Heating an airing cupboard

[PBC_1966]

There are many things which they can rightly specify to ensure proper operation and safety. Insisting on a particular level of circuit protection because they CBA to design their equipment properly is not one of them.

Why is specifying overcurrent protection any different from any number of the other things you think they can specify?

If he has made something whose internals need the protection of a 10A fuse then he must put that fuse in the internals.

How do you feel about a manufacturer of a water heater specifying the maximum supply pressure of the water to which it should be connected?

If the heating section can withstand a maximum of 80 p.s.i., should the manufacturer be able to say in the installation instructions that the unit should not be connected to a water supply system exceeding that pressure, or do you think he should incorporate a pressure regulator just so that you can couple it up to a 300 p.s.i. supply if you feel like it?

 

[ban-all-sheds]

Why is specifying overcurrent protection any different from any number of the other things you think they can specify?

Ib ≤ In ≤ Iz

5 ≤ 64 ≤ 100

As long as Ib ≤ In ≤ Iz he may not insist that Ib = In ≤ Iz, or by how much In may exceed Ib

How do you feel about a manufacturer of a water heater specifying the maximum supply pressure of the water to which it should be connected?

The same I would feel about him specifying the voltage with which it should be supplied.

If the heating section can withstand a maximum of 80 p.s.i., should the manufacturer be able to say in the installation instructions that the unit should not be connected to a water supply system exceeding that pressure, or do you think he should incorporate a pressure regulator just so that you can couple it up to a 300 p.s.i. supply if you feel like it?

You are beginning to sound like someone who thinks that if a circuit has a 32A OPD it will somehow manage to force 32A through an appliance.

 

[PBC_1966]

As long as Ib ≤ In ≤ Iz he may not insist that Ib = In ≤ Iz, or by how much In may exceed Ib

Why not?

How do you feel about a manufacturer of a water heater specifying the maximum supply pressure of the water to which it should be connected?

The same I would feel about him specifying the voltage with which it should be supplied.

Which is?

You are beginning to sound like someone who thinks that if a circuit has a 32A OPD it will somehow manage to force 32A through an appliance.

What are you talking about? I asked you if you think a manufacturer should be able to specify the maximum pressure of the water supply. Well?

 

[ban-all-sheds]

Why not?

Because the OPD is not there to protect his equipment. It is there to protect the cable.

Which is?

That there is nothing wrong with that.

What are you talking about?

The way that you seem to be unable to tell the difference between a high water pressure, which would damage the equipment, and a high-rated OPD, which will not.

I guess I would consider a defence from you along the lines that you can tell the difference but you were hoping that people here would be too stupid to.

 

[PBC_1966]

Why not?

Because the OPD is not there to protect his equipment. It is there to protect the cable.

It's there to protect whatever you intend it to protect. If the manufacturer specifies a certain maximum for the equipment, then it's there's to protect the equipment as well.

That there is nothing wrong with that.

So why do you think he should be able to specify that his Transmogrifier must be connected to 240V (plus or minus whatever percentage) but that he should not be able to specify the overcurrent protection provided? Should he be able to specify that it must be connected to an earth, or should he be obliged to make it double insulated?

The way that you seem to be unable to tell the difference between a high water pressure, which would damage the equipment, and a high-rated OPD, which will not.

It could under fault conditions, which is why the manufacturer specifies suitable protection.

This is ridiculous: A manufacturer of a piece of equipment specifies all sorts of things about the way that the equipment should be installed and used for proper, safe operation, and you seem to accept most of them. There is absolutely no reason why specifying a maximum fuse/MCB size in the electrical feed should not be included in his requirements, yet for some reason you seem to think this is an exception.

 

[ban-all-sheds]

It's there to protect whatever you intend it to protect.

Really?

I'd like to use it to protect my car from damage from birds that have been eating dark berries.

If the manufacturer specifies a certain maximum for the equipment, then it's there's to protect the equipment as well.

No it is not - that is not what it is for and the manufacturer has no jurisdiction to say that it is.

So why do you think he should be able to specify that his Transmogrifier must be connected to 240V (plus or minus whatever percentage) but that he should not be able to specify the overcurrent protection provided?

