Jeremy Harris Posted September 25, 2018 Share Posted September 25, 2018 1 hour ago, Ed Davies said: If it was likely to be switching more quickly (e.g., multiple small immersions being switched on and off to approximately follow the changing output of PV as I have in mind) then SSRs would be preferable. You might be interested in the PV diverter I built some years ago (which is working fine, but now via a wireless link): https://picaxeforum.co.uk/threads/photo-voltaic-immersion-heater-power-diverter-safety-warning.24286/ (re-reading this old thread about the PV diverter I see that I mentioned your web site, @Ed Davies...) Link to comment Share on other sites More sharing options...
Ed Davies Posted September 25, 2018 Share Posted September 25, 2018 @JSHarris, thanks, yes, had seen that (and thanks also for the blog link) but not at all suited to my use-case for reasons I won't derail this thread with but might be worth discussing separately. Link to comment Share on other sites More sharing options...
dpmiller Posted November 5, 2018 Share Posted November 5, 2018 On 25/09/2018 at 09:11, JSHarris said: FWIW, I've had a 25 A rated SSR switching our equivalent to an immersion heater on and off reliably for a couple of years or so. The heat sink needed is modest, and the alloy case it's screwed to does a good enough job. The big advantage is logic level control in my case, as I switch the SSR directly via a microcontroller pin. For a simple application like switching an immersion from an existing low power programmer/thermostat I'd just use a relay, though, as @dpmiller suggests. You can make a neat job of this by using a small DIN rail case and fitting a plug-in relay that fits a DIN mounting socket base. The most compact case with a DIN rail is probably one of the ones intended for use with a DP isolator. You used to be able to buy these on their own cheaply, but a quick web search has failed to come up with one. I've used the small Wylex ones for jobs like this, but can't for the life of me find the same ones now, which is a shame. Guess what I tripped over at the back of the BES catalogue: https://www.bes.co.uk/wall-mounted-rcd-mcb-enclosure-18840 1 Link to comment Share on other sites More sharing options...
Onoff Posted November 5, 2018 Share Posted November 5, 2018 (edited) 10 minutes ago, dpmiller said: Guess what I tripped over at the back of the BES catalogue: https://www.bes.co.uk/wall-mounted-rcd-mcb-enclosure-18840 CPC do 'em cheap as though only IP20: https://cpc.farnell.com/olan/ol40005/enclosure-ip20-2-module/dp/EN84797? TLC & CPC both offer the Wylex one at just over £3. ESE2 is the Wylex reference. https://www.tlc-direct.co.uk/Products/WYESE2.html? https://cpc.farnell.com/wylex/sfese2/general-purpose-enclosure-ip40/dp/PL11751? Edited November 5, 2018 by Onoff Link to comment Share on other sites More sharing options...
dpmiller Posted November 5, 2018 Share Posted November 5, 2018 Funny that, innit? When we were talking about this last they seemed to be about eight quid or something? Link to comment Share on other sites More sharing options...
Ed Davies Posted November 5, 2018 Share Posted November 5, 2018 Is a DIN mounted relay “similar switchgear” for the purposes of the 17th edition amendment 3 rule about metal boxes (the one mostly relevant to consumer units)? Is that why they're cheaper now, because they should only be used in non-domestic applications? (Seems a daftly worded paragraph to me. AIUI the problem is poorly made, so high resistance, connections in high current circuits causing overheating. Therefore the problem is not whether there is “switchgear“ present but whether there are connections not protected by a low-enough current limiter (fuse or breaker). Why does a consumer unit have to be metal when a connection box in the loft for a lighting circuit can be plastic? Either can have poor connections. Perhaps they should have said metal boxes for connections if the current is not limited to 32 amps, or whatever. Similar sort of thing with the special rules for low voltage lighting circuits. The problem isn't the low voltage, it's the high current. Low voltage, low current lighting (e.g., LED) doesn't need anything special but it's caught up in this badly worded mess.) Link to comment Share on other sites More sharing options...
Dudda Posted November 5, 2018 Share Posted November 5, 2018 On 24/09/2018 at 16:45, Dudda said: Have this in my house. Have it on a standard immersion timer currently as it's not long in and still slowly raising the temperature of the slab. Haven't needed it much yet as the heating season is only starting. Plan to connect it to a thermostat on the wall in the soon somehow. How would I go about connecting this to a wall thermostat? I've a three core and earth and a cat-6 cable going to where I want the wall stat in the main living area. Want something simple and not overly complicated to go with the simple heating element. Still have my UFH wills heater on a timer and want to change it to the thermostat. The plugin relay, solid state relay, microcontroller pin, logic level control, etc. replies are a bit above my knowledge. What am I telling the electrician to install and if possible a shopping list of parts if I’ve to order online in advance? 1 Link to comment Share on other sites More sharing options...
PeterW Posted November 5, 2018 Share Posted November 5, 2018 2 hours ago, Dudda said: Still have my UFH wills heater on a timer and want to change it to the thermostat. The plugin relay, solid state relay, microcontroller pin, logic level control, etc. replies are a bit above my knowledge. What am I telling the electrician to install and if possible a shopping list of parts if I’ve to order online in advance? Ok so the simplest would be to use the thermostat to drive a contactor - you can pick one up for change of £10 and an enclosure is £3-4 at most so that will sort your switching via either a pipe stat (non intrusive) or via a room stat. 1 Link to comment Share on other sites More sharing options...
Onoff Posted January 17, 2020 Share Posted January 17, 2020 Old thread I know but could I... Use a Willis heater and small <15L tank to create a self contained, non vented system to heat 1 towel rail and 1 small UFH loop? Link to comment Share on other sites More sharing options...
PeterW Posted January 17, 2020 Share Posted January 17, 2020 Why ...?? Connect the Willis direct with a 5 litre expansion vessel and be done with it. Link to comment Share on other sites More sharing options...
Onoff Posted January 17, 2020 Share Posted January 17, 2020 2 minutes ago, PeterW said: Why ...?? Connect the Willis direct with a 5 litre expansion vessel and be done with it. This to avoid connecting my two new, clean loops into the old rotten system. So a pump, the Willis, the two loops, a couple of 2 port valves and a 5L expansion vessel? Trying to imagine the circuit. For the floor loop I've already got that under floor probe in that you kindly sent me years ago. Link to comment Share on other sites More sharing options...
PeterW Posted January 17, 2020 Share Posted January 17, 2020 Why valves ..??? Filling loop to the UFH manifold, auto air vent on the circuit and the pump and Willis in line. No valves, just the pump and Willis wired in parallel off the same switch. Expansion vessel somewhere in the circuit - not really that important where if there are no valves. Alladin now do auto venting towel rail plugs that may also help you get the air out of the top of the towel rail. Link to comment Share on other sites More sharing options...
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