Shower problem...

[MasterAbacus]

Hi all,

Shower Mira Play, not heating up as it should.

It has three settings... Low, Med, High...

Low... no heat given at all, right throught the range...

Med... Temperature dial has to be almost at full to be nice and comfortable
(OVer time this has had to be increased to full to get heat.)

High... good solid heat right through the range, however when on for longer periods... ie over 5 mins it trips the mcb. (Not good running down stairs to reset it, esp when dripping wet from the shower)....

Any ideas on this? how it could be fixed.... I have spoken with Mira, got someone not very bright on the phone, and all they seemd to want to do is send an engineer out.....


Just in addition to this, the shower is wired, no more than 5 meters from CU, with 10mm cable, and 63RCD protected and a 40MCB.... This is the spec suggested from Mira, when installing this unit... the only difference is i have a fan running from the Shower switch.... could this push the 40mcb too far, hence the trip at high power? Would I do any harm in replacing the 40, with say a 45 mcb?

Im thinking ive got two problems here... whats you thaughts?

 

[rjb]

The fan will be an inductive load I assume so like flouresants there's a power factor de-rating going on maybe??. Don't know for a fact, just a suggestion.

What is the power of the shower and fan?

Can you try isolating the fan and trying the shower again to see if it trips the MCB.

 

[MasterAbacus]

Cant believe I never put this in the post...The shower is Rated at 9.5kw, not sure about the fan.... I could find out , but it will be a propper pain in the rectum to disasemble and look at lables etc... as it was a pain to set into place.... Ill do it only if i really need to tho...

Im thinking the heater tank is at fault in the shower, hence the loss of heating on low and med... from what iv worked out so far the tank works on the elements... i bit like an emersion heater....

 

[ColJack]

your element will be all scaled up..

how old is the shower?

do you live in a hard water area?

as winter sets in the water in the mains gets colder so showers have to work harder to heat it..

how big is this fan? ( physically ) just your standard extractor fan?

do you really think it's a good idea to run a fan from a 40A supply? you don't mention fusing it down...

 

[MasterAbacus]

The shower is about 12 months old....

Water isnt really a problem i dont think....it can be a bit cloudy tho....

Fan is a standard extractor fan, about 4 inch across... Its not fused down.

 

[Steve]

Disonnect the fan as soon as. It NEEDS fusing down. Did you connect it in 6 or 10mm² cable, like the rest of the circuit? You should have done, but i'd love to see you get 10mm into a fan.

Though your fan will only be 20 watts or so - the shower is 9500 watts.

When the shower is on high, it draws the full 9.5kw regardless of what temperature setting its on.

At 230 volts, 9.5kw is 41.3 amps, but I wouldnt expect this to trip after 5 mins - I'd give it half an hour.

Either way the circuit aint designed properly.

 

[MasterAbacus]

It was an exisitng curcuit... I only replaced the fan with a new one, and the shower with a new shower about a year ago....Oh and added a RCBO pretection for the shower. Seperate CU for shower /Fan set-up. Using existing 10mm Cable, and the teeny 1.5 that was inplace for the Fan

Ive not problems pulling the fan and maybe wiring it into the lighting curcuit instead...... I asume this will not require fusing down either, if i just place it on this curcuit.... as its all run in 1.5mm and prodected with a 6MCB....

From the calculation youve given me, the 40amp MCB that protecting the shower, should be fine for longer, but will i have any other issues if i was to upgrade the MCB with a 45 AMp... just so im above the calculations?

 

[rjb]

Master Abacus

After my yesterday post about loading of fans I decided to have an investigation as I wasn't sure myself. Most fans at rated at 0.25 Amps, but more powerful ones will be about 0.5 Amps. (This is from NICEIC most frequently asked questions to helpline book - questions concerned taking power for fan from lighting circuit)

Either way it is not going to affect your total demand much as your shower drawing 41.3 Amps.

 

[MasterAbacus]

So if my shower is drawing 41.3 Amps, then why do the Manufacturer state it requires a 40 Amp fuse....... Sureley this is just wrong.

This is obviosly an area i need to brush up on, but learning is always good.

 

[rjb]

What you are saying does sound odd doesn't it.

Perhaps they have forgotten that we now run on a harmonised 230v not 240v.

If 240v it would had been 39.58 AMPS

 

[plugwash]

Well whether it is in spec on a 40A breaker depends on whether the shower is rated at 9.5KW @ 230V or 9.5KW @ 240V. Even if it is overloaded that kind of overload is going to take hours to trip if it ever does.

my first thought would be to use a clamp meter to see how much current is actually flowing, this should tell you whether it is a dodgy shower or a dodgy breaker.

 

[MasterAbacus]

"clamp meter"..... thats a new one..... Maybe a new toy i be needing....

 

[MasterAbacus]

The Technical spec says...

Mira Play 9.5 kW- A 9.5 kW 240 V AC (8.3 kW 230 V AC) heater.

 

[rjb]

I don't understand this or I'm missing something very strange.

9.5 kW @ 240 = 39.58 Amps
8.3 kW @ 230 = 36.09 Amps

Someone is this correct thinking or am I daft as a brush.

Oh Clamp meters

http://www.sercal-testequipmentsales.co.uk/clamp-meters-13-c.asp

 

[ColJack]

rjb....

when have you ever seen a voltage supply even close to the "harmonised" 230V?

we're not now, and never will be harmonised with the euro voltage..

we run on 240.. they set the tollerances so that we fall into the upper limits..

most unloaded supply voltages round here are in the range of 250 volts..