**** Pump and MCBs!

[charliegolf]

I am off main sewage, and have a 2 cu m holding tank which is emptied by a grinder pump. After 11 years, the pump died. The company changed the pump and after fitting it, had an Oh Dear! moment. The dedicated circuit for the pump is 10A, and this one apparently, has a higher start current. The fitter suggested sheepishly, a higher rated MCB. (16A type c).

Next problem: my CU is an MK from 1995- all fine, no problems ever. But MCBs are different apparently, and not available...

Question: Can my electrician swop the 10A pump MCB with the 20A garage one (I use diy power tools and a door operner in there) without endangering life or limb? I'd also look for a 16A replacement on ebay, as all the suppliers are suggesting.

Does using a 20A 'endanger' me or the pump?

Thanks

CG

 

[securespark]

What size is the circuit cable?

What size is the switch gear?

Is there RCD protection for the pump?

What brand and model is the pump and what size?

 

[charliegolf]

2.5 mm sq;
Not sure
Yes
Pentax DTR 200

CG

 

[JohnW2]

Roughly how long is the 2.5mm² cable?

Kind Regards, John

 

[charliegolf]

Approx 15m John.

 

[JohnW2]

Approx 15m John.

In that case, and provided that the cable is not buried in insulation, then 2.5mm² cable would almost certainly be OK with a 20A Type B MCB (your electrician would take some measurements to check, but it almost certainly would be OK).

Whether a 20A Type B MCB would tolerate the starting current of your pump without tripping is something I can't answer. It obviously would be less likely to trip than your present 10A one, but I can't be certain whether it would be OK.

Kind Regards, John

 

[securespark]

What does it say on the rating plate on the pump/ paperwork?

How many kW, current etc....

 

[Simon35]

What does it say on the rating plate on the pump/ paperwork?

How many kW, current etc....

Google sez 1.5kW.....so 12A at 240V

 

[JohnW2]

Google sez 1.5kW.....so 12A at 240V

I'm not sure that I understand your arithmetic - by my reckoning, 1.5kW at 240V is about 6.25A.

In any event, I imagine that what is being quoted is probably the running current, whereas the OP's problem is related to the start-up current (which could be several times greater than the running current).

Kind Regards, John

 

[EFLImpudence]

1500/240 = 6.25A

Too slow.

 

[charliegolf]

Th

I'm not sure that I understand your arithmetic - by my reckoning, 1.5kW at 240V is about 6.25A.

In any event, I imagine that what is being quoted is probably the running current, whereas the OP's problem is related to the start-up current (which could be several times greater than the running current).

Kind Regards, John

Exactly so...

 

[securespark]

Pentax DTR 200

I asked what the pump was, not what camera you have...

Start-up's are usually around 4-5 times FLC.

In the case of 6.25A, that would be 25 - 31.25A.

Installation ref method D would give 2.5 a maximum CCC of 29A.

I would say 2.5 would be OK.

 

[bernardgreen]

www.pentax-pumps.it/en/Prodotti/dettaglio-prodotto/dtr/78/p

Probably explain why some photographers produce such krap images.

personally I prefer Mono pumps

http://www.mono-pumps.com/en-uk/grifter_pump_system?productid=11

 

[JohnW2]

Start-up's are usually around 4-5 times FLC. In the case of 6.25A, that would be 25 - 31.25A.

The OP's B10 (I assume it's Type B) is tripping on startup. Whilst that could happen at 30A, it is more likely to need closer to 50A, so I suspect that the start-up current is probably greater than you suggest.

Installation ref method D would give 2.5 a maximum CCC of 29A. I would say 2.5 would be OK.

Are you assuming that it is buried SWA?

Whatever, I don't think the CCC needs to be high enough for the very brief start-up current. It's whether the MCB trips, and if the Zs is low enough (if a Type C MCB were used) that actually matter, isn't it?

Kind Regards, John

 

[JohnW2]

1500/240 = 6.25A .... Too slow.

I said "about 6.25A" since that would only be exactly true if PF=1. Since it's probable that the PF of a pump is far from unity (unless adequately compensated) the current could actually be a fair bit higher than that figure.

Kind Regards, John