MK Grid Plus with Moulded Surface Box

[JohnW2]

Am I missing something here? I am very familar with using MK Grid Plus components. Most of my experience relates to flush fitting or metal surface boxes. I was sure I'd also used while moulded surface boxes, but maybe not!

With flush fitting or metal surface boxes, the lugs on the side of the grid frame locate in appropriate places, such that when one fully tightens its screws, it is in the correct position in relation to the faceplate. As I've just discovered, if one uses a white surface box (e.g. MK2142 for 4-gang), there is nothing for the grid frame lugs to locate with, so that if one tightens the screws fully, the frame is much too far from the faceplate. I'm sure this problem didn't exist with the previous generation of MK grid stuff. The current MK documentation contains the not-very-explicit comment:

An integral design feature automatically ensures that the modules fit perfectly into the frontplate in flush fitting installations.
Some manual adjustment may be required for surface mounted applications

Is this referring to the problem I've described? Does it mean that I have to adjust the screwing in of the frame screws so that the frame is just at the right height (but flapping around all over the place) and then use the faceplate screws to sort-of tighten things up? That would seem odd, and not very satisfactory. It would seem to make much more sense to use spacers on the frame screws, so that one could then properly tighten those screws - but I see no mention of spacers. ... or am I completely missing something?

Kind Regards, John.

 

[Lectrician]

This is why the screws are captive.

Align the grid tabs with the front of the box, the front of the tabs marginally back from the rim of the box.

I must be honest, the original MK grid was far superior in build quality, but the modules could where not the easiest to remove (OK, not too hard, but not as easy as the newer range).

The thing that I get annoyed with with the new range is that only one set of terminal screws are accessible with the module in the grid - With the old range you could build your grid and then wire. With the new range you need to wire atleast one side of each module before clipping into the grid.

 

[JohnW2]

This is why the screws are captive.
Align the grid tabs with the front of the box, the front of the tabs marginally back from the rim of the box.

Thanks. I guess that's what I was describing as my interpretation. I presume that the doing up of the frame screws is pretty critical, because one is relying on tension in them (a very odd engineering situation) to hold the faceplace firmly against the box. Don't you think it would be better to improvise some spacers?

This I must be honest, the original MK grid was far superior in build quality, but the modules could where not the easiest to remove (OK, not too hard, but not as easy as the newer range).

The original range certainly didn't have this problem. I don't recall how easy/difficult it was to remove the modules, but I'm sure I managed!

The thing that I get annoyed with with the new range is that only one set of terminal screws are accessible with the module in the grid - With the old range you could build your grid and then wire. With the new range you need to wire atleast one side of each module before clipping into the grid.

Agreed.

Kind Regards, John.

 

[333rocky333]

I make up the space with 3.5 mm washers or 4 mm nuts and washers over the thread to within tolerence then use the plate for the last tension if that makes sense
I find it gives a more secure fit.

The grid frame dont fit tight on metal i recall or plastic boxes, it relies on the sides resting on the plaster or wall material rather than the box.
The exception is the metalclad surface switch box which has indents each side.

 

[JohnW2]

I make up the space with 3.5 mm washers or 4 mm nuts and washers over the thread to within tolerence then use the plate for the last tension if that makes sense
I find it gives a more secure fit.

Yes, that's precisely what I was thinking of doing. The 'flapping about all over the place' approach just doesn't seem good to me!

I have to wonder why on earth they did not simply mould in some bits in the white surface boxes for the grid's lugs to locate with (analagous withg what happens with flush/metal boxes)?

Kind Regards, John.

 

[333rocky333]

Quite often the screws get pulled through the plastic front plates to get them tight,more so with the two gang, thats why i started using spacers.

 

[JohnW2]

Quite often the screws get pulled through the plastic front plates to get them tight,more so with the two gang, thats why i started using spacers.

