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Distribution board has 63A fuse and ESB fuse is 80A. How do I utilise the extra 17A

  • 14-11-2016 11:10pm
    #1
    KCross
    Registered Users, Registered Users 2 Posts: 12,136 ✭✭✭✭


    I have the "increased supply" (16kVA) from ESB Networks and they have confirmed to me that the fuse on the ESB side of the meter is an 80A fuse. I believe the standard fuse is a 60A fuse (12kVA supply).

    The main fuse on the distribution boards is rated 63A
    I have a few electric hungry devices, the two main ones being:

    - Heat Pump
    - Electric Car

    The heat pump runs at 22.5A (it takes more starting current but it has a soft starter) and the car runs at 32A and they run daily at the same time (during night rate electricity). The car, in particular, draws a constant 32A for several hours every day. The heat pump cuts in/out as it sees fit so its "on time" is variable but they do run at the same time at least once a day.

    Add in a few other devices and I am close to the main distribution board fuse which is, by default, 63A is every house.

    So, my question, to all those RECI certified electricians out there is what is allowed, from a domestic regulation perspective, to "unlock" the extra 17A between 63A(on the board) and 80A(in the meter box)?

    Example: Can I simply take the 40A C-Type RCBO on the distribution board that controls the car charger and wire it outside the main 63A fuse on the board? i.e. connect it direct to the supply coming into the distribution board or do I have to wire a second distribution board or what other options are there?

    Note: I dont want to go down the route of priority switches. I want to utilise the 80A. I paid for it so I want to use it.

    I am obviously not planning on doing this myself. I will be getting a certified electrician to do it but I want to hear what my options are before I get someone out.

    The house was built in 2011 and the tails were upgraded to allow for the increased supply so I should be able to draw the 80A without burning the house down!

    thanks
    KCross
    Tagged:


«1

Comments

  • #2
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,602 Mod ✭✭✭✭2011


    Has the main fuse ever blown?


  • #3
    Tuco88
    Registered Users, Registered Users 2 Posts: 1,053 ✭✭✭Tuco88


    It's there for good fuse discrimination, you will not be able to "tap into" into it, we'll you shouldn't and it would be very poor practice to to so.

    In the event of a fault or overload you will want your 63amp mcb or fuse to trip.Allowing you to fix or reset the problem. If the 80amp goes the ESB will have to be called and paid for ,and will want to know why it happened.

    You will need to look at your incomer, I'm not sure if a 100 amp supply is available.


  • #4
    KCross
    Registered Users, Registered Users 2 Posts: 12,136 ✭✭✭✭KCross


    @2011, no it hasn't blown but I don't have the car long (a few months) and the heat pump is going to be running more with the winter coming so I'm thinking it's a possibility. Would rather get ahead of it if possible.

    @tuco88, I must be missing something then. If a standard connection (12kVA) with a 60A ESB fuse is the normal, what use is the increased supply (16kVA-80A) if all I can do is still just go to 60A like everyone else? The form I filled in when requesting the connection said a continuous 70A was allowed on the supply. Your response doesn't make sense to me. Can you explain what the increased supply has given me?


  • #5
    Tuco88
    Registered Users, Registered Users 2 Posts: 1,053 ✭✭✭Tuco88


    With a 12kva mic supply, A consumer unit will have a 50 amp followed by the ESB 63/60 amp fuse. For discrimination tails protection so on.

    With a 16 kva mic supply, A consumer unit will have a 63amp followed by the ESB 80amp.

    There is a 20 kva mic available and a 29 kva single phase mic available also if I remember thats a 100/125 amp ESB fuse.

    Your 63amp fuse/mcb won't blow/operate at 63amps on the button it will draw more current depending on fuse/mcb characteristics.

    Have you measured the loads accurately?


  • #6
    KCross
    Registered Users, Registered Users 2 Posts: 12,136 ✭✭✭✭KCross


    Ok, I misunderstood the rating on the fuse board of a standard connection then. I thought everyone had a 63A fuse. Apparently not.

    In relation to measuring the load, I know the car charger is drawing 6.6kW. The car shows me that being drawn and I have also got a kWh meter attached to it so I know that's right. It draws that power continuously.

    The heat pump draws various power levels depending on demand. The best I have to calculate that is one of those clip on meters. Not sure if you'd consider that accurate but the amp figures I quoted above are from the manufactures data sheet so I presume they are reasonably accurate.

