Connection of back-upgenerator to TN-C-S domestic installation

**Needless to say neutral earth link at generator windings.

You need to make sure that when running on genset at least 3 things are true.
Firstly it is adequately earthed, even if the suppliers earth is missing - as the cause of the power cut may also mean loss of the supply neutral/earth external to the building. 

Secondly, that there is no condition when the NE bond in the service head from your DNO, and the one from your genset are both connected at the same time - or the one you are not using will look like a neutral earth fault to the supply you are using, and the RCDs wont like it, and by the way arguably its an ESCQR non compliance.

Thirdly the ADS may not operate smartly with the reduced PSSC from the genset, so you are more reliant on the RCD/RCBOs for your fault protection.

Its not normally necessary to switch the earth, and if you do, you need to be certain that no parts on either side of the break can be touched simultaneously, but double pole change-over of L and N is essential, and in a way that is break first make second, but I think you do have that.
as regards SPD, it will do no harm, its not clear if it will add much, it needs to be the sort suitable for TT and protected by a level of  ADS that the genset can operate . 

Apart from the switched earths where I am sucking my teeth,  I don't see anything to worry about. Wait a bit and see what others say though.
Mike.

Kendo51 said:

Q.1.is this 3 pole manual transfer idea (switching earths) idiotic/unnecessary/ not advisable ?

This type of installation is covered by legislation - Regulation 21 of the Electricity Safety, Quality and Continuity Regulations (ESQCR) ... or Regulation 22 if you are in Northern Ireland. 

A 3-pole transfer switch is unlikely to meet the requirements of G99 (or G99/NI) and hence legal requirements (ESQCR).

The transfer switch should disconnect only live conductors from the DNO supply (L&N for single phase, L1-L2-L3&N for three-phase 4-wire) but retain connection of DNO's means of earthing.

Kendo51 said:

Q. 2. Should I include a type 1 SPD to the 20amp 30ma generator supply enclosure inside distribution cupboard given large metal shed and lighting strikes ? 

Do you have Type 2's already in main house and garage?

Other issues ...

1. some of the protective devices will need to be suitable for bi-directional operation ... particularly RCDs/RCBOs.
2. Is the garage TT (you say you have earth electrodes) ? If so, then perhaps another electrode connected to MET is required in the house ... in this case, in "island mode", the garage is likely to be considered TN-S and the house TT (so check RCD requirements for final circuits).
3. Does the generator have an internal N-PE link? If not, a system referencing switch should be used ... or tcan he additional contact in the transfer switch used to make that connection when operating "off grid" ("island mode")?
4. just to note you might well be removing selectivity by having 30 mA RCBO for generator.
5. Current ratings of consumer units needs to be checked ... see Regulation 551.7.2 (v) of BS 7671:2018+A2:2022+A3:2024

This type of installation is really now a "prosumer's electrical installation" and in addition to Section 551, you will need to apply Chapter 82 of BS 7671.

Use of BS 7671 is actually mandated by ESQCR where you have a switched-alternative (backup generator) supply.

Hi mapj1 and Thankyou for your advice and assistance.

That was my reasoning and thoughts on for a 3 pole manual transfer (L. N. E) switch (make before break as you'd mentioned) was to ensure the generator set up and indeed it's earthing arrangement can be fully isolated from the DNO supply. Earth switching seems bit unnatural but to me was best means of ensuring complete separation as you'd said fault could occur further up DNO network and supply N being lost and thus earth connection to my property. Equally when running genset (DNO power failure )and fault occured on my side if not separated would result in fault current on the network.

The short circuit protection on genset is only breakers by look of it so would definitely be installing either additional protection on genset or at genset supply to house prior to manual bypass.

From what you have advised it would be prudent for me to check from earth rods at garage to the DNO earthing after neutral earth link to ensure that they are separate and not linked with an unknown extraneous part I haven't thought of.

Again Thankyou for assistance. Hopefully more will respond to see if my earth switching thought is valid.

