32A Ring Main + 20A Fused Spur For AirCon Unit

[electricity_bill]

I had an aircon/heater unit installed a few years ago, and it recently
stopped working (burning smell) and I started to look into it.

It was connected into the 32A ring main with a 20A rated DP Switch -
and a loose connection at the switch had totally burnt through, blackening
the surrounding cables and leaving the unit supply open circuit.
[I'm guessing the unit itself is OK and it was a loose connection]

I disconnected the unit fairly quickly and I'm now looking to put it back in.

Looking on the manual/plate, it recommends a 20A Fused Spur for this unit.

The plate on the unit says: "min crt amps 19.3" .... "use 20A max time delay fuse or HACR type circuit breaker".

Is it a bad idea to connect this straight into the ring main ?
Is it safe ?

Thanks,
Bill

 

[securespark]

A 20A fused spur?

You mean a 20A radial?

You should not be connecting any load greater than 13A onto a ring final.

Fit a radial circiut back to the board.

 

[Steve]

I had an aircon/heater unit installed a few years ago, and it recently
stopped working (burning smell) and I started to look into it.

good idea!

It was connected into the 32A ring main with a 20A rated DP Switch -

Not good!

and a loose connection at the switch had totally burnt through, blackening the surrounding cables and leaving the unit supply open circuit.

This is probably nothing to do with the above. Good job you spotted it though.

[I'm guessing the unit itself is OK and it was a loose connection]

Probably. Do you have a maintenance contract for the air con unit?

I disconnected the unit fairly quickly and I'm now looking to put it back in. Looking on the manual/plate, it recommends a 20A Fused Spur for this unit.

What does it ACTUALLY say?

Is it a bad idea to connect this straight into the ring main ?

yes. Judging by all the 20A's dotted about above

Is it safe ?

NO! It needs its own dedicated radial circuit form the consumer unit, which an electrician will fit for you.

Thanks,
Bill

Your welcome.

 

[electricity_bill]

What does it ACTUALLY say?

I just went and had another look and it doesn't say "Fused Spur" at all
(sorry). The "20A Fused Spur" phrase actually came from someone I contacted at the air con company, who stated that the unit should be
(and are generally) wired onto 20 fused spurs.

We do have warranty for a while yet. But the installer and supplier are different - they would replace a faulty unit, but I suspect it is actually fine.
It's just that the installation is something I'm not so relaxed about and
i would like to be on solid ground if I question it.

Looking at the unit, it actually says (near the namplate):
"use on single outlet circuit only unless all amp values on nameplate are 7.5 or less"

And looking on the nameplate for amps, it has under COOLING:
7.6A
and under HEATING:
COP ... 7.3 AMPS
ELEC HEAT .. 3400 Watts
ELEC HEAT TOTAL AMPS 15.3

Plus the "min crt amps 19.3 use 20A max time delay fuse or HACR type circuit breaker" and some less relevant figures.

"single outlet circuit" - means radial from consumer unit ?

Looks like a new radial then.

Thanks,
Bill

 

[ericmark]

HACR type – This marking indicates the circuit breaker is suitable for use with the group motor installations typically found in heating, air conditioning and refrigeration equipment. The NEC 2005 no longer has this marking requirement. The electrical industry determined that circuit breakers are considered suitable for use with such equipment without any further testing, therefore, the HACR marking is no longer required on air conditioning and refrigeration equipment or on circuit breakers for use in these applications. The requirement for this marking has also been removed from the UL 1995 product standard for HVAC equipment.

from Square D manufacturer.

In the main these were moulded breakers not the standard MCB as designed for the inrush of a motor. I am not saying you can't use a moulded breaker in a house but it would be unusual and they will not fit in a standard consumer unit. Likely today we would use a Type C or D MCB.

Clearly this should not be from the ring final but it would seem the instructions are rather dated or the unit is not designed for domestic use. Why any electrician in their right mind would connect to a ring final I do not know.

This

stile of consumer unit has been used for years for supplies to showers, garages, and would suit for a supply to a Air Con if no room in the main consumer unit but not what I would call nice to look at.

And I would say this is the main problem. You want something both functional and looking good. Using cooker isolators and cooker connection units will look reasonable but some where it needs the protection device.

Your not the only one to get it wrong. I was on a re-fit of a NEXT shop where some one thought the large supply needed to go to the Air Con control panel but in fact it needed to go to the roof getting a 150mm² cable to the roof was a mammoth task. I will guess some one has made the same mistake with yours and not allowed for needing such a large supply and have used the ring final to cover their mistake.

 

[denso13]

8 year old thread!

 

[ericmark]

Thanks missed that. Wonder how it ended up listed with the new stuff?

 

[ban-all-sheds]

Was it really?

 

[JohnW2]

Was it really?

Does anyone (apart, perhaps, from you) really care?

Kind Regards, John

 

[ericmark]

Yes it was. I have googled things in the past and found an old thread that way but this was on the main current page.

 

[ban-all-sheds]

Does anyone (apart, perhaps, from you) really care?

Probably.

I know that you just don't get it, that your life is arranged around a permanent attitude of DGAS, but I cannot be the only person who does care about competence.

 

[ericmark]

I cannot be the only person who does care about competence.

What has competence got to do with it? We were talking about me answering an old post as I had not looked at the date and it had appeared in current listing. Nothing about the post subject its self.

 

[ban-all-sheds]

What has competence got to do with it?

Paying attention to dates.

it had appeared in current listing.

this was on the main current page.

That's what I was questioning - at the time of posting this the topic at the very bottom of Page 1 of the forum topic list has a latest post date of 26th April 2015, 01:34, so I couldn't see how this topic could have been on p1 when its latest post date would have been 8th March 2007, 22:32

 

[denso13]

To be fair to eric I also saw it at the top of the first page. There was a spam post which I reported and has obviously caused confusion. It has been removed leaving eric's post in place. There are probably more important things to worry about though.

 

[JohnW2]

To be fair to eric I also saw it at the top of the first page. There was a spam post which I reported and has obviously caused confusion. It has been removed leaving eric's post in place. There are probably more important things to worry about though.

I can confirm that. A silly message was posted to the (8-year-old) thread, which brought the topic to the top of the current list. I suggested that the mods should remove it, which they did, but by then it was too late, and eric (and probably others) had already found it there at the top of the list (and not noticed the date of previous posts in it).

Kind Regards, John