E
E
ed-ectrician
Weird thing is it worked ok for 2 yrs then went wrong. Too much water when washing etc would cause rcd to trip but both rcd and mcb are ok!!
B
bugsy
Is it possible there is a fracture of the element which when underload (heating ) breaks causing an open circuit as the element expands .
- Feb 25, 2011
- 9,547
- 6,486
- 10,256,798
- If you're a qualified, trainee, or retired electrician - Which country is it that your work will be / is / was aimed at?
- United Kingdom
- What type of forum member are you?
- Practising Electrician (Qualified - Domestic or Commercial etc)
- Business Name
- Richard Burns
You need to review the whole circuit and mat again.
You have a 30mA RCD protected circuit a 16A MCB a 6mm² cable (single radial I assume) connected to a switch of some sort and then to a power backbox (connected correctly? the power back box should not be able to take 6mm² cables) then the controller is fitted on the back box (how is the controller set up? Are there jumper switches? what are the displays if any on the controller on start up?) the controller is designed to take no more than 16A.
From the power box there are three pairs of wires each pair going to one of three underfloor heating mats (in the same room?), there are some unused terminals for a floor sensor (possibly) and (possibly) a pilot wire terminal unused.
There is no floor sensor (is the controller temperature sensor clear of dust and debris)
The floor heating mats appear to be 2 x 2.2kW and 1 x 6.6kW(really?), it is not known if there is an earthing grid associated with the mats, make of the mats is unknown.
There does not appear to be an earth fault as the RCD does not trip.
The current anticipated would trip a 16A MCB in about 10 seconds. The measured current on start up is not known.
The controller has been working for 2 years satisfactorily but has (in the last ....days) stopped working and when powered up starts and then cuts out, then starts, then cuts out...... (possibly not calling for heat yet and so not tripping MCB, but MCB was holding when it was working, is the controller staged i.e. only powering the mats by PWM or such like)
The heating mats have individual continuity on each (24, 24 , 8 ohms).
The insulation resistance of the mats is unknown.
The insulation resistance of the circuit up to the power box with and without the switch is OK.
The controller and power box from another location, where they are working, have been used in place of the original and the fault recurs (so the fault is not in the controller or back box).
The instructions state that when using a contactor (not used in this instance?) a snubber should be fitted across the load terminals.
When each mat is connected individually the fault recurs (so not a current loading issue)(only a triple fault on every the mats or a cross connection between the mats could cause this if the fault is in the mats.)
[Right no faults on fixed wiring, controller or mats (except loading), your heating is fine madam, that will be £250, oh yes the resetting? it is typical of these units, just ignore it, that is what I am going to do!:nonod:]
Does the controller start up OK without the mats connected?
Does this controller work in the other location?
Do you have the specs / instructions for the controller, power box or mats that you can compare to current readings?
Did anything change just before the heating failed (any work DIY or Professional)?
Well I give up!
You have a 30mA RCD protected circuit a 16A MCB a 6mm² cable (single radial I assume) connected to a switch of some sort and then to a power backbox (connected correctly? the power back box should not be able to take 6mm² cables) then the controller is fitted on the back box (how is the controller set up? Are there jumper switches? what are the displays if any on the controller on start up?) the controller is designed to take no more than 16A.
From the power box there are three pairs of wires each pair going to one of three underfloor heating mats (in the same room?), there are some unused terminals for a floor sensor (possibly) and (possibly) a pilot wire terminal unused.
There is no floor sensor (is the controller temperature sensor clear of dust and debris)
The floor heating mats appear to be 2 x 2.2kW and 1 x 6.6kW(really?), it is not known if there is an earthing grid associated with the mats, make of the mats is unknown.
There does not appear to be an earth fault as the RCD does not trip.
The current anticipated would trip a 16A MCB in about 10 seconds. The measured current on start up is not known.
The controller has been working for 2 years satisfactorily but has (in the last ....days) stopped working and when powered up starts and then cuts out, then starts, then cuts out...... (possibly not calling for heat yet and so not tripping MCB, but MCB was holding when it was working, is the controller staged i.e. only powering the mats by PWM or such like)
The heating mats have individual continuity on each (24, 24 , 8 ohms).
The insulation resistance of the mats is unknown.
The insulation resistance of the circuit up to the power box with and without the switch is OK.
The controller and power box from another location, where they are working, have been used in place of the original and the fault recurs (so the fault is not in the controller or back box).
The instructions state that when using a contactor (not used in this instance?) a snubber should be fitted across the load terminals.
When each mat is connected individually the fault recurs (so not a current loading issue)(only a triple fault on every the mats or a cross connection between the mats could cause this if the fault is in the mats.)
[Right no faults on fixed wiring, controller or mats (except loading), your heating is fine madam, that will be £250, oh yes the resetting? it is typical of these units, just ignore it, that is what I am going to do!:nonod:]
Does the controller start up OK without the mats connected?
Does this controller work in the other location?
Do you have the specs / instructions for the controller, power box or mats that you can compare to current readings?
Did anything change just before the heating failed (any work DIY or Professional)?
Well I give up!
