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Old 01-11-2017, 05:02 PM   #1
AlanHarper
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Default Converting an Urn into a Boiler

This is the process I went through to convert a cheap 30lt Tea Urn into a boiler for my new home brewery. The premise was to build up all the necessary kit for as little outlay as possible - "she" wouldn't let me do it otherwise...

PICTURE_1

I got this from an online auction site for the princely sum of ����£10. It had been used only once and was in very good condition and if things didn't work out I had not lost much money.

PICTURE_2

The plastic base is removed by unscrewing the three brass retaining screws and this reveals the electrical wiring built in to the base and a loose stainless steel ring that has the Mains Switch and two indicator lights - the only controls on this particular version of Chinese origin Urn. There are many similar versions of this type of urn for sale on the internet so the following wiring MAY be the same across the range but you may find slight differences in other types.

PICTURE_3 and PICTURE_4

The various components of the urn are detailed in picture 3 with the circuit diagram shown in picture 4.

This urn has two heating elements (G) that are connected to individual relays on the small circuit board (E) that are, in turn, switched on and off by the Max Temp Thermal Cutout (I) - the Keep Warm TCO. The Heating and Warming lights are switched at the same time as the relays showing the user what is happening.

The mains supply comes in and goes directly to the double pole switch (B) and the printed circuit board [PCB] (E).

Circuit Protection

This is handled by two components.
1) The Thermal Fuse (C) hidden under a clamp in the middle of the heater base and shielded with heat proof sleeving is in the Neutral line and feeds the heating elements and the PCB. If this ever blows then everything will stop working and it MUST be replaced - under no circumstaces is this to be shorted out!!!
2) The Boil Dry Thermal Cut Out (H) is the first component in the mains Live feed and will switch everything off if the elements ever get too hot - it should automatically reset if water is added to the dry tank but I am not going to test this out.

Circuit Action

With the urn plugged into the mains, and the switch off, nothing will happen. Turning on the switch will supply mains to the printed circuit board as long as the two Thermal Cut Outs (TCOs) are closed. The red Heating light comes on as the two relays switch on and connect the heating elements to the mains. The water starts to heat until the Keep Warm TCO opens at 92 C. The relays then switch off and the heaters go off in turn. The Warming light comes on at this point - I won't explain why here but it does and things stay like this until the water cools down to the point that the Keep Warm TCO closes again. There is some hysteresis here so the water in the urn will be kept on or about the temperature of 92C.

Modification

To make this urn into a useful "boiler" we must change the temperature at which the relays are turned on and off. This is done by replacing the TCO (I) in the circuit with a variable control that can detect the heating temperature and switch the relays.
I bought a BURCO HOT WATER BOILER TEA URN THERMOSTAT AND CONTROL KNOB (component numbers: 082620290 and 082620359) from the web (Picture 5) for ����£26 to do the job.
Removing the TCO from the base of the urn gave me a convenient place to clamp the temperature sensing bulb using a spare heat-sink clamp I had kicking about in my spares box (Picture 7). I drilled three holes in the base next to the Mains switch to mount the control (Picture 6). The wires that went to the TCO conveniently connect to the two spade terminals of the Burco control.

The new circuit layout is now that shown in Picture 8. Note the detail in the picture showing the published APPROXIMATE temperature settings for the given value shown on the control knob. I have yet to test these values but I will make a note what the true values are when I do a further mod to the boiler to add a thermometer to the casing.

Testing

All that is required now is to check all the wiring - to see there are no loose connections or shorts - bolt it all back together, fit the control knob (Picture 9), put water in the boiler and power it all up. (Picture 10).

Conclusion

This modification worked very well and only cost me a total of ����£36 to get a fully controllable boiler that can furnish me with hot water at a range of temperatures up to 103C (supposedly) for mashing and sparging - something I have yet to do but watch this space.

After testing I was forced to do a further modification which will be detailed in a later thread.
Attached Thumbnails
PIC_1.jpg   PIC_2.jpg   PIC_3.jpg   PIC_4.jpg   PIC_5.jpg  

PIC_6.jpg   PIC_7.jpg   PIC_8.jpg   PIC_9.jpg   PIC_10.jpg  


Last edited by AlanHarper; 01-11-2017 at 11:21 PM. Reason: Correction of spelling etc.
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Old 01-11-2017, 08:50 PM   #2
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Good informative post,I’m lazy and spent the extra £40 and got a 30l Burco which boils away nicely
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Old 01-11-2017, 11:50 PM   #3
AlanHarper
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UPDATE to Boiler Conversion.

The Burco control, when set to No.6, did not produce a rolling boil as is required (from what I have read in this website and elsewhere) when boiling the worst and hops. This requires a modification to the circuit in Picture 8 above to "force" the situation but still maintain the usefulness of the variable control.

