The "Megger" is the brand name of a well known international company that makes a few kinds of meter. But you often see the term "Megger" used to describe a meter, it usually means a meter can measure in millions of Ohms resistance. It is handy to have of course, for measuring things like insulation and appliance resistance. But expensive and not perhaps necessary, also if its an insulation tester they usually test with a 500 volt DC charge, which would fry a boilers pcb probably. You can of course get lower and higher voltage insulation testers.
However we are talking about what engineers usually use and not what old codgers like myself have used in the past for certain things. I hasten to add not sticking it across a boiler circuit. Handy for immersion heaters though.
Once again insulation testers are extremely expensive and you do need to know how to use them properly. The usual price for a cheap one but safe is about £150 or so. The "Megger" insulation tester itself is probably £250 or more brand new. And if you buy one second hand get it checked and calibrated about £40 or so. The thing is unless your a "sparks" you may never get your money back on it. And watch out for cheap Chinese imports. Although being fair many of the well known brands seem to be made there as well.
You never know how well a cheap meters safety features work. Although a lot of testing is done dead circuit, its not always easy to remember whether you have turned the "eleccy" off or not if the isolating switch is miles away or if your a try that guy or gal and switch the "eleccy" on and off each time you make an adjustment to see if "that" works. If the pressure is on you can forget whether you have turned it on or off. Don't forget I am talking real world not college course. In the event you get it wrong you will need all the safety features working properly. Being fair to Chinese imports though I simply do not know how good their meters are, it would be interesting to find out.
Make sure any meter is BS and CE marked. Incidentally CE is not a safety mark, it is just to say the goods can be sold in the EU. Check its safety marks, you can find a list of EU and Brit approvals on the internet.
Fluke make a multi meter for gas service engineers I think they call them HVAC engineers its the 116, but it is expensive, but worth it.
What I have found though, is that it usually only differs from cheaper models by being able to measure micro amps, which are handy for testing flame detection probes. but other than that, you can usually find the same features on cheaper meters. And anyway probably flame detection probes on domestic boiler are usually cheap enough to carry a spare with you to try out.
Please don't get mixed up, over mega Ohms expensive meters may be able to test in mega Ohms but they do not test insulation.
Anyway there is a cheaper Kane meter DM393 C about £80 that does very much the same job as the 116 and I suppose there are a few more makes about as well. But you could probably do a passable fault finding job with a cheap meter. The thing is you have got to know what you are measuring, they are easy to use, its just getting to know what it is telling you that is harder.
Most guys I suppose go by what their experience tells them the fault could be and just change the part they think it is, without electrical testing. But an electrical test for say resistance can confirm your idea that the fan motor has gone. There is nothing worse than buying an expensive part, turning on the juice and you still get "no go" anyway its lazy. How do you recover the money paid out for the part? Some suppliers sell on a none return basis, I know HRP did on their PCB's. You want to be sure its broken before you spend out for a new one. So its worth while doing a bit of study to find out how to use a multi meter properly.
Must admit its often difficult to do so in an occupied house if the boiler is in a tight cupboard full of gear and people running all around you shouting "When will you be finished". We sure need a gas engineers simple to understand multi meter reference book. There you go you computer "Whizz kids" a gap in the market for you, write a test app for a mobile or laptop and Google may buy you out for a few million.
