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Struggling to get the Webasto Top C to start up.


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Just had a another look and another go at enhancing the photo.

 

I can now identify the circulating pump so if you take the rearmost hose (the hot outlet) off the bulkhead fitting and place your thumb over the fitting itself to stop water back flowing from the header tank and catch what comes out of the hose. I think you will get some alternate slugs of water and air. When no more air comes out quickly put the hose back on. (I still think fitting bleed points would be a better long term solution).

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47 minutes ago, Tony Brooks said:

Remember that it is best to consider that any air trapped in pipework will NOT be forced to move downwards and will be very likely to stop circulation. Air can only move upwards.

Would the air not move downward even if it was being pushed by water? I think Mike mentioned earlier that once the airlock is dealt with any remaining air in the system should be pushed around and find the natural high points in the rads and header tank etc.

 

The supply pipe to the webasto will always enter on a bend, which means it will have its own little air trap there. Can anyone recommend a bleeding valve which would fit onto the black hose pipe?

 

I will try bleeding the unit again tomorrow when the sun comes back. I managed to get a few bubbles out of my new bleed valve coming off the calorifier but am fairly confident that the airlock has to be between the header tank and the Webasto. I can't work out why it would be after the Webasto on the flow pipe, and even if it was it wouldn't cause any issues as it would be pushed around the system until it finds a high point. The issue must be that there is air in the return (supply) pipe which flows directly from the header tank down to the Webasto.

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6 minutes ago, Kelbs said:

I think Mike mentioned earlier that once the airlock is dealt with any remaining air in the system should be pushed around and find the natural high points in the rads and header tank etc.

 

The point being that the natural high points each need a way for the air to escape. A rad has an air vent, the header is open to atmosphere. You need to identify ALL the high points that don't have an air vent, and fit one to each.

 

 

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4 minutes ago, Kelbs said:

Would the air not move downward even if it was being pushed by water? 

 

Only on small bore pipe with a much more powerful pump.  The engine pump can often blow the air out of a calorifier coil but it's on a B* great engine so the power is not low, the Webasto pump is low power because otherwise it would have to use loads of amps instead of the 3 it does.

Fit a T piece with the T pointing up and then put any decent valve on it or even an automatic bleed valve, but in my experience they drip forever.

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10 minutes ago, Detling said:

Only on small bore pipe with a much more powerful pump.  The engine pump can often blow the air out of a calorifier coil but it's on a B* great engine so the power is not low, the Webasto pump is low power because otherwise it would have to use loads of amps instead of the 3 it does.

Fit a T piece with the T pointing up and then put any decent valve on it or even an automatic bleed valve, but in my experience they drip forever.

Any advice on where I could find a T for the 28mm hose? And then what sort of valve could I put on that?

 

I'll try to call in to The Boat Yard after work tomorrow and see what they have.

 

Edited by Kelbs
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If all else fails:

 

Get a 28mm compression T but probably one with a 22 or 15mm fitting where you will fit the bleed point and two spare olives and a short length of 22mm pipe cut in two.

 Fit the two lengths of pipe into the fitting and do them up tight.

Remove the two pipes and slide the nut off the free end.

Refit the pipes using the spare olives.

You now have pipes with just olives on the ends.

Push the hose well onto the pipes and use hose clips on the hose on the T side of the olives.

 

Alternatively you may be able to get a couple of hose barb fittings to screw into a suitable T.

 

Personally I would use a radiator bleed valve with suitable adaptor(s). The T does not need to an equal T, you can get them with one reduced branch or with a BSP thread to screw into but you may need a really good plumber's supplier for 28mm.

 

Edited by Tony Brooks
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29 minutes ago, Kelbs said:

Would the air not move downward even if it was being pushed by water? I think Mike mentioned earlier that once the airlock is dealt with any remaining air in the system should be pushed around and find the natural high points in the rads and header tank etc.

 

The supply pipe to the webasto will always enter on a bend, which means it will have its own little air trap there. Can anyone recommend a bleeding valve which would fit onto the black hose pipe?

