Domestic Electrical Question

[Guest eight]

MCB or RCD tripping?

[ChumpusRex]

Rubbish.

Google "shower with built in pump". Some showers do work only on mains pressure, but not all of them. These days there is an increasing trend towards power showers and these often have pumps.

A conventional "electric shower" is not pumped. It is plumbed direct to the mains cold supply, and heats the water directly. As they use a pressurised water supply, they do not have a pump.

There are "power showers", which take dual hot/cold feeds from a low pressure water supply, and use a pump in the order of 100W to push the water through the shower head. As they have dual hot/cold supplies, they contain no heating element.

The problem with "power showers" is that they require adequate stored hot water and a central heating system capable of reheating the store at an appropriate rate. It's pretty common, for the old low pressure style of system to be borderline or inadequate, especially if it was already undersized (e.g. flat conversions).

The advantage of an electric shower in this case, is that it doesn't need any fancy plumbing or heating upgrades. Just a mains cold water supply and a fat electrical connection. Therefore when a bath has been converted to a bath/shower, the retrofit of an electric shower has been very common.

[winkie]

You could always just follow the Hare Krishna movement and take cold showers all the time.

..all depends whether you are a cold shower person or a warm bath person.

[ntb]

Rubbish.

Google "shower with built in pump". Some showers do work only on mains pressure, but not all of them. These days there is an increasing trend towards power showers and these often have pumps.

Chumpus Rex saved me the bother of responding except to say that you can get pumped electric showers for use in very low water pressure situations.

An electric power shower would need an input of 20 - 30 KW to heat the water adequately which makes them infeasible. Therefore, not rubbish.

[Gigantic Purple Slug]

Chumpus Rex saved me the bother of responding except to say that you can get pumped electric showers for use in very low water pressure situations.

An electric power shower would need an input of 20 - 30 KW to heat the water adequately which makes them infeasible. Therefore, not rubbish.

Can you get electric showers with pumps ? Google says yes. They are actually quite common. The last three houses I have lived in have had showers with pumps of some sort, two external to the shower, one integrated.

If so, your first statement was clearly false : Electric showers work from mains pressure. No pumps involved.

Deal with it.

[geezer466]

It is almost certainly your internal wiring....

The current cable is underrated and unable to carry the amps required for the shower so it fails at the weakest point.....The fuse which is a deliberate weakest point to stop the cable overheating and catching fire in enclosed spaces like under your boards where there is lots of combustible material....

9Kw shower needs 10mm twin flat earth to be efficient. Any installer who upgrades the shower will be duty bound to upgrade the box and fit RCD'S.

There are no real shortcuts I am afraid, from here it is impossible to see what sort of cable you have from the box to the shower unit or what sort of condition it is in... Installing a lower KW shower may not solve your problem at all.

http://community.screwfix.com/threads/cable-size-question-from-a-non-electrician.58776/

[libspero]

MCB or RCD tripping?

Nothing like that installed, just an old fuse box (think large versions of the ones you still find in plugs).

Electric showers work from mains pressure. No pumps involved. If the fuse box and wiring dates from the 30's then it will likely contain some lead sheathed cable and rubber insulated cable. The rubber will have perished by now.

You may be lucky - often the entire wiring was run through conduit and can be replaced like for like without any chopping out. Check in the loft and you should be able to find some conduit visible below the insulation if this is so.

I think you will need a full rewire.

Helpfully the wiring from the fuse box runs up the wall behind. Some of the cables do indeed sound as you describe (metallic casing).. but most of them, including the one for the shower seem to be the modern plastic type. I presume the shower was installed some time after the house was built and thus has newer electrics.

Frustratingly the chunky cable which I'm fairly certain is for the shower drops down from the roof into a false ceiling in the bathroom.. so it looks like it's going to be a pig to get at without hacking into the ceiling. Nothing's ever straight forward..

[MrPin]

Frustratingly the chunky cable which I'm fairly certain is for the shower drops down from the roof into a false ceiling in the bathroom.. so it looks like it's going to be a pig to get at without hacking into the ceiling. Nothing's ever straight forward..

Every DIY disaster starts with a small screwdriver.

