have one.
You will need an expansion tank - mine is 5litres.Webasto say the minimum collant quantity is 4litres but suggest 8 litres is better.
A very knowledgeable poster on here some years back (Davidxxxx? East Coast based) who was a professional installer recommended a pressurised system. Diagrams for this canalso be found on the MellorOnline website.
A mixture of antifreeze and distilled water will be needed.
Webasto fuel pumps are expensive, even second hand but lots of aftermarket pumps are on offer on ebay and elsewhere but I have no first hand experience of them. A search for Webasto 30.2 fuel pump should bring up some results.

 

[Lomax]

I have two Kalori Silencio 2 5.5kw matrix heaters connected to a Thermo Top C. The heater will run for a short (20minutes) with coolant flow directed to just one matrix, with fan on full but sooner or later the thermo top will turn itself off. I think matrix heaters are rated on the basis of a 100degree C difference between coolant and air flowing over the matrix.So if the coolant was 90 degree C the air would need to be minus 10 degrees C. Even so I have been surprised at how little heat they produce. The thermo top c needs to run out at least half power - if at that level the coolant temperature continues to rise it will switch off. Not so much a problem if you plan to always run both matrices at once. The silencio range purports to be low noise and perhaps they are compared to the ones with more poweful fans (needed to push the air through ducting) but they can still be a bit obtrusive. They use significantly less power though. The matrix material appears to me as aluminium.

Thanks, lots of useful info there! It sounds like I should be looking for passive radiators instead. I could fairly easily fit a 150-170cm long one in the saloon, and one 100cm long in the cabin, but I have no idea what I should be looking for - would standard domestic radiators work? What about material and the risk of galvanic corrosion?

You will need an expansion tank - mine is 5litres.Webasto say the minimum collant quantity is 4litres but suggest 8 litres is better. A very knowledgeable poster on here some years back (Davidxxxx? East Coast based) who was a professional installer recommended a pressurised system. Diagrams for this canalso be found on the MellorOnline website.
A mixture of antifreeze and distilled water will be needed. Webasto fuel pumps are expensive, even second hand but lots of aftermarket pumps are on offer on ebay and elsewhere but I have no first hand experience of them. A search for Webasto 30.2 fuel pump should bring up some results.

I knew a header/expansion tank would be needed but wasn't prepared how expensive these are - the original Webasto 5L tank costs well over £100! For a plastic tank! Does anyone have any suggestions for a cheaper option? There's a lot of chinese aluminium header tanks on eBay for around £40, but they seem to top out at 2.5L capacity...

As for the fuel pump, I guess if the required volume per tick was known then I could get a chinese copy with the same specification - but a friend of mine did this and it soon failed, shedding lots of metal filings into the fuel. If I go down this route perhaps a second filter after the pump could be worthwhile?

Edit: Found this in the Thermo Top C/E Marine Water Heater Installation Instructions:

For information the fuel dosing pump dispenses 0.063ml of fuel every ‘tick’.

 

[Lomax]

Looking at "normal" radiators, I am surprised by how low power they seem to be - for example a single panel 160x30cm radiator has an output of just 1000W with a delta T of 60°C, or have I misunderstood something? I can only (easily) fit two radiators, one 160cm long and one 100cm, which together won't come anywhere near 5kW, so I'm not sure what to do. Perhaps combine radiators and a matrix?

 

[Lomax]

While it appears to be well established that frequently cycling one of these heaters on/off will cause issues, I've seen differing opinions on whether cycling between full & half power causes more wear and/or coking - can anyone clear this up? I think having enough dissipation to keep it running on full will make it uncomfortably warm on board, not to mention the fuel cost. Based on electric fan heater use 2.5kW seems like it should be enough to stay comfy on a typical winter day, since a 2kW fan heater gets reasonably close. 2.5kW is also a more realistic amount of dissipation from passive radiators - I wouldn't know where to put additional ones. My boat is 45' loa with a 10' beam, but I don't intend to heat the wheelhouse or forecastle, which leaves a ~20' by ~10' living area (though it's only 8' wide on the inside, above the gunwales). I have perfect locations for two radiators: one can be 55" wide and the other 40" wide - both 20" tall. Using basic single panel single convector radiators (I don't want them to be too deep) it looks like I'd get something like 2.1kW of heat dissipation - add to that the radiation from the pipework and I'm probably pushing 3kW in total (based on 70W/m for the pipes). Will I damage the heater with this set-up?