P
pennywise
I know it's a simple thing but has the programmer been set to remote stat and not on floor probe mode, sorry you've probably been there for hours going through every permutation so this is probably a moot point.
Last edited by a moderator:
E
ed-ectrician
i think I might just keep repeating "It's not your fault" over and over again until she cries...
not your fault (Good Will Hunting) - YouTube
Seriously though I think it's ripping up floor and rewiring time....
Far too much load on one 15a controller anyway, it's no wonder it's not working for one reason or another. I can bill for my fault finding and advise to rewire. I'm not doing it though, sounds like a right pain in the arse and I'm too busy haha!
Seriously everyone thanks LOADS (pun?!) for your help on this. It makes me feel better knowing I have tried all the likely things and done what you guys would've done too. Makes me feel like less of a failure
Ed
not your fault (Good Will Hunting) - YouTube
Seriously though I think it's ripping up floor and rewiring time....
Far too much load on one 15a controller anyway, it's no wonder it's not working for one reason or another. I can bill for my fault finding and advise to rewire. I'm not doing it though, sounds like a right pain in the arse and I'm too busy haha!
Seriously everyone thanks LOADS (pun?!) for your help on this. It makes me feel better knowing I have tried all the likely things and done what you guys would've done too. Makes me feel like less of a failure
Ed
E
ed-ectrician
Yeah I checked this, thanks mate. I love pennywise too. And NOFX etc - reminds me of my youth! Went to see them all and lagwagon at deconstruction tour in east london when i was like 16 and a right little punker!
P
pennywise
I only got to see Pennywise once with Jim Limburg still fronting them and a couple of times since with the new guys, it's not the same
having said that the new singer sounds like dexster holland so it's should be the perfect combination of the offspring and Pennywise but it just doesn't work . I saw NOFX this year at download festival very funny and always good. Hopefully bad religion will be touring next year
E
ed-ectrician
Hello again everyone. Sorry, I still have a problem with this. The fault before was because the load was too big. if you go back and read the posts before you will find that there is a 16a controller switching a huge load which is about 46 amps. It is wired in 2.5mm cable and on a 20amp breaker (not done by me I have more than a passing grasp of ohms law! am remedying the problem although wish i wasnt now!!)
So a contactor looked like an idea to take the weight of the switching load (assuming the 16a quoted on the breaker is a switching load?!) but the problem is that it is wired in 2.5mm cable so, before i let client know that this is the last option, is there anything else I can try. i cant think of anything else to be honest but to wire it in bigger cable and either use a contactor or put more controllers in (there were three heating mats hooked up to one before)
Thank you all for help so far
Ed
So a contactor looked like an idea to take the weight of the switching load (assuming the 16a quoted on the breaker is a switching load?!) but the problem is that it is wired in 2.5mm cable so, before i let client know that this is the last option, is there anything else I can try. i cant think of anything else to be honest but to wire it in bigger cable and either use a contactor or put more controllers in (there were three heating mats hooked up to one before)
Thank you all for help so far
Ed
A
ashrow
ED
you really need to explain more or find your original thread and continue there
Note electric under floor heating at 200w per meter at 10 meter square will equal how many amps ?
I have only ever connected 2 x 10 meter mats,
Where have you got this massive load from ?????
you really need to explain more or find your original thread and continue there
Note electric under floor heating at 200w per meter at 10 meter square will equal how many amps ?
I have only ever connected 2 x 10 meter mats,
Where have you got this massive load from ?????
E
ed-ectrician
Hi there, if you read back to the beginning it should(!) explain. They are heating a massive room on underfloor alone (I have advised against this) using four mats - all around 24 ohms(ish for sake of argument) They had all four mats on one 16a controller (!!) and it kept tripping out (it was also spurred off the ring - bloody hell!) so the spark who was before me left one mat on the spur and took the other three and put them on one controller on its own breaker (20a using 2.5mm T&E) - surprise surprise the controller burned out and i have been trying to sort it. Last option is to advise rewiring the system and for now temporarily putting one mat on the controller in question and leaving the other two unused for now.
As i said contactor looked like a plan but still have problem of cable and breaker being too small.
Thoughts?!
As i said contactor looked like a plan but still have problem of cable and breaker being too small.
Thoughts?!
E
electric will
A
ashrow
Ed my fault, just browsed back (but not read 100%)
Are all the mats run back to the same location ?
Are all the mats run back to the same location ?
E
electric will
I make it about 11 m2 per mat if using the 200w/m ones, anyway if you want to use one controller, you could switch a four pole contactor, main feed from cu would need upgrading to poss a 10mm cable, just wondering if it could be ran on four x 2.5mm radials on 16m mcb's?
E
ed-ectrician
E
ed-ectrician
Will there's no space at the board! Was thinking standalone contactor (between stat and mats right?) but in any case needs new cable
E
electric will
Going to have to uprate the cable then and use a contactor. Control circuit for controller and contactor will need fusing down though
E
ed-ectrician
Will can you expand mate. I.e verbal block diagram!! E.g breaker, big cable, stat, conractor, mats etc with fusing down explained in there too. Thanks mate!!
Similar threads
OFFICIAL SPONSORS
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc
