New Shower

[AJB1]

Dear People
I have a query for you.
I have recently had to install a new shower and found a bargain at B&Q
The shower is a Gainsborough 9.5KW shower. I have installed as per instructions and was chuffed when I first tried it. Spent at least twenty mins getting hot.

Anyway a couple of times after the installation the trip switch has tripped out and the shower has turned freezing as the water still flows until the switch is pressed on the shower.
Thinking that the shower must be faulty I whipped it off and took it back to B&Q and got a replacement, only to install it and have the same problem. It trips the trip switch after about 8mins usage.

Shower---Gainsborough Deluxe 9.5KW
45A main switch located outside bathroom
40A trip in Crabtree SB6000 Consumer unit (can't find any bigger trips than 40A anywhere)(Does anyone know of any other types of trip that would fit?)

Cable 10 mill and runs up along wall to ceiling, enters and runs through floor (length so far is about 10m) to main switch, returns from switch to shower unit on top of bathroom ceiling insulation and down to shower unit inside wall. Cable full length about 15m maximum.
The consumer unit is fairly old so I'm thinking that the 40A trip switch (which is what is recommended) is possibly overly sensitive and is tripping out after the 8mins. Is this possible? It was ok with our previous shower although it was only a 8.5KW

I didn't think that two shower units would have the same fault so I'm looking elsewhere for a cause.
The shower is great if you jump in have a quick splash and jump out before your 8 mins are up )
Any suggestions gratefully received.
AJB

I know I'll probably end up fitting a shower CU of 50/60A but I want to explore every possibility before forking out the extra expense.

 

[breezer]

Current (Amps) = power / voltage

9.5 kw =9500 watts

9500 watts / 230v = 41.3A

 

[AJB1]

Hiya breezer
I see that your calculation involves only 230v is this the normal voltage of british households? I thought it was 240!!!
Also surely the maximum power consuption would only occur when the shower was on red hot. The shower is probably set at about midpoint so would this mean that the amp usage would be less?
regards
Andrew

 

[Adam_151]

While not adviseable to design circuits as to be overloaded, a little overload like that shouldn't cause the breaker to operate, at least not within the hour.

also the 9.5kw rating is possibly at 240v, in which case the 230v rateing would be just over 8.8kw which would mean it would take 39.6A at 240v and 38.2A at 230v

 

[Adam_151]

Hiya breezer
I see that your calculation involves only 230v is this the normal voltage of british households? I thought it was 240!!!

Officially its 230v, +10% -6%, which gives a range of 217v-253v, in really nothing has changed, the voltage you'd measure with your meter is unlikely to be much different to that which you could have measured pre-'95 (which is when the changeover in official volatage happened

Also surely the maximum power consuption would only occur when the shower was on red hot. The shower is probably set at about midpoint so would this mean that the amp usage would be less?
regards

Yes and no, usually your shower will have two dials, one for temp, and one for off, cold, warm, and normal full heat, if its only on the warm setting, it takes less power than on full, but the temp dial does not affect the power taken, it changes the flow rate, the amount of power is constant, the amount of water that power goes into varied.

Power = 4200 x temp rise x litres per second

 

[AJB1]

Thanks for that Adam_151
I'll have to try and do some research into finding a trip that will fit my CU which is 45a or bigger.
Regards
Andrew

 

[baldelectrician]

Amongst other things, that's what you get for buying a gainsborough shower.

I fit a lot of showers - at least 3 a month, and over the past year I have fitted, amongst others 5 gainsborough showers.

Of the 5 gainsborough showers 4 of them have been faulty.

You may need to change down to an 9kw to lessen load.

 

[securespark]

We had a Gainsborough that was installed in the house in 1986, and I've just changed it for a new Gainsborough, and the old one was still working!

I don't like them, but when you get offered a 9.5 shower with 2 year wty for well under 50 quid from a w/saler, you take their arm off!

A 40A breaker should be fine for 41.3A.

I'm running mine on a hager 40A breaker with shower times up to 20mins with no tripping worries at all.

