Yeh, but 25kw???
Home power question
- Thread starter hellarda
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Yeh, but 25kw???
well 10 servers, 3 home pc's switches routers (a lot of cisco stuff is going in soon)
8 2000W pa amps
a load of studio stuff + outboard + monitors
all adds up
(then theres the rest of the house hold stuff, toaster, kettle, microwave etc etc
8 2000W pa amps
a load of studio stuff + outboard + monitors
all adds up
(then theres the rest of the house hold stuff, toaster, kettle, microwave etc etc
Soldato
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ok well, i am running a few servers for testing and and experiments(
Few servers isn't a farm. Few speakers isn't Glastonbury.
Don't over analyse it all to much!
Best advice so far. Incoming cable will define the maximum supply available assuming you can get someone to increase the fuse size.
Worth measuring your actual consumption if you haven't already - PC power supply rated at 1kW is extremely unlikely to actually draw 1kW etc. Don't forget diversity - it's unlikely you'll have every appliance running in the house at the same time all running at maximum load. I'd personally just get on with it, save your money and worry when breakers start to trip. If they do, move some higher load devices onto a circuit with less existing load.
A simple domestic (unless its a really huge place) is not going to need more than 100A SPN... you might not even have 100A at the moment, its more than possible its a 60A fuselink in the service-cutout
Think of it as a thermally equivelent load, unless you are heating water... or the house in winter than 25kw is a lot of heat if you were drawing it for any length of time and your electricity bill would be ****ing massive!. Plus you'd have the local constrabuly beating a path to your door as the heat signiture from your roof would look like something else!
Might interest you to know that most of the electricity network is based on 2kw for a 4 bed house with gas heating (averaged out of 1/2 hr for whole estates)... that normally works out generous, you'd be using a lot if your electricty bill averaged out as even half of that continiously
Think of it as a thermally equivelent load, unless you are heating water... or the house in winter than 25kw is a lot of heat if you were drawing it for any length of time and your electricity bill would be ****ing massive!. Plus you'd have the local constrabuly beating a path to your door as the heat signiture from your roof would look like something else!
Might interest you to know that most of the electricity network is based on 2kw for a 4 bed house with gas heating (averaged out of 1/2 hr for whole estates)... that normally works out generous, you'd be using a lot if your electricty bill averaged out as even half of that continiously
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Main fuse is normally max 100a in a domestic property, you can get bigger fuses 200 or 300a but these are normally for commercial and industrial properties and or places which would also use 3 phase.
Changing the main fuse would require talking to your local DNO and i guess they arent gonna want to increase it, cos the substation your running from will only have a 300 or 600a fuse on that phase itself shared between all the houses on that phase from the substation, high load buildings normally have the supply arrangements negotiated during the planning to sort all this out.
Best you can do is use upto 150a cos the main fuse shouldn't blow until about 1.5 x the rated limit.
Your consumer unit will probably have a 100a main switch so you would need 2 consumer units and split the load across them to keep it under 100a each.
Your would also need to rewire the circuits as 2.5 rings arent rated for 32a long term only in short-ish bursts, so if your pulling that much long term you dont really wanna use 2.5 rings
Would probably be best to wire some new circuits in larger cable like 4mm or 6mm for long term use.
But overall im guessing your not gonna be pulling that much power to make it worth doing all this tbh
Changing the main fuse would require talking to your local DNO and i guess they arent gonna want to increase it, cos the substation your running from will only have a 300 or 600a fuse on that phase itself shared between all the houses on that phase from the substation, high load buildings normally have the supply arrangements negotiated during the planning to sort all this out.
Best you can do is use upto 150a cos the main fuse shouldn't blow until about 1.5 x the rated limit.
Your consumer unit will probably have a 100a main switch so you would need 2 consumer units and split the load across them to keep it under 100a each.
Your would also need to rewire the circuits as 2.5 rings arent rated for 32a long term only in short-ish bursts, so if your pulling that much long term you dont really wanna use 2.5 rings
Would probably be best to wire some new circuits in larger cable like 4mm or 6mm for long term use.
But overall im guessing your not gonna be pulling that much power to make it worth doing all this tbh
A correctly designed and installed circuit will carry its design current indefinatly, a ring final is no different in this regard, the fact that domestic circuits never run at anything approaching design current for most of the time is a side issue
Sorry but this makes no sense and sounds pretty dangerous to me. You shouldn't run a fuse above its rated capacity (or at its rated capacity) for any significant length of time - it will shorten its life and eventually trip.
As for increasing the size of a ring main from 2.5mm to 4mm because it's not meant to handle 32A in 'short-ish bursts' I completely disagree. 4mm would only be used if the cable runs were particularly long to reduce volt drop (and increase fault current to trip the breaker in the event of a fault). 2.5mm is rated to 24A, as it's a ring main assuming it required 32A that's 16A down each side well below the 24A maximum cable rating.
