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  1. #1
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    Opinions on point of isolation



    Hi,

    Just wanted to get people's opinions regarding points of isolation for split a/c units and whether you have to supply a point of isolation both inside and out. I usually supply one at the outdoor unit with rotary isolator to be locked off if required and depending on outdoor unit location (ease of access) I'll supply one inside too. If the outdoor unit can be accessed easily I'll just supply one outside. I have worked on stacks of units that only have one point of isolation (outside) but have had some engineers say it needs both and some say not. I've also worked for several big companies where outside only is how they do it. It seems when you speak to electricians they are the same, some say it's fine as it can be locked off and some say it needs to be at either end.

    What do other engineers do and is there actually a right or wrong way to do it? This is UK regs so will probably differ elsewhere I pressume, is it simply so it can be isolated safely whilst working on or protection? As most systems are fuse protected at the condensing unit anyway before it comes through to the indoor unit.

    Just interested in getting others opinions on the matter as it seems to vary alot and abit of a grey area.

    Thanks



  2. #2
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    Re: Opinions on point of isolation

    I'm not an electrician but was under the impression that isolation should be within reach of the item of plant.

    Personally over the years I have refused to work on plant without local isolators.

    18th Ed....
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  3. #3
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    Re: Opinions on point of isolation

    To me reading those regs I would say that there should be a point of isolation at both ends. I use electricians for all the mains work and I've had them say one point of isolation is fine because it can be locked off yet others say different. It seems with air conditioning it's abit of a grey area, like I said above I've worked for companies where single isolation is standard.

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    Re: Opinions on point of isolation

    It used to be that you could run a seperate mains to the indoor, therefore that could be isolated. Now we just have the interconnecting cable which is nearly always a multicore, bit more awkward to isolate in my experience but can be done if regs insist on it. I'm aware that comms and mains should be seperate but i've had no issues with using a single multicore.
    Mostly found in the southern part of this green and pleasant land.

  5. #5
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    Re: Opinions on point of isolation

    Yes years ago some of the unit were mains to the indoor unit so you would run it through a switched fuse spur. Now a days it's all mains to outside, I work on loads of sites where there is only one point of isolation and that's at the outdoor unit because that's where the supply goes. At the same time I do also see units where there is another point of isolation on the indoor unit where the interconnecting has been switched to isolate the indoor unit. But when you ask which is the correct way of doing it you seem to get mixed opinions, even from electricians.

  6. #6
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    Re: Opinions on point of isolation

    There are times when I wish that installers also had to carry out maintenance/service works.

    There were times when you needed to perform some action at the indoor unit that needed the power off for a short period. On some units this action would allow you to perform a 'reset' after a fault condition.

    Now consider the time and effort required to carry out that act without local isolation and with an outdoor unit three floors away and half way across a roof.

    1. Identify fault.
    2. Secure tools and access ladders at work area.
    3. Gain access to roof after climbing three floors.
    4. Isolate unit.
    5. Return to work area.
    6. Recover tools etc
    7. Confirm that power is actually isolated.
    8. Perform remedial/service work.
    9. Repeat steps 2.
    10. Repeat step 3.
    11. Reinstate power.
    12. Repeat step 5.
    13. Repeat step 6.
    14. Check that unit is working okay.

    With local isolation the job is..

    1. Step 1
    2. Step 4
    3. Step 8
    4. Step 11
    5. Step 14

    Sorry, this is a very old rant of mine, but maybe you've suffered from it sometimes.
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  7. #7
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    Re: Opinions on point of isolation

    I do both install and service and maintenance so I know where you're coming from that's why I add local isolation on units that are awkwardly positioned outside ie 3 floors away. But i have been there when I've had to do breakdowns on units I've not installed and had to do the walk as described. Install only guys are the worst as they give no thought what so ever to the job, so long as it goes in and works when tested they couldn't care less if the unit is serviceable.

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