To RCD or not RCD an Economy 7 Board

[baldsparkies]

A pre 2008 economy 7 installation has recently recieved single rcd consumer units. There are 7 circuits in total being used on the boards.
Now for the problem, Prior to the install well there were no problems, however we have been called in on a number of occasions, because despite 4 other sparkies from various firms attending they can find no reason for the rcd's tripping. To explain this is an elderly peoples complex. and consists of self contained flats. A number of the tennants have reported, tripping of the rcd's during the charge time ie when the E7 supplies kick in. Insulation resistance and load resistence readings are all good, which is why the other guys are unable to find faults. My guess would be the rcd's dont like being energised under load and subsequent tripping leaves the entire install without power. Now we are talking about elderly people being left with no heating or immersion fed hot water as a result of this. Far from good. I feel that either you install rcbo's (Very expensive) or get rid of the damn rcd's and rely on good earth fault return paths to do there job. after all the rcd's are there to supplement not replace a good earthing system. And to be fair a lack of heating for these poor souls is far more dangerous than the very unlikely shock hazard that may or may not occur to a fixed appliance which is only energised during the night. After all you wouldn't fit an rcd to hospital life support equipment. And these guys need there heat. What are your thoughts on this my learned friends.

 

[telectrix]

time delay RCDs might cure the problem, not sure if they are compliant, though. not had anything to do with them myself.

 

[Adam W]

Is there even a requirement for rcd protection as a result of installation method, skilled or instructed person etc?
you could test the heaters themselves and/or contact the manufacturer.

 

[SirKit Breaker]

This is one where you need to apply more common sense than regulations. Only you can risk assess the situation, because none of us have seen the set up.

Are the RCD's of good quality and testing out OK?

Cheers..........Howard

 

[Adam W]

Well yes if all fails and as a last resort you could make a deviation to the regs for the reasons you stated, but it would be better not to have to if possible.

 

[baldsparkies]

Time delay is certainly a good option, its just the thought that if a fault occurs they lose the lot, now that can't be good.
The point is we tested the N/S Heaters and the immersion elements and they are clear as a bell even at 1000v. (Dont worry no electronics involved.)
Because of the installation dates, there was know reason to fit the damn rcd's but as regs go you cant undo whats been done although as a deviation I would argue that the risk of hyperthermia outways any possible supplementary shock protection benefits vs nuisance tripping. God knows why anyone would want to fit an rcd to Economy 7 CU's anyway. As far as requirments I would agree that because there fixed appliances you could also argue the skilled or instructed persons point. although these are domestic installs the occupants are tennants in kind, being housing association. So they would be classed commercial premises.

 

[baldsparkies]

This is one where you need to apply more common sense than regulations. Only you can risk assess the situation, because none of us have seen the set up.

Are the RCD's of good quality and testing out OK?

Cheers..........Howard

They are all Wylex Howard, and yes I tried them by swapping out on the dual rcd boards for the normal/peak circuits. 5 propertys have had the problem so far, the latest is a 93 year old lady who offered us tea and jammy dodgers, she knew her way to my heart mate.
Forgot to say x1 x5 half tripp and 180 degree jobbies are all good.

 

[malcolmsanford]

As it's a N/S system I assume the heaters are fitted via a Spur unit. So the RCD protection is, again assuming, for cable buried in a wall.

We all know that there really is only one course of action to this and that is run the installation surface. I would really think hard and fast about removing the RCd protection as if anything happened you would be in serious trouble.

Not even sure if RCBO's would get you out of trouble if it is what you think it is and the change over. Have you tried ramp testing the RCD's though to be honest as it's 5 different RCD's not all can be faulty.

I think you will have the devil's own job persuading whoever owns/run this complex that it is going to cost money to repair this fault. This may be the reason you are the 5th guy to be looking at this, as they have all come up with solutions that will cost money to implement, and most likely have had to walk away.

Personally I would write a report telling them your solution, in my case it would be to run surface either in a containment system or MICC which can be quite unobtrusive if bare and is then painted. That your capable of undertaking the work and would offer a quote if required.

