how many flu tubes

[maguire]

How many 58W flu tubes constitute an need for a C type mcb, I am having a dispute with a company maintenance guy I say it is unnessecary to have a C type for 5 doubles (10 Tubes)
As a matter of interest there is a D20 on a radial running a warm air extractor on a plug top ??
DM

 

[ericmark]

It would all depend on type of fluorescent tubes and method of switching. If one considers a 6A supply then with 58W tubes with HF ballast units likely you could run around 16 tubes even with a B type and single switch but if you use a induction ballast then on a single switch you could find problems once you went over 8 tubes. However split them with 4 tubes a switch and likely 14 lamps will start with no problem.

The problem with inductance start is that some are for 220v some 230v and some 240v and if you have 240 volt ballast units then you can get problems starting but they use less power. With 220 units powered from 240 volt a 58W fitting can draw nearly 100W.

I had a job lighting some tunnels with 60W 110v fittings and I considered should be able to have 32 units but to be on safe side I would use 25 units per run plugged into a 16A outlet. When they tripped I used the meter and measured 25A draw. Lucky the units had the option of 110 or 127 volt supply and swapping first 20 to 127 volt supply dropped the current draw to 14A and so no more problems.

I then took a unit and started to play with it in the workshop. Remove the power factor correction capacitor and the current draw near doubled and in service it is something never tested so they will fail in time so current used will rise in time.

Also unlike a bulb where if one increases the voltage the current increases in proportion with the fluorescent using a inductance control gear it seems to be more like a logarithmic increase and 220 to 240 can double current draw.

However most commercial premises are now turning to HF fluorescent which use near the rated value over quite a voltage range typicality 210 to 250 volt AC or DC feed so current draw can be much reduced. Also they produce slightly more light and the tubes last up to 5 times longer with less reduction in light output as they age.

And as yet I have not considered the different inrush as one moves from make to make. In an ideal world the current draw of a new system would be measured and logged and when it started to rise the maintenance electrician would change all the power factor correction capacitors or which is far more likely tubes would all be changed as set time and fittings would all be changed at a set time. However we don't live in an ideal world and although I have seen tubes all changed when 10% have failed getting management to understand labour costs mean using HF lighting and changing all tubes every 3 years is cost effective seems to be like banging ones head against a brick wall.

 

[ColJack]

bet you wish you hadn't asked now huh?

 

[vsynth]

'Ask Elvis' comes to DIYnot!

 

[maguire]

cheers mate, very informative, and well explained, I will have to check whats been fitted, but I have a suspicion that it will turn out to be a mixed bag as the existing are not all the same in appearance but cant tell by looking
DM