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rgriffiths

Webasto heating problem

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I have a Webasto that is set up to heat three rads as well as the water in the calorifier. The radiators get red hot but the water only gets to luke warm and I cannot work out why.

 

The setup is quite simple as per the diagram and photo. I have bled the system, flushed it through and even installed bleeding valves at all the high places including the loop to the calorifier (which is horizontal under the bed). The raditor cut off valve as seen in the picture was added to direct more hot water through the calorifier loop but when adjusted (or closed) the Webasto just winds down as it has got up to temperature.

 

The whole sounds like an air lock in the calorifer loop but I just wondered if this set up is sensible, or should/could it be going the calorifer and then the rads in series?

Heating.jpg

Heating 2.jpg

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Having the calorifier in series before the rads would mean that when the calorifier is cold, all the heat would go in to it, leaving the radiators cold. Coming to a cold boat would mean waiting for the calorifier to heat up before getting any warmth anywhere else.

My boat heating is very different, with a stove, back boiler, calorifier and finrads in series, but it suffers from this problem. Takes a couple of hours before the stove puts out any heat when lighting it up with the boat cold as it is throwing every joule at the calorifier. Means shivering until the water is up to temperature.

Sorry, can't offer any suggestions on how to improve things with your Webasto.

 

Jen

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1 hour ago, rgriffiths said:

The raditor cut off valve as seen in the picture was added to direct more hot water through the calorifier loop but when adjusted (or closed) the Webasto just winds down as it has got up to temperature.

 

This tells us there is no water circulating through the calorifier. The task is to find out why. An air lock is the favourite candidate. Can we see a photograph of the calorifier please?

 

For circulation to happen we need three things:

 

1) A circuit

2) Fluid

3) Motive force

 

If all three of the above are present, circulation WILL occur. Therefore one or more of the above is missing. We know there is a motive force (from the pump) because the rads heat up. So iot must be 1) or 2), or both. 

 

 

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Thanks Mike. I have added a bleed valve at the top of the calorifer and bled this circuit from this point for a considerable time. I am fairly certain that there is fluid. There is also a circuit as per my diagram. Firstly I am interested to know if this set up is sensible and could potentially work.

Heating.jpg

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If the coil is higher than the enter and exit points of the pipe into the calorifier then there could be air in it. On my horizontal tank I have one coil pipe at the bottom and one near the top so no air is trapped. 

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I have an Eberspacher and I expect your circuit is similar. Somewhere on the calorifier circuit there should be a valve to throttle the flow through the calorifier and balance the system.  You need to measure the temperature in and out of the coil, and the differential is how you know when it is set right.  If this balancing valve is too far open, the return line will be a similar temperature to the flow line and hot water returning to the heater will cause it to cycle as it will appear the system does not need more heat. If the balancing valve is too far closed, the return line will feel cool and there will be insufficient flow through the calorifier to produce hot water.   My money is on an air lock, but once you've fixed that or ruled it out, you should know where this balancing valve is and ensure that it is set according to the Webasto instructions.

  • Greenie 1

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13 hours ago, rgriffiths said:

I have a Webasto that is set up to heat three rads as well as the water in the calorifier. The radiators get red hot but the water only gets to luke warm and I cannot work out why.

 

The setup is quite simple as per the diagram and photo. I have bled the system, flushed it through and even installed bleeding valves at all the high places including the loop to the calorifier (which is horizontal under the bed). The raditor cut off valve as seen in the picture was added to direct more hot water through the calorifier loop but when adjusted (or closed) the Webasto just winds down as it has got up to temperature.

 

The whole sounds like an air lock in the calorifer loop but I just wondered if this set up is sensible, or should/could it be going the calorifer and then the rads in series?

Heating.jpg

Heating 2.jpg

Just out of interest, and because I'm just about to plumb in my own radiators, shouldn't the radiators have one side to the feed and one side to the return? 

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1 hour ago, Sea Dog said:

I have an Eberspacher and I expect your circuit is similar. Somewhere on the calorifier circuit there should be a valve to throttle the flow through the calorifier and balance the system.  You need to measure the temperature in and out of the coil, and the differential is how you know when it is set right.  If this balancing valve is too far open, the return line will be a similar temperature to the flow line and hot water returning to the heater will cause it to cycle as it will appear the system does not need more heat. If the balancing valve is too far closed, the return line will feel cool and there will be insufficient flow through the calorifier to produce hot water.   My money is on an air lock, but once you've fixed that or ruled it out, you should know where this balancing valve is and ensure that it is set according to the Webasto instructions.

My system has precisely that valve. As well as balancing the radiators on set up the valve was put in to the calorifier so it can be totaly isolated if we want or can be balanced with the heating rads so all works well together. When we have it shut off the rads get hot quicker than if we want to use the coil in the cauliflower when the rads take longer to get hot but do still get hot and so does the cauliflower. The trick is as you say the valve being at the right setting.

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The drawing is for a  "single pipe system" where the first radiator from the boiler gets hot, the  last one only tepid.

Was common on house systems years ago.

2 pipe system has a flow and return pipe to each radiator.

  • Greenie 1

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11 minutes ago, Boater Sam said:

The drawing is for a  "single pipe system" where the first radiator from the boiler gets hot, the  last one only tepid.

Was common on house systems years ago.

2 pipe system has a flow and return pipe to each radiator.

OK thanks for that. I'm planning a two pipe system. Rather like series v parallel for batteries!

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17 minutes ago, Boater Sam said:

The drawing is for a  "single pipe system" where the first radiator from the boiler gets hot, the  last one all of the radiators get only tepid.

Was common on house systems years ago.

2 pipe system has a flow and return pipe to each radiator.

 

Corrected that for you!!!

 

:D

 

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5 minutes ago, system 4-50 said:

Why should that be?  Can you explain why?

 

Because the motive force making the water divert from the bypass pipe underneath and go up through the radiator and back down again is less than microscopic. 

 

If one-pipe worked, why does everybody bother fitting two pipes?  

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8 minutes ago, Mike the Boilerman said:

 

Because the motive force making the water divert from the bypass pipe underneath and go up through the radiator and back down again is less than microscopic. 

 

If one-pipe worked, why does everybody bother fitting two pipes?  

So if the main pipe "under the radiator" were throttled slightly this might be overcome?  Fitting a one-pipe system is just so much easier to find room for.  I'm fitting rads for a webasto at the mo'.

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3 minutes ago, system 4-50 said:

So if the main pipe "under the radiator" were throttled slightly this might be overcome?  Fitting a one-pipe system is just so much easier to find room for.  I'm fitting rads for a webasto at the mo'.

 

Partly, but the bypass is there so the radiator can be turned OFF without stopping the other rads working. SO if you turn the rad OFF then the limited flow through the throttled bypass is all that is heating the rest of the system. 

 

If you don't want to turn individual rads OFF, then scrap the bypass and install them all in series. 

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2 minutes ago, Mike the Boilerman said:

 

 

If you don't want to turn individual rads OFF, then scrap the bypass and install them all in series. 

And then the first gets hot and the last is tepid!  Touche!

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On 17/10/2018 at 21:56, Mike the Boilerman said:

 

For circulation to happen we need three things:

 

1) A circuit

2) Fluid

3) Motive force

 

If all three of the above are present, circulation WILL occur. 

Unless there is a blockage. Do you KNOW that water can flow freely through the calorifier and associated pipework?

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