12v power supply for diesel heater

[ASD289]

Hi,

I am in the process of setting up a diesel heater to warm our conservatory and need to provide 12v power to it. I have purchased a CCTV distribution box which essentially has a 30amp convertor wired to distribution board. My plan is to remove the distribution board and wire the power supply directly. The reason for going down the CCTV distribution box route is the power supply is the same as commonly used in these setups but they have exposed terminals which I really do not like the look of. The CCTV box provides the same PSU but in a locked metal box. My question is, the box does not appear to be earthed (unless it is earthed through the screws connecting the PSU to the box?) and as it's metal I assume it should be? Should I run a earth wire from the Earth terminal on the PSU to one of the screw holes which were holding the distribution board in place?

This is the box I have
18ch 12v Dc 30a Cctv Power Supply Distribution Box Lock Security Multiple Camera | eBay - https://www.ebay.co.uk/itm/354028722531?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=dm0owbdorea&sssrc=2047675&ssuid=3Zacs1rTSce&widget_ver=artemis&media=COPY

Thanks

 

[DPG]

Looks like a class I product, ie. not double insulated, so should have an earth connection. As you say, this may be provided via the screws holding the power supply module to the metal enclosure.

Is there definitely an earth connection at the incoming terminal block where the mains input cable connects to?

 

[ASD289]

Looks like a class I product, ie. not double insulated, so should have an earth connection. As you say, this may be provided via the screws holding the power supply module to the metal enclosure.

Is there definitely an earth connection at the incoming terminal block where the mains input cable connects to?

Yep, has connection for earth (see pic)

Plan is to wire a standard plug using 2.5mm flex and connect to the 3 terminals on the right

 

[ASD289]

Might be a silly question but can I test by using a multimeter on the earth terminal and the box to see if there is continuity?

 

[DPG]

Might be a silly question but can I test by using a multimeter on the earth terminal and the box to see if there is continuity?

To a degree. You can do a basic resistance test with a multimeter. A proper test would be an earth bond test - this would test the connection while it was carrying current, but it needs a specific tester.

 

[ASD289]

I don't have one of those testers unfortunately. I done a test by touching the earth terminal and the screw in the fixing and there is a connection so looks like it is earthed through there. Thanks for you help

 

[James]

2.5mm is too big to fit in a standard 13A plug.
use 1 or 1.5mm flex

 

[brianmoooore]

As well as the proposed flex being oversized, I would think the PSU itself is as well. These heaters are designed for use on boats and in trucks, caravans, etc, and are intended to be able to run from the battery. I don't know the spec. of the one you have, but a particular 2kW one, which I do have experience of, draws just under 2A at 12 volts

 

[James]

As well as the proposed flex being oversized, I would think the PSU itself is as well. These heaters are designed for use on boats and in trucks, caravans, etc, and are intended to be able to run from the battery. I don't know the spec. of the one you have, but a particular 2kW one, which I do have experience of, draws just under 2A at 12 volts

On startup, the glow plugs can draw 8A or more, but yes when running less than 2A is about right.

 

[ASD289]

The heater I have on order is the 8KW one. From what I have read up they can draw roughly 10amps on the power up cycle dropping down to quite low once running. I was thinking it is better to have the PSU over sized then possibly under?

Thanks for the tip on flex size, will get some 1.5mm flex.