Showers on 5 core cable?

2011

Tuco88 wrote: »

Would a 3phase RCD still work correctly in such case?

5 Core cable one phase for each shower and shared neutral across the 3...

It would work, yes.

Xwebstar

It may also work but you'll be breaking another rule by creating a potential nuisance

I can't remember which specific rule that is but it's there somewhere

2011

Xwebstar wrote: »

It may also work but you'll be breaking another rule by creating a potential nuisance

I can't remember which specific rule that is but it's there somewhere

You are correct that it isn’t permitted but that is not the question thy was asked

Tuco88

2011 wrote: »

It would work, yes.

Once the current in, is the same as the return current so..

I was just curious to if the current returning on the neutral would have any effect in different scenarios... As to when all or just 1 or 2 showers are on?

Bruthal

Tuco88 wrote: »

Would a 3phase RCD still work correctly in such case?

5 Core cable one phase for each shower and shared neutral across the 3...

They do.

2011

Tuco88 wrote: »

Once the current in, is the same as the return current so..

I was just curious to if the current returning on the neutral would have any effect in different scenarios... As to when all or just 1 or 2 showers are on?

Assuming the circuits are all healthy the phasor sum of the currents flowing in will be opposite and equal to the currents flowing out regardless of how many showers are switched on. As such the RCD will not trip.

Bruthal

Tuco88 wrote: »

Once the current in, is the same as the return current so..

I was just curious to if the current returning on the neutral would have any effect in different scenarios... As to when all or just 1 or 2 showers are on?

Yes the vector sum over the 3 phases and N will be 0 once no current is taking another path (earth fault).

If the neutral was left out and the 3 neutrals of the showers connected together in a star setup, the RCD still functions properly, as the vector sum of the 3 phases are still 0 with no neutral used.

So 3 phases to a motor with no neutral used, and an RCD will function properly to monitor the phases for residual current.

Ubbquittious

How much to get 3 phase in a house? Opens up possibilities so it does. Be tempted to get it for fluting around

2011

Ubbquittious wrote: »

How much to get 3 phase in a house? Opens up possibilities so it does. Be tempted to get it for fluting around

How long is a piece of string? There is no fixed price as there are so many variables. There is also an increased fixed fee. At this time our focus should be on reducing energy consumption and costs.

Tuco88

Thanks for the info lads.

cgarrad

So it looks like while doable the 3 single phase runs would be better.

Thanks for all the info, way more than I expected

2011

cgarrad wrote: »

So it looks like while doable the 3 single phase runs would be better.

Yes

Thanks for all the info, way more than I expected

If we see confusion we always add to it

autumnalcore

Just had three phase removed from my house added by previous owners you'd be mad to add it. invest the money in insulation, highly insulated water/buffer tanks, solar water heating. and you won't be needing a three phase heat pump, electric showers and will save a fortune in the long run

Effects

Ubbquittious wrote: »

Be tempted to get it for fluting around

What kind of fluting around do you want to do with 3 phase?

cgarrad

autumnalcore wrote: »

Just had three phase removed from my house added by previous owners you'd be mad to add it. invest the money in insulation, highly insulated water/buffer tanks, solar water heating. and you won't be needing a three phase heat pump, electric showers and will save a fortune in the long run

Had to get an upgrade as it was on a legacy 8kva, €1000 either way so mad not to get it in my eyes.

irishfire

cgarrad wrote:

Had to get an upgrade as it was on a legacy 8kva, €1000 either way so mad not to get it in my eyes.

Late to the game but once it's registered as a domestic connection the standing change should be the same for single/three phase. Your only variables are Urban/Rural & 24h/Dual Tariff meter

Obviously not the norm however so needs to be careful organised to make sure you don't end up registered as commercial, can be changed afterwards but easier to get it right from the start

cgarrad

I just signed up thru Bonkers for the cheapest bundle, paying standard standing charge and PSO.

14.8 cent unit rate as well.

autumnalcore

cgarrad wrote: »

Had to get an upgrade as it was on a legacy 8kva, €1000 either way so mad not to get it in my eyes.

Fair enough thats cheap there must have already been three phase on the pole.

8kva sounds terrible but in reality its probably fused 12kva at least at the cutout its a bit like a fair usage policy.

Xwebstar2

autumnalcore wrote: »

Fair enough thats cheap there must have already been three phase on the pole.

8kva sounds terrible but in reality its probably fused 12kva at least at the cutout its a bit like a fair usage policy.

May have been an older setup

25amp ESB fuse was common in old houses

Xertz

3P makes sense in most continental countries because that’s how they’ve opted to load balance on their networks. ESB just always preferred hefty single phase connections, even where 3P is available.

