Jump to content

Changing from 3 phase supply to monophase with 3 phase chaudiere.


Le 47
 Share

Recommended Posts

My father in law is considering changing from 3 phase to monophase supply.

The only issue remaing is the 3 phase water heater.  My take on this is that there would be no problem because if there is a monophase supply to each of the 3 phase points on the heater (3 seperate elements I presume) it will work OK. Thiswould be different for a 3 phase motor though.

Am I right about this as EDF seem to think I am barmy.

Thanks

Link to comment
Share on other sites

I would have expected a 3 phase water heater to have inputs/contacts for the live of each phase and no neutral (i.e. all three phases cancelling out inside the water heater). Assuming this is as yours I cannot see how you could connect a single phase supply to the heater. New heater element or heater.

3 phase is pretty dangerous (e.g. 380/400V - which is a lot worse than single phase) so, if you are unsure about what you are doing and how it works then I'd get in somebody who does know.

Ian
Link to comment
Share on other sites

[quote user="Le 47"]

My father in law is considering changing from 3 phase to monophase supply.

The only issue remaing is the 3 phase water heater.  My take on this is that there would be no problem because if there is a monophase supply to each of the 3 phase points on the heater (3 seperate elements I presume) it will work OK. Thiswould be different for a 3 phase motor though.

Am I right about this as EDF seem to think I am barmy.

Thanks

[/quote]

Can FIL not do as my neighbour does, and have both?

She has monophase throughout the house, and 3-phase for the cooker and water heater.

Spongebob.

Link to comment
Share on other sites

Thanks for the replies so far.

We will check to see if there is a neutral supply and find out if it can run on both mono and triphase.

Re keeping one 3 phase point that defeats the object really as 3 phase supply needs to be used in a balanced way which at times can prove to be difficult. that is the principal reason for seeking a change to mono.

Expanding this point a little further ' bloke down the pub' said to me that in UK on 3 phase the usage charged to the customer was 3 times the use on the most used phase and he thought it would be the same here.In other wordsd a system that would be more expensive. I took his comments with a pinch of salt but you never know!

 Has anyone the inside track on this - is it an urban myth or is there any truth in the idea?

Thanks again.

Link to comment
Share on other sites

Sorry gluestick, the connection could simply be made in the fuse board. At the moment the power to the chaudiere is via 3 fuses each supplied by one phase.

Simply supplying each fuse from the same phase would deal with the supply of electric power to the three elements of the chaudiere (if that is indeed the case.

Clearly there is at least one more issue i.e. is there a neutral or not on the heater. This will be checked along with a hunt for literature tomorrow.

Thanks for the reply.

Link to comment
Share on other sites

You need to remember that with 3 phase, each phase is actually out of phase. Thus there is a world of difference between supplying all phases of a 3 phase supply to a device and putting the "same phase" to each of the 3 supplies !!!

I would recommend calling in an electrician as 3 phase can be dangerous due to the higher voltages and things are not always as simple as you are assuming !!

Ian
Link to comment
Share on other sites

Curiouser and curiouser...............

If you ask EDF to change the supply to Single Phase, then you will have One Phase and a Neutral, thus giving 230v potential.

If the ballon is Three Phase then it won't work, as it needs, as Deimos states, the out of phase logic to deliver a higher voltage.

Three Phase does not necessarily require a Neutral: a Neutral connection is normally supplied for equipment which requires a higher voltage, it seems.

Interesting data here: http://en.wikipedia.org/wiki/Three-phase_electric_power

 

 

Link to comment
Share on other sites

[quote user="Deimos"]You need to remember that with 3 phase, each phase is actually out of phase. Thus there is a world of difference between supplying all phases of a 3 phase supply to a device and putting the "same phase" to each of the 3 supplies !!!

I would recommend calling in an electrician as 3 phase can be dangerous due to the higher voltages and things are not always as simple as you are assuming !!

Ian[/quote]

Phase angle is only a factor in rotary equipment (alternators,motors, etc),in resistance loads such as heater elements equal phase loading is important and is usually achieved by using 2 phases per element thus eliminating the need for a neutral, however this means that each part of the element has an operating voltage of 380/440v.

If the elements are supplied separately by each phase and then to a common neutral then they will be 220/240v, but if you want to convert this setup to single phase supply you must check the load of each element as you will be tripling the load on the supply cable.

Far better to change the element to a single phase type which should be obtainable from the suppliers or manufacturers of the chaudiere.

cheminot
Link to comment
Share on other sites

I have just installed a new electric heater and the instructions shows how to connect it with either 3 phase or single phase, we are over there at half term and i'll bring the instructions back with me if you are still interested, an if I remember (senior moment again)

The heater is made by dedietrich or something like that.

 

Steve

Link to comment
Share on other sites

[quote user="Deimos"]You need to remember that with 3 phase, each phase is actually out of phase. Thus there is a world of difference between supplying all phases of a 3 phase supply to a device and putting the "same phase" to each of the 3 supplies !!!

I would recommend calling in an electrician as 3 phase can be dangerous due to the higher voltages and things are not always as simple as you are assuming !!

Ian[/quote]

Phase angle is only of importance in rotary applications(alternators, motors etc) particularly in multiple source generation. For resistance loads such as heater elements equal distribution of load is important. In most 3 phase heaters the elements are connected across 2 phases in a 1-2,1-3,2-3 configuration to provide equal load without the need for a neutral but of course this means that the elements are rated at 380/440v each. This means they are unsuitable for single phase operation.

If they are connected with a single phase to each element going to a common neutral then it will be possible to use a single phase supply but you have to bear in mind that the load on the single phase supply will be tripled.

Most manufacturers supply single and 3 phase heaters for their chaudieres so the best solution would perhaps be to change the heater unit for the single phase type.

cheminot
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...