Please tell me you're not a spark.
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32A ring isn't truely rated for 32a is what i mean
its under reg 433.1.5 i believe, also would depend on installation method, cable grouping factors and other factors to reach the true carrying capacity.
its under reg 433.1.5 i believe, also would depend on installation method, cable grouping factors and other factors to reach the true carrying capacity.
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by running upto 150a is a rough guide but it will probably run well over 100a safely maybe need to look at the fuse rating tables for its safe no trip load, but this isnt ideal but its the only option if you dont want to pay for a real solution
@ Alex s
You might be able to help me here, can you tell me how a ring rating is calculated as ive asked a few people and i cant get an answer tbh
For example 32a for a 2.5 is common knowledge but how is the calculated, cant see it in the regs
@ Alex s
You might be able to help me here, can you tell me how a ring rating is calculated as ive asked a few people and i cant get an answer tbh
For example 32a for a 2.5 is common knowledge but how is the calculated, cant see it in the regs
I agree you don't want to run a 32A ring main at 32A for long periods of time but that's because of the breaker size, not the cable. The circuit should be designed so that the breaker will trip before the cable catches fire!
Also agree other factors such as grouping & installation are important - that 24A was based on concealed cable.
Sorry - if you are a spark, you're clearly in the right place with the 17th edition regs to hand
I correctly designed and installed ring is rated for 32A, this is why we can connect them to a 32A circuit breaker or fuse.
Note that correctly designed and installed in the case of a ring means (and i'll take your word on the regs, my 17th is in the van, only got 16th on the desk) in terms of 433.1.5 that tha cable must have a current carrying capacity of at least 20A when installation method and derating factors considered. and and its installed in such a way that not all of the load ends up close to one end (eg. you don't shoot down a length of dado for 25m hitting 50 twin sockets and then come back down it, you have leg A hitting sockets 1-3-5-7-etc and B hitting 2-4-6-etc on its way down)
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I see what you mean alex s
that Ib < In < iz so in that case its another way of saying what i was saying that 2.5 on a 32a mcb isnt truely rated for long term use, either the mcb should be smaller or the cable larger to make In < Iz for long term use.
Also things after installation like loft insulation will cut Iz by 50% if its covers the cable for 500mm
that Ib < In < iz so in that case its another way of saying what i was saying that 2.5 on a 32a mcb isnt truely rated for long term use, either the mcb should be smaller or the cable larger to make In < Iz for long term use.
Also things after installation like loft insulation will cut Iz by 50% if its covers the cable for 500mm
You need to know circuit length, ring circuit or radial circuit.
In short work out maximum load (kW) on a circuit
Assuming 230V you now know maximum the current
Ensure cable has sufficient capacity to carry this current - critical otherwise things catch fire and lawsuits start. If it's a ring main you can half this value (hence 24A rated cable in a ring capable of supplying 32A).
Size the breaker to protect this cable - again breaker must trip before cable is overloaded.
BS7671 (17th edition) will give you information on cable current carrying capacities & grouping factors. As you say how the cable is installed will reduce the maximum current it can carry safely. It's pretty hard going to read on it's own so worth picking up something more digestible like Electrical Installation Calculations by B.D Jenkins...
It then gets quite complex with earth loop impedance which is required to calculate fault currents - you need to make sure that the conductors all the way back to the incoming mains have low enough resistance to ensure that the fault current will be high enough to trip the device protecting the circuit. You should be able to calculate earth loop impedance (Zs) or get it from test results. Hopefully the two sources above are a starter for 10.
OP - sorry for going a bit off topic
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So you're going to have 8 PA amps on all at once and all at full volume?
If so, apart from being weird the cost of a run electric supply isn't the issue. Paying the bill is. ~£10 per 3 hours use.
£72 per day.
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Thanks for the reply alex s, you seem to know quite abit about elecs so its useful talking to you, im just training atm, did my 17th 2 weeks ago
" If it's a ring main you can half this value (hence 24A rated cable in a ring capable of supplying 32A)."
This is the bit i cant find info on, the tables give capacities for radial / single cable use and theres no clear calculation to find the capacity when wired as a ring
seems like it could be as simple as:
2.5 radial = 20a , 2.5 ring = 32a so its 1.6 x or 60% increase but i would love to see an official answer for it tbh
" If it's a ring main you can half this value (hence 24A rated cable in a ring capable of supplying 32A)."
This is the bit i cant find info on, the tables give capacities for radial / single cable use and theres no clear calculation to find the capacity when wired as a ring
seems like it could be as simple as:
2.5 radial = 20a , 2.5 ring = 32a so its 1.6 x or 60% increase but i would love to see an official answer for it tbh