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pgrange

Webasto thermo top c only warm

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Hello everyone 

 

I have a webasto top c heater connected to a calorifier, towel rail and 2 radiators  I ran the heater whilst connected to WTT. I ran only 1 rad upto 50 deg then opened the 2nd rad. Immediately the temp drops to 40 deg then after some time the temperature climbed and topped out at 47 deg. Opening the towel rail the temp dropped again and when the calorifier was opened the temp dropped to 35 deg and couldn't climb any further.  The rads have been balanced.  It's a 57ft boat so I'm wondering do I require an additional pump to increase the flow although there seems to many people running on similar boats with similar loads no problem at all. I'm only running the bedroom rad and towel rail which gets warm but it would be handy to heat the hot water at the same time. Any help would be greatly appreciated. 

 

Many thanks 

 

 

Peter 

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⁹Where are you measuring the temperatures?

What are the inlet and outlet temperatures at the heater after at least an hour with everything on?

What are the inlet and outlet temperatures at the cauliflower?

What size are the rads?

N

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1 minute ago, system 4-50 said:

When you've solved your problem I'd like to know more about your use of WTT.

I think the world is your turtle - That White Trailer Trash - is nowhere safe ?

 

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1 hour ago, Ex Brummie said:

What is the output of your Webasto, and what is the combined heating/ hot water load?

 

Thanks for replying. 

 

It's a 5kw heater. As for load everything on the boat was existing other than the towel rail which is 400w. Looking at the size of the rads I'd say 1kw based on similar design / size plus the calorifier 1.5kw? Rough estimate 3.5 to 4kw.

 

Thanks 

1 hour ago, BEngo said:

⁹Where are you measuring the temperatures?

What are the inlet and outlet temperatures at the heater after at least an hour with everything on?

What are the inlet and outlet temperatures at the cauliflower?

What size are the rads?

N

I'm just relying on the temperature as stated in Wtt. 

 

Thanks 

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1 hour ago, system 4-50 said:

When you've solved your problem I'd like to know more about your use of WTT.

Hi 

 

I got it just to see what it does. Its really monitoring software that can also log fault codes. Is there anything specific you'd like to know?I may be able help. 

 

Thanks 

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12 minutes ago, pgrange said:

Thanks for replying. 

 

It's a 5kw heater. As for load everything on the boat was existing other than the towel rail which is 400w. Looking at the size of the rads I'd say 1kw based on similar design / size plus the calorifier 1.5kw? Rough estimate 3.5 to 4kw.

 

Thanks 

I'm just relying on the temperature as stated in Wtt. 

 

Thanks 

For those of us who have no idea what you are talking about WTF is WTT ?

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1 minute ago, Alan de Enfield said:

For those of us who have no idea what you are talking about WTF is WTT ?

Oh sorry! It's diagnostic software. Webasto Thermo Test 

 

Peter 

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I don't think increasing the flow rate will do much, unless the Webasto is turning itself down because it has got up to running temperature.  Is it?

The temperature drop when opening up another device is to be expected, as you are adding cold water to the circulating system. The flow temperatures seem low, (especially the 35 degrees, which isn't even lukewarm.) although I've never measured ours. Our Webasto runs for an hour at a time, and is usually still on full output when shut down. It runs calorifier heating, and two radiators. More info required, I think, as per BEngo's post.

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2 hours ago, pgrange said:

Hi 

 

I got it just to see what it does. Its really monitoring software that can also log fault codes. Is there anything specific you'd like to know?I may be able help. 

 

Thanks 

Does it need a hardware componenent and if so, is it expensive?

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11 hours ago, system 4-50 said:

Does it need a hardware componenent and if so, is it expensive?

Yes it requires a USB dongle. The lead itself is comprised of 3 wires. 12v +ve and - ve supply plus a signal wire which connects in my case to the webasto wiring harness. I got mine on ebay for about £45 for both the dongle and a copy of the WTT software. 

 

Peter 

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11 hours ago, Iain_S said:

I don't think increasing the flow rate will do much, unless the Webasto is turning itself down because it has got up to running temperature.  Is it?

The temperature drop when opening up another device is to be expected, as you are adding cold water to the circulating system. The flow temperatures seem low, (especially the 35 degrees, which isn't even lukewarm.) although I've never measured ours. Our Webasto runs for an hour at a time, and is usually still on full output when shut down. It runs calorifier heating, and two radiators. More info required, I think, as per BEngo's post.

As I say I have about 4kw of load. I don't have any means of measuring the temp other than what WTT reports but I know just by touch alone its not very warm when all appliances are working.  

 

This morning I set the timer for 2.5 hours. WTT reports the heater running at "full combustion load" for just over an hour. It then goes into a shut down and cooling cycle before ramping up again even though the temp doesn't reach anywhere near its max. After the initial shut down the heater ramps up again with WTT reporting PL to FL which I read as Partial Load to Full Load.  This will then run at full load until the 2.5 hours are up and then shuts down and cools off.  

 

Any ideas? 

 

Thanks 

 

Peter 

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It sounds to me like, though you may think you have balanced the radiators, you haven't got the flow right. The symptoms sound to me like there's not enough flow in the radiators, so they don't dump enough heat and the return getting back to the Webasto is hot.  This will cause it to go to low output. Open all the radiators fully up and see how you get on. You should find a throttle valve in the calorifier circuit: as a rough set up adjust this (from cold) until the return is noticeably cooler than the feed, but not greatly so or cold. The exact instructions for this balance ought to be in the manual for fine tuning once you've got the thing up and running. 

