Power supply issues with a MegaFlo water cylinder

[Alder32]

Having some real problems with an unvented 250L MegaFlo cylinder which I'm hoping someone can help with. At the end of my tether!

Basically every time the bottom, main element kicks in it causes the 13A fuse in the wall plug to blow. The top booster element is fine but doesn't give enough hot water for a shower.

The unit is connected to a timer so that the main element comes on over night when the economy 7 rates apply.

As the unit is new I've had the engineers out and replaced the element which they thought was short circuiting. And the've also replaced the thermostat part.

But the problem is still happening. Has anyone experienced this with a MegaFlo before or have any clues what the problem might be. Feels like I'm running out of options!

Thanks!

 

[kai]

Domestic Megaflows tend to come with 3kW elements nowadays, and mine does (It's actually 2.8kw @ 230volts), but in my case the immersion's just a backup for the Gas Central Heating Boiler.

It could be an earth fault somewhere in the megaflow or its wiring - is it fed from a standard 13amp plugtop, or a 13amp DP switched fuse-connection unit (e.g. MK K330-WHI etc)?

13amp plugtops have been known to overheat when used to run immersions, the 13amp DP fuse-connection unit is the safest option.

 

[Alder32]

Domestic Megaflows tend to come with 3kW elements nowadays, and mine does (It's actually 2.8kw @ 230volts), but in my case the immersion's just a backup for the Gas Central Heating Boiler.

It could be an earth fault somewhere in the megaflow or its wiring - is it fed from a standard 13amp plugtop, or a 13amp DP switched fuse-connection unit (e.g. MK K330-WHI etc)?

13amp plugtops have been known to overheat when used to run immersions, the 13amp DP fuse-connection unit is the safest option.

I'm not 100% sure what kind of plug it is. It's a switch in the wall with a 13 amp fuse that you can pop out and change. The supply goes from that into the timer which is where I think it may have been incorrectly wired.

 

[Taylortwocities]

Does the fuse still blow if you disconnect the wires from the MegaFlo terminals?

If it does still blow then you need to look elsewhere (the timer?) for the problem.

If it does not blow then you need to test:

What is the resistance of the MegaFlo's element

Do Insulation Resistance tests on the element to earth

 

[Alder32]

Does the fuse still blow if you disconnect the wires from the MegaFlo terminals?

If it does still blow then you need to look elsewhere (the timer?) for the problem.

If it does not blow then you need to test:

What is the resistance of the MegaFlo's element

Do Insulation Resistance tests on the element to earth

I'll get them to try that when they come back. Thanks for your help!

 

[kai]

From what I have been reading above...
As the timer is wired downstream of your FCU, is there a chance that the timer was wired incorrectly, so that when it comes on, it shorts out due to a wiring error perhaps??.

A fuse-connection unit is what I have on my one - a photo of mine is attached to assist. The pair of FCU's control the Immersion(L) and Boiler(R) respestively.