garden pump
- Thread starter mackeral
- Start date
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The pump will be few hundred watts to kilowatt or so, capacitor start induction motor unless its an absolutely enormous building. (if in doubt 'phone the makers though, don't take my word for it then complain if that one requires something special) An RCD may not be mandatory, but like the shower, I get a much warmer feeling if there is one. Certainly it limits the scope of any damage too, if foul water gets in where it should not.
A 13A RCD protected fused spur would probably be more than enough. (although cable length needs to be considered when deciding cable diameters if its at the wrong end of the site.)
Hope that sets you in the right direction.
A 13A RCD protected fused spur would probably be more than enough. (although cable length needs to be considered when deciding cable diameters if its at the wrong end of the site.)
Hope that sets you in the right direction.
No need for an RCD - you do not want nuisance tripping on one of these!
thanks guys,
Reading John Whitfields Electricans Guide "Garden lighting, pond pumps and so on should preferably be Class 3. Where 240V equipment must be used, it should be Class 2... If accessible Class 1 equipment is used its supply system must allow disconnection within 0.4 secs....
Then again it is not a 'pond pump' being installed in this instance so i feel 5 secs should be adequate.
any more for anymore?
Reading John Whitfields Electricans Guide "Garden lighting, pond pumps and so on should preferably be Class 3. Where 240V equipment must be used, it should be Class 2... If accessible Class 1 equipment is used its supply system must allow disconnection within 0.4 secs....
Then again it is not a 'pond pump' being installed in this instance so i feel 5 secs should be adequate.
any more for anymore?
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if you are using normal mcbs it doesn't make any difference to your design anyway.
mcbs have two seperate trip systems
a fast trip (magnetic)
and a slow trip (thermal)
the slow trip deals with small but sustained overloads and is pretty much useless as a means of short cuircuit protection.
the fast trip either trips fast (the mcb spec requires under 0.1 sec iirc) or it doesn't. It doesn't get significantly faster with larger currents and it doesn't tend to trip at all with smaller currents.
hence your aim when using a mcb is to ensure that a short will cause enough current to hit the mcbs maximum fast trip point (5x rating for a type B) regardless of whether the cuircuit requirements say 5 sec or 0.4 sec or 0.2sec.
designing cuircuits for fuses is a very different matter but if this is a new install i doubt you will be doing that.
mcbs have two seperate trip systems
a fast trip (magnetic)
and a slow trip (thermal)
the slow trip deals with small but sustained overloads and is pretty much useless as a means of short cuircuit protection.
the fast trip either trips fast (the mcb spec requires under 0.1 sec iirc) or it doesn't. It doesn't get significantly faster with larger currents and it doesn't tend to trip at all with smaller currents.
hence your aim when using a mcb is to ensure that a short will cause enough current to hit the mcbs maximum fast trip point (5x rating for a type B) regardless of whether the cuircuit requirements say 5 sec or 0.4 sec or 0.2sec.
designing cuircuits for fuses is a very different matter but if this is a new install i doubt you will be doing that.
B
Big_Spark
Mackeral, Lectrician is right, there is not any need for an RCD or RCBO of a supply to a Sceptic tank.
I have installed a large number of suipplies for these over the years, normally Klargester units, and all they need is a dedicated Spur to power them.
If you install a seperate enclosure and feed this with small 6mm DI tails from the meter, install a 40A Double Pole Isolator with the output feeding a 6A or 10A Type C MCB (depending on the size of the Tank). This should then feed an Switched fused spur adjacent to the unit. This circuit should be in SWA, and either 2.5mm or 4mm. 2.5mm SWA will cover you easily for volt drop out to about 40m on the average sceptic tank so this should be sufficient. The Fuse in the spur should be rated be 13A to ensure that it does not pop the fuse without you knowing.
I have always rigged up visible and audible warning systems for Klargesters in the event of loass of power. These are no things that you want failing for too long.
I have installed a large number of suipplies for these over the years, normally Klargester units, and all they need is a dedicated Spur to power them.
If you install a seperate enclosure and feed this with small 6mm DI tails from the meter, install a 40A Double Pole Isolator with the output feeding a 6A or 10A Type C MCB (depending on the size of the Tank). This should then feed an Switched fused spur adjacent to the unit. This circuit should be in SWA, and either 2.5mm or 4mm. 2.5mm SWA will cover you easily for volt drop out to about 40m on the average sceptic tank so this should be sufficient. The Fuse in the spur should be rated be 13A to ensure that it does not pop the fuse without you knowing.
I have always rigged up visible and audible warning systems for Klargesters in the event of loass of power. These are no things that you want failing for too long.
thanks fwl and plug,
for convenience and due to the layout of the house and out buildings the supply will be from a f/spur of a double socket outlet. This will be protected by a HRC fuse.