1. Install a single phase 32amp incomer socket ( will be supplied from generator in event of outage)to the exterior of house.

You're probably thinking correctly, but just to be absolutely clear (in formal terms and for others reading this) the thing on the outside of the house should be a plug (inlet), rather than a socket - the trailing part (from the generator) should have shrouded socket tubes, rather than exposed pins.

When generator supply is used the whole installation house including garage would be effectively TT system

The generator's system would almost certainly be TN-S - the local electrode acting as the "source" earthing (the first T) and c.p.c.s connected to N via the generator's N-PE link (so TN). To create a local TT system, you'd need two separate electrodes, for for the generator and another for the installation.

The usual approach is you use a DP change-over switch (for single phase) and have Earth solidly connected to both a local electrode and the DNO's earth. In Grid mode it's then TN-C-S as before, and TN-S in generator mode.

You local TT sub-installation for the workshop makes things more interesting. You could leave that as TT, even in generator mode, but you'd need at least two electrodes then, one for the generator and another separate one for the garage/workshop. You just need to make sure that the sum of the two electrode resistances is still gives a low enough loop impedance for ADS etc for your TT system (as your generator electrode is likely to have a higher resistance to Earth than the DNO's).

One problem with that approach though is the proximity of the generator to the workshop - if it's within reach (2.5m?) they need to be on the same earthing system - which they won't be if the workshop is TT and the house TN. One option then is to bring the workshop onto the house TN system during island mode - perhaps a 3rd pole in your change-over switch could achieve that - but you'd have to be very careful how things were arranged both in grid-connected and island mode - as you'd want to ensure the workshop wasn't connected to the DNO earth, or within reach of the DNO earth, at any time, including when in island mode. Rating a change-over switch contacts to switch between a DNO Earthing facility and extraneous-conductive-parts (e.g. the workshop, presuming it's sat on the ground) can get "interesting" as the currents involved may include distribution network diverted neutral currents, which aren't related to the generator's output rating (consider why you might need 10mm2 main bonding even for tiny installations).

Maybe one option to consider is to make both the house and workshop one common earthing system - TT in grid mode and TN-S in island mode.

Diagrams often help. For starters, here's one I prepared for earlier threads, for a simple change-over arrangement:

   - Andy.

Hi gkenyon, Thankyou for your assistance.

Wow! a lot for me to digest with your comprehensive response very much appreciate it.

Just to clarify in case I haven't framed my query and questions correctly.  My query is solely in relation to my own home and installing a back up generator to be used only in the event of a mains failure situation, with provision via a manual bypass (break before break) as per regulations so as to ensure I'm not syncing, paralleling or exporting to the grid. On this basis I believe what I'm suggesting is outside the scope/ doesn't come under G99/NI or ESQCR 

With that in mind this is my understanding / rational, bear with me. 

gkenyon said:

This type of installation is covered by legislation - Regulation 21 of the Electricity Safety, Quality and Continuity Regulations (ESQCR) ... or Regulation 22 if you are in Northern Ireland. 

I do live in N.I so for completeness so regulation 22 states: 

22.  Where a person operates a source of energy as a switched alternative to a distributor’s network, they shall ensure that that source of energy cannot operate in parallel with that network and where the source of energy is part of a low voltage consumer’s installation, that installation shall comply with British Standard Requirements.

Following from this and in ref to ESQCR guidance notes found here: GUIDANCE ON THE ELECTRICITY SAFETY, QUALITY AND CONTINUITY REGULATIONS 2002

These regulations are for the most part for distributor's, suppliers of energy exported paralleling onto the network/grid.

Section E part 1:(page 7) Citation, commencement and interpretation.  (**parts of note**)

" distributor"

Since the Regulations do not differentiate between licensed and non-licensed operators, the requirements apply equally to owners and operators of both public and private electricity networks **supplying** industrial, commercial and residential consumers or street furniture (see definition of network). The term distributor is intended to encompass operators transmitting and distributing electricity under the terms of the Electricity Act 1989 (as amended by the Utilities Act 2000).

