installing a macerator and 3KW water heater

[greyham]

Hi Could some someone please help with the following:

I am looking to run a supply to an 600W macerator and a 3KW heater located within a toilet/shower room in an out buildng at the back of the garden. There is already a 30mA RCD protected board with a 20A spare way. I'm looking at supplying the macerator and water heater from the same circuit and run it in 2.5mm twin and earth however I have a couple of questions.

1. Can I install fused connection units within close vicinity to the sink and the toilet or would it be best to locate them outside of the room.
2. I have a couple of wiring diagrams in my album and would appreciate if you can have a look and see which would be best baring in mind I'm aware the water heater would be close to the 13A fused connection unit.


Apologies if the diagrams are a bit crude but, hopefully they will give you some indication as to what I'm proposing.

Any feedback/help would be gratefully received.[/img]

 

[ban-all-sheds]

When you apply for Building Regulations approval what will you say will be the way you'll ensure compliance with Part P?

 

[bernardgreen]

We have a domestic mascerator and sewage pump so I am speaking from 30 years of experience.

Run separate cables from the house to the out house for the heater and the mascerator if possible. But in any event use the largest cross section cable you can.

On a single cable the effect of the voltage drop along the cable when the heater is drawing 3 Kw has to be considered. Low voltage at the mascerator may prevent it starting efficiently and this will add to the wear on the mascerator's motor.

The start up current on a mascerator motor can be many times higher than the running current. You might need a slow acting MCB to avoid it being tripped when the motor starts. If there is material still in the mascerator's "teeth" when it starts then the over current can last for a significant and MCB tripping time.

Do not use the mascerator supply cable to feed any sensitive electrical or electronic equipment. The voltage spikes when the mascerator turns off can be very large and disrupt computors or similar if on the same MCB.

If the building is not heated then consider fitting an anti frost heater to the mascerator and its pipework . In cold weather the mascerator contents might freeze and do a lot of expensive damage to the mascerator.

And above all not not allow anyone to put disposable nappies or wet wipes into that toilet. Stripping and cleaning a jammed up mascerator is not a pleasant task. ( I had the stained T shirt )

 

[Chri5]

Why did you have a T-shirt in the mascerator

 

[greyham]

Thanks for your response Bernard. the board I am intending supplying the macerator from is only 5ft away and has a main RCD protected isolating switch rated at 63A. There is a spare 20A breaker within this board that I am intending on using to supply both the heater and the macerator however, I am not entirely sure whether to seperate the two circuits so that they can be individually isolated at point of use (i.e. 13A FCU's located next to the toilet 0.3m away at low level) or have the FCU's outside of the room located on the wall but, clearly labelled as to what they isolate?

 

[Chri5]

What if little Jonny turns round when having a wee ?

Common sense should tell you that low level 300mm from the toilet is NOT a prudent, considered design. Water source and electrical switches / sockets and spurs shouldn't be in near proximity. 600mm from fixed water sources in the minimum.

Put the fused spurs at high level and run down un joined 1 piece lengths to the heater and mascerator.

Re-read Bernards post, his advice is well judged since he speaks with 1st hand knowledge.

 

[greyham]

Thanks for your responses the only trouble I now have is that the board only has one spare way as the others are supplying various lighting/power supplies within the building. Hence why I'm asking whether I can supply both items from the same 20A MCB although am I right in thinking the general consensus is no?

 

[ban-all-sheds]

And above all not not allow anyone to put disposable nappies or wet wipes into that toilet. Stripping and cleaning a jammed up mascerator is not a pleasant task.

Basically the only way of maintaining the slightest semblance of serviceability is to impose on pain of repair the same rules as for a small yachts sea toilet - if it hasn't passed through you it doesn't go in the bowl.

 

[ban-all-sheds]

Hence why I'm asking whether I can supply both items from the same 20A MCB although am I right in thinking the general consensus is no?

Greyham - when you apply for Building Regulations approval (I count at least 3 notifiable elements in this work), what will you say will be the way you intend to comply with Part P?

That's not a rhetorical question - what you plan to do might have a major influence on the advice you should be given here.

 

[greyham]

I plan to install a small 3KW water heater and a macerator to supply a toilet which is located in a summer house at the rear of the garden it will only be used for a couple of months of the year and is not intended to be inhabited. There is a shower present in the area as the previous owner let this out however the macerator that was there has since failed and there was previously no provision for a water heater in this particular area.

I intend to supply the two items which are to be supplied by twin and earth cable buried in the wall. They will be fed from Fused spurs located at high level. In all honesty I am thinking of calling an electrician to look at this but, thought I would get some feed back off of here before calling one out. So as I said before any feedback would be gratefully received.

 

[ban-all-sheds]

I plan to install a small 3KW water heater and a macerator to supply a toilet which is located in a summer house at the rear of the garden it will only be used for a couple of months of the year and is not intended to be inhabited. There is a shower present in the area as the previous owner let this out

Let it out as what?

If it had a shower and a WC, did it also have sleeping accommodation? If so, have you removed the latter? (It's capability that matters, not your intentions.)

If the building is of a class exempted in Schedule 2 of the Building Regulations then the regulations for the water heater and WC don't apply, but the electrical ones still do, including notification.

In all honesty I am thinking of calling an electrician to look at this but, thought I would get some feed back off of here before calling one out. So as I said before any feedback would be gratefully received.

If you're intending to notify it will almost certainly be cheaper to use a registered electrician, in which case all the design and installation decisions can only be made by him.

Do the specs for the s**t-mincer say anything about startup current, fuse rating, cable size etc?

 

[bernardgreen]

Do the specs for the s**t-mincer say anything about startup current, fuse rating, cable size etc?

The Installation Guidelines June 1979 when I installed it only say that it is recommended to use 4 core PVC SWA cables. No mention of current or size. But then in 1979 things were different. installers were allowed to think about what was needed.

cynic mode OFF

 

[Chri5]

You can spur from a MCB, so if you only have one MCB you could run 2 x TE cables, 1 to each f/spur.

You would get away with 1 x TE and 2 x fuse spurs (just) the fused spurs could have 13 amp fuses in them and could run 2 x 13 amp load, which is on the very edge of being overload.

OK we know that the 2 x spurs will not be running 2 x 13 amp loads- but the potential to do so is there, hence why I'd suggest 2 x cables to the same MCB would be better.

 

[bernardgreen]

fused spurs could have 13 amp fuses in them

A normal 13 amp fuse might blow when the mascerator starts if it has a lot of s**t and paper already in its teeth giving a heavy starting load. Check with the manufactures about that.

Also check about starting dry. Does this mascerator have a built in positive displacement pump ( PDP ) ? Some types of PDP must never be run if dry, this is only a problem when run for the first time when it has to be wetted ( normally by removing a screwed in plug and adding water ) or after a very long period of not being used and it has dried out.


I should add that if installed properly and then used thoughfully the ones from reputable suppliers seldom give any problems.

 

[ban-all-sheds]

Here we go again - the **** has woken up.

Will you please provide a reasoned, logical, intelligent and mature explanation of why I should not have asked this:

• When you apply for Building Regulations approval what will you say will be the way you'll ensure compliance with Part P?

When you do, please bear in mind that we do still regularly see people here who think that they can DIY electrical work and then get an electrician to "sign it off".