- Reaction score
- 3,010
As title,
Megaflo hot water cylinder has three 3KW immersion elements. Each fed from an FCU in 2.5mm 3093Y flex.
On the surface all looked good.
Initial testing showed no earth continuity on two of the elements.
Closer inspection showed all FCU covers were loose.
Further inspection showed all three dry lining back boxes were smashed. The CPC from the first FCU to the second was broken, probably when the face plates were screwed on.
The FCUs are fed in 6mm T&E and each spurred off the previous, so two 6mm conductors in the terminals and the 2.5mm flex. When the face plates had been screwed on the inflexibility of the 6mm conductors had pushed the back out of the back boxes and broken some of the screw lugs.
MKs documentation state the FCUs are good two 6mm in each terminal but also state each FCU is good for 20Amps. My calcs put the current going through the last FCU at 12Amps, 24 for the second and 36 for the third. Now, this is only current through the terminals and not that being switched, would this challenge the FCU?
I have been tasked with getting it working....
I cannot see how the original set up can be safely put back into service, more from the physical constraints in the back boxes than anything else so intend to use the 6mm to feed a small CU and run each FCU off its own 16Amp MCB with an RCD protecting all three.
all will be tested and certified afterwards but the R1+R2s are likely to be zero as the new radial circuits are going to be less than a meter long, how would you record this?
Hope this is clear but kind of thinking it might not be.
Megaflo hot water cylinder has three 3KW immersion elements. Each fed from an FCU in 2.5mm 3093Y flex.
On the surface all looked good.
Initial testing showed no earth continuity on two of the elements.
Closer inspection showed all FCU covers were loose.
Further inspection showed all three dry lining back boxes were smashed. The CPC from the first FCU to the second was broken, probably when the face plates were screwed on.
The FCUs are fed in 6mm T&E and each spurred off the previous, so two 6mm conductors in the terminals and the 2.5mm flex. When the face plates had been screwed on the inflexibility of the 6mm conductors had pushed the back out of the back boxes and broken some of the screw lugs.
MKs documentation state the FCUs are good two 6mm in each terminal but also state each FCU is good for 20Amps. My calcs put the current going through the last FCU at 12Amps, 24 for the second and 36 for the third. Now, this is only current through the terminals and not that being switched, would this challenge the FCU?
I have been tasked with getting it working....
I cannot see how the original set up can be safely put back into service, more from the physical constraints in the back boxes than anything else so intend to use the 6mm to feed a small CU and run each FCU off its own 16Amp MCB with an RCD protecting all three.
all will be tested and certified afterwards but the R1+R2s are likely to be zero as the new radial circuits are going to be less than a meter long, how would you record this?
Hope this is clear but kind of thinking it might not be.
