Splitting 230V and 115V on device entrance

[Bertsbolts]

One problem I see is if the boiler is on a 240 delta system the installer might want to balance the load on the delta by placing the Boiler pump power on the A&B or the C&B phases that do not have 120V to ground.

This is true. One of the questions I ask their engineer, manager, etc. is what type of electrical source they have on site. If they have any panel that is brought in from the main from the street, it likely possesses a neutral circuit with 230/240V single phase. Barring switch gear for industrial machines where those may just be three phase with a ground and no neutral. So, after asking, I recommend not installing it on a 3 phase panel, unless someone wired a neutral bus to use for control circuitry. These aren't huge power usage boilers. 15A MOCP on the boilers, which when under full load with a 120 pump attached I have never seen one go above 10A. Some pumps hit 3.8A for 230V 1Ph.

 

[Besoeker3]

In UK and EU residential it is just simply 230V.

 

[jim dungar]

In UK and EU residential it is just simply 230V.

Which is totally irrelevant to the OP question which is based on the United States NEC.

I understand you wish our system was the same as yours, but it ain't ever going to happen. Our government does not have the legal authority to tell us to remove 'legacy' systems, which is one reason we have some many different ones.

Personally, I try to never read your posts on this topic.

 

[gene6]

Which is totally irrelevant to the OP question which is based on the United States NEC.

The OP appears to be a product design engineer personally I go by KISS if I had to choose between two similar HVAC equipment brands and one needed a 3 wire + ground and one needed 2 wire + ground I'd choose the two wire.
If I ran a HVAC mfr business I'd want all my equipment to be single voltage thats the standard for HVAC. big equipment is 480 with 24 volt controls or 208-240 with 24 volt controls. Sure gas with 120 volt controls.
Pumps, fans blowers etc are all single voltage.

Just look at ductless heat pumps most are 240V, now if a customer wanted to buy a bunch of 120/240 minisplits I'd say whoa now wouldn't it be simpler to get a 240 one? I think thats Besoeker3's point. KISS

And having worked across the pond that 230 they have can be lots of different types of 230 every kind you can imagine there is not really just one simple type. UK has more like 240 than 230, Germans have 230 but it can be ungrounded or grounded, Spain has 220Y127 where as up north Sweden has 400Y230, sure they usually only use the '230' legs, but it comes from a lot of different systems and you have to know how it was 'earthed' if even earthed at all.

 

[gene6]

There are cases when I use an autotransfromer to power single voltage equipment that would not fly if that same equipment was split phase dual voltage.
It makes your product more versatile and competitive to be single voltage.

 

[jim dungar]

The OP appears to be a product design engineer personally I go by KISS if I had to choose between two similar HVAC equipment brands and one needed a 3 wire + ground and one needed 2 wire + ground I'd choose the two wire.
If I ran a HVAC mfr business I'd want all my equipment to be single voltage thats the standard for HVAC. big equipment is 480 with 24 volt controls or 208-240 with 24 volt controls. Sure gas with 120 volt controls.
Pumps, fans blowers etc are all single voltage.

Just look at ductless heat pumps most are 240V, now if a customer wanted to buy a bunch of 120/240 minisplits I'd say whoa now wouldn't it be simpler to get a 240 one? I think thats Besoeker3's point. KISS

And having worked across the pond that 230 they have can be lots of different types of 230 every kind you can imagine there is not really just one simple type. UK has more like 240 than 230, Germans have 230 but it can be ungrounded or grounded, Spain has 220Y127 where as up north Sweden has 400Y230, sure they usually only use the '230' legs, but it comes from a lot of different systems and you have to know how it was 'earthed' if even earthed at all.

You don't need to use a neutral conductor in order to take advantage of the benefits offered by a 120V to ground system, such as cheaper L-G filters.

You may absolutely use 2 wire, 240V L-L, equipment in the US. So why do so many dryer, HVAC, and range manufacturers go through the hassle of adding a third wire to their product? I am pretty sure they are not doing it because it costs more.

 

[gene6]

You don't need to use a neutral conductor in order to take advantage of the benefits offered by a 120V to ground system, such as cheaper L-G filters.

I don't know anything about all that, all I know is as a electrician if two brands of appliances whatever they may be do exactly the same thing and brand A needs a 12/2 MC and brand B needs a 12/3 MC, all other things being equal I'd choose brand A because its simpler.

So why do so many dryer, HVAC, and range manufacturers go through the hassle of adding a third wire to their product?

I cant recall of any equipment other than a residential range or dryer that does.
All the HVAC I do is 480 or 208-240 no neutral. And we do a ton of HVAC.

 

[jim dungar]

I don't know anything about all that, all I know is as a electrician if two brands of appliances whatever they may be do exactly the same thing and brand A needs a 12/2 MC and brand B needs a 12/3 MC, all other things being equal I'd choose brand A because its simpler.

