Boiler power control

[jmc]

Can anyone spot any difference besides price?

TIA John

No. I can't see any signifcant difference, except that the components are set out slightly differently.

Thanks for the quick reply.

Are they similar to the one you got, mentioned here:

The device I bought on eBay is still being advertised here:

http://www.homerweb.com/vintage/38KW-40 ... 89113.html

[andyCo]

Just an update. I now have one of these power regulators and have tried it out in a lash-up fashion to boil about 10 litres of water using a 2.75 kW kettle element.

It comes with absolutely no instructions and the description on eBay is rubbish, but the device has just two terminals so I connected it in series with the load and it seems to do the job quite nicely. It varies the power smoothly from zero to max, and AFAICT there's very little power loss at the max setting

Just got one of these, Before I wire it up can I just check that I'm about to do it right, am I just splitting the live to my element through the controller ?

Thanks in advance

Andy

Yes, that's basically it.

Cheers bud


Andy

[darkonnis]

Good thread, I'm after one of these for my little 8L boiler (1.5kW element) which as you can imagine is a bit mental once it gets going.
I'm happy enough getting in there with the tools and the like so longs as I know roughly what I'm meant to be doing and have all the necessary bits, especially with electrickery, anything else I'm less bothered about.
So, for the sake of argument lets say I've got the one of these 3.8k adjusters (note this is the last working link I could find on this thread), what else would I need?
Project box?
Plug sockets (got wire)
Lets say the biggest element I'll use it to control is 2kW, would I also need a bigger heatsink?

Thanks for any help gents, just trying to make sure I get this right in a oner
Cooky

[Dr. Dextrin]

Are they similar to the one you got, mentioned here:

The device I bought on eBay is still being advertised here:

http://www.homerweb.com/vintage/38KW-40 ... 89113.html

Yes, they look pretty much the same as my one.

[jmc]

Thanks again.

Like darkonnis I'd appreciate help on using one of these for a power controller in a separate project box.

I can see that it may be easier to fit it to base of buffalo type boiler, but I'm planning on converting a 70L pot to a boiler so I'd rather it was separate to keep things cooler and make it a bit future proof.

For example would a metal project box provide reasonable RF screening?

Can / should a larger heatsink be used with a 3kw element?
TIA John

[Dr. Dextrin]

Good thread, I'm after one of these for my little 8L boiler (1.5kW element) which as you can imagine is a bit mental once it gets going.
I'm happy enough getting in there with the tools and the like so longs as I know roughly what I'm meant to be doing and have all the necessary bits, especially with electrickery, anything else I'm less bothered about.
So, for the sake of argument lets say I've got the one of these 3.8k adjusters (note this is the last working link I could find on this thread), what else would I need?
Project box?
Plug sockets (got wire)
Lets say the biggest element I'll use it to control is 2kW, would I also need a bigger heatsink?

Thanks for any help gents, just trying to make sure I get this right in a oner
Cooky

Probably the minimum you need is some sort of enclosure to stop you touching the live bits and to keep splashes off it and a way to feed the mains in and out again. You need to connect the incoming live wire to one terminal of the device and the live wire to the load to the other terminal. Remember to earth any metalwork that's touchable.

The main unknown is the heatsink. I suspect that in free air the one it comes with might well cope with the 3.8 kW that's claimed, although it will get pretty darned hot. So 2 kW probably wouldn't tax it too much. The problem comes if you put it in an enclosure. Whether it would cope with a 2kW load under those conditions is guesswork. Ideally you'd probably want to mount a heatsink externally (which can be a bit awkward) or install a fan to waft air from the outside (a PC fan would need a 12V power supply of course, but it's still probably a simpler option).

Or you could just try it and see how hot it gets. But if the entire enclosure gets too hot you may need to worry about the other components and/or your insulation failing.

Or mounting it in the base of a tea urn type thing might have its attractions (see post by The_blue).

Beyond that, there are various other things you may or may not be bothered about:

1) On/off switch, bypass switch, indicator light, etc.
2) Mains interference can be a bit fierce.
3) Fuse.

Re jmc's query: a metal box will certainly help with RF screening but a lot of the interference goes up the mains cable. An RF filtered input socket, appropriately rated, helps a fair bit. But unfortunately the one I used from Rapid (see one of my earlier posts) seems to have been discontinued and most of the others I've seen have been a fair price.

[jmc]

Good thread, I'm after one of these for my little 8L boiler (1.5kW element) which as you can imagine is a bit mental once it gets going.
I'm happy enough getting in there with the tools and the like so longs as I know roughly what I'm meant to be doing and have all the necessary bits, especially with electrickery, anything else I'm less bothered about.
So, for the sake of argument lets say I've got the one of these 3.8k adjusters (note this is the last working link I could find on this thread), what else would I need?
Project box?
Plug sockets (got wire)
Lets say the biggest element I'll use it to control is 2kW, would I also need a bigger heatsink?

Thanks for any help gents, just trying to make sure I get this right in a oner
Cooky

Probably the minimum you need is some sort of enclosure to stop you touching the live bits and to keep splashes off it and a way to feed the mains in and out again. You need to connect the incoming live wire to one terminal of the device and the live wire to the load to the other terminal. Remember to earth any metalwork that's touchable.

The main unknown is the heatsink. I suspect that in free air the one it comes with might well cope with the 3.8 kW that's claimed, although it will get pretty darned hot. So 2 kW probably wouldn't tax it too much. The problem comes if you put it in an enclosure. Whether it would cope with a 2kW load under those conditions is guesswork. Ideally you'd probably want to mount a heatsink externally (which can be a bit awkward) or install a fan to waft air from the outside (a PC fan would need a 12V power supply of course, but it's still probably a simpler option).

Or you could just try it and see how hot it gets. But if the entire enclosure gets too hot you may need to worry about the other components and/or your insulation failing.

Or mounting it in the base of a tea urn type thing might have its attractions (see post by The_blue).

Beyond that, there are various other things you may or may not be bothered about:

1) On/off switch, bypass switch, indicator light, etc.
2) Mains interference can be a bit fierce.
3) Fuse.

Re jmc's query: a metal box will certainly help with RF screening but a lot of the interference goes up the mains cable. An RF filtered input socket, appropriately rated, helps a fair bit. But unfortunately the one I used from Rapid (see one of my earlier posts) seems to have been discontinued and most of the others I've seen have been a fair price.

Thanks for very useful answer.
Looks like choice is cheap and dirty (RFI wise ) with simple 3.8kw reg in a project box, or more sophisticated one like you made (if one has good electronics knowledge), which sounds like it could be quite expensive with all the add ons needed
or off the shelf eg Hogarth's one.

I did a quick search and I think Hogarth's choice is most available off-the-shelf solution but with VAT and extras ( thermal compound heatsink etc) looks like its £55-£60, which is probably more than I can afford (or justify to myself) at the moment.

[Dr. Dextrin]

As a guide, I think I probably spent £60 to £70 making my own and also had to wait a fair while for bits to arrive from the far east. But then I did go for all the add-ons.

[jmc]

As a guide, I think I probably spent £60 to £70 making my own and also had to wait a fair while for bits to arrive from the far east. But then I did go for all the add-ons.

Thanks for the update.

It looks a lovely piece of equipment,
but unfortunately I don't think I have the skills or budget to make one like yours.
ATB John

[Hogarth]

I'm very pleased with my off-the-shelf job. Works well. One thing I've noticed, though, is that despite the integral RF suppression, the fuse box under the stairs buzzes like mad when it's in use. I don't know if this will cause any wider interference.

[Fil]

have you tried listening to the radio while its in use?