Single phase in say Spain is often limited to 16amps, which is ridiculously small. I know I had that in a studio apartment and tripped the main breaker quite regularly. In Ireland single phase is pretty beefy.

My view of it is you’re introducing a lot of unnecessary complexity and cost.

Also definitely consider a modern hot water storage system with a heat pump and solar inputs. You’ll have much more pleasant showers.

A lot of the calculations around immersions being hugely inefficient are based on the old copper tanks, which are ludicrously badly insulated and the use of just a resistance element.

A good tank is almost like a thermos flask and you’ll get very, very little heat loss, if it’s installed correctly. Add a pump and you’ll have very good water pressure and far more luxurious showers.

Also if you’re using locally pumped electric power showers they are very noisy. Whereas a central pump (well located and isolated on an anti vibration pad) is likely to be far less annoying.

Just be very aware of where you site the pump.

Ours is in a basement and you wouldn’t really know it’s running at all. However some are located right in the middle of the bedroom areas with a hot press. Definitely creates extra noise.

Also bear in mind a hot press with a modern hot water heater will neither have space to store towels nor will it be hot. They’re fridge freezer sizes units and they don’t bleed heat so, you’ll just have a big appliance in a press. If you can site or somewhere like a ground floor, a garage or a basement it makes a lot more sense noise wise.

2011

Xertz wrote: »

A lot of the calculations around immersions being hugely inefficient are based on the old copper tanks, which are ludicrously badly insulated and the use of just a resistance element.

Immersion elements are almost 100% efficient.

See link.

The issue is the cost per unit of electricity is so high it does not make financial sense to heat water with electricity. The cost to heat water this way is simply too high.

A well insulated hot water cylinder makes sense regardless of how the water is heated, gas, oil electricity, solar etc.

Bruthal

2011 wrote: »

Immersion elements are almost 100% efficient.

See link.

The issue is the cost per unit of electricity is so high it does not make financial sense to heat water with electricity. The cost to heat water this way is simply too high.

Thats because electric heating being 100 percent efficient is only looking at the very last part of the process, but we pay for the full process from station to heater. It would be similar to saying a car is in the high 90s efficiency wise if we only look from the gearbox to the wheels.

A well insulated hot water cylinder makes sense regardless of how the water is heated, gas, oil electricity, solar etc.

Yes.

Xertz

2011 wrote: »

Immersion elements are almost 100% efficient.

See link.

The issue is the cost per unit of electricity is so high it does not make financial sense to heat water with electricity. The cost to heat water this way is simply too high.

A well insulated hot water cylinder makes sense regardless of how the water is heated, gas, oil electricity, solar etc.

The storage in an uninsulated tank is hugely inefficient. You’re heating the air around the tank and losing most of the energy. The fact that an immersion tank will go cold quite rapidly when the element is off and that the hot press / airing cupboard is usually about 35°C should give an indication that it’s losing about as much heat as a radiator!

Also if you’re using heat pumps or solar you’re bringing in sources of free energy. The heat pump is effectively collecting energy from the air and concentrating it in your storage tank and solar is using the sun.

If you’ve a very efficient tank and a good installation even natural gas starts to make way more sense as a hot water source because of the kWh price difference, certainly compared to using simple resistance heaters anyway.

The fact that a resistance element is 100% efficient in terms of producing heat from electricity is all well and good if you’re able to put all that energy straight into the water and keep it there.

If you’re going to put in a complicated water heating system, involving multiple showers and a lot of bathrooms heat pumps and solar are the way to go for both cost of running and environmental impact.

2011

Xertz wrote: »

The storage in an uninsulated tank is hugely inefficient. You’re heating the air around the tank and losing most of the energy. The fact that an immersion tank will go cold quite rapidly when the element is off and that the hot press / airing cupboard is usually about 35°C should give an indication that it’s losing about as much heat as a radiator!

As above this applies to all cases whether heating by electricity, gas, oil, solar etc.
Everyone agrees that it is best to use good insulation, no argument there.

It does not change the fact that immersion elements are simply too expensive to use as such they are best avoided if there is an alternative.

Xertz

I’m not saying they’re not too expensive to use. I’m just challenging the notion that stored hot water, when heated with the right sources and stored in efficient tanks is more inefficient than using electric shower.

There’s a lot more going on in the comparison than a simple statement that an element converts 100% or the electrical energy into heat.

Solar is effectively free energy (other than pumps and controls)
Heat pump is more than 100% efficient as it’s moving heat around, not generating it directly from electricity.