"generator" (page 8)

For the purposes of the Regulations, generators operate high voltage equipment and are particularly associated with the provision of electrical energy to consumers via networks (see definition of network). The intention here is to include medium and large scale generating plant incorporating substations and electric lines to which the public may have access.

**Operators of any sort of generation in domestic situations are not expected to comply with the requirements placed on generators.**

However, all operators and consumers should note that they **may still be caught** by the requirements of Part VI Generation. Generators should note that they are exempt from implementing certain requirements within generating stations (see regulations 12 and 16).

So within the ESQCR guidance notes "generator" **may be caught by** part VI Generation, lets take a look at this:

J. GENERATION (page 31) (PART VI) 21. Switched alternative sources of energy.

21 This regulation deals with islanded mode only, i.e. a source of energy which operates as a switched alternative to the supply from the local distributor’s network.

An example of such an arrangement would be an emergency standby generator which is called upon to **generate after loss of the supply from the distributor’s network**, and which is disconnected before the load is transferred back to the supply from the distributor’s network following restoration.

When supplying load, the switched alternative source of energy is never connected **in parallel**with the **distributor’s network**, even for short durations.

In these circumstances operators should ensure that the switched alternative source of energy cannot be paralleled with the distributor’s network.

In particular, operators should comply with the principles enshrined in BS7671 Requirements for Electrical Installations (see definition at regulation 1(5)) and the Electricity Association’s Engineering Recommendation G.59/1 (Amendment 1, 1995) Recommendations for the Connection of Embedded Generating Plant to the Regional Electricity Companies’ Distribution Systems. It should be noted that these Regulations do not deal with sources of energy supplying installations which are not connected to distributors’ networks. Such installations should comply with BS7671.

**With all the above reviewed I see ESQCR regulation/,conditions satisfied with what I'm suggesting,  apologies if I'm misconstruing, I'm open for correction.

With ref to:

gkenyon said:

A 3-pole transfer switch is unlikely to meet the requirements of G99 (or G99/NI) and hence legal requirements (ESQCR).

G99/NI again is mainly regarding paralleling, syncing and exporting to the network/grid. **lets get a look** 

Find out more about the Distribution Code for Northern Ireland | Northern Ireland Electricity Networks

Page 11: 2.5 This document applies to systems where the Power Generating Module(s) can be paralleled with a Distribution Network. Where the Power Generating Module(s) can only be used as an alternative source of energy to supply the same electrical load within the Customer’s Installation the requirements of Section 7.4 of this EREC G99 apply.

So page 53: 7.4 Switched Alternative-Only Operation

7.4.1.1  Under this mode of operation it is not permissible to operate a Power Generating Module **in parallel** with the Distribution Network. Regulation 22 of the ESQCR (NI) states that it is the Generator’s responsibility to ensure that all parts of the Power Generating Module have been disconnected from the Distribution Network and remain disconnected while the Power Generating Module is operational. The provisions of this EREC do not generally apply and the **earthing, protection, instrumentation etc**. for this mode of operation are the responsibility of the Generator, however, where such a Power Generating Module is to be installed, the DNO shall be given the opportunity to inspect the equipment and witness commissioning of any changeover equipment and interlocking 

7.4.1.2 The changeover devices shall be of a ‘fail-safe’ design so that one circuit controller cannot be closed if the other circuit controller in the changeover sequence is closed, even if the auxiliary supply to any electro-mechanical devices has failed. Changeover methods involving transfer of removable fuses or those having no integral means of preventing parallel connection with the Distribution Network are not acceptable. The equipment shall not be installed in a manner which interferes with the DNO’s cut-out, fusegear or circuit breaker installation, at the supply terminals or with any metering equipment.

