Boiler power control

[Samahon]

Nothing crossed nor odd about my post. I simply stated that inside my unit I have a PSR-25 SSR controlled by a 1W Pot.
The ampmeter is wired in-line with the output from the relay...

The PSR-25 Power Control module is a high power, full wave AC phase angle controller that is both compact and easy to use in applications where power needs to be controlled. It is capable of powering a boiler up to 6KW (25A) 240V ac. The PSR regulates and governs the amount of power supplied to the load, by controlling the phase angle of the AC supply. The low thermal impedance and high electrical isolation provides the user with greater flexibility over a range of applications. The module is well suited to the subject matter of this thread. Heating elements are certainly one of the applications that we as brewers need to control and the PSR gives us an easy to install module that works pretty much out of the box IMO. I bought mine 18 months ago and it works flawlessly, it cost me £27.00 just for the SSR, but I just looked and they seemed to have shot up to around £35.
There are cheaper alternatives to the PSR-25 but they are a little more in-depth. Still using the phase-angle principle with some of them requiring DC to power the switch on the SSR...

I'll post a wiring diagram up if anyone wants it, I'll also open the waterproof enclosure that it is installed in and take some photos to try and add to the threads contents...

I would like to stress that anyone NOT confident with high voltage 220v - 240vac should consult a qualified electrician and have them wire it up. Not only will the unit be a lot safer to use in the home, but the ratings of the components will have been adhered to, giving you a tool for boiling your HLT that should last many years. Remember, 88% of fires in the home are electricity/gas related... Not wanting to sound paranoid and frighten the membership. but if that's what keeps you safe then so be it. Please be extra careful...

[Kev888]

Hi,
I think my confusion was just because I didn't realise the PSR-25 is a power controller, I took it to be a simple SSR in the original post. I've been looking at some data sheets now, and it certainly looks the business; I'd be most keen to hear where you got it and how well it works for you, as I'd been considering building something based around a triac which probably wouldn't be so refined.

Can you make subtle changes to the vigor of the boil with it? I had a lower powered module (for a drill) once, but it wasn't really fast enough to control the very first bit of the phase.

Cheers
kev

[Samahon]

You can get one here... They work great for our needs and are very easy to wire together. Never had any problems with the unit.
Subtle changes can be made to a rolling boil enabling you to draw back the power to the element and have the boiler simmering. The ampmeter makes this a simple procedure...

Hope it helps...

[Kev888]

Ah, excellent. Many thanks for the info! I've been trying to decide between going gas and upgrading my element power; the controlability of the extra power is a key part of it, for me.

Cheers
Kev

[Samahon]

Yeah, I know what you mean by power decisions... I used to use propane exclusively and couldn't see by it. Now the refills have got that expensive it really does push a brewer towards electricity. I have 2 elements installed into my boiler, 1 @3Kw and the other at 2.5Kw. I have the controller connected to the 3Kw heater and only ever charge the 2.5Kw element if I know I'm pushed for time. Just running the 3Kw element lets me get other things done while the boiler is coming up to temps. Switching to electric really saved me money as well and you dont have to worry about your bottle running out half way through a boil...

Glad it helped Kev...

[Dr. Dextrin]

Gosh, this thread seems to have grown while I wasn't looking.

Personally, I'd prefer to end up with this unit sealed in a watertight metal case with an external heatsink. That'll protect it against accidental flooding and should also mitigate any fire risk somewhat in the event of a serious failure. For that reason, I'm not keen on using fans for ventilating the heatsink (also, PC fans don't have a very long life IME and will add significantly to the cost).

The ammeter idea is a good one, though, and I'll probably add something like that. But possibly it might be better to measure an RMS (or at least rectified) output voltage as otherwise the reading will depend on the load resistance and I'd like to be able to use this with several different heating elements. Of course, you really want to measure the square of the current (or voltage) so you have a power meter, but that's probably getting too complicated.

BTW, anyone know the correct way to suppress RF on the input/output leads? I was thinking maybe ferrite beads, but that's not an area I know much about.

[Hogarth]

Interesting thread! I recently changed to a 19l brew length for the usual reason and I now get a tropical storm in my boiler instead of a gentle bubble. So I'm on the look-out for a cheap and easy solutions.

Can I just confirm ... it's not a good idea to use the manual 'output' setting on my PID together with the SSR, because the electric company won't like it?

[Kev888]

Gosh, this thread seems to have grown while I wasn't looking.

Personally, I'd prefer to end up with this unit sealed in a watertight metal case with an external heatsink. That'll protect it against accidental flooding and should also mitigate any fire risk somewhat in the event of a serious failure. For that reason, I'm not keen on using fans for ventilating the heatsink (also, PC fans don't have a very long life IME and will add significantly to the cost).

