Flooring Tripping RCD

Jamie Harper · Jan 6, 2020

DPG said:
I know what you meant, but it is not wise to remove the earth on a known faulty circuit. Especially in a bathroom.

Out of interest, why did you bother testing if you were going to ignore the dangerous results anyway?

Its not in a bathroom, its in a kitchen.

It's not that i was always going to ignore dangerous results? My main issue was always ensuring the resistance between L and N were maintained. I never expected this to occur, if i had measured the L & E when i noticed the nick in the cable i would have corrected it, but unfortunately i didnt test it...

Its not a dangerous result either? it if were a direct short i would be more concerned, but this obviously shows a very minor error, hence why i cant see an issue with just not connecting the Earth?
I am well aware it is not 'advised' to do this but before i do anything i would like to know people thoughts on what issues it could cause and why it shouldnt be done?

telectrix · Jan 6, 2020

it is dangerous. diss the earth wire and you could end up with a floor that's "live". look what happened to those 3 horses at epsom or wherever. might be a stimulant for break dancing, but not advised.

DPG · Jan 6, 2020

Apologies, not sure why I assumed bathroom. But the principal is the same.

It's a shame it wasn't measured after the first covering layer went down, but no going back now. Who layed the levelling compound? I would be getting them back rather than leaving a potentially dangerous situation.

Jamie Harper · Jan 6, 2020

DPG said:
Apologies, not sure why I assumed bathroom. But the principal is the same.

It's a shame it wasn't measured after the first covering layer went down, but no going back now. Who layed the levelling compound? I would be getting them back rather than leaving a potentially dangerous situation.

It really is a shame, and unfortunately is was me who did it all. Only myself to blame.

Just out of curiosity, what voltage is supplied to the mat, is it just straight 230V or is it usually stepped down?

Like I say, it is not advised at all and i fully understand that. It's just that i see a very small leakage to ground via the Live, and there is no way anything could be touching the wires, no central heating or cabinates, its all effectively insulated by the self level and laminate flooring. It does make me nervous considering this, but i would like some solid proof that it would cause an issue, as currently i cant see any direct danger?

DPG · Jan 6, 2020

These things happen. We all make mistakes.

What you need to bear in mind now though is that you and your family will probably be walking barefoot on this floor. And you do realise how small a current has to be to cause injury?

Jamie Harper · Jan 6, 2020

Another idea one of my engineering colleges had was to try and' burn off' the fault. Obviously the fault is very minor and not a direct short. If I was to use a form of power supply and connect the Live and Earth of the mat up, it could potentially burn the fault away, but i am a little skeptical of doing this. I have seen this method used in various scenarios, but dont want to completely destroy the floor if there are other methods.
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DPG said:
These things happen. We all make mistakes.

What you need to bear in mind now though is that you and your family will probably be walking barefoot on this floor. And you do realise how small a current has to be to cause injury?

Thats the thing, it doesnt take much at all, especially with high voltages used.
I guess it depends on how insulating the self level and flooring would be?

Midwest · Jan 6, 2020

I came across a L-E fault once, where a lighting circuit cable had been nicked by a nail. Had been left like it for years. The whole wall was at supply voltage. Didn't come to notice, until the client decided to have their bathroom refurbished, and the plumber got a shock off touching the wall and water pipes. Never would of believed a plastered wall could conduct electricity, but saw it for myself, so I wouldn't leave it as is @Jamie Harper.

As posted before here I think, there are companies out there, that boast they can trace the exact location of the damage, and repair it. Think its expensive, but might be a solution for you.

James · Jan 6, 2020

It is unfortunate that there is some damage to the heating cable.

it is absolutely not advisable to just remove the earth connection.

anyone who was to work on the circuit in question could be in danger due to a LIVE (earth connection)
the earth cable in the heating tape will be surrounded by ground (levelling compound, concrete etc) it will act like a grid and try to bring that section of floor up to 230v. it will be reduced voltage due to contact with the surrounding ground.
there will be a constant current flow from live to earth that will increase your electricity bill.
voltage of your floor will vary depending on many factors outside your control. ground water level, humidity, cracking or other damage to floor or substrate, salinity, spillages etc.
if the circuit is supplied via an rcd or rcbo, it will cause nuisance tripping anyway as there will be times when there is enough current flow to real earth to trip the device. If it is not rcd protected, then see below.
it is quite feasible that one evening, maybe many years from now when the conditions are just right, your wife, child or grandchild will get up in the night, walk in with bare feet and turn the tap on for a glass of water. By holding the well bonded tap and standing on the faulty floor they make the circuit complete and you have to come down to find them dead on the floor in the morning.

Thankfully,
I am one of the majority of electricians that has never had to explain myself to a coroners court or a family of the deceased. I don't know what would be worse but I ~~hope~~, ensure by good morels and working practices that I am never in that position.