[libspero]

9Kw shower needs 10mm twin flat earth to be efficient. Any installer who upgrades the shower will be duty bound to upgrade the box and fit RCD'S.

There are no real shortcuts I am afraid, from here it is impossible to see what sort of cable you have from the box to the shower unit or what sort of condition it is in... Installing a lower KW shower may not solve your problem at all.

http://community.screwfix.com/threads/cable-size-question-from-a-non-electrician.58776/

This is a section of the cable where it runs through the roof..

I agree with you that it looks like it's probably not up to the high power requirement.. hence considering the upgraded wiring or just bunging in a lower power shower.

Regrettably since discovering the false ceiling it looks like the latter is going to be the far easier.

[libspero]

Every DIY disaster starts with a small screwdriver.

[MrPin]

That cable might not be big enough.

[Neptune]

That cable might not be big enough.

In theory/regulation its provably not the right size. But theres loads of safety factor in that and that cable ran the old shower no problem for how many years?

How many amps is the fuse rated too.

That cable looks like 6mm2 and can be protected by a 40 amp fuse. Have you tried a higher rated fuse.?

But frankly showers and electricity can be downright dangerous and having read what ive written Im wondering why would you follow my advice.

I would pay a good electrician to come in a replace the old Wylex fuse box youve got with a decent RCB protected current standard consumer unit.Its very hard to go wrong with trip switches and proper rated MCBs. They are proper good bits of kit which will protect your house and you and family. Then rewire the shower and get thatdone properly. Have the rest of the wiring checked and that it can take the loads youre putting on it.

[ntb]

Can you get electric showers with pumps ? Google says yes. They are actually quite common. The last three houses I have lived in have had showers with pumps of some sort, two external to the shower, one integrated.

If so, your first statement was clearly false : Electric showers work from mains pressure. No pumps involved.

Deal with it.

You are talking ******. There are showers with pumps. I don't doubt that is what you had. They were not however electric showers. Electric showers heat the water with electricity. They aren't powerful enough to heat a pumped water supply. Pumped showers use stored hot water or heated direct with gas from a combi boiler. Deal with that.

[ntb]

This is a section of the cable where it runs through the roof..

I agree with you that it looks like it's probably not up to the high power requirement.. hence considering the upgraded wiring or just bunging in a lower power shower.

Regrettably since discovering the false ceiling it looks like the latter is going to be the far easier.

That could even be 4mm T&E

Yes, circuits added over time will be to the prevailing regulations which continuously evolve.

Replacing the cable is notifiable and needs to be tested and certified either by a spark or building control. You will need the paperwork if you sell your house.

[libspero]

In theory/regulation its provably not the right size. But theres loads of safety factor in that and that cable ran the old shower no problem for how many years?

How many amps is the fuse rated too.

That cable looks like 6mm2 and can be protected by a 40 amp fuse. Have you tried a higher rated fuse.?

But frankly showers and electricity can be downright dangerous and having read what ive written Im wondering why would you follow my advice.

I would pay a good electrician to come in a replace the old Wylex fuse box youve got with a decent RCB protected current standard consumer unit.Its very hard to go wrong with trip switches and proper rated MCBs. They are proper good bits of kit which will protect your house and you and family. Then rewire the shower and get thatdone properly. Have the rest of the wiring checked and that it can take the loads youre putting on it.

The fuse is actually a 30 amp fuse.

I'm as puzzled as anyone as to how the first shower ever worked. Yes, we used it for over a year (from when we bought the house) before it died and it never popped a fuse.

When I first had the new shower put in I just asked the guy to replace it like for like (I read the rating off the bottom of it myself when he first asked what it was) He never corrected or questioned me during the installation.

All a bit odd, but if the fuse is well under the rating of the wire that's probably a good thing. I'll get someone in to swap out the fuse box and just get the lower power shower.

[libspero]

That could even be 4mm T&E

Yes, circuits added over time will be to the prevailing regulations which continuously evolve.

Replacing the cable is notifiable and needs to be tested and certified either by a spark or building control. You will need the paperwork if you sell your house.

No plans to replace any cables myself. The problem is (looking at where it runs) I don't think an electrician is going to be able to very easily change it either.