7.4.1.3 The direct operation of circuit-breakers or contactors shall not result in the defeat of the interlocking system. For example, if a circuit-breaker can be closed mechanically, regardless of the state of any electrical interlocking, then it shall have mechanical interlocking in addition to electrical interlocking. Where an automatic mains fail type of Power Generating Module is installed, a conspicuous warning notice should be displayed and securely fixed at the Connection Point

**And crucially** 7.4.1.4 The Power Generating Facility shall use an earth electrode independent from the Distribution Network.

**So with ref to the G99/NI and from my understanding of it, I'm complying by not syncing, exporting paralleling to the DNO/Grid and network, my generator is to be used in "mains fail state"  I will be using a manual "break before make" supply bypass switch.

With ref to the earthing arrangement my thoughts for switching earth within the manual bypass is exactly because of 7.4.1.4 and to comply with BS7671 maintaining cpc continuity and earthing protection/main and supplementary bonding for the installation

My additional thought is if DNO has a power outage with fault on N conductor my house supply being TN-C-S  id have no earth if had my generator earth connection tied to DNO and I'm running the generator to supply the house and it developed a fault the resulting fault currant would be back feeding onto DNO network . 

gkenyon said:

Do you have Type 2's already in main house and garage?

I will be installing a type 2 SPD in the replacement main db in the house as explained as existing boards are old, as the garage is effectively TT it has a Type ! locally as required due to increased likelihood of lightening strikes given its a steel structure. 

gkenyon said:

1. some of the protective devices will need to be suitable for bi-directional operation ... particularly RCDs/RCBOs.

I wont have any bi-directional voltage/current ? what im proposing isn't back feeding its merely providing an alternative supply with a manual bypass, supply from generator into 32amp single phase socket on side of house the socket runs into house and into bypass switch as an alternative/ back-up supply.

gkenyon said:

2. Is the garage TT (you say you have earth electrodes) ? If so, then perhaps another electrode connected to MET is required in the house ... in this case, in "island mode", the garage is likely to be considered TN-S and the house TT (so check RCD requirements for final circuits).
3. Does the generator have an internal N-PE link? If not, a system referencing switch should be

Yes because my house supply is TN-C-S and cannot export the earth to a metal outbuilding so armour is earthed in the house db for circuit protection and armour is isolated (not connected) at garage db , garage db gets earth from 2 no earth electrode pits so is TT.  Technically my suppling generator will be TN-S as it will have neutral earth link (tied neutral) as opposed to floating neutral)in winding/alternator because generator will be suppling multiple pieces of equipment and when in use generator with be connected to the earth electrodes, so fo all intense and purposes the supply when enters the house will be TT .

For clarity the generator location will be out the back of garage (outside )with supply coming from it directly into 32amp socket on side of house as described previous ( bearing in mind this socket when on mains supply, is on isnt connected to anything and is isolted by the manual bypass , when generator is running the garage still gets it supply from house db via the generator , im not back feeding through garage db board to house db.  you cant use the generator to supply garage in "island mode" a generator in island mode (floating neutral) is only suppose to supply 1 item of class 2 equipment for multiple appliances and or back up power generator must be used with tied neutral as you say N-PE link.

gkenyon said:

4. just to note you might well be removing selectivity by having 30 mA RCBO for generator.

You saying the house db boards RCDs will operate before the rcbo covering the generator supply into house db?

gkenyon said:

5. Current ratings of consumer units needs to be checked ... see Regulation 551.7.2 (v) of BS 7671:2018+A2:2022+A3:2024

The house consumer unit (s) (2 currently 8 way mem with bs88 and 4 way mem 2000 mcbs) are being  replaced with one large board 2 rcd main switches, the new db wont be overloaded. 

gkenyon said:

This type of installation is really now a "prosumer's electrical installation" and in addition to Section 551, you will need to apply Chapter 82 of BS 7671.

Use of BS 7671 is actually mandated by ESQCR where you have a switched-alternative (backup generator) supply.