The ammeter idea is a good one, though, and I'll probably add something like that. But possibly it might be better to measure an RMS (or at least rectified) output voltage as otherwise the reading will depend on the load resistance and I'd like to be able to use this with several different heating elements. Of course, you really want to measure the square of the current (or voltage) so you have a power meter, but that's probably getting too complicated.

BTW, anyone know the correct way to suppress RF on the input/output leads? I was thinking maybe ferrite beads, but that's not an area I know much about.

heh heh, well if you will turn your back..

I think I too would go with the sealed box approach, or at least fan-less, just to avoid mechanical weaknesses. Though I do brew out in the cold garage where mechanical things have a tendency to suffer a bit from moisture and cold.

Presumably direct voltage or current readings from most ac meters would be useful but only indicative of power - relying on how the meter recognises and averages the effect of phases being truncated in time rather than (necessarily) amplitude. If you wanted to make the readout more load-independent, maybe you could have a very small dummy load inside the box with a mA meter measuring the current through that. Of course when you connect the main load in parallel that will likely affect things to some degree (due to the impedence of the supply causing the available voltage to drop), but at least it won't change quite so directly in relation to the element impedence.

EDIT: not sure about rectifying the sampled voltage though; I suspect it would be quite critical - if the smoothing were too little then the current wouldn't be consistant (even though now unidirectional) yet if the smoothing were too great (relative to the load) you'd probably effectively make a constant DC power supply at the maximum amplitude of the original wave - usually at about 300VDC until the phase clipping began to affect amplitude as well as time/power...

I can't say that I've supressed RF at this sort of level myself before, so maybe someone else could help; I've generally just bunged on a filtered IEC socket but the ones I've used aren't rated to that sort of current..

Cheers
Kev

[Blue Sky]

Anybody built a burst-fire regulator using the UNITED AUTOMATION - BFM-TH-UAL - TRIGGER MODULE?
PDF.doc >>HERE<<
Just wondering what a suitable Triac would be?

More interesting power control stuff >>HERE<<

[JabbA]

A timely thread for me! I'm hoping to convert my set-up to a PID Arduino based HERMS system over Christmas and have been thinking about regulating the boil elements as well.

From doing a little reading of the links posted above burst-fire regulation seems to be the way to go with regard to minimizing RFI to the Arduino circuitry but I'm wondering how will it affect the life span of the cheapo Tesco kettle elements? Any thoughts?

Cheers,
Jamie

[sparky Paul]

Nothing crossed nor odd about my post. I simply stated that inside my unit I have a PSR-25 SSR controlled by a 1W Pot.

That's where the confusion started for me, the PSR-25 is most definitely not a SSR, or Solid State Relay. I wouldn't want anyone to rush out and buy a SSR thinking they could use it as a stand alone power controller/regulator.

Can you make subtle changes to the vigor of the boil with it? I had a lower powered module (for a drill) once, but it wasn't really fast enough to control the very first bit of the phase.

They work well on basically resistive loads like heater elements, you should get a good degree of control. For technical reasons, they are not so good on inductive loads like motors, particularly on less than half power.

[sparky Paul]

Just wondering what a suitable Triac would be?

The BTA series triacs are usually the easiest to get hold of. A BTA20-600 will give you enough headroom, being capable of switching 20A with suitable heatsinking. Go for a BTA25 if you want belt and braces.

With regard to the safety of these circuits, I would echo what Samahon said earlier. All parts of these power controller circuits operate at mains voltage, including the control potentiometer, and unless you are absolutely confident that you know what you are doing, they are best left alone.

The control circuit on a SSR is generally isolated from the mains. The control circuit on a phase angle controller, and the burst fire module above, is not.

[Hogarth]

For a more ready-made option, would this one from Farnell be okay?

[sparky Paul]

For a more ready-made option, would this one from Farnell be okay?

I think these have been mentioned before, and they are a nice neat solution. The only thing to bear in mind is this bit in the spec...

Maximum recommended unit load at 20ºC ambient, (without extra heatsink) 10 A
Maximum recommended unit load at 40ºC ambient, (without extra heatsink) 5 A

...providing you make sure there is adequate additional heatsinking, such as mounting to a substantial metal casing, they can be used to the full 15A rating and should do the job perfectly.

[Kev888]

Interesting; this integrated controller doesn't seem to require an external filter - I've been looking at the PSR-25, and whilst good value in itself, its data sheet suggests its used with an RFI filter (one with an in-line choke, not just a simple parallel network), and that costs about £55!

BTW, just looked back at the cheap version Dr Dextrin found, and the seller seems to have withdrawn all their items from sale..

Cheers
Kev