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  1. C

    Ohm value of transformer

    For those of you who work with onsite MV-LV transformers, does anyone know the line to earth ohm value of a transformer? I'd like to include that in the loop impedance path. Similarly when stepping down LV to LV. View: https://Upload the image directly to the View: https://Upload the image directly to the
  2. R

    Lower the voltage of a three phase 220v delta wiring system with auto transformers

    Hi all, I have a three phase 220v delta wiring system but the real voltage is about 240-245V by measuring between the pairs RS, RT, TS. I want to lower it to about 220V so I was thinking to use three auto-transformers 240-220V wired like this: I expect to find 220V between the transformer...
  3. R

    Halogen to LED- Transformers?

    Hi, I was hoping for some advice on replacements for the spotlights in our kitchen. There are currently over a dozen (!), spotlights in the kitchen- all halogen. Many of them have died now, and I’m obviously looking to replace them all with suitable LED replacements, but I’m not sure a) what...
  4. E

    Skinflint Seeks Free Advice on burnt-out LED Transformer

    Morning. The LED light above my bath doesn't work. I yanked all the stuff out the ceiling and found this. So far, so good. But hark! I have come to the conclusion that something is wrong with the transformer. Worst case: it may never transform again. If I just buy another one with the...
  5. M

    Question about transformers and on-load tap changers (OLTCs)

    Hi, I have a network with hundreds of busbars (ranging from 33kV to 6.6kV). I have some electrical loads connected at the far end of the network via 2-winding transformers and I am analysing the voltage drops at the point of load connections. Some of these busbars experience around 10%...
  6. B

    Down lights and transformers

    Hi , just looking for some advice on some downlighting and where I stand , a client has provided me with 4 transformers with thermal cut out for there 4 down lighters which are not working , upon inspection of the 4 the down lighters themselves are not fire rated (ground floor flat) (2 story...
  7. D

    IR test with transformers and dimmer on circuit

    Evening Chaps On a job at moment and testing lighting circuits that have a lot of down lighters and a dimmer. Am I correct that if I disconnect live neutral and cpc from board join L-N together with all switches in closed position and test this to cpc and do IR test I have pretty much proved no...
  8. A

    MR16 replacement not working

    Hello, I am simply trying to replace an MR16 LED spotlight that has stopped working. However when I put the bulb in and turn on the light it simply flashes and turns off and won't turn on. Is anybody able to help me with why this might be happening? The old bulb has the following: Sainsburys...
  9. N

    Insulation Resistance test with 12v transformers

    I am installing a C/U and the kitchen has some old Down lights installed with 10 x 12 volt transformers connected. I know I could disconnect all the transformers but I don't plan to do that as it will be a real pain due to how the plasterboard has been bodged. Some opinions suggest the IR...
  10. N

    Introduction & Advice wanted

    Good afternoon, I've currently got a metal and plastic recycling facility, we normally just take in plastics but are licensed for metals. We've recently recieved some transformers to be recycled, from what I know, 500KVA Dry transformers, they weigh about 1500kg each and I've got 3 with all...
  11. exdevonboy

    LV Transformers & Radio Interference

    Hi all, A customer has recently replaced some of his 12V MR16 down-lighter bulbs with LED bulbs instead. One of the transformers (which were old) failed a month or so after he installed the new bulbs and I was asked to replace both of his existing LV transformers. They supply 4 No downlighters...
  12. A

    Led downlighters flickering

    Hi guys, Had a little job today where some led downlighters were flickering it was 3 out of about 15. I checked the voltages on the 3 which told me the transformers for each one are broken. Confirmed this by testing a working one which was a getting a steady 11.5 to 12v ac. I was just wondering...
  13. R

    MR16 halogen with dimmer replacement

    Hi, I believe this is a DIY job but do correct me if I am wrong. I have a number of spot lights MR16 50w which are on dimmers and I would like to change them to LED. They all have individual transformers and I am unsure as to whether I would have to change the transformers also. Your advice...
  14. M

    client does not want to pay? but work is not complete complaining??