 

[AJB1]

also the 9.5kw rating is possibly at 240v, in which case the 230v rateing would be just over 8.8kw which would mean it would take 39.6A at 240v and 38.2A at 230v

This is what it says in my instruction manual, I have copied it for you to look at if you want by the link, and these figures are what I went by and thought my 40A breaker would be sufficient. So I thought try the shower first, changed it and still had the fault. So I wondered if it could be the mcb being overly sensitive because of its age.
Wiring

We had a Gainsborough that was installed in the house in 1986, and I've just changed it for a new Gainsborough, and the old one was still working!

The first shower we had was a 7.2kW gainsborough and it was brill till it finally stopped heating the water. We didn't buy it, we un-installed it from a friends flat. She had it in for a couple of years before I took it out and then we stored it for another couple of years until we moved. I then installed it and it lasted another 8 years. So the Gainsborough shower lasted for at least 12 years which is very good for a hard water area.
My mother in law has a Gainsborough 8.5kW that she has had for at least 9years with no trouble.
The last shower we had was a Triton, I had trouble fitting it and got no customer support and it only lasted 2 years and found that because I live in a hard water area I couldn't rely on any customer support (guarentee)
Which is why I went for another Gainsborough.

Anyway thanks everyone for your help.

 

[Adam_151]

also the 9.5kw rating is possibly at 240v, in which case the 230v rateing would be just over 8.8kw which would mean it would take 39.6A at 240v and 38.2A at 230v

This is what it says in my instruction manual, I have copied it for you to look at if you want by the link, and these figures are what I went by and thought my 40A breaker would be sufficient.

Yeah, that seems to agree with what I thought, no reason a 40A breaker shouldn't be fine

So I thought try the shower first, changed it and still had the fault. So I wondered if it could be the mcb being overly sensitive because of its age.

Could be, its what I'd consider next, try swapping the breaker for another 40A one, make sure you get the same letter it should be a B type breaker

 

[AJB1]

So I wondered if it could be the mcb being overly sensitive because of its age.

Could be, its what I'd consider next, try swapping the breaker for another 40A one, make sure you get the same letter it should be a B type breaker

This thought has crossed my mind I just haven't got round to it. I have another mcb at 40A which is the supply for the cooker. There is no type B it just says on the side of the trip

Type 1
40A
Crabtree
Crabtree Electrical Industries Ltd
Category M6 BS3871
240V ~ 1ph SB6000
240/415V ~ 3ph
ref temp 40°c
Made in England

I have searched the web and cannot find anything bigger than a 40A trip. There are however some sites that say some mcb's are usable in different CU's. The trouble is I would need to physicaly see the trip to know if it would fit into my CU.

Regards
Andrew

 

[Adam_151]

Yeah you can use that one, its a type one, breakers used to be numbered instead of lettered a while ago, two different standards they are made to.

 

[AJB1]

Thanks Adam
I'll try swapping the trips later on and let you know how I get on.
regards
Andrew

 

[Steve]

What did the people at B&Q say when you told them this shower was faulty? I only ask because if you gave them your name and adress, and gainsbrough find the shower not to be faulty, they have every right come chasing you for wasting their time and the £80-160 for a wasted shower (unless they re-sell it). You should have tested it with your own means first (ie. an electrician), who would have told you the problem, possibly over the phone. Better still, install it right first time.

 

[AJB1]

What did the people at B&Q say when you told them this shower was faulty? I only ask because if you gave them your name and adress, and gainsbrough find the shower not to be faulty, they have every right come chasing you for wasting their time and the £80-160 for a wasted shower (unless they re-sell it). You should have tested it with your own means first (ie. an electrician), who would have told you the problem, possibly over the phone. Better still, install it right first time.

OOOOHHHH I see I've done it all wrong
So Sorry
I'm only trying to save myself some money

Installing the shower as per instructions--cost=£70 thats fitted, by me.
Run into a prob
Call out an electrician--expensive I fear, that's out.
Call an electrician on the phone, recommend they come out, expensive too I fear, so that's out as well.
Join a friendly forums for some advice, cost= nothing--do that.
Get some good advice and hopefully get problem sorted.
Now that's what I call using my head and probably saving myself a small fortune.

As for B&Q they never asked for any details so as far as I'm concerned that's their problem. I couldn't give a figs bottom. I have just eliminated a possible problem at no cost to myself.

Regards
Andrew