US Split-Phase to EU Heat Pump Not Working

[RaymondR]

I suspect it's not just the cycle rate which causes the problem.

My limited understanding of multi phase AC power is that the three phases are 120 degrees apart. When using a single phase one gets a nice clean bi directional sine wave (moderated to some degree when applied to inductive and capacitive loads)

My experience with US appliances which use 240 volt power feeds is that rather than live, neutral and earth into a three pin plug as is the case with European 240 volt AC power. the US appliances have a live, a live and a neutral and 240 volts are used within the appliance for resistive loads, such as heating coils only, and that things like motors and timers are 110 volt AC devices (this experience was decades ago)

Many modern appliances, such as aircons, now exploit more electronics for more precise and energy saving purposes and the sine wave signal inherent in the single phase AC arrangement is exploited for timing purposes.

Could it be that the double hump voltage peaks produced by combining two live phases to produce 240 volts AC are indigestible to devices designed for the nice sinuoucity of a pure single phase current?

[s/v Jedi]

Originally Posted by RaymondR

I suspect it's not just the cycle rate which causes the problem.

My limited understanding of multi phase AC power is that the three phases are 120 degrees apart. When using a single phase one gets a nice clean bi directional sine wave (moderated to some degree when applied to inductive and capacitive loads)

My experience with US appliances which use 240 volt power feeds is that rather than live, neutral and earth into a three pin plug as is the case with European 240 volt AC power. the US appliances have a live, a live and a neutral and 240 volts are used within the appliance for resistive loads, such as heating coils only, and that things like motors and timers are 110 volt AC devices (this experience was decades ago)

Many modern appliances, such as aircons, now exploit more electronics for more precise and energy saving purposes and the sine wave signal inherent in the single phase AC arrangement is exploited for timing purposes.

Could it be that the double hump voltage peaks produced by combining two live phases to produce 240 volts AC are indigestible to devices designed for the nice sinuoucity of a pure single phase current?

L1 and L2 have a 180 degree phase shift. When you run a 230V/50Hz appliance on US 240V then you only connect L1, L2 and ground. The Neutral isn’t used. This means the appliance sees a perfect sine wave just like you get between L1 and N as well as between L2 and N, see attached diagram.

[RaymondR]

Hi Jedi,

Not sure about that diagram, looks to me that summing those two phases with the phase angles they have would give a zero resultant.

[Montanan]

I'm not an expert electrician [and have not stayed at a Holiday Inn Express recently] but isn't the OP dealing with a SINGLE phase, residential US power source, and not a two phase source. Seemingly one is just splitting a single phase [240 V becoming two 120 V circuits] and not two shifted phases.

????

Sincerely, [& nearly clueless in Montana].

[s/v Jedi]

Originally Posted by RaymondR

Hi Jedi,

Not sure about that diagram, looks to me that summing those two phases with the phase angles they have would give a zero resultant.

Let me explain: the graph has a Y-axis which is voltage. For the L1 to N and the L2 to N, the N is referenced to 0V (zero volt) so you get exactly the voltage by measuring the distance between the sine and the 0V horizontal line.

But when we use L1 to L2, there is no neutral. The voltage seen by the appliance, at the peak of the sine, is +120V on L1 and -120V on L2. The difference between them is a subtraction, i.e. 120 - -120 and when subtracting a negative value, you add the absolute value, so 240V.
To do it visually, measure the distance between the L1 and L2 sines and see how many Volts is between them on the Y-axis. You can even use a ruler to measure the distance, then measure the same distance along the Y-axis from zero upwards.

This is the beauty of the beast: when there is no 240V service and you use an adapter to connect to a 120V service, the adapter connects both L1 and L2 to the L conductor of shore power. Now you get 120V aboard on both the L1 and L2 conductors and everything works… except the two are in phase instead of shifted 180 degrees. ———->>>>> so a 240V appliance gets two equal, synchronized sine waves and thus it sees 0V (not 120V) and it simply doesn’t power up. This is the best feature of the 120/240V system right behind 120V being less lethal than 230/240V.

In my reference diagrams, I always put an isolation transformer first, which can pass 230V or 240V but it can also transform 120V to 240V. By not grounding the secondary winding terminals, you get a floating 240V and you can label the terminals L1 and L2 instead of L and N. Next you get an EU 230V model Multiplus and reprogram it by disabling its grounding relay and setting inverter voltage to 240V and inverter frequency to 60Hz. Now you can re-label its L terminals to L1 and its N terminals to L2. No Neutral yet.