 

Even once fully set up, your load isn't large for the size of heater - these like to be run hard or they start short cycling which will let them coke up.  I tend to run mine in bursts of an hour, listening for short cycling. Many run them  like home central heating, but they don't really like it.  

 

Of course, you may have another problem, but the above is worth a try before you go fixing a serviceable Webasto for want of a decent load.  Good luck!  :)

 

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2 hours ago, Sea Dog said:

It sounds to me like, though you may think you have balanced the radiators, you haven't got the flow right. The symptoms sound to me like there's not enough flow in the radiators, so they don't dump enough heat and the return getting back to the Webasto is hot.  This will cause it to go to low output. Open all the radiators fully up and see how you get on. You should find a throttle valve in the calorifier circuit: as a rough set up adjust this (from cold) until the return is noticeably cooler than the feed, but not greatly so or cold. The exact instructions for this balance ought to be in the manual for fine tuning once you've got the thing up and running. 

 

Even once fully set up, your load isn't large for the size of heater - these like to be run hard or they start short cycling which will let them coke up.  I tend to run mine in bursts of an hour, listening for short cycling. Many run them  like home central heating, but they don't really like it.  

 

Of course, you may have another problem, but the above is worth a try before you go fixing a serviceable Webasto for want of a decent load.  Good luck!  :)

 

Thanks sea dog. 

 

The flow to the radiators are open fully including the calorifier. I have the returns set from quarter to half a turn. Are you suggesting to open the return valves fully? 

 

Peter 

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58 minutes ago, pgrange said:

Thanks sea dog. 

 

The flow to the radiators are open fully including the calorifier. I have the returns set from quarter to half a turn. Are you suggesting to open the return valves fully? 

 

Peter 

Yup, at least temporarily to see how the Webasto runs with a full flow.  Restrict the calorifier a bit as (perhaps a bit counter intuitively) the hot flow needs to pass through a bit slower to dump heat into the tank and return to the heater at a lower temperature. Otherwise, with it fully open, it'll allow very hot water to pass through too quickly and return causing the Webasto to cycle.  The rads ought to dump enough heat for it not to be a problem there.

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1 hour ago, Sea Dog said:

Yup, at least temporarily to see how the Webasto runs with a full flow.  Restrict the calorifier a bit as (perhaps a bit counter intuitively) the hot flow needs to pass through a bit slower to dump heat into the tank and return to the heater at a lower temperature. Otherwise, with it fully open, it'll allow very hot water to pass through too quickly and return causing the Webasto to cycle.  The rads ought to dump enough heat for it not to be a problem there.

Thanks for that. I'll try that when I get back tonight ?

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5 hours ago, pgrange said:

This morning I set the timer for 2.5 hours. WTT reports the heater running at "full combustion load" for just over an hour. It then goes into a shut down and cooling cycle before ramping up again even though the temp doesn't reach anywhere near its max

I don't have a timer but I see the full load for just over an hour and then the shut down on my newly commissioned thermotop C so I have a similar problem.  It is amazing there is so little info (that I can find) on the net and from the manufacturer.  I will get WTT when I have fully recovered frrom my current Norovirus (excuse me, I have to go some place...).

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44 minutes ago, system 4-50 said:

I don't have a timer but I see the full load for just over an hour and then the shut down on my newly commissioned thermotop C so I have a similar problem.  It is amazing there is so little info (that I can find) on the net and from the manufacturer.  I will get WTT when I have fully recovered frrom my current Norovirus (excuse me, I have to go some place...).

Yes I've trawled all sorts of forums looking for info. An dark art indeed. I do know from trawling the net that some thermo top c heaters specifically the units originally designed for auto applications do shut down after an hour. My particular unit originally came from a Renault truck but with a timer it'll keep on running for longer than an hour. 

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It should ramp up to 82 degrees then cycle down to around 74, it sounds like the ECU is faulty and thinks the water temp is higher than it actually is.

Hope this helps, let me know, I have a good second hand one if you need it.

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33 minutes ago, mick55 said:

It should ramp up to 82 degrees then cycle down to around 74, it sounds like the ECU is faulty and thinks the water temp is higher than it actually is.

Hope this helps, let me know, I have a good second hand one if you need it.

I am dubious about the ECU being faulty.  This type of problem seems to occur more often than would be likely due to faulty ECUs.  But I am no expert.

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I am guessing that the temperature monitoring uses a thermistor and between ECU or thermistor I would suspect the thermistor first, if indeed a thermistor is used. If so is there any chance of you measuring its resistance across a range of temperatures and then comparing it with Webadto data ------------ if you can find it.

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1 hour ago, mick55 said:

It should ramp up to 82 degrees then cycle down to around 74, it sounds like the ECU is faulty and thinks the water temp is higher than it actually is.

Hope this helps, let me know, I have a good second hand one if you need it.

The heater has just been repaired and a new ecu fitted. 

28 minutes ago, Tony Brooks said:

I am guessing that the temperature monitoring uses a thermistor and between ECU or thermistor I would suspect the thermistor first, if indeed a thermistor is used. If so is there any chance of you measuring its resistance across a range of temperatures and then comparing it with Webadto data ------------ if you can find it.

If I only put 1 rad on the temperature will ramp up well last 50 degrees. I haven't run it too as I've been testing it but I think the temp reading the heater is reporting is accurate 

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You say it ramps up well past 50, what water temperature is the WTT actually showing on the graph? after an hour it should be showing 84 at full load before going down to part load, even if the flow is not good, at least some part of the system should be getting hot enough that you cannot keep your hand on it, the whole of the system cannot run lukewarm after an hour of full load, it is just not possible on a small system such as yours.

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