    I presume I'd have to pay for the next MIC up? What work would need to be done inside the house to support it? Would the CU have to be changed?


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  • #7
    Dardania
    Registered Users, Registered Users 2 Posts: 3,612 ✭✭✭Dardania


    +1 to tuco88 noting on measuring the actual draw to each appliance. And their advice generally

    E.g. With the heat, the onboard display might say 6.6kw but does that account for conversion losses in the charger? So it might be a bit higher.

    And for the heat pump data sheet, again the manufacturer might be noting a max demand worst care load there-the reality might be you can reduce that amount to something more reasonable. Don't some of those heat pumps have a resistive heater to boost water temperature or similar? The Laod quoted might include that. So measure the actual load - you have a split cool ammeter you are clamp on so you should be able to get a feel for it.

    In practice your hair ighest load experienced will possibly be the heat pump starting up (in rush for a few secs) and the car pulling full current at the same time.
    If you have a C curve MCB in the consumer unit, it should allow a bit of excess current for that start up until things settle down.


  • #8
    KCross
    Registered Users, Registered Users 2 Posts: 12,136 ✭✭✭✭KCross


    Dardania wrote: »
    +1 to tuco88 noting on measuring the actual draw to each appliance. And their advice generally

    E.g. With the heat, the onboard display might say 6.6kw but does that account for conversion losses in the charger? So it might be a bit higher.

    And for the heat pump data sheet, again the manufacturer might be noting a max demand worst care load there-the reality might be you can reduce that amount to something more reasonable. Don't some of those heat pumps have a resistive heater to boost water temperature or similar? The Laod quoted might include that. So measure the actual load - you have a split cool ammeter you are clamp on so you should be able to get a feel for it.

    In practice your hair ighest load experienced will possibly be the heat pump starting up (in rush for a few secs) and the car pulling full current at the same time.
    If you have a C curve MCB in the consumer unit, it should allow a bit of excess current for that start up until things settle down.

    Im confident of the car charger figures. I've an app that connects to the car and it gives realtime power graphs. I've also cross checked the total power consumed over a charge as there is a kWh meter attached to the charger. The car is definitely drawing a constant 6.6kW's for several hours at a time.

    The HP during normal operation draws 40A max on startup and settles to 22.5A when running. During the very cold weather it occassionally has to supplement its power by adding in resistive heating. It is capped at 4kW extra resistive heating and in that mode its max operating current is 40A. This is a rare occurrence but it can happen which is why I think I might have a problem come the winter as that resistive heating has not been used since I got the car. I can disable the extra 4kW easy enough but I'd rather not.

    With the heat pump and the car charging together I am almost certainly in the 50A+ bracket and possibly more with resistive heating added in. I think I am cutting it fine. All it would take would be an oven or something to be turned on along with the base house load for lights/TV's etc and I could blow that 63A fuse.

    Is there no such thing as a 70A consumer unit fuse? That extra few Amps would be enough.

    What confuses me is the section of the ESB form (NC2) which says that 70A is max allowed for a 16kVA connection. In reality it seems that 63A is the max since thats whats in the consumer unit.
    https://esbnetworks.ie/docs/default-source/publications/connection-to-a-single-domestic-dwelling-or-farm-premises-application-(nc2).pdf

    Here is the section that describes the currents on that form
    401585.jpg


  • #9
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,602 Mod ✭✭✭✭2011


    I haven't wired a domestic installation in a very long time, however I am sure that the "standard" 12 kVA 2supply has a 63A switch fuse in the main distribution board backed by an 80A ESB fuse.


  • #10
    KCross
    Registered Users, Registered Users 2 Posts: 12,136 ✭✭✭✭KCross


    2011 wrote: »
    I haven't wired a domestic installation in a very long time, however I am sure that the "standard" 12 kVA 2supply has a 63A switch fuse in the main distribution board backed by an 80A ESB fuse.

    That isnt what the ESB engineer told me on the phone yesterday. He said 12kVA supply has a 60A fuse and 16kVA supply has an 80A fuse. What you are saying is also at odds with what @tuco88 said above about 50A in CU followed by 63A. Maybe they changed their practices?

    Otherwise, whats the point of paying for the increased supply?


  • #11
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,602 Mod ✭✭✭✭2011


    KCross wrote: »
    That isnt what the ESB engineer told me on the phone yesterday. He said 12kVA supply has a 60A fuse and 16kVA supply has an 80A fuse. What you are saying is also at odds with what @tuco88 said above about 50A in CU followed by 63A. Maybe they changed their practices?