    currently took over someones job on a control 4 system "huge home automated system" due that being an extra they paid my boss separate for this. alot of lighting has Big transformers which had to be put local to the control 4. doing this i had to make connections "wagos and tape" due to many...
  15. N

    12V LED Drivers

    I am gradually replacing filament & halogen bulbs with LED versions. Whilst some LED lamps work okay with standard 12V transformers, the transformers don't like low current devices, resulting in flickering. Since the idea is to save money and energy, I don't really want to outlay large sums of...
  16. E

    small building site temp distribution

    I am setting up some temps on a small site consisting of approx 3 110 transformers 2 portacabins offices sitting on top of each other, a portacabin toilet and a portacabin drying room. The supply is a 3 phase DB. Im thinking use 1 phase for the trannys, 1 phase for the offices and the other...
  17. H

    Help with led problem!

    Hi I have been to replace 2 bathroom wall lights from mr16 to 2 new led lights, however due to wiring issues, I have had to put the transformers in the loft. The lights will not work and I believe it is due the the length of the existing 12v cables and the fact the new led lights do not draw...
  18. happyhippydad

    Voltage drop and it's effect?

    Hello all, just been thinking over Voltage drop!! 1. Where does the 3% and 5% figures for voltage drop (VD) come from? Appendix 4 (BS7671) gives the figures but why the different values between lights and sockets? 2. Also permitted voltage levels are -6% and +10% from 230V giving a min of 216V...
  19. polo1

    12v MR16 to LED

    Hi guys, this feels like a bit of a "simple simon" question and despite having fitted hundreds of down lights, don't think I've done this before... Customer changed existing 12v MR16 lamps for MR 4.5w leds. Didn't change the transformers though and is suffering from the leds flickering when on...
  20. H

    MR16 LED's

    Hi, I was in the wholesalers last week and was getting MR16's to use as a demo for a client. I was going to get the driver to go with them, however the sales rep said that you can directly replace the current halogens with the LED's. I did as he said and they seem to work fine. I thought that...
  21. B

    Buzzer dimmers.?

    Hi, I've read a few threads about buzzing dimmers on here but still have a query and would like some advice please.; Customer has x4 low voltage downlights with electronic transformers for halogen lamps fitted to each downlight. These transformers are 60VA each (Saxby model ET60T-R 20-60VA...
  22. J

    Commercial Type D RCBOs

    Dear all, I have to protect a 13 amp ring main which is currently protected by a type b rcbo.The circuit is going to be used by step down transformers from the US.Notorious for tripping on start up.I thought a change to a type D rcbo would cure this,however neither MEM or Crabtree make a type D...
  23. S

    Polarity of LED 12V MR16 downlighters

    Hi all Was asked to fit two transformers for shop window display. there was 8 12V down lighters in total split into two circuits and both switched through a timer, The owner wants to replace the 8,12V dichroic MR16 bulbs with 12V MR16 LED 1.8w bulbs. The reason he wants to replace the dichroic...
  24. N

    Industrial Fault current on a 11'000 transformer

    Hi guys, haven't posted in a while. Working at a hospital now, we have 2 11KV transformers on site. We only run 1 at the time , the other is just used as a backup (close a bus coupler to bring it in). Being a nosy git, I asked about running both transformers at the same time. Obviously this...
  25. A

    Domestic ELV lighting fault

    Hi I am currently training to be an electrician but am only part qualified at the min. A friend of mine has asked me to fix some ELV downlights in his kitchen. Apparently when he switches them on sometimes it can take up to 10 mins for the lights to actually come on other times it can be a few...
  26. S

    Doorbell problem

    Hi, Any idea's, 1 doorbell, 4 chimes, 2 transformers, 1 of the chimes works from 1 transformer (now not working) & the other 3 works off another transformer. So one of the chimes have stopped working. I checked the voltage on the secondary side of transformer & this was o.k & voltage at the...
  27. D

    Fire damage after loft insulation installed

    Hi all, went to quote up a rewire on lighting circuit in a bungalow today. It turns out that they had new insulation laid just over 2 weeks ago. The insulators had left room around the light fittings (recessed 12v 50w halogens) but they totally covered up the transformers. After a quick look...
  28. D

    what frequency do 'HFAC' low voltage transformers (like varilight) typically output?