[geezer466]

No plans to replace any cables myself. The problem is (looking at where it runs) I don't think an electrician is going to be able to very easily change it either.

Not so much a question of replacing old cable.....

Look at it this way.... You can disconnect the old at both ends and chop it back to where it is out of sight under the boards/in the ceiling. Not a case of replacing it entirely, don't even have to use the same cable run.

Sparkys are good at this and have all sorts of odd tools are their disposal like odd bits of curtain track..

The house I live is in is over 100 years old and has a lot of the old installations still under the boards including some bellwire which was an old fashioned fire alarm installation.... It has a cellar and when we had the boards up in the front half of the house some years back we found the remnants of an old wire and bell call system. We think a housekeeper resided in the basement rooms and was on call for the family in the house.

[ntb]

You don't have to follow the same path though. If feasible, straight out of the back of the CU to the outside wall. Up and around and then into the back of the isolator. Back out if neccesary and then in to the back of the shower.

[SNACR]

I would check there's no drip/leak in the roof causing a short.

[XswampyX]

You just tape the new cable to the old one and then pull it through. It's not rocket science.

[libspero]

You just tape the new cable to the old one and then pull it through. It's not rocket science.

It works best if the rocket you want to replace it with is the same size or smaller though.

This would probably work for the isolator mounted in the false ceiling, but the shower is mounted against a solid internal wall, so presumably the cable runs down through the plaster. I doubt there's a few extra mm to spare.. otherwise I would have been thinking along the same lines as you.

I guess the only options would be pulling off all the tiles and ploughing a deeper groove, or as someone else suggested.. Take the cable in through the wall behind. Either way it is increasingly looking like a major project.

[onlyme2]

Well at least the shower cable is modern PVC - often the case as a common upgrade that would not have been on an original install. Who knows what the actual power drain the old shower was -old / furred up with internal thermal protection it might have been spending a lot of time thermally tripped and draing a lot less than full power - the new replacement running at full bore not so. As is you might just have to derate the shower unit you fit, Modern CU with mcb and rcd or rcbo protection definitely a better option however if you have old lead sheathed or rubber wiring as has been mentioned you will be looking at having that replaced most likely, no registered electrician will want to change the CU without ensuring such cable is safe. So it is not the replacement of the shower cable that will caue the major cost, nor the CU, it will potentially be the other wiring.I;ve seen old fixed rubber wiring in a shocking state, falling apart with just slight movement so best be rid if you have it.

[Rare Bear]

I doubt if there are many 'old' Indians who used that trick.

We had a 170A welder come in for repair once that had a roll pin for a fuse.

The place I come from only got AC power in the mid 50s, consequently there was lots of old DC bits and pieces still around before I left there in the 80s. The usual thing when fitting a power where a welder would be used was to use an old 15 Amp socket. No fuses in the old round pin plugs and the actual DC switchgear was seriously tough. Of course you did tend to end up with a mixture of things and various odd looking adapter leads.

[knock out johnny]

I guess the only options would be pulling off all the tiles and ploughing a deeper groove, or as someone else suggested.. Take the cable in through the wall behind. Either way it is increasingly looking like a major project.

You never know - when I took my mum's house (which had last been rewired in the 1960's) I considered a complete rewire, but an electrician friend suggested to test the wiring (circa £300ish - it was best part of a days work for two) and suprisingly he gave it a clean bill of health and told me just to change the fuse boxes to modern units

I can't remember the name of the testing he did, but it may be worth considering if the alternative is a full rewire

[Orleans]

I doubt if there are many 'old' Indians who used that trick.

We had a 170A welder come in for repair once that had a roll pin for a fuse.

Haha, I've seen that kind of bodgery several times as well. Mainly because the arc welders commonly for sale to DIY types are on the limit of what a domestic 13a plug can handle, making the constant fuse blows a real faff.

Another old Indian trick in a similar vein is to splice the supply wire in a Y-piece arrangement with two 13a plugs on the end, to be plugged into separate sockets at once, in theory doubling the amperage. (It doesn't work since a double socket is only rated 20a and not continuously at that, and is seriously lethal in the event of one plug being left out!)