Then on the output of the Multiplus, you connect an Autotransformer. L1 and L2 to its winding and they continue to its output terminals via a breaker. The center tap on the output now becomes your new Neutral and you have the familiar 120-0-120 setup just like every house in the US, even when you have 120V shore power. If you want a grounded neutral, you can connect a jumper from the center tap to the ships ground busbar and now you can use single-pole breakers for all 120V groups and a double-pole breaker for 240V groups just like for a house.

I personally am in favor of a floating system so I don’t install that jumper, which means I need double-pole breakers for 120V as well as 240V (everything the same, easy to change groups from 120 to 240) but of course only possible with the isolation transformer or when you don’t have any shore power at all (which is becoming the standard in the future I think… as we all get large solar arrays while reducing power requirements with more efficient appliances)

Also, by not grounding the center tap at the auto transformer, I can install multiple autotransformers which enables the distribution groups with a rotary source selection switch I have in the advanced diagrams.

[RaymondR]

Lot to ponder on there and I tend to the opinion (based on no more than intuition) that the simple graph tends to misrepresent the real situation.

Three phase power consists of three phases 120 degrees apart. Intuitively it appears that connecting two of them in series leaves a gap of 120 degrees which would appear to create a contorted sine wave output.

[s/v Jedi]

Originally Posted by RaymondR

Lot to ponder on there and I tend to the opinion (based on no more than intuition) that the simple graph tends to misrepresent the real situation.

Three phase power consists of three phases 120 degrees apart. Intuitively it appears that connecting two of them in series leaves a gap of 120 degrees which would appear to create a contorted sine wave output.

Three phase? No, this is single phase… L1 and L2 are from one phase and are shifted 180 degrees, not 120 degrees like in 3-phase.

[marti972]

The schematic would be very helpful. I am thinking about skipping the initial conversion from AC to DC and hoping the internal DC is a single voltage. Then you could try to source a rectifier, that will take 230V/60h (or if you prefer 115V/60h) to that DC voltage. Then the second part of the units power source, could use this DC to make the AC at it's required internal hertz. Basically, we need to know what DC voltage, the inverter in the unit wants.


The initial AC to DC conversion stage from a domestic (North American) heat pump, might be used, assuming it outputs the right DC with enough current. Of course this would violate the warranty and any safety certifications the thing meets. Also assuming you don't kill yourself, by not being skilled with electricity.

[DShant]

Hey QuantumH I know you took a lambasting here for some reason but can you at least tell us how you fixed the problem?


I'd certainly like to know from interest sake and if I ever need to do it myself.

[senormechanico]

Originally Posted by quantumh

You have already what what what? The trouble is you just do not know what you are talking about when it comes to electronics, "Jedi".


I have already told you the nature of the conVERsion going on here but you are a) Unable to understand that I was seeking to communicate with individuals educated in the subject at hand, and b) Unable to understand what happens to the signal in a switching power supply.


Look, I have my problem solved now. Mods please close this thread, and I am unsubbing.

What a doofus. He joins CF, says he knows everything, but wants free advice and gets p.o,ed when he gets good advice...

[RaymondR]

Originally Posted by s/v Jedi

Three phase? No, this is single phase… L1 and L2 are from one phase and are shifted 180 degrees, not 120 degrees like in 3-phase.

Went and had a look at some schematics of the US system and found it fairly confusing but it appears that a street transformer provided with 220, or more, volts to the primary winding, and a centre tapped 220 volt secondary which provides either 220 from the ends and 110 volts between each of the end outputs, which are designated L1 and L2 to the centre tap, designated as "neutral".

If this is so and each of the 110 volt "phases" are used to achieve load balancing and that some of these loads may be reactive it would appear to make for some interesting modifications to the simple phase angle/voltage sine curve.

[s/v Jedi]

Originally Posted by RaymondR

Went and had a look at some schematics of the US system and found it fairly confusing but it appears that a street transformer provided with 220, or more, volts to the primary winding, and a centre tapped 220 volt secondary which provides either 220 from the ends and 110 volts between each of the end outputs, which are designated L1 and L2 to the centre tap, designated as "neutral".

If this is so and each of the 110 volt "phases" are used to achieve load balancing and that some of these loads may be reactive it would appear to make for some interesting modifications to the simple phase angle/voltage sine curve.

And the center tap is grounded with a rod so as to polarize the transformer output. The 180 degree phase shift is fixed by it being a center tap on the secondary winding. I come from EU power systems but over the years have started seeing the reasons/advantages for the Americans to opt for their setup and it works very well.

[RaymondR]

One learns the advantages when there's contact with a faulty 110 volt lighting network 100' up an oil rig derrick.