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archmoco

Hello can anyone help. I'm in a house now about 5 years, the primary heating for the house is via wood burning stove connected and providing heat into a 1000ltr accumulator tank. The secondary heating is via an immersion connected to  3 atp 3.5 kw time clocks, house has economy 7 of peak electric. one of the time clocks has been replaced with a boost button . All three apt timers are now broken, the switches work fine manually on/off to powder immersion but the mechanical clock elements do not rotate any more

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ProDave

Why 3 time clocks for one heater?

 

It's not unknown for mechanical clocks to break.

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archmoco

the immersion is commercial '3 phase?' so set up as 3 individual time clocks each giving 3kw so when all 3 are on give 9kw, engineer had set it up this way due to size of water the immersion had to heat

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Andy™
2 hours ago, archmoco said:

the immersion is commercial '3 phase?' so set up as 3 individual time clocks each giving 3kw so when all 3 are on give 9kw, engineer had set it up this way due to size of water the immersion had to heat

 

someone who knows what they are doing would have used 1 timer feeding a contactor to switch them all rather than 3 timers

Edited by Andy™

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Geoff1946

You seem to me to have answered your own question; you have three duff timers. But, as suggested above it's a strange, perhaps unique set up. 

The only logical reason I can think of for doing this is to allow the power input to be scheduled at 1, 2, or 3kw at different times, but who would be bothered which such a complex set up?

If you're not sure what you are doing, just remember you now have 400 volts at your finger tips rather than 230!  

 

Afterthought -  Are you in UK,  because three phase domestic is rare ?

Afterthought 2   Presumably there is a neutral ?  (Three phase heaters I've encountered didn't have.)

Edited by Geoff1946

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Tony S

With Economy 7 I would assume this is a UK install.

 

3 phase immersion heaters are quite common for large properties. As has been mentioned normal practice would be one thermostat and a contactor.

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rapparee
19 hours ago, Geoff1946 said:

You seem to me to have answered your own question; you have three duff timers. But, as suggested above it's a strange, perhaps unique set up. 

The only logical reason I can think of for doing this is to allow the power input to be scheduled at 1, 2, or 3kw at different times, but who would be bothered which such a complex set up?

If you're not sure what you are doing, just remember you now have 400 volts at your finger tips rather than 230!  

 

Afterthought -  Are you in UK,  because three phase domestic is rare ?

Afterthought 2   Presumably there is a neutral ?  (Three phase heaters I've encountered didn't have.)

Sounds more like 3 elements running at 230v 3kw each 

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SPECIAL LOCATION
On 11/01/2019 at 20:27, archmoco said:

Hello can anyone help. I'm in a house now about 5 years, the primary heating for the house is via wood burning stove connected and providing heat into a 1000ltr accumulator tank. The secondary heating is via an immersion connected to  3 atp 3.5 kw time clocks, house has economy 7 of peak electric. one of the time clocks has been replaced with a boost button . All three apt timers are now broken, the switches work fine manually on/off to powder immersion but the mechanical clock elements do not rotate any more

 

1000ltr....???

 

That's a fair amount of water to be storing/heating..?

 

And all these timers have failed in under 5years??

Sounds like someone fitted some cheapo timeclocks..

 

So I am guessing your immersion is something similar to this type of beastie...?

https://www.fastlec.co.uk/syb914-backer-9kw-industrial-immersion-heater-14-inches.html?gclid=EAIaIQobChMIsriulonr3wIV55PtCh1LYQvaEAQYAyABEgLjRvD_BwE

which can be configured 3x Single phase or 1x Three phase...

 

Has the wiring set-up been messed up when this boost button was fitted?

 

Has it worked fully since the boost was fitted?