New Circuit Details

Picture 11 details the ammended circuit to include the new Override "Rolling Boil" switch. The wires going to the variable control were re-terminated to include suitable wires and connectors to attach to an additional switch that was fitted adjacent to the mains on/off switch. A green switch of suitable power rating was chosen do differentiate between the two (Picture 12). Additionally I inverted the switches to make them "on" when pressed down - not essential but was done for neatness.

The wire from the "spare" terminal on the Neutral side of the mains switch is taken to the new switch to provide the supply for the internal neon lamp in the new switch.

Tap Modification

To make the emptying of the boiler a lot easier I decided to add a 10mm copper spout to the tap. The tap was first removed from the urn and dismantled to inspect the innards of the tap. The body of the tap was clamped in a vice and a 10mm drill bit was used to widen the spout hole. A short piece of 10mm copper pipe was "forced" into the new wider hole by clamping both in a vice and slowly compressing the tube into the tap body. This ensures a leak proof fit. The 10mm spout was made long enough to attach tubing so the boiled and cooled wart can be gravity fed into the FV. A "standard" ball tap was considered as a complete replacement for the original tap but the hole size in the urn body would need to be enlarged and I did not have a big enough hole cutter to do the job neatly so this was rejected (I've still got the tap so I might use it for a bigger Mashtun sometime in the future).

Testing

Testing the unit produced a continuous rolling boil which should do the job nicely - though that still has to be proved with my first wort production.

Brewing Stand

I have designed a movable Brewing Stand to hold the boiler and Mash Tun and FV. This will be the subject of an additional post.
Attached Thumbnails
PIC_11.jpg   PIC_12.jpg   PIC_13.jpg  

Last edited by AlanHarper; 02-11-2017 at 12:32 AM. Reason: Spelling etc. and new tap details
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Old 02-11-2017, 11:01 AM   #4
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Great post , I love reading these DIY projects, I'm not too clued up on electrics or the terminology but I understand most of what you have done.

Just wondering about the green switch, does that bypass the thermostat and make the boiler run at full power when it is turned ON? which in turn gives you the rolling boil required, sorry for the daft question.
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Old 02-11-2017, 11:54 AM   #5
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well done, and thanks for taking the time to edit all the photo's with labels too ..

What hop filtering are you planning on employing? most folks would have replaced the supplied tap with a ball valve alternative as that can more readily accept fittings on the back side for hop filtration and on the spout end for plumbing up to a drain hose to feed the FV. tho i do like the simple spout mod with copper tube that you came up with

hope she brews as good as she looks. Im sure she will...

ps beer will boil at higher temps than 100c so it may be expedient to disconnect the NC thermal switch from the pot base so such temps wont trip it mid boil..
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Old 02-11-2017, 02:36 PM   #6
AlanHarper
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Quote:
Originally Posted by deeboi View Post
Great post , I love reading these DIY projects, I'm not too clued up on electrics or the terminology but I understand most of what you have done.

Just wondering about the green switch, does that bypass the thermostat and make the boiler run at full power when it is turned ON? which in turn gives you the rolling boil required, sorry for the daft question.
Yes That is exactly what it does. Not a daft question at all. It does the same function as holding down a trip switch on the kettle - all you have to do is stand well back...
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Old 02-11-2017, 02:47 PM   #7
AlanHarper
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Quote:
Originally Posted by Fil View Post
well done, and thanks for taking the time to edit all the photo's with labels too ..

What hop filtering are you planning on employing? most folks would have replaced the supplied tap with a ball valve alternative as that can more readily accept fittings on the back side for hop filtration and on the spout end for plumbing up to a drain hose to feed the FV. tho i do like the simple spout mod with copper tube that you came up with

hope she brews as good as she looks. Im sure she will...

ps beer will boil at higher temps than 100c so it may be expedient to disconnect the NC thermal switch from the pot base so such temps wont trip it mid boil..
Hi there, yes I am planning to use a hop bag initially that is suspended from the handles of the urn. I had thought about the ball valve type of tap to replace the current one as I think I mentioned earlier but that would have required widening the current hole for the tap and there would be no going back if things went wrong.

In mittigation the current tap is not at the bottom of the urn so there is probably 2 or 3 pints of liquid below the tap level and this would leave pleanty of room for settled hops etc to not be drawn off - I'm not bothered about wringing all I can from the boiled wort - what is a few pints (and don't say a good night out!)?

As for the Boil Dry TCO I don't think it will be and issue but as I have yet to brew anything with the unit yet I may change my mind about leaving it in circuit - time will tell.

Last edited by AlanHarper; 02-11-2017 at 02:48 PM. Reason: spelling - again.
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