    Otherwise, whats the point of paying for the increased supply?

    Like I said, it's been a while, I could be wrong :)
    I work exclusively in the industrial sector (excuses, excuses.......)


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  • #12
    17larsson
    Registered Users Posts: 467 ✭✭17larsson


    2011 is right. The standard ESB 12kVa supply is 80A fuse at the supply and 63A at the customers end


  • #13
    Dardania
    Registered Users, Registered Users 2 Posts: 3,612 ✭✭✭Dardania


    Interesting wording on page 91 of this:
    https://www.esbnetworks.ie/docs/default-source/publications/national-code-of-practice

    ...MCB of not less than 63A...

    Maybe there's a higher rated MCB possible? I've seen adjustable , albeit lower current ones for precisely matching a motor overload - maybe you could get a 70A MCB?


  • #14
    Water John
    Registered Users, Registered Users 2 Posts: 21,808 ✭✭✭✭Water John


    One would wonder is this area being deliberately obfuscated.


  • #15
    Steve
    Registered Users, Registered Users 2 Posts: 22,584 ✭✭✭✭Steve


    What meter have you OP?

    The max I've seen direct is 63A fed with 16sq, above that you need CT's.


  • #16
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,602 Mod ✭✭✭✭2011


    Steve wrote: »
    What meter have you OP?

    The max I've seen direct is 63A fed with 16sq, above that you need CT's.

    According to the National Code of Practice for Customer Interface:

    Single phase whole current meters will be used to measure loads up to 80A per phase. In general, three phase whole current meters will be used to measure loads over three phases up to 80A per phase. Current transformers with matching meters will be used to measure loads in excess of 80A per phase. Allowances for potential load growth should always be made.


  • #17
    Steve
    Registered Users, Registered Users 2 Posts: 22,584 ✭✭✭✭Steve


    2011 wrote: »
    According to the National Code of Practice for Customer Interface:

    Single phase whole current meters will be used to measure loads up to 80A per phase. In general, three phase whole current meters will be used to measure loads over three phases up to 80A per phase. Current transformers with matching meters will be used to measure loads in excess of 80A per phase. Allowances for potential load growth should always be made.

    Same as yourself, I haven't done this in a while. Back in my panel building days ESB would not allow a fuse over 63A to a WC meter - domestic or commercial. 80A required a CT chamber with copper busbar links.

    Maybe it's all changed now, don't know. :)


    ED:

    On reading that, ESP will accept a 80A BS88 fuse protecting the meter. However, they say a NZ type fuse should be on the board incomer.. do these go above 63A?


  • #18
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,602 Mod ✭✭✭✭2011


    Have a look at page 3 of this.
    It states that a 12 kVA supply can have an average maximum demand of 52 A over 10 minutes. In my opinion a 50 A fuse is undersized for this as the fuse rating is less than the design current.
    Whereas the 16 kVA supply can have an average maximum demand of 70 A over 10 minutes. In this case I feel that a 63 A fuse is undersized for this as the fuse rating is less than the design current.


  • #19
    KCross
    Registered Users, Registered Users 2 Posts: 12,136 ✭✭✭✭KCross


    17larsson wrote: »
    2011 is right. The standard ESB 12kVa supply is 80A fuse at the supply and 63A at the customers end

    If that's the case what fuses exist for the increased supply(16kVA)?

    @Steve , I have a modern day/night ISKRA digital meter.


  • #20
    Tuco88
    Registered Users, Registered Users 2 Posts: 1,053 ✭✭✭Tuco88


    Whats the point in a 12 kva when it's fused the same as a 16 kva?

    Did the ESB engineer not say this to you over the phone.

    It's been a while for me too in the domestic seen 😆


  • #21
    Tuco88
    Registered Users, Registered Users 2 Posts: 1,053 ✭✭✭Tuco88


    2011 wrote: »
    Have a look at page 3 of this.
    It states that a 12 kVA supply can have an average maximum demand of 52 A over 10 minutes. In my opinion a 50 A fuse is undersized for this as the fuse rating is less than the design current.

    Whereas the 16 kVA supply can have an average maximum demand of 70 A over 10 minutes. In this case I feel that a 63 A fuse is undersized for this as the fuse rating is less than the design current.

    If you have the 12kva mic, your maximum demand for ten minutes is 52 amps as stated. Personally I won't like to be pushing it with a 63amp fuse?