I don't see how it would be classed as "prosumer electrical installation" this from my understanding is for renewables tied to DNO and supplementing DNO supply and feeding grid with any access correctly installed system such as that needs to see DNO supply active to operate and isolate when DNO outage. energy storage (battery banks and the like are needed ) along with interlock with DNO to use this power during an outage.

Would you mind referencing the section within it that related to use of a back up generator which is isolated by way of manual bypass from the DNO?

I appreciate BS 7671 is mandated, to me there is more risk tying generator to DNO earth during an outage/fault on network for reasons I've explained, Again welcome all assistance and help if I'm misinterpreting   

Kendo51 said:

2.Wired back to a 20amp double pole rcbo enclosure in distribution cupboard.

20A RCBO for a generator that can supply 7.5kVA.  Shouldn't that be 32A?

Kendo51 said:

I will be installing a type 2 SPD in the replacement main db in the house as explained as existing boards are old, as the garage is effectively TT it has a Type ! locally as required due to increased likelihood of lightening strikes given its a steel structure. 

The Type 1 would be required in the garage ... but also because of the MET in the house, one might be required on entry of the feed from the garage at the house.

Kendo51 said:

I don't see how it would be classed as "prosumer electrical installation" this from my understanding is for renewables

'Prosumer' is defined as combining a consumer installation with generation ... yes, original intention of including Chapter 82 was to facilitate renewables, but the definitions are what they are, and the 'modes of operation' are identical ... In fact, a local generator is shown (2nd item from top-right) in Fig 82.1. Any combination of items in Fig 82.1 and it's effectively a PEI. Have a look at Regulation 823.

Kendo51 said:

you cant use the generator to supply garage in "island mode" a generator in island mode (floating neutral)

'island mode' does not mean 'floating neutral'. Please see Definition in Part 2 of BS 7671, and usage in Chapter 82. (Regulation 824.2)

Kendo51 said:

With ref to the earthing arrangement my thoughts for switching earth within the manual bypass is exactly because of 7.4.1.4 and to comply with BS7671 maintaining cpc continuity and earthing protection/main and supplementary bonding for the installation

My additional thought is if DNO has a power outage with fault on N conductor my house supply being TN-C-S  id have no earth if had my generator earth connection tied to DNO and I'm running the generator to supply the house and it developed a fault the resulting fault currant would be back feeding onto DNO network . 

The guidance is to keep DNO earth connected even though you aren't using it as a means of earthing directly (you connect an earth electrode to the MET yourself, but keep DNO earth connected also).

You may well be connected anyway if you share extraneous-conductive-parts such as metallic pipes with other installations.

If you disconnect DNO earth, there may (in some installations) be problems with Regulations 411.3.1.1.

Safer overall to keep DNO earth connected.

Kendo51 said:

My additional thought is if DNO has a power outage with fault on N conductor my house supply being TN-C-S  id have no earth if had my generator earth connection tied to DNO and I'm running the generator to supply the house and it developed a fault the resulting fault currant would be back feeding onto DNO network .

The IET guidance and Chapter 82 has been reviewed by DNO for safety. This is why the Neutral from DNO is disconnected, but the PE is not. See Regulation 826.1.1.2.2.

Kendo51 said:

Would you mind referencing the section within it that related to use of a back up generator which is isolated by way of manual bypass from the DNO?

Regulation 826.

Hi Simon, very much appreciate your feedback, was wondering who would highlight this lol. whilst you are technically correct with your answer biased on the peak power of the generator being 7.5kva and capacity to trip the 20amp protection, peak usage is best avoided and is really for very short term use to allow for inductive loads/motors start up etc.

If the 7.5kva was a load (and not a supply) rated circuit protection would have to be sized according.as you've said.

Given we are talking of a back up emergency supply to my property 20amp is more than enough to keep main things running, with the 20amp protection it will serve a few purposes.