You say your idea is a bit controversial, I am amazed that you have not been hammered for even suggesting it.

you have your profile hidden so I don't know your electrical skill set,

if you are a professional electrician SHAME ON YOU

if you are a diy guy
Please look at what I have written above, whatever expense and/or inconvenience is incurred, is not important. we all screw up every now and then. its how we deal with it that makes us who we are.

Bottom Line, your options are.

1.. rip the floor up and do it again, this time get it right.
2...cut the cables off where they enter the ground, put a radiator on the wall.
3....SAVE MONEY AT THE EXPENSE OF PEOPLES SAFETY.

electric al · Jan 6, 2020

I know its disappointing to think you've messed up by not testing it before the floor went down .
I can also see that you don't want to take the floor up now it's done.
The question is , can you live without underfloor heating ?
Someone may not live if you have a live earth fault and do what your suggesting .

Midwest · Jan 6, 2020

I was thinking the OP is the home owner, might be wrong.

Strima · Jan 6, 2020

To even suggest disconnecting the earth means you should not be doing any sort of electrical work. It is often said on the forum to 'get an electrician in', this is a prime example of why it is said.

Two options:

1. Disconnect the mat and chop off the conductors so they can never be connected.
2. Rip the whole lot up and start again.

The vast majority of manufacturers will insist on testing at various points of installation to avoid this scenario.

James · Jan 6, 2020

Midwest said:
I was thinking the OP is the home owner, might be wrong.

I agree, I think they are the home owner.

I understand the risks of electricity and am almost shaking at the thought of one of my grandchildren being electrocuted in my own home, therefore I ensure it is SAFE.

I could not deal with anyone being killed or injured by my own incompetence. let alone one of my loved ones.

but just think all of you, how would you feel if you have managed to save a couple of grand by not re-doing a bad job and your granddaughter paid with her life?

replace the word granddaughter with anyone you feel is going to cause you to breakdown if you killed them.

I will not respond to this thread again, I will end up getting emotional and saying something I shouldn't.

electric al · Jan 6, 2020

Midwest said:
I was thinking the OP is the home owner, might be wrong.

Well yeah I was assuming that too . Surely knowing the danger of such an action you wouldn't willingly leave someone else to pick the slack up

westward10 · Jan 6, 2020

@Jamie Harper you have options here as quoted in several posts in this thread. Your suggestion of removing the protective conductor is not one of them and no member on here will condone this.
Thread closed.

SamDavies · Mar 17, 2025

Very interesting topic. I was glad to come across it but unfortunately, I didn't manage to find here any results, what was there reason why RCD was tripping? I actually planning to install a heating floor in the bathroom myself, and I was wondering:
What type of flooring will suit best for heating flooring?
30mA RCD would be enough for the whole bathroom or it should be for heating floor only?

Avo Mk8 · Mar 26, 2025

SamDavies said:
Very interesting topic. I was glad to come across it but unfortunately, I didn't manage to find here any results, what was there reason why RCD was tripping? I actually planning to install a heating floor in the bathroom myself, and I was wondering:
What type of flooring will suit best for heating flooring?
30mA RCD would be enough for the whole bathroom or it should be for heating floor only?

I'm sorry nobody has responded to your post! Here are my thoughts:

Re the discussion in this thread, I believe the issue was that a hole was made, accidentally into the UFH cable, and that damaged it. The UFH heating wire appears to be the type with a metal sheath around the heating element, and the damage to the outer sheath and insulation, combined with moisture or ionic contamination, has resulted in a resistance between the element and the earth sheath low enough to trip a RCD.

I imagine you are considering using a UFH heating mat kit?
When you ask what flooring will suit best, I think you are asking about the finish - tiles, engineered wood flooring, vinyl, etc. All these can be used. Obviously if you put carpet or rugs on any of them you reduce the heat input to the room.
You might be governed a bit by what floor structure you have to work with. If it's a solid floor I'd go for porcelain or ceramic tiles as the finish. Floor lay up something like: insulation board, heat mat, self levelling screed, adhesive, tiles.
It it's a suspended wooden floor you might be better off not using tiles, or at least not using large format ones. I've used heat mat with an engineered bamboo wood flooring over in a bathroom. It handles the moisture well, but the warmth on your feet is not as marked as with porcelain tiles.
Vinyl tiles (LVT etc.) or sheet vinyl, would be fine if you use those that are suitable for ufh.

If the UFH is the sole method of heating the room, you will need to do the heat loss calculations to determine what sort of power is needed. If your UFH is supplementing existing heating, and it's just to make the floor cosy, then the sums are less important. There are plenty of calculators out there on the internet.

30mA RCD should be fine for "the whole bathroom", but what else would you be running - towel rail?

Do lots of research before buying anything. Use the right materials for the floor construction. You will no doubt need an underfloor temperature sensor/ thermostat/ programmer, and it all needs wiring up to the regs, regarding zones, appropriate workmanship etc.
if you don't get the floor construction right, after a few years people might be walking on a floor that crunches, is cracked, or tiles wobble, or grout is coming away between the tiles. The techniques and workmanship are important! Good luck!