I cant recall of any equipment other than a residential range or dryer that does.
All the HVAC I do is 480 or 208-240 no neutral. And we do a ton of HVAC.

I agree 2 wires are easier than one, and manufacturers are free to build equipment that way.

But the OP was about a 3-wire system and equipment.

 

[Besoeker3]

Which is totally irrelevant to the OP question which is based on the United States NEC.

I understand you wish our system was the same as yours, but it ain't ever going to happen. Our government does not have the legal authority to tell us to remove 'legacy' systems, which is one reason we have some many different ones.

Personally, I try to never read your posts on this topic.

Perhaps you should. It is just simpler, not just for us but for UK and the whole of the EU.

 

[CoolWill]

Perhaps you should. It is just simpler, not just for us but for UK and the whole of the EU.

They've got the single-voltage system perfected, now if only they would import some dentists.

 

[kwired]

I don't know anything about all that, all I know is as a electrician if two brands of appliances whatever they may be do exactly the same thing and brand A needs a 12/2 MC and brand B needs a 12/3 MC, all other things being equal I'd choose brand A because its simpler.

I cant recall of any equipment other than a residential range or dryer that does.
All the HVAC I do is 480 or 208-240 no neutral. And we do a ton of HVAC.

Residential grade gas furnaces are typically 120 volt but if there is a AC or heat pump also associated with it it is nearly always 208-240 volt.

A lot (not all) of industrial machines are designed with 208-240 and/or 480 input ability and if 120 volt controls are used they are separately derived within the unit.

 

[gene6]

Residential grade gas furnaces are typically 120 volt but if there is a AC or heat pump also associated with it it is nearly always 208-240 volt.

A lot (not all) of industrial machines are designed with 208-240 and/or 480 input ability and if 120 volt controls are used they are separately derived within the unit.

Right on,
thinking back to all the HVAC of every kind I see, I really can't think of any at all that use the residential range / dryer MWBC configuration with a neutral. I don't get out of the north east much so not sure about the rest of the US, perhaps out west its standard to have a 120/240 to a heatpump or a furnace boiler?
Residential hot tubs do sometimes have a 120V pump and a 240V heater.
But Id say even that is less common.

But the OP was about a 3-wire system and equipment.

The OP was stating his frustration with the two voltages in his design.
The suggestion to him is eliminate one of the two voltages and simplify the design.
If it ends up being 120 or 240 either way if its one voltage it will be easier and cheaper to manufacture and install.
If a customer does not have the correct voltage an autotransfromer can be used say from a 277V circuit so it opens him up to more potential use cases and customers. 120/240 is painting your self into a corner.

 

[LarryFine]

If it ends up being 120 or 240 either way if its one voltage it will be easier and cheaper to manufacture and install.

Well, that depends on the the currents; lower voltage can require greater wire and circuit sizes.

 

[jim dungar]

The OP was stating his frustration with the two voltages in his design.
The suggestion to him is eliminate one of the two voltages and simplify the design.
If it ends up being 120 or 240 either way if its one voltage it will be easier and cheaper to manufacture and install.

Yes.
If there is no reason to use a neutral, in your design, then don't include one. Just because a system can deliver something doesn't mean you need use it.

My point was there is no reason to consistently discuss world wide voltage systems when the OP is asking specifically about getting 120V on a US system. There are other times and places to discuss the merits of different system voltages, but until legislation is passed mandating the removal of all existing residential systems, most of our members have to deal with 120/240V systems on a daily basis.

 

[gene6]

we currently supply the boiler with two different power sources. This bugs me for various reasons.
My solution is ....

the OP is asking specifically about getting 120V on a US system.

That is not what he was asking, he stated it bugs him having to use two different voltages and he came up with a solution, we offered another take on the problem which he may not have been seeing.

 

[jim dungar]

That is not what he was asking, he stated it bugs him having to use two different voltages and he came up with a solution, we offered another take on the problem which he may not have been seeing.

I read the OP as complaining about having to run two circuits, a 240V 2w and a separate 120V 2W. The question was could it a single MWBC be used instead.

 

[gene6]

His main problem is the two voltages. He wants a common disconnect for safety, he proposed one possible solution then he got feedback from a 'bean counter':

My reason for reaching out here is because a bean counter wants to argue that it won't work right. ☺ So backup was required. ☺ Thanks

I would advise this bean counter to reject the MWBC idea as it could only limit sales options. A 120/240 appliance could only have the effect of a reduction of sales opportunities, never an increase.
There are sales opportunity that wont work with a MWBC that exist now.

These aren't huge power usage boilers. 15A MOCP on the boilers, which when under full load with a 120 pump attached I have never seen one go above 10A. Some pumps hit 3.8A for 230V 1Ph.

A 2100 VA load at most, it easily can be served by a single two wire ckt