Two shower priority units in series

2011

pauldavis123 wrote: »

Does three phase have bands like the 8, 12 and 16 kVA ones of single phase?

Yes it does. Small 3 phase supplies use whole current metering, large 3 phase supplies could be at several MAV.

I can't find any info on domestic three phase, any pointers?

You just apply for it, but you would need to be able to justify it.

pauldavis123

So what's the difference between 29 kVA single phase and 29kVA three phase, assuming a domestic setting, two instant showers and an electric car. No priority switches.

2011

pauldavis123 wrote: »

So what's the difference between 29 kVA single phase and 29kVA three phase, assuming a domestic setting, two instant showers and an electric car. No priority switches.

Lots of differences but mainly you won’t get a single phase supply that large.

pauldavis123

2011 wrote: »

Lots of differences but mainly you won’t get a single phase supply that large.

I could be wrong as I'm only looking for some guidance here, but page 5 of

https://www.esbnetworks.ie/docs/default-source/publications/esb-networks-dac-statement-of-charges.pdf

has 29kVA listed in single and 3 phase.

2011

pauldavis123 wrote: »

I could be wrong as I'm only looking for some guidance here, but page 5 of

https://www.esbnetworks.ie/docs/default-source/publications/esb-networks-dac-statement-of-charges.pdf

has 29kVA listed in single and 3 phase.

I stand corrected, I have never seen this.
Personally speaking if I really wanted a larger supply I would prefer to pay extra and get all of the benefits of a 3 phase supply (there are many).
A 29kVA single phase supply makes little sense.

However (as previously stated) I still feel that the most sensible approach is to simply get rid of the instantaneous showers.

17larsson

2011 wrote: »

Thanks for the clarification, I was confused

I agree with listermint's post above.

If you are correct it should not be too difficult to link to a data sheet stating this can be an issue.

Sorry for the slow reply, I had forgotten about this.

This is the response I got back when I asked the question about priority units (with shower having priority) to the manufacturer of this charger (Tesla);

This should not be a problem as long as there is no vehicle connected to the charging station.
When this would switch off during a charge session, it could damage the contactor inside the unit.

If it can only be done during charge sessions it is better to check for a different solution.
It would be better to have some sort of pilot control (like the Maxem) to be able to reduce the charging speed or even stop the charging through removal of the pilot signal instead of removing power altogether.
Maxem doesn’t sell outside of the Netherlands yet, unfortunately.

No specs in the reply but I was obviously wary of giving priority to the shower after that email.
Teslas can be timed to start charging after a certain time so it is not really an issue giving priority to the charger once the charge start time is set to after midnight

Sleeper12

Worth putting in to the equation is most EVs are changing at the night rate. Possibly 11am to 7pm. Most people don't shower between these hours.

punisher5112

Sleeper12 wrote: »

Worth putting in to the equation is most EVs are changing at the night rate. Possibly 11am to 7pm. Most people don't shower between these hours.

11 to 8 winter 12 to 9 summer

2011

17larsson wrote: »

When this would switch off during a charge session, it could damage the contactor inside the unit.

Based on your professional experience as an electrician do you accept this explanation?

I don’t.

If a contractor can be damaged by being de-energized, the wrong contractor has been specified. Sound like a major design flaw to me!
Wouldn’t you agree?

17larsson

Switching a contactor on and off under full load increases the chance of it failing eventually. I don't know the spec on it maybe it is a cheap one that can't handle that load but, electrician or not, if they tell me it can't handle turning on and off regularly on full load then I'll make sure to avoid that when I'm installing this brand

Tuco88

I see your point to comply with the car maker, but it does sound very odd regards the contactor.

I see contactor's switched under load all the time at work, and can last for years when designed correctly. I still see old sprecher+Schuh contactors in use on 5.5kw vac pumps some with vsd some not. Anyone in the pharma game will know the abuse vac pumps get from an operator armed with a DCS.

2011

17larsson wrote: »

Switching a contactor on and off under full load increases the chance of it failing eventually. I don't know the spec on it maybe it is a cheap one that can't handle that load but, electrician or not, if they tell me it can't handle turning on and off regularly on full load then I'll make sure to avoid that when I'm installing this brand

I see your point, but as Tuco88 says this is done with motors all the time. At work we were working on 300 kW compressors, these units despite their size actually have star delta starters. That is a large load started using contactors switching on and off many times per day every day of the week with no issues. These units are over 10 years old too! Not a problem once properly specified.

DarrenG

Hello,

I am in a similar situation to that described by Crazyhorse99. We have got two electric showers in our house and we've a priority unit which only allows one shower to operate at once.

We are now hoping to have a 32A electric vehicle charger installed. Standard practice when installing EV chargers in houses with an electric shower (as far as I can tell) is to install a priority unit between the charger and the shower so only one could be used at a time (giving priority to the shower).

The company I've spoken to re installing the charger have assured me a priority switch can be installed along with the EV charge point. The net result would be only one shower or the charger could operate at any one time, and priority would be given to the showers as it is now.

Also does the EV charger point need to be connected next to the Mains supply? Could the cable to the EV point come directly from the fuse box? The fusebox in the house is located at the at the back of the house and the incoming mains supply is located at the front of the house. Bringing a cable from the mains supply to the fusebox (about 30 metres of cable) would be needed. I am just wondering if that’s possible to take the supply for the EV point from the fuse box?

Any advice and help is most welcome

pauldavis123

The connection can be after the meter, you will have to get ESB networks to do the work thought of you plan on altering the "tails" coming out of the meter. This will cost a few euro.

Running the wire may be cheaper.

You will need heavy armoured wire to run 30 meters, at least 16mm SWA (I think) which is expensive.

DarrenG

Thanks for the response. I'll follow up with the installer and also with the ESB.