Electrical Pump Advise sought for DIY

[tony_park]

Hi guys,

newbie here, please go easy!

I've got a query regarding an existing installation on a pumping station pump issue, which I'm hoping you can help with.

Our house is off mains sewage, and as such we have a sewage treatment plant, and a pumping station. In the pumping station we have 2 pumps, a new one installed last week, and one that has been in about a year. When the older pump starts to pump, due to the float being lifted, it trips the power to our garage circuit.

The power to the sewage and the pumping station should be protected by a 30a RCD, however when the pump is active, its tripping the power to the garage, rather than just tripping the RCD switch. Would anyone be able to advise on why this is happening, and how we can ensure that its the RCD in the garage that trips?

Thanks in advance
Tony

 

[DPG]

Hi guys,

newbie here, please go easy!

I've got a query regarding an existing installation on a pumping station pump issue, which I'm hoping you can help with.

Our house is off mains sewage, and as such we have a sewage treatment plant, and a pumping station. In the pumping station we have 2 pumps, a new one installed last week, and one that has been in about a year. When the older pump starts to pump, due to the float being lifted, it trips the power to our garage circuit.

The power to the sewage and the pumping station should be protected by a 30a RCD, however when the pump is active, its tripping the power to the garage, rather than just tripping the RCD switch. Would anyone be able to advise on why this is happening, and how we can ensure that its the RCD in the garage that trips?

Thanks in advance
Tony

If you have two 30mA RCDs in series then there is no way to make one trip before the other. Indeed they both may trip.

Does the garage feed need RCD protection?

 

[tony_park]

Hi,

thanks for your response, sorry, wrong terminology. The garage is protected by an MCB, and the sewage processing, by the RCD. Sorry for the typo!

Thanks again
Tony

 

[DPG]

Dont forget, an RCD trips on an earth fault and an MCB trips on either overload or short circuit faults

 

[snowhead]

Did the old pump trip the power before the new pump was installed?
Was there a fault with the old pump that was replaced or is the new pump additional?
Presumably the new pump doesn't trip?
Who fitted the pump, did they check the reason for the older pump tripping?

Do these pumps move the sewage to the mains sewer?

What controls are there for the system as a whole, were these replaced?

The old pump would appear to be tripping on excessive current either because it's faulty or because it's jammed or overloaded.

 

[tony_park]

Hi,

please see inline comments:

Did the old pump trip the power before the new pump was installed?

No, when the new pump was installed, the older pump appeared to be working fine. However due to the amount of water it was having to process, need to have the second pump as a backup.

Was there a fault with the old pump that was replaced or is the new pump additional?
Presumably the new pump doesn't trip?

The new pump replaced on that failed, probably due to overwork, and is something that we're looking to resolve, as all water that is either used, or falls on our house, is passed via the sewage treatment. From speaking to a neighbour, they pipe out their surface water directly out to ditches in nearby fields, and this is the plan for us. However currently we're stuck with the system left with us by our previous house owner.

Who fitted the pump, did they check the reason for the older pump tripping?

I fitted the pump. Suspect its wear and tear, as the previous pump had been in for a couple of years.

Do these pumps move the sewage to the mains sewer?

No, clean water output from the sewage system. All solid materials are left in the sewage treatment plan, and just water output to the pumping station.

What controls are there for the system as a whole, were these replaced?

Pumps are fitted with floats, when the water level is high enough, the float lifts, the pump turns on. No other controls are present.

The pumps are connected to an external double socket, which is uses a serial connection to the sewage treatment, then back to the garage and its RCD. The pumps are using their factory fitted plugs, and show no sign of water ingress etc.

As I mention, we're looking into alternatives for getting rid of surface water, to reduce the impact on the pumps significantly. However my concern is that there is something wrong with the setup of the electrics which is causing the MCB to trip and not the RCD.


Hope this helps, thanks again!
Tony

 

[snowhead]

As per DPG post earlier, MCBs and RCDs trip for 2 different reasons.

If it's tripping the MCB it's because the current drawn by the pump, or possibly a fault in the wiring connected only with that pump, exceeds the MCB rating.

The pump or wiring would not appear to have any earth faults otherwise the RCD would trip.

Does the older pump always trip the MCB or is occasionally?
The first course of action would be to use a clamp ammeter on the pump to measure it's actual current draw.

 

[Lucien Nunes]

If there is a fault on the motor that is causing excessive power consumption, an MCB will trip and not the RCD. Likely causes would be a damaged winding or capacitor, which might not stop it running but are likely to develop into a complete failure.

What is the power rating of the pump motor? You mention the pumps are plugged in; are these 13A plugs or what kind? It is unusual for a 32A MCB to trip on prolonged overload without a 13A plug fuse failing first, although it can happen with high surge loads or intermittent short-circuits as the MCB can respond faster than the fuse. What is the type letter of the MCB ahead of the current rating (B, C, D e.g. B32)

There is a possibility that the starting surge of the pump was always near the threshold of the MCB instantaneous trip, and that has got a little more sensitive or the surge has got slightly greater over time, i.e. not much has changed but now it's the wrong side of OK.

 

[tony_park]

Hi,

will need to check the power being used by the pump when it starts up, and will confirm once known.

The MCB is NCB32 - and I believe the plugs have 13a fuses.

From what I've experienced in the past, its when the pump fires up, that the power trips, so it may be the initial surge causing the problem. How easy is it to check the power being used on the circuit? I suspect possibly easiest to check the normal load, and then add the power from above, when the pump starts up?

Assuming that the load is reaching the limit, would it then be contacting an electrician to install a higher rated MCB to take into account the surge?


Thanks
Tony

 

[Strima]

May just need an MCB with a higher tripping curve installing. Looking at the part number you have a B type MCB installed, you may well require a C type.

Do the manufacturers instructions mention anything about inrush currents on start up?

 

[OnlQQker]

I removed the pumps from an extremely large celler 4 years ago and replaced them with a Saniflo.
I also was in a gym where one saniflo dealt with the 1 female toilet/ 3 showers/ 2 sinks and another one dealt with the same in the male changing room.

They are cheap to run and never once played up in over the 3 years I was in the gym! Not much bigger than 2 brief case's put together!

 

[Megawatt]

Hi guys,

newbie here, please go easy!

I've got a query regarding an existing installation on a pumping station pump issue, which I'm hoping you can help with.

Our house is off mains sewage, and as such we have a sewage treatment plant, and a pumping station. In the pumping station we have 2 pumps, a new one installed last week, and one that has been in about a year. When the older pump starts to pump, due to the float being lifted, it trips the power to our garage circuit.

The power to the sewage and the pumping station should be protected by a 30a RCD, however when the pump is active, its tripping the power to the garage, rather than just tripping the RCD switch. Would anyone be able to advise on why this is happening, and how we can ensure that its the RCD in the garage that trips?

Thanks in advance
Tony

Tony I would think that the lift station should have its own circuit not on the garage circuit. I guess when the pump starts it’s to much inrus current that’s tripping the breaker. What size is your pump ?

 

[Floody]

You should have a data plate on the pump itself, giving you the starting current and the running current, amongst other info. Chances are its tripping on high starting current. Pumps and motors starting current can be 3 to 8 times its operating current. Let us know