Routing cable from loft to consumer unit in kitchen

[NewbieDiz]

Hi

I am in my first year studying/apprenticeship in electrics and need little help if pos routing a cable from the loft to the kitchen on the ground floor of a two storey house.

The cable is 2.5mm for a heat pump for a shower running to a fuse spur in the loft from the CU.

I have seen on hear suggested running it down the cavity or maybe in YT2 trunking all the way down to the consumer unit.
Is there any of ways of routing the cable?

 

[londonboy]

I usually do things like that externally. Armoured or conduit?

 

[NewbieDiz]

Sorry if this comes across stupid but you would drill to the outside and then clip it down the side of the house and re-enter next to CU

 

[riveralt]

Are you saying that the heat pump is on its own circuit - and it runs from the CU to the FCU and then to the heat pump?

Or is it a spur from a ring final or radial circuit?

What power output of the heat pump - what is the MCB and RCB situation?

Is the heat pump (shower) in the kitchen?

Is there a problem with running the cable through the first floor floorboards because if you are going through the loft you may have to derate the cable.

 

[PrenticeBoyofDerry]

Routing it through the cavity is not recommended.
So either on outside wall, internally through trunking or chasing out in permitted safe zones.

 

[londonboy]

Yes. I usually run it straight up through the soffits into the loft.

 

[NewbieDiz]

It will be on its on circuit running off a 16amp MCB.
The heat pump is being installed in the loft directly above the bathroom.
Derate the cable

 

[londonboy]

Won't the electrician your working with help you with this, at the weekend?

 

[NewbieDiz]

Would usually but he is away on holiday for two weeks and was going to try and do it myself

 

[riveralt]

It will be on its own circuit running off a 16amp MCB.
The heat pump is being installed in the loft directly above the bathroom.

I assume then that the CU is in the kitchen.

Derate the cable

Yes - you will have worked out the design current lb and ensured that the overcurrent device ln is greater than or equal to lb.
Then you will have determined the current carrying capacity of the cable after using the formula in the OSG. Add to this issues of voltage drop (probably not a problem in this instance) and how the cable is routed e.g. derating may be required if your cable goes through insulation.

 

[holmslaw]

..

 

[Steve]

Hold on, I think some people might be confused here.

A HEAT PUMP is a device for extracting heat from the air or the ground outside, and dispersing it indoors, using some kind of refrigeration system. They cost £1000's and involve an outdoor and indoor unit.

A SHOWER PUMP is a device for boosting the pressure to a gravity fed pump. They cost £100's.

The two are completely unrelated devices.

@ the OP, please be clear what it is you're doing.


A half-arsed job would be taking it down the outside of the house in conduit.

A proper job would be routing through the inside of the house. This would usually involve going through a service duct such as an airing cupboard or a soil stack/pipework boxing, understairs/overstairs cupboards etc.

 

[1john]

sounds like it may be a heat recovery ventilation unit, doubt it needs a 16A supply though, they are normally very low power.

 

[Wangerman]

Do it in 3 core flex and pin it to the skirting board

 

[tonyelectric]

I would check the rating of the pump, if its less than 3Kw and there is no specific reason why you want it on a dedicated supply i'd spur it off the ring circuit which will make your job much easier and less destructive.

If you do need to go from the CU to the loft then as others say there is two methods that you can use, down the outside in armor or by chasing/under floor etc inside. YT2 looks awful in domestic jobs IMHO, I always feel it's a bit temporary, so your choice will be dictated by what your customer wants (many people have a aversion to there floors and walls being ripped up), draping don a cavity is bad because the cable is unsupported and therefore pulling by its own weight, plus it can be a so and so to do with wall insulation etc.

As you are going it alone as a newbie, keep it as simple as requirement and regs permit (plus doing a good job), that mantra will save you many headaches in your career!