 

I will try bleeding the unit again tomorrow when the sun comes back. I managed to get a few bubbles out of my new bleed valve coming off the calorifier but am fairly confident that the airlock has to be between the header tank and the Webasto. I can't work out why it would be after the Webasto on the flow pipe, and even if it was it wouldn't cause any issues as it would be pushed around the system until it finds a high point. The issue must be that there is air in the return (supply) pipe which flows directly from the header tank down to the Webasto.

When filling the system it starts to fill from the lowest point and the water flowing in gradually pushes the upwards until the system is full but if you have any high points such as the calorifier coil or the ends of those hoses air will be trapped. At that time there is no normal circuit flow, just the water level rising and if it has no up hill way out the air will be trapped.

 

As already explained a number of times centrifugal pumps can not pump air so air in the pump stops circulation. Detling explained the other part of it. Simply not enough power or volume, especially in large pipes where there is enough space for water to creep past under the air.

 

 

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Drop the heater as low as the flexible exhaust will allow.  While you're about it, fit isolation valves in the black hoses, to allow  removal of the unit for service or swop out, without draining the whole system. Get a spare unit off Ebay for that cold night when the unit packs up and you really want some heat.

 

And get a lead and some diagnostic software!

 

Just my opinion!!!!

 

  • Greenie 1
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Thanks for that Tony. I couldn't get the plastic pushfit pipe to fit inside the felxiable pipe, even when heated and lubricated, does the copper pipe have a smaller outer diameter, if so then that may well work.

 

Just thought and they actually have to be the same size to fit into the same fittings. 

Edited by Kelbs
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15 minutes ago, Kelbs said:

Thanks for that Tony. I couldn't get the plastic pushfit pipe to fit inside the felxiable pipe, even when heated and lubricated, does the copper pipe have a smaller outer diameter, if so then that may well work.

 

Just thought and they actually have to be the same size to fit into the same fittings. 

You can fit brass compression fittings onto plastic pipe as long as you use metal inserts in the plastic pipe and do not over-tighten it. A suitable compression to BSP fitting (maybe a compression - BSP - BSP Bras fitting) will allow you to fit a hose tail.

 

The bulkhead fitting seem to have a BSP thread with a hose tail screwed onto it. I don't know the size but it looks nowhere near 28mm. You should be able to unscrew the hose tails and fit a suitable T onto the bulkhead fitting with the hose screwed onto it to take the hose.

 At the boiler end you can use a very short length of hose on the  boiler and then a BSP T with hose tails. As I said I very much doubt B&Q or even Screwfix will stock what you need or even know what you are talking about.

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Right, quick update. I went into the boat yard to buy various bits for the bleed points but was advised to try bleeding the webasto unit again. This advice was from a Webasto installer. I've just finished bleeding and there was a lot of air in there but I think this was mostly steam from the boiling of the water. Apparently the pump is plenty strong enough to push the air bubbles to the natural bleed points.

 

Still there is no real progress.

 

The pump seems to work fine for a minute or two, I can hear the water moving around the inside of the boat but then heater starts to heat up the pump appears to turn itself off. So I am now thinking that it may be a pump issue instead of an airlock.

 

I opened the pump up, as recommended by the seller, and turned the blades inside which moved freely, which would indicate that the pump is ok. Perhaps its an internal electrical problem? I have no idea. 

 

I think I may just send the unit back, unless there are any Webasto installers who service the Bath area and fancy coming out over the weekend?

 

 

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Said it was air at the start drop the webasto unit so it is near the floor it’s only three screws to do this as the exhaust and fuel pipe will bend this will make it so the water pipes supplying unit are not going uphill to unit getting rid of air traps

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3 minutes ago, chevron said:

Said it was air at the start drop the webasto unit so it is near the floor it’s only three screws to do this as the exhaust and fuel pipe will bend this will make it so the water pipes supplying unit are not going uphill to unit getting rid of air traps

I've bled the air out of the system though, I don't think this is the issue.