Because supplying too many volts will damage it.

A circuit with the capability to supply more current than it needs will not damage it. I did not realise that you don't understand that, and that you really do think that if a 1200W appliance is connected to a 32A circuit then 32A will flow through the appliance and damage it.

Were that the way it worked then of course the maker would have to specify the current limit. But it isn't, and he may not.

Should he be able to specify that it must be connected to an earth, or should he be obliged to make it double insulated?

Subject to any rules for his type of product and/or how/where it is used, that choice is up to him.

It could under fault conditions, which is why the manufacturer specifies suitable protection.

How could a circuit fault cause too much current to flow through the equipment?

A manufacturer of a piece of equipment specifies all sorts of things about the way that the equipment should be installed and used for proper, safe operation, and you seem to accept most of them.

I accept the ones where not doing it would cause damage.

There is absolutely no reason why specifying a maximum fuse/MCB size in the electrical feed should not be included in his requirements, yet for some reason you seem to think this is an exception.

It is an exception, because using a higher rated device will not cause damage.

 

[JohnW2]

Why not?

Because the OPD is not there to protect his equipment. It is there to protect the cable.

That might be an electrician's view of the usual function of an OPD, but a manufacturer is surely free to specify any requirements they wish as regards safe installation and use of their equipment - whether that be in relation to positioning, ambient conditions or anything else - and I can't see why that can't include a requirement that the equipment be protected by an external OPD of some specified rating.

Kind Regards, John

 

[ban-all-sheds]

Inappropriate positioning might damage or impair it.

Unsuitable ambient conditions might damage or impair it.

An OPD which can pass more current than the equipment needs will not damage or impair it.

 

[JohnW2]

It is an exception, because using a higher rated device will not cause damage

Not to the cable of the circuit (if it is properly designed), but it might cause unnecessary damage to the equipment - and MIs are full of 'requirements' intended to avoid or minimise damage to the equipment.

Kind Regards, John

 

[JohnW2]

An OPD which can pass more current than the equipment needs will not damage or impair it.

Not even under fault (in the equipment) conditions?

Kind Regards, John

 

[ban-all-sheds]

How can using an OPD which has the capability of allowing more current than the device draws actually cause damage to the equipment?

 

[ban-all-sheds]

Not even under fault (in the equipment) conditions?

If the manufacturer requires protection of his product from damage caused by faults in his product then he should make that protective function part of the product.

 

[JohnW2]

How can using an OPD which has the capability of allowing more current than the device draws actually cause damage to the equipment?

It obviously would not be the 'cause' but, in the event of the fault in the equipment, it could allow the equipment suffer damage (or suffer more damage) than would have been the case if the manufacturer's requirement for a lower-rated OPD been adhered to.

Kind Regards, John

 

[JohnW2]

If the manufacturer requires protection of his product from damage caused by faults in his product then he should make that protective function part of the product.

Ideally, yes, but I still don't see why they cannot decide not to do that but, instead, require the user to provide that protection externally. Hell, they could specify that the equipment must only be installed in rooms with pink walls if they wanted!

Kind Regards, John

 

[PBC_1966]

It's there to protect whatever you intend it to protect.

Really?

I'd like to use it to protect my car from damage from birds that have been eating dark berries.

Whatever you intend it to protect against excess current. But you knew that.....

If the manufacturer specifies a certain maximum for the equipment, then it's there's to protect the equipment as well.

No it is not - that is not what it is for and the manufacturer has no jurisdiction to say that it is.

From whom or what does the manufacturer need "jurisdiction" to say "This equipment should be supplied via a fuse not to exceed 10 amps" or something similar?

The great god BS7671? Then perhaps this time you'll answer the question I asked you earlier: Does or does not BS7671 state that manufacturer's instructions should be taken into account when installing equipment?

It could under fault conditions, which is why the manufacturer specifies suitable protection.

How could a circuit fault cause too much current to flow through the equipment?

When the fault is in that part of the circuit which is within the equipment. Or you want an example of a fault outside the equipment which could result in excess current through it? A broken neutral on a polyphase or 3-wire single-phase system.