 

:C

 

 

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Badger

1 32amp supply to. Contactor via 6 or 10mm then three separate connections via a fused spur 13amp to. Each eater via the secondary side of contactor and then time clock fed and supplying the contactor coil to. Engernise contactor on secondary side job done easy peasy 👍😁

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ProDave

1000 litres is pretty normal for a heating system based on a stove and back boiler, also for pellet stoves. The theory is a stove runs best on a long hot burn, so you have a large capacity tank to allow the stove to work long and hard to heat it, then it will provide several days heat before the stove is needed again.

 

The only thing poor about this install is using 3 single phase timers rather than one timer and a contactor.   

 

And you need something like 9KW of heat for such a big tank, a single 3KW heater would take too long for any meaningful heat input.

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Andy™
49 minutes ago, Badger said:

1 32amp supply to. Contactor via 6 or 10mm then three separate connections via a fused spur 13amp to. Each eater via the secondary side of contactor and then time clock fed and supplying the contactor coil to. Engernise contactor on secondary side job done easy peasy 👍😁

 

apart from 3x 3kw is over the limit for a 32a circuit...

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Badger

Oh yes it would need a 40 amp my error 

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ProDave
32 minutes ago, Badger said:

Oh yes it would need a 40 amp my error 

But it's 3 phase so one 3 pole 16A mcb in a 3 phase board.

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Badger

But its being used on a single phase supply from what I read on the op post

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ProDave
1 hour ago, Badger said:

But its being used on a single phase supply from what I read on the op post

Re reading it I think you are right.

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SPECIAL LOCATION
2 hours ago, Badger said:

But its being used on a single phase supply from what I read on the op post

 

53 minutes ago, ProDave said:

Re reading it I think you are right.

 

I wonder if for some unknown reason it has actually been wired as three individual circuits...?

 

3x 16A MCB via 3x 2.5mm T&E's...

 

Maybe..  Mr installer has misunderstood original spec and just wired for a single 3Kw immersion element and time clock..

 

Then finds out it is actually a 3x 3Kw element...

so pull in two more 2.5mm cables & two more timeclocks... rather than replacing with a single 10.0mm??

 

:CGuinness

 

 

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ProDave

That could be.  I will never forget the one where I followed the spec and wired for a "boiler"  When it arrived the "boiler" was actually a dual immersion off peak unvented water cylinder.  I think that was the job that taught me to question the spec.

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Andy™
14 hours ago, SPECIAL LOCATION said:

 

 

I wonder if for some unknown reason it has actually been wired as three individual circuits...?

 

3x 16A MCB via 3x 2.5mm T&E's...

 

Maybe..  Mr installer has misunderstood original spec and just wired for a single 3Kw immersion element and time clock..

 

Then finds out it is actually a 3x 3Kw element...

so pull in two more 2.5mm cables & two more timeclocks... rather than replacing with a single 10.0mm??

 

:CGuinness

 

 

 

could be, but he could have still used a contactor and 1 time clock

 

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SPECIAL LOCATION
9 hours ago, Andy™ said:

 

could be, but he could have still used a contactor and 1 time clock

 

 

Ah...  yes but... no but....

 

Perhaps his cheapo time clocks (that fail after only 5 years) were much much cheaper than going via the Contactor option???

 

Money talks.....:|

 

so 3x clocks = money savings = profit for mr Spark..

who then drifts off into the sunset never to be seen again??

 

Just guessing???

or maybe he was just as direct descendant of the late great Mr Heath Robinson?

 

Guinness 

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SPECIAL LOCATION
14 hours ago, ProDave said:

That could be.  I will never forget the one where I followed the spec and wired for a "boiler"  When it arrived the "boiler" was actually a dual immersion off peak unvented water cylinder.  I think that was the job that taught me to question the spec.

 

Even when there is a written spec....

The Spec is never Set In Concrete.....

 

The golden rule...

If the lady of the house changes her mind...

It doesn't matter how nearly finished you were...

The Spec HAS Changed!!!!

 

Which isn't a problem as long as you have quoted or refenced the spec in your costings such that any changes WILL incur additional costs!

 

Guinness

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