    Hi, I'm replacing low voltage halogen with MR11 and MR16 LED bulbs. AC supply would be simplest because of existing wiring, but I'm concerned about LED flicker: Characterizing and Minimizing LED Flicker - Lighting Solutions | DigiKey I'm looking at varilight transformers: VARILIGHT...
  29. T

    Commercial High power 12v leds

    Hi guys, Im changing some down lights in a hairdressers with high ceilings and need some high power directional (38degree or thereabouts) 12v leds. Preferably ones that will work with the existing transformers but i no thats hit and miss depending on what transformers they have already. Ive...
  30. N

    LED Driver

    I have recently bought a reel of SMD LED strip lighting. I know it's suggested that you use an LED driver to power these but they seem very expensive. I was wandering if I could use a standard electronic transformer used for powering LV spotlights, as long as I meet the minimum load? I struggle...
  31. C

    Buzzung dimmer

    had a look round a friends where there's x8 12v down-lights witch all have individual 20-60va dimmable electronic transformers, these lights are switched by a 400w GET dimmer switch which buzz's quite loudly when they are dimmed but works fine if the switch is fully on you can also hear some...
  32. R

    Domestic led lighting interferance

    Hi All Has any one else had this issue, ive recently replaced some 12V down lights for LED lamps and supplier confirmed the existing transformers were ok, anyway since fitting if they turn the lights on the radios will go off any were in the house and it does not matter what station they listen...
  33. I

    Insulation resistance low voltage lighting

    I have recently qualified and am coming towards testing a re-wire. I have fitted 30 low voltage downlighters with transformers. Apart from removing the bulbs do I need to do anything else before pumping 500volts through the circuits. ie will 500volts damage the transformers or are they removed...
  34. jason121


    Had a few drinks last night with a mate from DNO high upin the ranks, let slip that DNO don’t want PV installed that’s why they takethe full 65 days for applications. Too much work for them altering network and processing paper work
  35. H

    Domestic 24 volt, 50 hertz, 81 watt pump

    I've got a very well made 24 volt, 50 hertz, 81 watt pump, however I do NOT have a transformer/converter. I'm from down-under, so we run on between 220 to 250 volts. Is there a nifty trick one can do to get this thing running on 240 volts? Can I put a different transformer in-line with a...
  36. V

    240v - 12v downlighter transformerkeeps blowing.

    Hi, I have replaced this twice and they have both blown within a few minutes of fitting. There are 3 lights on the circuit each with their own transformer and a dimmer switch. This installation has been up for 10 years with no problems till now, the other 2 lights are fine. 2 transformers...
  37. C

    Domestic under cupboard lighting help

    hi i am at ajob and the customer has already fitted the under cupboar lights all of which are different which is somewhat annoying. i have brought the transformers for them and the are the correct rating. i just dont have a clue how to fit them. this is the first time i have ever had to fit...
  38. T

    Domestic Circuit tripping with tranformers.

    I have just replaced some dimmable transformers. But they keep tripping the circuit, the transformers a new and I installed first without a dimmer switch. If I disconnect them the circuit stays closed, is there a way to test the transformers?
  39. M

    Testing transformers

    Hi this is my first post on here> Can anyone help me with testing 12v transformers? I've tested low voltage bathroom fan transformers ok, but not low voltage light transformers. I'm using a Megger, and some of the transformers say 'dont test with a megger' on them? I guess i'm missing a trick...
  40. K

    Lutron Dimmer

    Hi Anyone got any advice which transformers I might use for Lutron Dimmers, my wholesaler isnt to sure if his bog standard 230/12V will suffice? Cheers
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