 

Dropping the unit will lower its overall height but the supply pipe will always have a bend, creating a little possible air trap, no matter how low it goes. Regardless of this I have spent the last two hours bleeding litres and litres of coolant out of the pipes, which would have pushed any air out, but the unit is still boiling the water and the pump seems to turn off. I don't see why the pump would turn off while the unit is still heating water if there was air trapped.

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This is from the manufacture fault finding site The installation location of the heater should be as low as possible to ensure self-venting of the heater and circulation pump. This applies in particular to the circulation pump (Thermo Top E and C only), which is not self-sucking.
The circulation pump may be installed in the location provided on the heater or remote from the heater integrated in the coolant circuit. The correct direction of flow through the heater must be observed (coolant outlet on top, coolant inlet on bottom), otherwise malfunctions may result. Are you sure that the pipes are also the right way round connecting to system 

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Ok, I've just lowered the pump by about 8 inches. When it says that the pump is not self sucking, does that mean its relying on the water feeding itself into the pump, then the pump can push it around, not pull it as well?

 

It still cut out, I will try draining the excess steam now (already scolded myself once today) then I will attempt a restart.

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1 hour ago, Kelbs said:

Ok, I've just lowered the pump by about 8 inches. When it says that the pump is not self sucking, does that mean its relying on the water feeding itself into the pump, then the pump can push it around, not pull it as well?

 

It still cut out, I will try draining the excess steam now (already scolded myself once today) then I will attempt a restart.

Yes and no - The pump can not either suck or blow air. If it tries the pumping impeller will just spin in the air and pump nothing. It may also do this if the pump is filled with half and half air and water. The pump relies on the head of water created by the header tank to initially fill the pump but with your pump and unit where it is the filling process is very likely to trap air in the pipework running to and from the boiler and also in the boiler itself unless you have a way of letting the air out (bleeding it).

 

Once the system is full and totally free of air then as the pump impeller spins it throws water outwards, creating a depression close to the inlet so water is drawn in so at that stage it is both blowing and sucking. As this is a closed circuit and water is considered incompressible the water expelled from the pump will find its way back into it to be circulated again. That would happen without the impeller creating a depression but it does so it all helps circulation.

 

Personally I have seen too many air-locked systems to put much credence in the advice that the pump will push air to the highest point, especially with 28mm pipework.

 

QUOTE:

I've bled the air out of the system though, I don't think this is the issue.

 

Dropping the unit will lower its overall height but the supply pipe will always have a bend, creating a little possible air trap, no matter how low it goes. Regardless of this I have spent the last two hours bleeding litres and litres of coolant out of the pipes, which would have pushed any air out, but the unit is still boiling the water and the pump seems to turn off. I don't see why the pump would turn off while the unit is still heating water if there was air trapped.

 

ANSWER

 

Because the water in the boiler boiled because of no circulation so the boiler overheat thermostat shut it down to prevent damage. Are you sure just the pump shuts down and not the whole unit? If it does then to me (no real expert) it sounds more like a control system fault.

Edited by Tony Brooks
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38 minutes ago, Mike the Boilerman said:

 

How does this not present exactly the same difficulty in priming the non-self-priming water circulator?

 

 

 

That was my thought as well but kept quiet because the OP seems to have other advice to the contrary.

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I tried to upload a video of the webasto trying to start up but it was struggling. I'm still at the same point. I've bled plenty by of coolant from multiple points on the system. Once the heater has cut out due to over heating it starts it's shut down cycle (I've assumed) in which cold water is easily pumped around the system until the unit is back to being w normal cool temperature. I don't know how this could work if there was air trapped.

 

Sorry I didn't reply to the bucket trick but it didn't seem like the best test for me.

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I bought a kit off eBay with a second hand webasto and the bucket of water and a funnel to bleed was the method I used to make sure the unit worked before going to the time consuming job of fitting.At least it should prove if in fact the unit is faulty or if it is the way the unit has been installed. My own webasto system was then installed knowing what air locks can do and ran without bleeding at all due to the way the header tank and location of the units and pipes.

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