    I have always seen the 16 kva as the standard now.

    Is the issue here with fuse sizes or lack off?


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  • #22
    KCross
    Registered Users, Registered Users 2 Posts: 12,136 ✭✭✭✭KCross


    Tuco88 wrote: »
    Whats the point in a 12 kva when it's fused the same as a 16 kva?

    Did the ESB engineer not say this to you over the phone.

    I agree. There must be some difference between the fuses between 12kVA and 16kVA otherwise paying for the increased supply is a scam.

    I have the increased supply. The ESB engineer confirmed that I have an 80A fuse. That is a fact.
    Tuco88 wrote: »
    I have always seen the 16 kva as the standard now.

    Its only the standard if you pay for it. The standard is still 12kVA unless you stump up the dosh. Do you mean the standard in that most people building a new house opt to pay for 16kVA? Why would they? Most dont need it.

    Tuco88 wrote: »
    Is the issue here with fuse sizes or lack off?


    So, yes, to get back on topic. My original question has nothing as such to do with the differences between 12kVA and 16kVA.

    The question is, the ESB new connection form(referenced earlier in this thread) says I can use 70A on a 16kVA supply and they have an 80A as their fuse for peaks/headroom above that.

    My CU has a 63A fuse so Im not able to utilise all of the increased supply.

    I want to utilise the 70A as I feel I am too close to the 63 right now. Is it possible(within regulation) to utilise the 70A and if so, how?


  • #23
    BoatMad
    Registered Users, Registered Users 2 Posts: 13,702 ✭✭✭✭BoatMad


    What do the wiring rules say on the subject , I've mislaid my copy of the 4th edition


  • #24
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,602 Mod ✭✭✭✭2011


    BoatMad wrote: »
    What do the wiring rules say on the subject , I've mislaid my copy of the 4th edition

    It doesn't provide a fuse rating for this.
    However ET101 does state that the protective device should have a higher rating than the design current and the design current for a 16 kVA supply could be up to 70 A (see above).


  • #25
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,602 Mod ✭✭✭✭2011


    However what ever main fuse is selected on the customer side it should be suitably rated to ensure that it will blow rather than the ESB fuse under overload conditions.


  • #26
    Dardania
    Registered Users, Registered Users 2 Posts: 3,612 ✭✭✭Dardania


    2011 wrote: »
    However what ever main fuse is selected on the customer side it should be suitably rated to ensure that it will blow rather than the ESB fuse under overload conditions.
    Difficult to achieve discrimination for overload of 70A, with an upstream of 80A...


  • #27
    BoatMad
    Registered Users, Registered Users 2 Posts: 13,702 ✭✭✭✭BoatMad


    2011 wrote: »
    However what ever main fuse is selected on the customer side it should be suitably rated to ensure that it will blow rather than the ESB fuse under overload conditions.

    I think nobody disputes this , but I suspect a 63A fuse on a 16kva capable distribution is incorrectly specified , the OP is correct in his assumptions that the distribution fuse should increase with the rise in input power ASSUMING the distribution board is correctly speced and wired for the higher power


  • #28
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,602 Mod ✭✭✭✭2011


    Dardania wrote: »
    Difficult to achieve discrimination for overload of 70A, with an upstream of 80A...

    Agreed, if it is 80A.....

    Someone from the ESB previously suggested it is a 100A fuse.
    I can't find anything definitive though.

    In my opinion it would've best for the REC to talk to the ESB to find out what size fuse is installed on their side and work back from there. I would be interested in measuring the load with the heat pump on and electric car charging.

    I remember measuring the load for heat pump for alarms house and it was under 23A.


  • #29
    Water John
    Registered Users, Registered Users 2 Posts: 21,808 ✭✭✭✭Water John


    HPs would vary a lot on input/output. But most would be under 25A. that would be about 16Kw output. Please correct me, if I'm out a bit.

    But looking to the future. A modern house could have HP + 2 EVs. That could be a base load during the night. What about the electric shower?
    Are we into the area of priority access no matter what is supplied?


  • #30
    BoatMad
    Registered Users, Registered Users 2 Posts: 13,702 ✭✭✭✭BoatMad


    Water John wrote: »
    HPs would vary a lot on input/output. But most would be under 25A. that would be about 16Kw output. Please correct me, if I'm out a bit.