That makes a lot of sense. The frame needs to be rigidly attached to the box. The faceplate screws then only have to hold the faceplate on, which requires very little torque. To use them, seemingly 'as intended' to tighten up the frame as well is going to need more torque and is just asking for trouble. This seems to be uncharacteristically poor design for MK.

I think I will definitely use spacers, which was my first inclination when I encountered the problem.

Kind Regards, John.

 

[securespark]

I have to preface this comment by saying I have never surface-mounted GridPlus.

Don't you just fit the grid and screw it in loosely, then when you fit the front plate to it it holds it tight as the front plate is now pushing against the pattress?

 

[JohnW2]

Don't you just fit the grid and screw it in loosely, then when you fit the front plate to it it holds it tight as the front plate is now pushing against the pattress?

It's not quite as simple as that. Don't forget that the front plate screws go into the grid frame, not the pattress. Although in practice one would get to the roughly the right situation at first try, consider approaching it gradually ....

...consider first the situation in which you attached the frame very loosely (i.e. didn't screw its screws very far into the pattress). When you attach the front flat (to the frame) and fully tighten the front plate screws, the front plate will be tightly attached to the frame, but that whole assembly (front plate + frame) will literally be hanging off and flopping around all over the place, with a substantial gap between front plate and pattress.

If you keep repeating the above, each time screwing the frame screws a bit further into the pattress (before attaching front plate to frame), the front plate + frame assembly will continue to 'flop about', but the gap between front plate and pattress will gradually reduce.

Eventually you get to the stage at which the gap between front plate and pattress reduces to zero, but is still not very tight attached. Go just slightly further and then, when you tighten the front plate screws, that causes the frame screws to pull on the thread in the pattress inserts and thereby tighten everything together, as desired. As has been pointed out, the catch is that if you very slightly overdo that process, the front plate screws will break through it as tightened. That's why I think that using spacers will be much safer, and more secure.

The concept of nearly all grid systems is that the grid frame first attaches (firmly) to the box/pattress, and then the front plate simply attaches ('loosely') to the frame. That's not what is happening with this rather poor (IMO) design.

Kind Regards, John.

 

[Chri5]

You could always use a needle file and emulate the bites per the surface metal b/box.

Thus the frame / grid lugs will sit / position as they do on the metal back box.

 

[JohnW2]

You could always use a needle file and emulate the bites per the surface metal b/box.
Thus the frame / grid lugs will sit / position as they do on the metal back box.

I don't quite understand that. What is needed is not to file anything, but to add some 'shoulders' on either side within the box, for the grid frame's lugs to sit on. Why they are not already moulded there is anyone's guess.

On the basis of what you're suggesting, I suspect that you probably don't realise that the problem is that, with the white surface box, the grid frame does not reach the sides of the box.

Kind Regards, John.

 

[RF Lighting]

Screw the grid up till the lugs are just past flush with the sides of the box. Pop the front plate on.
Done.

Dead easy.

 

[JohnW2]

Screw the grid up till the lugs are just past flush with the sides of the box. Pop the front plate on.
Done.
Dead easy.

I guess that's what they intend, but it really isn't very satisfactory. If you tighten the front plate screws enough to hold everything firmly together (so that you can't slide the whole front plate + grid frame assembly around relative to the box, you're getting perilously close to the torque that will cause the screws to break through the front plate (I've already done it once!).

As I said before, the 'norm' for grid systems (including all other MK grid configurations, as far as I am aware) is for the grid frame to be solidly attached to the box, so that the front plate screws have to do nothing more than stop the front plate falling off - hence no need for excessive tightening. As I've said, I just don't understand why there are not some 'shoulders' at the sides of the white surface box for the frame lugs to sit on - just as with the metal boxes.

Kind Regards, John.

 

[JohnW2]

Just an update, for anyone interested ....

I make up the space with 3.5 mm washers or 4 mm nuts and washers over the thread to within tolerence then use the plate for the last tension if that makes sense.

I've just been experimenting, and it seems that two standard M4 nuts (total thickness fractionally under 6mm) on each side is just about perfect for the required spacing.

Kind Regards, John.