 

[nickblake]

I would RCBO it if one trips thenyou dont loose the lot it may also find where the unit is thats causing it to trip ,you could do a earth leakage test using a clamp meter , i wouldnt want to not put RCDs in as these units are on at night when every one is sleeping if a fault does occour you need the breaker to trip as quickly as possible

 

[baldsparkies]

Thanks for all your replies,
The crazy thing is if the boards had been left alone ie on mcb's only none of these issues would be happening. Bear in mind the installation is 8 years old so if left untouched it would not have been a problem because it complied with the regs at the time of the install. Now some bright spark as gained a boat load of money doing a totally unneccasary change to all the E7 boards, and walked away leaving all these tripping problems. I know I am old school, but as far as I am concerned, a fixed appliance such has a N/S Heater is fine without rcd protection provided the earth fault return path is up to the task regarding disconnection times of the mcb's. Its never been an issue in the past. Then along comes the 17th and wham rcd's are flavour of the month regardless, along with all the associated problems.
It pays to remember that there is no substitute for a good earth return path. Rcd's are for additional protection not a substitute, and in this case they are doing more harm than good. I accept the regs and work to them, but sometimes you do wonder !! Rant over. Sorry lads.
Just another point, I am finding a lot of guys are failing older installs just because there is no rcd. it needs to be remembered that not all situations require rcd protection where rcd's are concerned. Off to work now, have a good day lads.

 

[andyb]

If this is an OAPs complex, then I would deem it to be under the control of a skilled or instructed person an I would not of fitted RCDs.
If it is thought that RCDs were required then at the very least i would fit a dual RCD board so that half the rooms would be heated in the event of a fault, and I would put the immersion element on its own RCBO so that they would allways have hot water.
You should never fit a single RCD to protect 7 E7 circuits.

However that's not helping here.
Have you tried testing with all the heaters switched on and all the MCBs on so that you are testing all circuits together?

The last thing to try is to energize the system during the day & test the heaters when they are hot. This may show up something.

The problem you have here is that someone came before you, did a risk assessment and decided that RCDs were required, It's now hard for you to say they were wrong, especially as the RCD now trips.

 

[morph]

7 N/S on one RCD is bound to cause issuess
rcbo job i would say

 

[baldsparkies]

There is definately no problem with the heaters or immersion or the integrity of the wiring. all checks out perfectly, not even a hint of problems with the readings, and the rcd's are all good. This fault occurs when the E7 kicks in under load as it would in any event. One elderly gent told me today that he was up one night and heard his rcd trip. He reset it and all was fine until the next night. Its deffo a problem when the E7 energises under load ?? The cheapest option I can think of is a time delayed unit. My preferance would be a normal mainswitch, under these circumstance, but if I go down that route I will need to explain my reasoning behind such a departure from the regs. As said had rcd's not been installed in the first place it would have been compliant at that time. But now they have been installed you can't revert back to there original level of protection. I may even see if the supply authorities would consider a more up to date change over system as opposed to the current contactors. Some how I will get there, not prepared to walk away like others have, its just not fair with the weather as it is.
Also Andy I am not as confident as you that a risk assesment was indeed carried out.
Who ever changed the peak rate boards for dual rcd boards, opted to change the E7 boards at the same time, and decided to fit an rcd as a main switch with little thought to discrimination or the consequences of nuisance tripping.

 

[morph]

if you had 7 rcbos you would have far less load per circuit on as E7 kicks in though

 

[baldsparkies]

if you had 7 rcbos you would have far less load per circuit on as E7 kicks in though

I agree with that Morph, but considering the financial outlay for the work thats been recently undertaken !!! The financial outlay for rcbo installs is going to be a hard pill to swallow. Its one suggestion to put to them for sure but I do feel time delayed could solve the issue at a fraction of the cost, although you still have 7 circuits going down in the event of a fault, at least it will hopefully only happen when a genuine fault occurs.
They are currently trying to get the original installer to stop ducking and diving and face up to the problem. After all, thats where the buck really stops from the way I see it.