And from a financial point of view, natural gas is cheaper per unit of heat produced. Although as Irish water systems are usually indirectly heated from very lossy old heating systems that can go way up. Also if you’ve a poor configuration of the boiler, you can waste a LOT of gas on indirect heating. A modulating, condensing boiler and a dedicated circuit to your storage tank heat exchanger and extremely good lagging (or very short run of pipes) makes all the difference.

Until Ireland gets way more renewables on stream (which will happen in the next few years with more off shore wind and so on), I would question the CO2 efficiency of heating with resistance elements anyway. An awful lot of that energy is coming ultimately from burning natural gas and the losses from power plant to immersion heater switch are very big. I know you can theoretically buy all your energy from CO2 neutral suppliers but the grid’s fuel mix has a way to go before we’re heading towards true carbon neutrality for electricity.

Your efficiency calculations have to be based on €/litre of hot water and also total CO2/litre of hot water. The rest it really just looking at narrow bits of the energy flows. Those are the only two figures that ultimately matter from a user and environmental impact point of view.

2011

Xertz wrote: »

A lot of the calculations around immersions being hugely inefficient are based on the old copper tanks, which are ludicrously badly insulated and the use of just a resistance element.

I was responding to this ^^^


I spent a number of years working on renewable energy sector in a design role so I am all for it.

Xertz

My comparison was instantaneous electric shower vs immersion. If you talk to a lot of Irish people they live in terror of leaving the immersion on, to the point that it’s become a regular joke in stand up comedy.

The whole problem (apart from the kWh cost) is those old cooper cylinders are laughably inefficient in terms of ability to store heat. They’re effectively a radiator with a loose fitting coat in many cases.

Basically my point was just that when I’ve discussed heat pumps and someone realises it involves “an immersion” (a storage tank) they immediately jump to this notion that because the water is stored it’s going to be astronomically expensive or grossly inefficient.

The majority of Europe uses very efficient stored hot water and has done for a long time. The use of those bare copper cylinders and the instantaneous electric showers is very much a UK and Irish speciality. I’m not sure why we were so slow to adopt better, more sophisticated and efficient solutions for heating and storing hot water. Took a very long time for that stuff to start appearing here.

2011

Xertz wrote: »

Basically my point was just that when I’ve discussed heat pumps and someone realises it involves “an immersion” (a storage tank) they immediately jump to this notion that because the water is stored it’s going to be astronomically expensive or grossly inefficient.

I haven’t heard of a storage tank ever being referred to as an “immersion”. Maybe I misread you post.

The use of those bare copper cylinders and the instantaneous electric showers is very much a UK and Irish speciality.

I haven’t seen a bare copper cylinder in a long time.

Instantaneous shower have a number of advantages:
1) Standalone system so a great back up to main shower
2) Unaffected by an uninsulated copper cylinder
3) Instant unlimited hot water always
4) Only heats the water required

I take your point though and I am all for good insulation and hot water storage. I would not install this as my main shower. However I would not consider heating water with a resistance element (other than a back up).

Xertz

I’ve seen plenty of them. They’re still common in any house here other than berg modern ones and I would not consider a lagged cylinder adequately insulated. Those 80s lagging jackets are fairly laughable attempts at energy efficiency.

I had this discussion with a few people. One guy in particular was switching off both solar circulating pumps and the heat pump on an extremely well insulated system because he was in that “immersion” mentality.

In general most pre 2000s Irish homes have very poor and often bordering on bizarre plumbing.

Even in getting plumbers into my own house recently the standard of workmanship is awful. There’s no attention to things like lagging pipes. We had a guy who removed all the lagging on the pipes in our boiler house - a room with a full louver door and left an area of bare metal that was at least the size of a large domestic radiator open to the breeze and then told me that it made no difference to efficiency!

This house was built in the 70s and has things like long runs of completely uninsulated copper pipe under the floors and that’s something I also saw being done in a brand new gas installation a few year ago in Dublin. Copper and PEX just run straight into cold sub floor areas without any lagging. Just lift the floor boards and jam it in.

Also long runs of completely uninsulated pipe work carrying domestic hot water though houses is very common.

We’re really not up to par on any of this and it’s no wonder we’ve such poor energy efficiency.

I just think sometimes starting with basics here would cut energy costs and use enormously. Get the cheap and simple things right before we start going on about deep retrofits.

2011

Xertz wrote: »

In general most pre 2000s Irish homes have very poor and often bordering on bizarre plumbing.

My home was built around 2005 and the electrical and plumbing work was horrendous.

Even in getting plumbers into my own house recently the standard of workmanship is awful.

That is what I have seen too. I ended up doing all of my own plumbing.