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Essential for Newbies: Monophase GSHP and 3 Phase Supply Screwup - no way back?

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    It's all in the title! My friend bought a mono-phase GSHP nominal usage 2 kW, Start Up 5 kW in the UK (currently sat awaiting him bringing it over), then realised that his 6kW supply (most Italian homes have 3kW supplies!) probably wasn't going to be up to it, given the hi-spec holiday home for paying guests he is building - so obviously he asked for a bigger supply - and the next size up is 9kW - unfortunately he has now discovered this will be a 3-phase supply. So, as I understand it that means max 3kW per phase and his GSHP won't work. He is getting 5kW of PV so maybe that can be made to help him during the summer when he will use it to run the underfloor pool heating but that doesn't help when the sun's not out.......

    Is there anyway back? He will try to swap with the supplier but the GSHP has been sat around for many months so it is a long shot.
    • CommentAuthormike7
    • CommentTimeApr 15th 2011 edited
     
    Converters are available to give 3 phase from single phase - here's a link: http://www.simplypowersupply.com/Single-to-3-Phase-Converter/RT-75KW-Rotary-Single-to-Three-Phase-Converter-10hp.aspx
    Not outstandingly cheap, I'm afraid.

    Edit: from Gavin: 'wrong way round there mike' . Ooops - should take more water with it.
    • CommentAuthorBen1974
    • CommentTimeApr 15th 2011
     
    Maybe they should contact the manufacturer and see if it's possible to have the GSHP converted to three phase. If they have 3 phase units in their range anyway it may not be that difficult.
    • CommentAuthorGavin_A
    • CommentTimeApr 15th 2011
     
    wrong way round there mike

    tbh, if it's given it's own phase, I doubt there'd be a problem with it briefly pulling 5kW on start up as everything's rated to take significantly more current than it says on the tin for a short periods of time.

    similarly I'd think the 6kW supply would cope providing he's got low energy lighting and electrical kit and not got an electric cooker / shower.

    not entirely sure I'd want to be the spark trying to explain this to the power company if the suppliers fuse did blow mind, so I'd install my own marginally lower rated mcb (or RCBO) than the suppliers fuse covering the entire installation before testing everything, and set it up in such a way that it could all be switched to 3 separate phases fairly easily if it did need upgrading.

    I'd think he needs to do some load calculations, and potentially some load shedding (lower wattage kettle, no tumble dryer, low energy washing machine etc) if he wanted to try this route. If he's going for a hi spec holiday home though I guess this might not be an option, as you can guarantee the guests will want to have the dishwasher, washing machine, microwave & kettle all running at once then try switching the heating on and wonder why it's all gone dark. 3 phase ought to work fine though for the heat pump at least, if he splits the phases right and gives it it's own 3kW phase... though it is a bit on the limits of what will be ok, and it depends on how long the start up phase is.
    • CommentAuthorGavin_A
    • CommentTimeApr 15th 2011
     
    coincidentally I've just had feedback from a PV customer who's had the electricity company doing grid monitoring for the last few weeks as their voltage was too high.. anyway, they've just worked out that their fridge draws 27amps at start up, which is over 6kW, so a temporary 5kW start up load really is nothing unusual if it only lasts for a few seconds or so.
  6.  
    That's very interesting Gavin - I do have a tame electrician who might be able to inform me as to Italian supply limitations; certainly the time the start up current lasts is less than a 'few seconds' but I'll have to get my friend to look up the spec again for the accurate figure as I don't remember.

    And you're right load shedding is not an option for a high end holiday letting, especially as the US market is likely to be targeted. However, there will be NO air conditioning! Repeat no aircon.....and as the GSHP will be heating the pool it won't be cooling the house.

    Thanks Duncan
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      CommentAuthorSteamyTea
    • CommentTimeApr 16th 2011 edited
     
    Posted By: GotanewlifeHowever, there will be NO air conditioning! Repeat no aircon.....and as the GSHP will be heating the pool it won't be cooling the house.


    Seems a bit odd to build a 'greener house' and then fly in residence several times a year. Though putting my economics hat on it is a good example of how improvements or innovations are governed by the market place.
  8.  
    My friend has to eat and this is how he does it - he has several v sml holiday cottages in Derbyshire and this is him 'going global' I suppose - actually it will also be where they retire in due course. We have (I hope) 'dialled out' the need for aircon at the design phase - at least for all but the most insistent Americans. And to put the flying issue another way - he has (will soon) have a house that can be rented by anyone - who chooses to come here and how they get here is not his responsibility.
    • CommentAuthorFred56
    • CommentTimeApr 16th 2011
     
    Can he get a soft start device? If I recall these are also known as inverter control starters. I have seen them installed on industrial equipment to limit the peak current draw. The idea is to crank the speed up rather just banging full current to the motor when the armature is stationary. I had them put on some conveyor systems I was responsible for. The aim there was to reduce the wear on the transmission but the principle was the same. Another company I worked used to add them to the big turbines on some of the machines. These were 45kVA vacuum turbine so you can imagine the start up current was huge without the inverter control.

    Try someone like Fenner - assuming they still exist.
  10.  
    You can (could) get motor rated circuit breakers that are designed to allow start up current for a limited time without tripping out, although the electricity co. here is very reluctant /won't fit them but your provider might be different.
    Peter
  11.  
    Thanks again all. Best solution is to get the (damn!) thing exchanged and friend is optomistic.........i'll report back on what happens.....

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