Underfloor Heating

[PrenticeBoyofDerry]

Along with many other sparks too, I shouldn't wonder.

I have no doubt, that be true!

 

[JohnW2]

[I presume you mean 4D2A] ...

No! Flat cable with CPC, as stated in table 4D5A, the only table I am aware this is mentioned, therefore applicable to the standard T&E.

Apologies - I misunderstood you. It was probably your reference to "4D5A" which confused me - are you saying that there was such a Table in 16th ed? (in the current regs, there is a 4D5 {and a 4D2A}, but no 4D5A).

Kind Regards, John

 

[ban-all-sheds]

That's what it should say but, as written, there is nothing about the wording which prevents one using 4D2.

There is unless you are stupid or perverse. Or barmy - I will allow that as a 3rd option.

In any event, as I said, 4D2 should be able to 'stand alone' for those who have not looked at (or aren't even aware of) 4A3...

I think you are on dangerous ground if you start saying that flawed readings of the regulations are acceptable when they stem from an insufficient knowledge of them.

 

[ban-all-sheds]

Apologies - I misunderstood you. It was probably your reference to "4D5A" which confused me - are you saying that there was such a Table in 16th ed? (in the current regs, there is a 4D5 {and a 4D2A}, but no 4D5A).

The 16th had a 4D5A.

But no 4D5B.

 

[JohnW2]

In any event, as I said, 4D2 should be able to 'stand alone' for those who have not looked at (or aren't even aware of) 4A3...

I think you are on dangerous ground if you start saying that flawed readings of the regulations are acceptable when they stem from an insufficient knowledge of them.

I stand by what I said. In any sort of document, Tables, Figures etc. should be able to 'stand alone'.

However, you're talking almost as if some 'danger' could result from using 4D2A instead of 4D5. The 'worst' that would happen is that you might think that some circuits were non-compliant when they were actually compliant - hardly a 'danger'!

Kind Regards, John

 

[PrenticeBoyofDerry]

Apologies - I misunderstood you. It was probably your reference to "4D5A" which confused me - are you saying that there was such a Table in 16th ed? (in the current regs, there is a 4D5 {and a 4D2A}, but no 4D5A).

Yes the 16th had a table 4D5A which is as table 4D5 in 17th, the table 4D2A are same in both 16th and 17th

 

[JohnW2]

Yes the 16th had a table 4D5A which is as table 4D5 in 17th, the table 4D2A are same in both 16th and 17th

Thanks for clarifying. Do I take it that there was also a 4A3 (or equivalent) in the 16th which directed one to 4DA5 for T+E?

Kind Regards, John

 

[PrenticeBoyofDerry]

Do I take it that there was also a 4A3 (or equivalent) in the 16th which directed one to 4DA5 for T+E?

That would be Table 4A2 which directs you to table 4D5 (which only exists as 4D5A in 16th, as there is no reference to the second letter of any tables under "Applicable Current Rating Tables" column) Much as it does for 4A3 in 17th.

 

[securespark]

4D5A appeared in the last version of the 16th Ed.: the brown copy.

 

[Taylortwocities]

So...back to the original question.

The UFH must have an RCD to protect it.
It seems that the only RCD on that board is the "Downstairs Plugs " RCBO.
My simple solution would be to take a spur from that RCBO to an FCU, fused at 13A, sited next to the consumer unit.
Do all the testing required by BS7671 including an RCD test
Connect up
Complete EIC
Fill out the underfloor heating installation schedule as required by BS7671 and secure this adjacent to the CU.
Job done.

 

[JohnW2]

...My simple solution would be to take a spur from that RCBO to an FCU, fused at 13A, sited next to the consumer unit. ...

Did we ever get to the bottom of:

Heating system is rated max 16A with the elements I have totalling a shade under 12A.

(particularly the 16A bit) ??

Kind Regards, John

 

[Taylortwocities]

16A is the max the controller will switch.
\His fixed load is 12A, so a 13A fuse is cushty..

 

[JohnW2]

16A is the max the controller will switch. \His fixed load is 12A, so a 13A fuse is cushty..

If your surmise is correct, then I agree with your conclusion.

If you were designing this, would you be happy to have a 'fixed 12A load' connected to a sockets circuit (essentially in terms of what was left for all the sockets) - particularly given that it appears to be the only downstairs sockets ('plugs'!) circuit?

Kind Regards, John

 

[Taylortwocities]

Yes I would be happy.
Given the following;

The >2KW guidance for loads on a ring final is to prevent a concentration of large load(s) on the ring.

My solution is for a "spur" off the ring taken from the 32A RCBO, a short length of 2.5mm to an FCU and then off to the UFH.

The main consideration would be the total load on that CPD, so it depends on a calculation of the max demand on that 32A breaker with the 12amp added in without diversity.

 

[JohnW2]

Yes I would be happy. ... The >2KW guidance for loads on a ring final is to prevent a concentration of large load(s) on the ring.

Indeed - but, as I indicated, that was not really my concern.

The main consideration would be the total load on that CPD, so it depends on a calculation of the max demand on that 32A breaker with the 12amp added in without diversity.

Exactly, and that was my concern. Given that it appears that this is the only 'downstairs sockets' circuit (presumably including kitchen and any utility room), I was wondering whether, with that 12A 'fixed' load, one's design calculation would estimate the max demand as being under 32A. Even with diversity applied to the UFH (is one allowed to with UFH - I'd need to look that up?), just a couple of appliances (say a washing machine and kettle) together with the UFH would probably get one close to, if not over, 32A. I suppose it depends upon how the designer regards 'max demand'.

Kind Regards, John