3 phase what KVA

Fatherted1

I am looking to do up 10 ensuite bedrooms in a disused b and b.

We as a family of 4 also plan to live there.

I have an order in for 3 phase with the ESB which can be put in easily enough. It's already on the street.

The top domestic kva is 29kva. I have the option of commercial kvas.

I've spoken to a few electricians who actually cannot advise me regarding pro/con.

Presume l need to speak to an electrical engineer. Based in Waterford, any ideas or recommendations greatly appreciated.

Thanks

kevin.m

Once you go above 29kVa, you are considered commercial, meaning commercial standing charges, which are usually higher than domestic. It may also preclude you from certain electricity rates.

I cant see why you would need more than 29kVA in a domestic house, even with 10 bedrooms.

Fatherted1

Thanks Kevin, l need to have ensuites so thinking about the electric shower requirements.

With 29kva, l understand l can only get 2 to 3 showers fitted under that kva.

I thought if l go higher kva, l could go with more electric showers.

There will be only one meter box going into the property.

Lenar3556

Is there an electric shower in all 10 bedrooms? There was very little foresight in whoever came up with that.

It would be possible to put controls in place to limit the number of showers which can be switched on simultaneously. But if it were me, I’d be looking to do away with the electric showers altogether and use an oil or gas water heating source to provide hot water to the whole place.

With that in a place, you might not need three phase at all.

kevin.m

You'd be mad to put in electric shows in 2024. Speak to a plumber for advice.

I'm no plumber, but I'd be thinking a large DHW tank heated with a heat pump, fed from a pump

Padre_Pio

https://www.boards.ie/discussion/comment/122730373#Comment_122730373

Not only are they inefficient and expensive, no one likes them.

I would be annoyed if my hotel or B&B had a crappy Triton electric shower instead of a pumped shower.

Better off getting a large DHW tank and a cheap night rate.

CelticRambler

Depending on the layout of the building and the proposed occupancy, a single hot water tank may be the worst option.

I'm in the process of renovating a large multi-room property (also ten points of delivery, according to the current plans) with a view to it being used for holiday-type accommodation; electrically heated water for each zone is the only one that makes sense. To have a single tank would mean heating a huge volume of water for perhaps only one person; and even if the accommodation was being used by three or four people, the individual pipe-runs could be twenty or thirty metres which is a hell of a lot of wasted water, depending on where they are.

I'm using a combination of small immersion heaters for the more frequently occupied zones, and on-demand boilers for the rooms/apartments that are likely to see intermittent short-term occupancy.

Calahonda52

As above re the hot water.

You should also consider centralised MVHR from the ensuites rather than 10 **** fans and meters of shiotty ducting and acres of mould.

Did it in a 10 room B&B in Lahinch, rooms were self contained in a block with a fire door so the MHVR works really well

Lenar3556

https://www.boards.ie/discussion/comment/122730436#Comment_122730436

I wouldn’t necessarily agree.

Modern hot water storage tanks have very low losses. Often less than 2KW per 24 hours - that’s about 20c per day if you heat with gas. So the cost of keeping the tank constantly heated is actually very little.
But you wouldn’t necessarily need storage at all. A gas fired instantaneous water heater in the region of 80KW could meet the requirements of 10 bedrooms comfortably, and it would only fire up when required.

You will have the distribution losses you mention, but these shouldn’t be huge. Even if we were to consider the worst case scenario of pumping 60degree hot water around a circuit 24hours a day so that each room has immediate access to hot water whether occupied or not - 10W per metre as a rough guide on a 1.25” pipe with 50mm of insulation looses less than 10W per metre in typical operating conditions. That’s might be another 3KW or 30c per day of gas costs.

In my view a centralised system, with a single source to maintain is a much better job than a myriad of electric water heaters. And when you consider that oil or gas is less than a third of the price of electricity, I wouldn’t be inclined to go the electric route at all.

CelticRambler

https://www.boards.ie/discussion/comment/122730684#Comment_122730684

Can't quite see the maths that gets you from 10W/m to 3kW, but at first glance, that's still a "stable" system, and (as you indicate) based on having/being able to install a simple circuit. These assumptions don't hold true when you have spurs of say 30m (unless one adds another 30m of pipe plus insulation for the return flow) and people who run the tap for five minutes to get enough hot water to splash on their face for ten seconds. There's also an awful lot of insulated hot water pipe and connections +/- shut-off valves that have to be installed and run through the entire property - along with the risk of leaks and other complications - for the sake of maybe two weeks' occupancy per year.

In my case, not living in Ireland, the gas vs. electricity costs are reversed, so that's another variable that changes the calculation (considerably!)

Calahonda52

re for the sake of maybe two weeks' occupancy per year.

I will deffo stay longer than two weeks 😀