FWL - i would be interested to know about your audible warning system...
for convenience and due to the layout of the house and out buildings the supply will be from a f/spur of a double socket outlet. This will be protected by a HRC fuse.
FWL - i would be interested to know about your audible warning system...
B
Big_Spark
OK Mackeral, I'll sort you out a drawing and post it.
EDIT
Found the old drawing and have uploaded and made it clearer.
EDIT
Found the old drawing and have uploaded and made it clearer.
B
breezer
FWL_engineer seems to be saying if you have no mains you will be in the .......
iirc with relays normally reffers to the state when the coil is off
so shouldn't the relay be a normally closed device?!
i also think fwl is trying to advise you to keep it as seperate from the rest of the house wiring as possible to make damn sure it stays powered
so shouldn't the relay be a normally closed device?!
i also think fwl is trying to advise you to keep it as seperate from the rest of the house wiring as possible to make damn sure it stays powered
B
breezer
thing is you have a siren and strobe going to tell you that you are going to get covered in ....... I am sure there is a joke in there some where
other thing is it g'teed to go off at 2 o'clock in the morning, so waht will you do turn it off and go back to bed, get up and forget.
i am not really knocking it, i do think its a good idea, but 102db sounder, bit too loud, and why not have the switch turn only the sounder off, that way strobe will cary on as a reminder
other thing is it g'teed to go off at 2 o'clock in the morning, so waht will you do turn it off and go back to bed, get up and forget.
i am not really knocking it, i do think its a good idea, but 102db sounder, bit too loud, and why not have the switch turn only the sounder off, that way strobe will cary on as a reminder
plugwash said:iirc with relays normally reffers to the state when the coil is off
so shouldn't the relay be a normally closed device?!
i also think fwl is trying to advise you to keep it as seperate from the rest of the house wiring as possible to make damn sure it stays powered
Plugwash, Relays can be manufactured in both states, and I have used both types on many occasions, although never for a sceptic tank. Plugwash, if the relay were normally closed, the circuit would be energised all the time!
Considering the critical nature of such equipment, I think that FWL_Egineers comments about keeping this seperate is spot on. Such a premises, if it needs a Klargester, will likely be on a TT supply due to it's rural location, this means that any circuits will be RCD protected, and FWL_Engineer made it clear that this should not go on one. I have not personally installed such plant, but I think it would be prudent not to have an RCD protecting it.
B
Big_Spark
Plug, most Power Relays are NO+NC or NO, some can be bought NC but these are no common.
If you go to RS website and put this code in the search bar 376-947, then click on the highlighted number in the list, it will open a Java window that shows the tech specs for the relay.
If you go to RS website and put this code in the search bar 376-947, then click on the highlighted number in the list, it will open a Java window that shows the tech specs for the relay.
If you build FWL's "come and look at me" alarm, I'd suggest that the rcd is then no bad thing, and I'd personally fit one. I have seen the effect of water in pumps both with and without rcd protection, and only the "with" was repairable. I dont really like the idea of a fault current flowing to earth through the water in the tank, potentially for very long time before the current rises by enough to blow a 13A fuse. Also as my life has been saved by an RCD, I guess my judgement is a little coloured in favour of them, so I respect that others have different opinions. However, I think the consensus is that the spur and 13A fuse is all you must have.
Worth asking where it will overflow to if the power goes off. If all it does is choke the soakaway, or flood from a manhole cover at the bottom of the garden, its not half as serious as if it erupts from the downstairs shower tray indoors. The only ones I have seen have been far enough in the sticks that an overflow is not such an issue, as its no worse than what the cows leave all the time.
Let us now how you decide, these 'special cases' are much more interesting than the run of the mill stuff.
Worth asking where it will overflow to if the power goes off. If all it does is choke the soakaway, or flood from a manhole cover at the bottom of the garden, its not half as serious as if it erupts from the downstairs shower tray indoors. The only ones I have seen have been far enough in the sticks that an overflow is not such an issue, as its no worse than what the cows leave all the time.
Let us now how you decide, these 'special cases' are much more interesting than the run of the mill stuff.
just an update...
went ahead with the install. The pump had a load of approx. 1.5A. It is located about 50m from the house and overflow is not an issue. I was concerned about nuisance tripping and decided the 100ma trip would suffice. Althought this does protect the whole house and is not ideal.
Thanks to FWL for the info and drawing. Liked the idea. How and ever constrained by 'budget'...
went ahead with the install. The pump had a load of approx. 1.5A. It is located about 50m from the house and overflow is not an issue. I was concerned about nuisance tripping and decided the 100ma trip would suffice. Althought this does protect the whole house and is not ideal.
Thanks to FWL for the info and drawing. Liked the idea. How and ever constrained by 'budget'...
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