    But looking to the future. A modern house could have HP + 2 EVs. That could be a base load during the night. What about the electric shower?
    Are we into the area of priority access no matter what is supplied?

    No we are into having a grid that can meet the demands as heating and transport move to electric power

    in the UK new build are now standard at 24KVA, in the US, 200-400A connections to houses are not uncommon

    we need to move on from the " rural electrification " era !


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  • #31
    Water John
    Registered Users, Registered Users 2 Posts: 21,808 ✭✭✭✭Water John


    I agree very much that we are or should be moving to a mainly electric environment. Do you think we have a plan? Like hell we have. No vision of the carbon neutral economy.


  • #32
    Dardania
    Registered Users, Registered Users 2 Posts: 3,612 ✭✭✭Dardania


    Water John wrote: »
    I agree very much that we are or should be moving to a mainly electric environment. Do you think we have a plan? Like hell we have. No vision of the carbon neutral economy.
    Plenty of consultations pop up on this topic to get involved with. One ongoing from Deptartment of Transport on Alternative Fuels Infrastructure:
    http://www.dttas.ie/public-transport/english/alternative-fuels-infrastructure

    Be glad Ireland isn't like central Rome: I understand their MIC is around 3kVA due to grid demands. Helps explain why a lot of appliances like dryers are coming with heat pumps nowadays


  • #33
    gctest50
    Registered Users, Registered Users 2 Posts: 9,605 ✭✭✭gctest50


    Water John wrote: »
    HPs would vary a lot on input/output. But most would be under 25A. that would be about 16Kw output. Please correct me, if I'm out a bit............

    Startup power for it might be a bit of an issue if everything else is powered on because of the feeble 60A


  • #34
    KCross
    Registered Users, Registered Users 2 Posts: 12,136 ✭✭✭✭KCross


    BoatMad wrote: »
    I think nobody disputes this , but I suspect a 63A fuse on a 16kva capable distribution is incorrectly specified , the OP is correct in his assumptions that the distribution fuse should increase with the rise in input power ASSUMING the distribution board is correctly speced and wired for the higher power

    Its a relatively new house and the electrician charged me extra for the increased tails and he wired the heat pump so he absolutely understood the extra demand and the fact it was a 16kVA supply. My guess is he decided to play it safe by using the standard CU fuse rating. From what I can see most of the CU's come with a 63A already supplied. His thought might have been, use that until he rings me.

    2011 wrote: »
    Agreed, if it is 80A.....

    Why?
    If you follow ESB's connection form they say a 12kVA supply can have 52A's(60A ESB fuse) and 16kVA can have 70A (80A ESB fuse). They are allowing 10A's in both cases above that for their fuse.

    How much headroom do you think is required?

    2011 wrote: »
    Someone from the ESB previously suggested it is a 100A fuse.
    I can't find anything definitive though.

    In my opinion it would've best for the REC to talk to the ESB to find out what size fuse is installed on their side and work back from there.

    Its defo an 80A. The engineer from the local ESB office who has ground knowledge of "his" network said it to me directly. The box it is in clearly shows "60A/80A" on it which means it can take a 60A or 80A fuse. I dont think there is any doubt its an 80A fuse in there.

    When I spoke to him he did say I could upgrade the connection and he said they could then upgrade the fuse to 100A or 125A using a "HKC" fuse or something.... HKC could be wrong there but something like that.... i.e. it wasnt a neozed fuse.

    2011 wrote: »
    I would be interested in measuring the load with the heat pump on and electric car charging.

    I remember measuring the load for heat pump for alarms house and it was under 23A.

    Would you consider a clip on meter showing kW's good enough for that exercise or does it need some more complex kit to answer your question?

    FYI: I have a clip on meter (the airtricity one) on the tails and with the HP, car charging and other "stuff" I have seen it exceed 12kW's. However, thats before we hit the winter with the extra resistive heating that the HP can call on. It might be OK but then again it might not.

    Does anyone know if there is a 70A fuse available that can be swapped into the CU instead of the 63A (assuming tails etc are up to spec)?


  • #35
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,602 Mod ✭✭✭✭2011


    KCross, I will reply later. Busy at work. No doubt the engineer from the ESB is correct. If he says the fuse is 80A I'm sure it is.


  • #36
    Water John
    Registered Users, Registered Users 2 Posts: 21,808 ✭✭✭✭Water John


    Good 2011, at least someone is keeping the lights on.


