Running new cable in roof space.

[stubuzz]

My family has just moved into a bungalow and the pictures they have sent me show that the air con has been tapped into the closest socket. The installers have used about 6 m of plastic trunking and it looks awful.

When i arrive, i plan on running a dedicated circuit from the fuse box to the air con. However, my wife tells me there is no access into the roof space and all of the current wiring is embedded in the walls.

 

What are my options?

[Crossy]

Cut access holes, run your cables, test, get your local man to patch up the holes.

 

[stubuzz]

Would i be better to cut a man sized access hole and fit a door/hatch?

Edited September 4, 2020 by stubuzz

[lopburi3]

Although still wire to dedicated breakers our last few units had normal outlet plugs attached from factory (9-13k size) as they use 1,500w or less of electric these days.  AC is not a huge draw - but they are often on for a long time so usage cost has more to do with that. 

 

As for plastic trunking split systems are used here and often fan coil and compressor units have to be a distance apart so pipes for gas/control electric and another for drain water are required and covered with such.

[stubuzz]

[lopburi3]

OK see what you mean but that is a five minute job to replace or a bit longer to paint.  Normal color here is white so not sure where/why he got that.   White should not look bad if done with 90 degree corner and follows wall.

[stubuzz]

What type of cable is needed to go above the ceiling? VAF,  THW?

[Crossy]

9 hours ago, stubuzz said:

What type of cable is needed to go above the ceiling? VAF,  THW?

 

Personally I'd go for singles in conduit to make it critter-proof, but VAF looped across the ceiling supports is the usual way to go.

[Crossy]

10 hours ago, stubuzz said:

Would i be better to cut a man sized access hole and fit a door/hatch?

 

We have a few access hatches near the "critical" junction boxes some of which I can get my shoulders through. No way I would be venturing on to the ceiling, I am not slim and silth-like

[thaibeachlovers]

10 hours ago, stubuzz said:

Would i be better to cut a man sized access hole and fit a door/hatch?

Absolutely. Need access to roof space for many reasons. What happens if your roof leaks?

Watch out up there as sometimes the ceiling will not support your weight. I almost fell through on top of my wife in bed below.

 

If doing wiring yourself make sure there is an RCD in your wiring. Mine saved my life a few times from Thai electrician leaving live wires exposed in the roof space.

 

Otherwise, screw ducting around the wall below the ceiling and run cable through it. I should have done that as it's dangerous up there.

[Crossy]

7 minutes ago, thaibeachlovers said:

I almost fell through on top of my wife in bed below.

 

I have heard of people bounding off wardrobes to "enhance the experience", but jumping through the ceiling takes the biscuit.

 

When does the movie come out? 

 

[thaibeachlovers]

1 minute ago, Crossy said:

 

I have heard of people bounding off wardrobes to "enhance the experience", but jumping through the ceiling takes the biscuit.

 

When does the movie come out? 

 

More likely I'd be in jail for manslaughter. If I'd fallen on her from the high ceiling, given my weight she'd have been lucky to survive. I had to walk on top of the interior walls given the ceiling was supported only by those skinny metal supports, and I slipped.

I should have used ducting below the ceiling- way safer even if not attractive.

I had to use a steel rod to span 30 feet to run the cables in the roof space and they touched the exposed live wires the "electrician" left for me. My newly installed RCD came in handy then.

[thaibeachlovers]

11 hours ago, stubuzz said:

The installers have used about 6 m of plastic trunking and it looks awful.

That's normal. Just paint it.

 

Otherwise, cut into the concrete wall, insert cable and plaster over. However, cable to dedicated circuit breaker probably better.

[Crossy]

2 minutes ago, thaibeachlovers said:

I should have used ducting below the ceiling- way safer even if not attractive.

I had to use a steel rod to span 30 feet to run the cables in the roof space and they touched the exposed live wires the "electrician" left for me. My newly installed RCD came in handy then.

 

The mini-trunking actually looks fine if done neatly, it soon becomes invisible.

 

I use a bamboo rod, Madam uses a duster on the end of it to evict the spiders from our high ceilings.

[thaibeachlovers]

Just now, Crossy said:

 

The mini-trunking actually looks fine if done neatly, it soon becomes invisible.

 

I use a bamboo rod, Madam uses a duster on the end of it to evict the spiders from our high ceilings.

I couldn't get a long bamboo up given where the hatch was. I used a very flexible ( thin ) bit of steel rod.

Not going up at all would be the safest option.

Anyway, I didn't expect exposed live wires, but I learned fast.

[stubuzz]

Thanks for the replies.

I have another idea. In the picture, unit 1 has a dedicated breaker in the consumer unit. I was thinking that i could upgrade the wire to 4mm and then run both units on 1 circuit. I could run the power to unit 2 from unit 1. This could be done by running cable in conduit on the outside wall.

I think both units are 9-12,000BTU.

If this is possible, what amperage MCB should be used?

[Crossy]

8 minutes ago, stubuzz said:

Thanks for the replies.

I have another idea. In the picture, unit 1 has a dedicated breaker in the consumer unit. I was thinking that i could upgrade the wire to 4mm and then run both units on 1 circuit. I could run the power to unit 2 from unit 1. This could be done by running cable in conduit on the outside wall.

I think both units are 9-12,000BTU.

If this is possible, what amperage MCB should be used?

 

What size is the current cable to unit 1?

 

A couple of 12,000 BTU units will be quite happy on 2.5mm² cable.

 

Try them on a 20A breaker (most are "C" curve so should withstand the start surge) failing that a 32A breaker would be ok.

 

Assuming there's nothing else on that circuit you could still use 2.5mm² as there's no danger of overload you just have to protect against short circuits.

[lopburi3]

I would find out the wattage usage of units (brand/model/size) as 4mm may not be required if modern units of that size.  Bit concerned they are mounted just below overhang at hottest location and not clear if they even have much room to draw air between house and condenser.  

[bankruatsteve]

Both are OK on the same circuit using 2.5mm² cable on a 20amp breaker.  Maybe put 2-pole isolator switch at each unit to facilitate maintenance.  

[bankruatsteve]

1 hour ago, lopburi3 said:

Bit concerned they are mounted just below overhang

Yeah.  I wonder how they will get the top off for cleaning/maintenance?  Not impossible, but doesn't look easy.

[sometimewoodworker]

6 hours ago, lopburi3 said:

 Bit concerned they are mounted just below overhang at hottest location and not clear if they even have much room to draw air between house and condenser.  

The mounting looks perfectly OK as far as distance from the house (our 3 outside units are the same distance from the wall) and since there is a ceiling under the roof they won’t get much heat from above.

[lopburi3]

Just now, sometimewoodworker said:

The mounting looks perfectly OK as far as distance from the house (our 3 outside units are the same distance from the wall) and since there is a ceiling under the roof they won’t get much heat from above.

The heat goes up and trapped by ceiling so will be cooling with its own heat.  Not good IMHO as does not appear to be any airflow out as whole area appears to be enclosed.  As for space from wall I can not see well enough but it appeared earlier that wall came out to hit AC but now see it is just darker blue paint next to drain pipe which I took as a wall edge.

[alacrity]

On 9/4/2020 at 8:00 PM, stubuzz said:

That's what they do, if you let them.

Always supervise.