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Two heating sources on one circuit.....?


Kristian

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I hope you can all shed some light on my question as I have a thought on providing hot water on a narrow boat during summer.....basically 1 coil two heat sources?....so whats to stop me putting a Webasto in the original circuit to provide hot water only during summer (I've a Kabola E7 which i don't want running during summer).....As long as the new Webasto is "T"ed into the same flow and return so the two systems don't fight each if ever they run together.... and ensure its "T"ed in before the original circulation pump I can't see an issue?.....any thoughts would be great.....

 

Thanks Kristian.....

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You can do this using domestic type non returns in each circuit or cheap solar system 1/2 " BSP 12/24 volt motorized ball valves ( 1 normally open and 1 normally closed) in each circuit, wired so that they are energized when the Webasto is powered up

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Using a Webasto (assuming small evaporator like a Thermo Top) just to heat water is not a good idea as it will cycle due to the low volume of coolant and prematurely coke up. it might be better to allow both on the same circuit with no valves so the coolant volume is increased and a greater heat sink is provided if you must do it. Not saying it will not work, but it will not work efficiently and you will incur costs associated with more frequent service intervals.

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Check out Dunsley Neutraliser.

 

http://www.dunsleyheat.co.uk/neutralizer.html

 

 

Check it out by all means if you can. Their website give no clue about how it works, just makes a load of claims about how great it is.

 

Or used to anyway, last time I tried to get a grip on what what on earth they are.

I suspect it's just a large empty box with lots of pipe connections welded onto it.

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Check it out by all means if you can. Their website give no clue about how it works, just makes a load of claims about how great it is.

 

Or used to anyway, last time I tried to get a grip on what what on earth they are.

I suspect it's just a large empty box with lots of pipe connections welded onto it.

 

We have tried to figure out how this thing is supposed to work too and it just gave us both a headache.

 

As far as I can tell, you need to set up various electrically operated valves and sensors around the system as well as this magic box.

 

Mike, I had actually hoped you might be able to enlighten us!

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Check it out by all means if you can. Their website give no clue about how it works, just makes a load of claims about how great it is.

 

Or used to anyway, last time I tried to get a grip on what what on earth they are.I suspect it's just a large empty box with lots of pipe connections welded onto it.

When I was working in did a couple of projects with supermarkets, using Stirling engines to provide heat and electricity for all of the supermarkets needs (refrigeration was provided using absorption or adsorption chillers).

 

To allow the supermarket to function in the event of Stirling engine failure (a regrettably common occurrence, despite using four Stirling engines per site), the existing heating and chilling arrangements were retained.

 

To allow the Stirling engines and oil fired boilers to work on the same circuit, and even at the same time, a "common header" was used. This was simply a ring of large bore pipe to which all heat sources and loads were connected. Perhaps the Dursley Neutraliser works on the same principle?

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When I was working in did a couple of projects with supermarkets, using Stirling engines to provide heat and electricity for all of the supermarkets needs (refrigeration was provided using absorption or adsorption chillers).

 

To allow the supermarket to function in the event of Stirling engine failure (a regrettably common occurrence, despite using four Stirling engines per site), the existing heating and chilling arrangements were retained.

 

To allow the Stirling engines and oil fired boilers to work on the same circuit, and even at the same time, a "common header" was used. This was simply a ring of large bore pipe to which all heat sources and loads were connected. Perhaps the Dursley Neutraliser works on the same principle?

 

 

Yes this is exactly the principle I think it works on, but I don't know for sure having never seen one in real meatspace.

 

As Dursley go to endless effort to avoid saying exacrtly how it works, I suspect it is blindingly simple and they are worried that like with magic tricks, once peeps find out they will be all like "oh so that's all it is!", then have a go themselves.

 

One difference is that your ring of pipe will also need a pump, which the Dursley box does not.

Edited by Mike the Boilerman
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Looking at this Dursey Box thing, I have fitted some very large adsorption chillers using lithium bromide as the working fluid, It is not one of them. Then I was thinking Heat Pump but looking at the drawings it is not one of them. It finally clicked in my little skull how it works !!!! the heat is transferred by the use of heat pipes. I have made something similar for solar.before using heat pipes If I was a betting man it has heat pipes in it. Heat pipes are a fantastic piece of kit and don't require any power to operate.

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Looking at this Dursey Box thing, I have fitted some very large adsorption chillers using lithium bromide as the working fluid, It is not one of them. Then I was thinking Heat Pump but looking at the drawings it is not one of them. It finally clicked in my little skull how it works !!!! the heat is transferred by the use of heat pipes. I have made something similar for solar.before using heat pipes If I was a betting man it has heat pipes in it. Heat pipes are a fantastic piece of kit and don't require any power to operate.

 

 

https://en.wikipedia.org/wiki/Heat_pipe

 

But Sir, I don't see why the heat needs moving around inside the overpriced Dursley Magic Box!

 

The Dursley is a buffer, designed to allow multiple heat sources to power a heat load. What function, exactly, would a heat pipe perform inside a Dursley Box?

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Unless I have been looking at this in the wrong way, I was thinking or the question was two heating sources on one circuit. Well this can be easily be archived by using heat pipes, lets say we were using a plate heat exchanger heat supply in exchanged heat out to where ever it is required.

 

You could always use a motorised valve to change over to another heat source say you were using the engine water, and a diesel boiler. You then start getting problems.

 

What they have there is I expect a partitioned unit keeping each heat source separated. In the centre they have a buffer tank. The heat pipe can transfer heat through into the buffer tank without mixing them together. You would then use the stored heat in the buffer tank to heat what ever you want, you could say it is like a thermal store. All fluids are always kept separate at all times. The good thing about this is if you wish you can use heat transfer oil within the same system.

 

A typical 12 mm heat pipe can quite easily transfer 420 watts between fluids The HT series heat pipes can work up to 270c If I wanted a multi source heat exchanger this is the way I would go.

 

Google CRS Heat pipes for additional information, this is the company I have used before.

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The problems with two heat sources are not how to make it work, but how to make it work safely, and efficiently (efficient in the technical meaning).

 

Its easy to make the rads get hot when either heat source is ON, but firstly you stop the heat source that is ON also heating up the heat source that is OFF.

 

Next, if one is solid fuel you need to stop circulation when it gets cool if pumped, and guarantee circulation when it is hot. Regardless of what the controls are set to do.

 

Next, you need to do all this without cutting off an open vent pipe or cold fill to each heat source.

 

All this requires a fair bit of careful thought, and a fair bit of wiring, pumps, power etc. So what happens when tha batteries go flat?

 

Those are my initial thoughts, more will probably occur later!

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When I was working in did a couple of projects with supermarkets, using Stirling engines to provide heat and electricity for all of the supermarkets needs (refrigeration was provided using absorption or adsorption chillers).

 

To allow the supermarket to function in the event of Stirling engine failure (a regrettably common occurrence, despite using four Stirling engines per site), the existing heating and chilling arrangements were retained.

 

As one person with Stirling engine experience to another - are you familiar with the machine Phillips used to use for demos? The one connected to a motor generator?

 

Richard

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If anyone is about to sit down and figure out a good way to do this, consider that there may be an immersion heater built into the calorifier too.

So you need to be able to isolate both boiler water circuits, not just one or the other or neither, so that the immersion heater doesn't end up heating a boiler that is off.

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Check it out by all means if you can. Their website give no clue about how it works, just makes a load of claims about how great it is.

 

Or used to anyway, last time I tried to get a grip on what what on earth they are.

I suspect it's just a large empty box with lots of pipe connections welded onto it.

 

It's basically a header, which provides a 'neutral point'

 

In doing so it allows pumped and gravity circuits to coexist without the pumped circuit affecting the gravity one.

 

Hence being called Dunsley Neutraliser... smile.png

 

BTW yeah you can have two or more heat sources if you really want; doesn't mean it's going to be easy, though the trick is avoiding making it over complicated. There's a few diagrams in my profile gallery which suggest ways how...

Edited by smileypete
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Mike I understand what you are saying. I must admit that Dursley don't give a lot away do they !. But looking at the picture of it you can see what looks like an exit union to me at the top of to unit.

I would expect that a thermosyphon would or could be used. In this situation.

 

The heat pipes that I have were used in the making of solar thermal hot water from a parabolic into a hot water cylinder, but we were using heat transfer oil for the first stage ( sun into the heat transfer oil) then within the oil a copper thermosyphon with water straight up into the tank.

 

For safety you can get them made up so they have a maximum working temperature of say 85c so they can never overheat the water. Unlike the vacuum solar tubes that can get up to 200c hence the use of an expansion tank within the system.

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As one person with Stirling engine experience to another - are you familiar with the machine Phillips used to use for demos? The one connected to a motor generator?

 

Richard

No,

 

The company that provided the Stirling engines for my projects was called SDK; Stirling get Denmark. It was an offshoot of a Copenhagen university. As a package, it used gas made from woodchip, in a gasifier to heat the helium in the Stirling engines. The whole shebang controled with state of the art computer controls, monitored 24/7 from Denmark.

 

Worked well for short periods, but hopelessly unreliable due to lack of development before being put on the market. Mainly poor material selection.

 

SDK went bust taking the division of the company I worked for with them.

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No,

The company that provided the Stirling engines for my projects was called SDK; Stirling get Denmark. It was an offshoot of a Copenhagen university. As a package, it used gas made from woodchip, in a gasifier to heat the helium in the Stirling engines. The whole shebang controled with state of the art computer controls, monitored 24/7 from Denmark.

Worked well for short periods, but hopelessly unreliable due to lack of development before being put on the market. Mainly poor material selection.

SDK went bust taking the division of the company I worked for with them.

I was involved in a project to use Stirling engines as heat pumps for cooling the detector in thermal imaging cameras. They would run down to minus 270 degrees

 

I'll see if I can find a description of the Phillips demo

 

Richard

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I was involved in a project to use Stirling engines as heat pumps for cooling the detector in thermal imaging cameras. They would run down to minus 270 degrees

I'll see if I can find a description of the Phillips demo

Richard

Thanks, they are fascinating things, but windy inefficient. It was the ability to run on locally sourced woodchip, that made my project viable. They generated 35kW of electricity and 200kW of heat.

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Thanks, they are fascinating things, but windy inefficient. It was the ability to run on locally sourced woodchip, that made my project viable. They generated 35kW of electricity and 200kW of heat.

 

Here you go, Page 50: https://books.google.co.uk/books?id=QwgHCAAAQBAJ&pg=PA50&lpg=PA50&dq=philips+stirling+demonstration&source=bl&ots=4jlIE0q-C9&sig=-Z_o4BgIiBXMo9j3wwdLXkqUrc8&hl=en&sa=X&ved=0ahUKEwi2wO-qgp7MAhVKDsAKHWtgDW0Q6AEIMDAG#v=onepage&q=philips%20stirling%20demonstration&f=false

 

A Versatile Demonstration Engine

 

Does that work? yes

 

Richard

Edited by RLWP
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Interesting. Did you use one in a prolonged practical application?

 

My experience was of a great idea, but underdeveloped. We had all sorts of problems, ranging from piston seal failure (many times, they never found a suitable material) to the stainless steel gasifier flue disintegrating due to the corrosive effects of chlorine in the wood of trees grown near the coast.

 

The reason the company I worked for had to be liquidated was because they sold the electrical and heat power outputs at a fixed price per kWh for a 15 year period, only subject to labour and fuel inflation, and agreed to pay the difference between that cost and grid energy prices when output was insufficient (which it was most of the time). When the manufacturer went bust they had no option but to get out as they could not obtain spares or get the machines maintained.

 

Edited to remove autocorrect induced errors.

Edited by cuthound
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