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  • #37
    BoatMad
    Registered Users, Registered Users 2 Posts: 13,702 ✭✭✭✭BoatMad


    80A and 100A Neozed fuses are available, though different bottle size to 63A, personally I think you could raise the fuse to 80A, the ESB fuse can handle considerable overcorrect and the neozed will go first any way

    just by opinion, Im an EE not a sparks


  • #38
    KCross
    Registered Users, Registered Users 2 Posts: 12,136 ✭✭✭✭KCross


    I see these D02 fuses for sale:
    50A http://uk.rs-online.com/web/p/bottle-fuses/3770308/
    63A http://uk.rs-online.com/web/p/bottle-fuses/3770314/

    The next step up is an 80A fuse but its a D03 so presumably that wont slot into my CU. If I were to use that I'd have to get a new CU plus I'd have no headroom to the ESB fuse so not a good idea either way.
    80A http://uk.rs-online.com/web/p/bottle-fuses/3770320/


    I presume adding a separate, in parallel, CU that handles, say, just the car charger on its own and is limited to 32A is not allowed?
    i.e. Does a 2nd CU have to feed off the main CU fuse and cant be independently connected to the tails?


  • #39
    BoatMad
    Registered Users, Registered Users 2 Posts: 13,702 ✭✭✭✭BoatMad


    KCross wrote: »
    I see these D02 fuses for sale:
    50A http://uk.rs-online.com/web/p/bottle-fuses/3770308/
    63A http://uk.rs-online.com/web/p/bottle-fuses/3770314/

    The next step up is an 80A fuse but its a D03 so presumably that wont slot into my CU. If I were to use that I'd have to get a new CU plus I'd have no headroom to the ESB fuse so not a good idea either way.
    80A http://uk.rs-online.com/web/p/bottle-fuses/3770320/


    I presume adding a separate, in parallel, CU that handles, say, just the car charger on its own and is limited to 32A is not allowed?
    i.e. Does a 2nd CU have to feed off the main CU fuse and cant be independently connected to the tails?


    Is the physical D03 fuse holder /disconnect bigger then D02. It could be a swap, most CUs are 100A rated


  • #40
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,602 Mod ✭✭✭✭2011


    KCross wrote: »
    My guess is he decided to play it safe by using the standard CU fuse rating.

    ...and he might be correct. As suggested earlier it would be prudent to measure the current taken when the heat pump is running, while charging the car and a few other "normal" loads are on. You may find that everything is OK.
    The car, in particular, draws a constant 32A for several hours every day.

    Are you sure?
    If this is correct it would cost about €7.40 for a 5 hour charge :eek:
    It would be cheaper to use a traditional fossil fueled car !!
    From what I can see most of the CU's come with a 63A already supplied.

    I think you are correct.
    How much headroom do you think is required?

    The rule of thumb is: If the fuses have the same characteristic then the upstream fuse should have a rating of at least 150% of the downstream to ensure discrimination. Here is a discrimination table to give you some idea.
    However in your case the fuses are not the same type, meaning different characteristics, so it is a little more complicated.
    Its defo an 80A. The engineer from the local ESB office who has ground knowledge of "his" network said it to me directly. The box it is in clearly shows "60A/80A" on it which means it can take a 60A or 80A fuse. I dont think there is any doubt its an 80A fuse in there.

    Fair enough.
    When I spoke to him he did say I could upgrade the connection and he said they could then upgrade the fuse to 100A or 125A using a "HKC" fuse or something.... HKC could be wrong there but something like that.... i.e. it wasnt a neozed fuse.

    I assume that you mean the electrician and you means a "HRC" (High Rupturing Capacity) fuse. I am sure that you are aware of the risk associated with this, you may blow the ESB fuse in the event of the distribution board becoming overloaded.
    Remember fuses are designed not to blow at their rated current. Have a look at some fuse curves here to give you some idea. As you can see from the graph a 50A Neozed fuse can survive a 70 or even 80A surge.
    Would you consider a clip on meter showing kW's good enough for that exercise or does it need some more complex kit to answer your question?

    Yes, they are generally referred to as "grip on ammeters". These provide very accurate readings. Your electrician should be able to do this for you. You can also install an Owl energy meter to keep an eye on it yourself.
    FYI: I have a clip on meter (the airtricity one) on the tails and with the HP, car charging and other "stuff" I have seen it exceed 12kW's.

