Ribbon Underfloor Heating by AHT - Heating

[HowardM]

Their products are 17th edition compliant as confirmed By The IET and JPEL/64.

A letter was distributed on 8th September 2008 to clarify that class II products do not require an earth in 753.415.1

The condition under 701.753 bathroom, wetrooms, swimming pools etc still applies as indeed it did under the 16th.

for confirmation may be worth while asking you NICEIC rep or contact the IET technical support helpline.

THE IET 01438 313311

 

[ssheen]

AHT products are 17th edition compliant as confirmed By The IET and JPEL/64.

A letter was distributed on 8th September 2008 to clarify that class II products do not require an earth in 753.415.1

The condition under 701.753 bathroom, wetrooms, swimming pools etc still applies as indeed it did under the 16th.

for confirmation may be worth while asking you NICEIC rep or contact the IET technical support helpline.

THE IET 01438 313311

HowardM is correct; Class II products, or products that are "double-insulated", do not require a built-in earth. However, they do require a 30mA RCD (753.415.1), which if wired properly requires an earth. The result is pretty-much the same.

You could wire an RCD without an earth, but most will not work in the manner designed by the manufacturer. That is, they do not plan on you being the earth. (I contacted PowerBreaker to make sure this was the case)

Sure, you can get around this by using an earth grid over the system, but my comment was about being "17th Ed compliant out of the box".

Keep in mind that no matter how a system is designed, without proper installation, it can still fail the regs.

 

[pjrich]

AHT products are 17th edition compliant as confirmed By The IET and JPEL/64.

A letter was distributed on 8th September 2008 to clarify that class II products do not require an earth in 753.415.1

The condition under 701.753 bathroom, wetrooms, swimming pools etc still applies as indeed it did under the 16th.

for confirmation may be worth while asking you NICEIC rep or contact the IET technical support helpline.

THE IET 01438 313311

Can you post a copy of this letter, because when I spoke to the NICEIC tech people last year (I am also the owner of an NICEIC contracting company) they advised me that electric ufh systems without an intergral earth had to have an earth grid installed over the top.

I am also a member of the IET and so far I have not seen an release from them that updates the requirements of the 17th edition wiring regulations.

I also spoke to a major manufacturer of carbon film heating and unofficially they said that the new regs were bad news for them because of the new earthing requirements for electric ufh systems in the 17th edition.

I would very much like to see this letter (who's it from?) that permits the use of unearthed electric ufh systems, because this is an important safety issue that needs evidence to backup this statement.

At present Uheat will only supply electric underfloor heating systems that we are 100% confident comply with all current regulations.

 

[HowardM]

I agree that the carbon film cannot be deemed as class II and does require a mesh however no definitive has been reached.

The product is double insulated and is signified on the product with the symbol of a box within a box. even if carbon film was double insulated it gets cut to size so is far from double insulated and if not sealed correctly after cutting then a potential problem.

 

[pjrich]

Thanks for posting the letter from IET.

So, this letter confrims that if the electric ufh is class II then an earth grid is not required unless unless its in a room containing a bath or shower. - Everyone agree?

Now, the next issue that ssheen raised was that an RCD needs an earth to operate. If this is the case, then class II without an earth will not comply with 17th edition because the RCD won't work.

When I went to college many years ago and we studied the workings of an RCD, an earth was not required because it operated on the imbalance of currents running through the live and neutral conductors. If this is not the case anymore then I think we need to see some documentation that proves that an RCD needs the circuits it supplies to have a cpc (earth). Perhaps it is just some RCD's that need an earth, like RCD spurs?

Tilers, if you buy from Underfloor Heating | Electric | Floor Insulation | Uheat you will not have to worry about all the tech talk above because we only supply electric ufh systems that comply with regs, are fully earthed and will work with RCD's.:hurray:

 

[Uheat]

Thanks for posting the letter from IET.

So, this letter confrims that if the electric ufh is class II then an earth grid is not required unless unless its in a room containing a bath or shower. - Everyone agree?

Now, the next issue that ssheen raised was that an RCD needs an earth to operate. If this is the case, then class II without an earth will not comply with 17th edition because the RCD won't work.

When I went to college many years ago and we studied the workings of an RCD, an earth was not required because it operated on the imbalance of currents running through the live and neutral conductors. If this is not the case anymore then I think we need to see some documentation that proves that an RCD needs the circuits it supplies to have a cpc (earth). Perhaps it is just some RCD's that need an earth, like RCD spurs?

Tilers, if you buy from Underfloor Heating | Electric | Floor Insulation | Uheat you will not have to worry about all the tech talk above because we only supply electric ufh systems that comply with regs, are fully earthed and will work with RCD's.:hurray:

could not have said it better myself.

:hurray::hurray::hurray::hurray:

 

[HowardM]

An RCD is there to monitor for inbalance in supply, some are connected to earth with a white fly lead others don't.

The AC sensing type uses another coil on the toroid which generates a seperate magnetic field, if this rises above a given thresh-hold the RCD will trip.

So I can say not all RCD require an earth.

 

[pjrich]

An RCD is there to monitor for inbalance in supply, some are connected to earth with a white fly lead others don't.

The AC sensing type uses another coil on the toroid which generates a seperate magnetic field, if this rises above a given thresh-hold the RCD will trip.

So I can say not all RCD require an earth.

Thanks for that, just read something similar on another website.

Does this mean that AHT heating mats are only compatible with some RCD's when there is no earth grid install?

 

[HowardM]

If there is an inbalance with or without an earth grid it will be detected, providing the RCD is not faulty, if the floor develops a fault and goes to earth there will still be an inbalance.

The wiring regulations show that you must not count on the RCD as the only form of protection.

There are installers that use RCBO (DC sensing) and inline RCD (AC sensing).

The thing is simply this 753.514 does have a lot of fault testing to carry out when commisioning, now if this is not done by the electrician or a DIYer has a go not knowing the regulations there is trouble to be had with all products.

We have to look at the fact that all products on the UK market have gone through major test with testing houses such as Nemko, Bsi, TUV or the like to say the conform to set standards.

 

[HowardM]

oops double posted ...

What I will add is its not the safety of a product that should be in question as that has already been tested but the competance of the installer,

All products are fit for their own purpose and should that be brought into question by suppliers / distributors / wholesalers

All products should be sold on merit of service, capability, compatability, etc. and since each individual is different and requirements can differ there is scope for all underfloor heating systems in the market place.