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Taylors 079D Diesel Heater Improvements


Quattrodave
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Evening all,

I have diesel warm air heating & a Taylors 079D drip fed diesel heater on board.  I have the install where its has a pressurised fuel tank which you pump up and then *try* to keep at a stable pressure so it has a steady drip rate and as such a steady stable burn.... However keeping the pressure stable is a pain and as such the burn is not stable.... So I have been toying with the idea of improving the Taylors heater for some time now, looking at the manufacturers site and list of parts they have a very over priced fuel / lift pump.  Looking at it its just an old SU style pump (Google part number AZX1307) which is commonly available, same pump that was on the old mini or morris minor....  Looking at how the lift pump works it holds fuel pressure in its chamber and only uses electricity when the pressure drops. By my calculations running the hear from it it would probably only 'tick' every 45 seconds or soand as such use very little electricity.  It should also sort out keeping the fuel pressure stable and as such the burn stable.....

 

So, then my throughts moved on a little... I wondered if I could use the little dosing pump like i have on the warm air diesel heater, I'd have to run up an adjustable circuit to run it but it should be really accurate and easy to set and use...  I had an Arduino board kicking about so have spent a couple of hours prototyping my proof of concept.

 

ArduinoHeaterController2.jpg.ec88f7e5213aa9c2f9601a7f15575426.jpg

 

So essentially it works, 2 buttons increase and decrease the pulses per second minute.  Currently has a min of 30 and max of 130.  It the moment it pulses an LED but won't be difficult to drive a TIP120 or something similar to drive the fuel pump.  The 'On' pulse has a set duration of 1/4 of a second and the 'Off' duration is changed to alter the pulse rate.  If anyone is interested the Arduino code is attached....

 

More updates to follow....

Arduino Code.docx

Edited by Quattrodave
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Arduinos are good, but those old electric SU pumps are the work of the devil. Can the Arduino also drive a little hammer to give the pump a tap when those funny contacts misbehave 😀

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Given the Taylors contraption expects constant pressure, I don't think a dosing pump is appropriate as it delivers a defined volume of fuel on every click. So I'd predict the downstream pressure in the pressurised fuel tank would steadily rise, or fall, depending on how accurately you manage to calibrate the number of clicks per minute to the fuel burn rate. Yes the burn rate will rise as the tank pressure rises so the thing will tend to self-balance but this may well lead to over-fueling of the Taylor contraption and therefore incomplete combustion and sooting.

 

The SU fuel pump seems a much better idea as it is a constant pressure device. Can it be calibrated though? Dave's idea of a little Arduino-controlled hammer to whack it when it stops seems an obvious solution to the known weakness in the SU design. 

 

 

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  • Quattrodave changed the title to Taylors 079D Diesel Heater Improvements
50 minutes ago, dmr said:

Arduinos are good, but those old electric SU pumps are the work of the devil.

 

Yes, I remember the 'points' in the back of them being problematic.  I was thinking about some electronic upgrade on that too... possibly an optical sensor to sense when it needs to 'fire'.

 

31 minutes ago, MtB said:

Given the Taylors contraption expects constant pressure, I don't think a dosing pump is appropriate as it delivers a defined volume of fuel on every click. So I'd predict the downstream pressure in the pressurised fuel tank would steadily rise, or fall, depending on how accurately you manage to calibrate the number of clicks per minute to the fuel burn rate.

 

I had 2 thoughts here: First i'm hoping the dosing pump would push a set amount through the 'drip' measuring device so increasing the pulse rate would increase the drip rate and the amount of fuel delivered.  Secondly, i might be able to skip the 'drip' measurement device altogether and deliver fuel directly to the burn pot.

 

I also wondndered if i can change the pulsewidth to the dosing pump (currently set to 1/4 of a second) and reduce the amount of fuel pumped for every pump... I'd guess it could be tweaked a bit...

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4 minutes ago, Quattrodave said:

I also wondndered if i can change the pulsewidth to the dosing pump

 

I'm no expert on dosing pumps but I always imagined they are a mechanical device with a spring, a solenoid, a chamber and a NRV. So each pulse of 12Vdc delivers a fixed volume of fuel regardless of the length of time of the pulse. 

 

Others here may know better....

 

 

 

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2 minutes ago, MtB said:

 

I'm no expert on dosing pumps but I always imagined they are a mechanical device with a spring, a solenoid, a chamber and a NRV. So each pulse of 12Vdc delivers a fixed volume of fuel regardless of the length of time of the pulse.

 

Agreed, but i was wondering if the pulse is reduced slightly the solenoid wouldnt have time to move as far and pump slightly less fuel....  It would be interesting to find out but not a show stopper...

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10 minutes ago, Quattrodave said:

 

Yes, I remember the 'points' in the back of them being problematic.  I was thinking about some electronic upgrade on that too... possibly an optical sensor to sense when it needs to 'fire'.

 

 

I

 

 

I think these have been available for many years, but much more fun to make your own.

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Many years ago I installed a Taylors heater on an old boat of mine. I supplied the fuel from the main fuel tank that was at a lower level than the heater. All I used was an electric in line pump. Not the SU type but the modern electronic type. The sort of thing which is available quite cheaply from somewhere like ASAP Supplies. It worked well and never gave a problem. This type of pump runs continuously and give a constant pressure. Not sure of the power consumption but probably very low.

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I take it there is no chance of getting it to run in header tank mode? Not enough height available on the boat to get the pressure required? Otherwise, that would be the obvious answer and use a float switch to turn the dosing pump on and off, or just use it as a day tank and manually refill.

What pressure is required? The Taylors web site gives no access to manuals that I could see at a quick glance.

I'd be thinking of using a pressure sensor to let the Arduino know when to turn the pump on and off. Something like this maybe. I've used them with water pressure and they can measure changes of only a few mb reliably. There are Arduino libraries already for easy interfacing. There are UK suppliers. No idea if these are compatible with diesel. This would need checking. If not, there are other pressure sensors. Measuring the actual pressure, rather than relying on a fixed pumping rate would be a much more reliable way of getting consistant pressure. You would need to work out a housing and o-ring sealing. There are industrial pressure sensors, with suitable housing, but the costs of these are high.

Alternatively, don't use the arduino at all, just a pressure switch to turn the pump on and off.

Is there air in the tank? This would act as an air spring, similar to an accumulator, or expansion tank in a boats water system and make pressure changes much slower and smoother. I am guessing this is thje way it is designed, since there is a hand pump to pressurise it. If you are not pressurising it this way, but having it entirely full of diesel, then pressure will vary a lot.  Perhaps fit an accumulator? Again, diesel compatibility would need to be checked.

Edited by Jen-in-Wellies
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