    This sounds like the Owl energy meter. It would provide a reasonable indication. How much above 12 kW and for what duration?
    It is about 4.4A per kW.
    However, thats before we hit the winter with the extra resistive heating that the HP can call on.

    That is about 17 A, so considerably more current. If this is simply a heating element heating a room it is a very expensive way to heat your home. I would suggest that you disconnect it (in an earlier post you said that this was an option).


  • #41
    Tuco88
    Registered Users, Registered Users 2 Posts: 1,053 ✭✭✭Tuco88


    Hold the phone,I rekon 2011 is right as usual:D. I am still in the stone age, it was the old 8KVA that was 60Amp ESB I am almost positive.

    The standard 12KVA is most certainly 63Amp switch fuse to 80Amp ESB.
    I had a look at my o'l shack :rolleyes:

    The 16KVA should be a 100Amp ESB would be logical thinking.

    If you contact the ESB and ask for a tech?


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  • #42
    KCross
    Registered Users, Registered Users 2 Posts: 12,136 ✭✭✭✭KCross


    2011 wrote: »
    ...and he might be correct. As suggested earlier it would be prudent to measure the current taken when the heat pump is running, while charging the car and a few other "normal" loads are on. You may find that everything is OK.

    I will do that over the next few days using the clip on meter thing.

    2011 wrote: »
    Are you sure?
    If this is correct it would cost about €7.40 for a 5 hour charge :eek:
    It would be cheaper to use a traditional fossil fueled car !!

    It runs on night rate electricity for about 3hrs depending on how low the battery is. Normal daily charge cost is about €1.50.

    2011 wrote: »
    I assume that you mean the electrician and you means a "HRC" (High Rupturing Capacity) fuse.

    No, this was the ESB engineer talking about the upgraded fuse that they would put in on the ESB side of the meter, not on the CU, if I upgraded the connection to 20kVA+

    And yes, HRC sounds right.


    2011 wrote: »
    This sounds like the Owl energy meter. It would provide a reasonable indication. How much above 12 kW and for what duration?
    It is about 4.4A per kW.

    Not above, just at 12kW, and for maybe 10-15mins until the HP went off.
    2011 wrote: »
    That is about 17 A, so considerably more current. If this is simply a heating element heating a room it is a very expensive way to heat your home. I would suggest that you disconnect it (in an earlier post you said that this was an option).

    This is built-in to the heat pump so its not just heating a room. It only kicks in in very cold weather when the heat pump cant maintain room temp on its own. It is inefficient even in that scenario but it doesnt come on much.


    Tuco88 wrote: »
    Hold the phone,I rekon 2011 is right as usual:D. I am still in the stone age, it was the old 8KVA that was 60Amp ESB I am almost positive.

    The standard 12KVA is most certainly 63Amp switch fuse to 80Amp ESB.
    I had a look at my o'l shack :rolleyes:

    The 16KVA should be a 100Amp ESB would be logical thinking.

    If you contact the ESB and ask for a tech?

    If thats the case the ESB guy I was talking to was a muppet then. He seemed confident of his answer to me and he said my 16kVA had an 80A fuse on the ESB side.




    I thought my OP was going to be an easy answer! I think the conclusion I've come to is that its a grey area and I wont get a definitive answer one way or the other.
    I'll just have to monitor the energy monitor closely and hope I dont hit an issue and deal with it if I do.


  • #43
    BoatMad
    Registered Users, Registered Users 2 Posts: 13,702 ✭✭✭✭BoatMad


    Yes, they are generally referred to as "grip on ammeters". These provide very accurate readings. Your electrician should be able to do this for you. You can also install an Owl energy meter to keep an eye on it yourself.

    to any electronic engineer ( and I design around CTs and hall effects ) they are always known ( and purchased ) as " clamp on" meters


  • #44
    BoatMad
    Registered Users, Registered Users 2 Posts: 13,702 ✭✭✭✭BoatMad


    by the way m, the way , I examined my own setup , 12KVA 1997 house , 63A on the CU and I would therefore expect 80A on the supply

    I Think for 16KVA I would expect 100A on the supply and 80A at the CU and I expect ESB engineer is , in fact , a muppet

    talking to a friend , he maintains the standard ESB fuse used to be 60A and now its 80A


  • #45
    KCross
    Registered Users, Registered Users 2 Posts: 12,136 ✭✭✭✭KCross


    BoatMad wrote: »
    by the way m, the way , I examined my own setup , 12KVA 1997 house , 63A on the CU and I would therefore expect 80A on the supply

    I Think for 16KVA I would expect 100A on the supply and 80A at the CU and I expect ESB engineer is , in fact , a muppet

    talking to a friend , he maintains the standard ESB fuse used to be 60A and now its 80A

    Thanks. That's a good data point.

    I do note the grey box that houses the ESB fuse has 60A/80A on it. Maybe they have short changed me and never gave me the 16kVA supply at all!

    I'll call them again and hope the muppet is out and I get someone else! :)


  • #46
    KCross
    Registered Users, Registered Users 2 Posts: 12,136 ✭✭✭✭KCross


    I rang them again and unfortunately I got the same guy! He is a techy and not reading off a hymn sheet.

    I asked him straight questions and have no reason to believe he is a muppet or lying to me but maybe he is.

    He said a 12kVA is 60A and 16kVA is 80A. They match the figures on the ESB fuse box itself where it shows "60A/80A". He said they dont put in 100A fuses unless you upgrade to the next MIC.

    He says that just because you have a 63A CU fuse doesnt mean you have an 80A ESB fuse. The 60A ESB fuse wont blow at 60A and most people would be nowhere near that anyway.


    He says that I can utilise the full 70A design current (referenced earlier in post #8) and as long as I use a CU fuse with a suitable curve the ESB 80A fuse will happily take any spikes. He mentioned that they have farmers with 80A fuses with milking parlours, cooling tanks, scrapers etc which would peak at 100A on startup and their 80A doesnt blow as long as its just a short burst on startup(0.5secs).

    What I see on the fuse box, what he is telling me and what is written on their new connection form all adds up.

    His suggestion was to have an 80A main isolating fuse on my side and then split the feeds up whatever way I want (e.g. car on one CU at 40A and everything else on another CU at 63A. The 80A isolator would be the main breaker which should blow well before the ESB fuse if you pick one with the right curve.

    From here all I can do is utilise the 70A I've paid for and see if his fuse blows. If it does its his problem. Thats the approach Im going to have to take.


  • #47
    Tuco88
    Registered Users, Registered Users 2 Posts: 1,053 ✭✭✭Tuco88


    Sounds good. Next step so is the search for a 80amp fuse bit odd to have two 80amp fuses in series regardless of fusing curve tho.

    If you can't get a suitable fuse, Maybe a 80 amp mccb might do the job alto a bit large in size, you can set operating sensitivity with some models.

    Keep us posted in what you do ☺


  • #48
    KCross
    Registered Users, Registered Users 2 Posts: 12,136 ✭✭✭✭KCross


    Tuco88 wrote: »
    Sounds good. Next step so is the search for a 80amp fuse bit odd to have two 80amp fuses in series regardless of fusing curve tho.

    If you can't get a suitable fuse, Maybe a 80 amp mccb might do the job alto a bit large in size, you can set operating sensitivity with some models.

    Keep us posted in what you do ☺

    If the ESB tech is right he is saying that everyone with a 12kVA supply who has a 63A CU fuse is doing exactly that as they have a 60A ESB fuse.

    Not a problem in most cases as people dont go near the 60A limit anyway.


    In relation to the 80A fuse. Do you know if a D03 fuse can slot into a D02 slot? My current 63A fuse is a D02. If I can just swap that for an 80A D03 i'd be up and running!

    See my earlier post...
    http://www.boards.ie/vbulletin/showpost.php?p=101682904&postcount=38


  • #49
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,602 Mod ✭✭✭✭2011


    It would be unwise to swap out a fuse for one with a higher rating without looking at the entire electrical installation. For example cabling and devices protected by the fuse installed at present may not be suitably rated for a larger fuse.


  • #50
    KCross
    Registered Users, Registered Users 2 Posts: 12,136 ✭✭✭✭KCross


    2011 wrote: »
    It would be unwise to swap out a fuse for one with a higher rating without looking at the entire electrical installation. For example cabling and devices protected by the fuse installed at present may not be suitably rated for a larger fuse.

    Sure.
    I know the tails are sufficient but I agree the CU needs to be looked at.
    Thanks.


  • #51
    Tuco88
    Registered Users, Registered Users 2 Posts: 1,053 ✭✭✭Tuco88


    KCross wrote: »
    Sure.
    I know the tails are sufficient but I agree the CU needs to be looked at.
    Thanks.

    No a 80amp is a DO3 it needs a larger holder. You will most likely need 16mm2 panel flex.


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