1. Upon designing out what power would be needed in the event of a power outage 20amp is the max I would require.

2. 20amp will ensure I don't draw on peak power (@ 7.5kva is 26.08amp @ 230v) from the generator inadvertently, if 32amp protection was used it would afford no overload protection to the genset. 32amp would need min of 9.25kva draw to trip.

3. Generator efficiency, loading and noise , as you can appreciate if i selected a smaller generator it would need to run full load for what i need which uses more fuel, has a higher running rpm at full load = more noise and shortened service life, By selecting a slightly larger genset which can supply what i need more easily it improves all these areas.  

4. Generator selection for me was biased on its "constant run" output rating and in my selection this particular unit its 6.25kva which equates to 5kw (800w per kva) or 22.72amp @220v  or 20.83amp @240 ( allowing for avr variation but generally accepted as 230v ) is average of 21.775amp @230v, so at 20amp im keeping just under "constant run rating" . 

This was my thought process on circuit protection for the genset, i am open to advisement / correction on this.

Much appreciated.

Hi Andy , Thanks for getting in touch. sorry for delay in responding I had answered back yesterday but hadn't hit the reply.

AJJewsbury said:

You're probably thinking correctly, but just to be absolutely clear (in formal terms and for others reading this) the thing on the outside of the house should be a plug (inlet), rather than a socket - the trailing part (from the generator) should have shrouded socket tubes, rather than exposed pins

That's correct male plug (exposed pins) mounted on the house as this only becomes energised via cable from generator which would be a female socket with generator end of lead being male .

AJJewsbury said:

The generator's system would almost certainly be TN-S - the local electrode acting as the "source" earthing (the first T) and c.p.c.s connected to N via the generator's N-PE link (so TN). To create a local TT system, you'd need two separate electrodes, for for the generator and another for the installation.

Yes i recognise its TN-S owing to the neutral earth link in generator.

Was refencing "effectively  TT" more to the fact installation during DNO supply drop and on gen supply earthing would be to the electrode's and not DNO earth point , bad selection of wording apologies.

AJJewsbury said:

You local TT sub-installation for the workshop makes things more interesting. You could leave that as TT, even in generator mode, but you'd need at least two electrodes then, one for the generator and another separate one for the garage/workshop. You just need to make sure that the sum of the two electrode resistances is still gives a low enough loop impedance for ADS etc for your TT system (as your generator electrode is likely to have a higher resistance to Earth than the DNO's).

AJJewsbury said:

One problem with that approach though is the proximity of the generator to the workshop - if it's within reach (2.5m?) they need to be on the same earthing system - which they won't be if the workshop is TT and the house TN. One option then is to bring the workshop onto the house TN system during island mode - perhaps a 3rd pole in your change-over switch could achieve that - but you'd have to be very careful how things were arranged both in grid-connected and island mode - as you'd want to ensure the workshop wasn't connected to the DNO earth, or within reach of the DNO earth, at any time, including when in island mode. Rating a change-over switch contacts to switch between a DNO Earthing facility and extraneous-conductive-parts (e.g. the workshop, presuming it's sat on the ground) can get "interesting" as the currents involved may include distribution network diverted neutral currents, which aren't related to the generator's output rating (consider why you might need 10mm2 main bonding even for tiny installations).

My though was to run another 10mm earth cable from nearest earth pit (I've 2 pits linked for garage TT 2m electrode in one and 1m in the other both cabling run separately into garage and joined in esco form esco I've main bonding to garage frame and from esco to garage db) nearest earth pit Appox 4 m from what will be generator location) to the generator this would tie all earthing, earthing rods steel garage and generator keeping them all at equal potential as genset location and steel garage are approx 1.5m apart.

There is approx 4m separation from garage to house building and some 6m to nearest house electric. if i was to install another earth rod just for generator 1. it wouldn't be as good a read than rods I've installed for garage 2. proximity of new genset electrode to existing electrodes wouldn't be of any benefit would just be an other extraneous conductive part effectively .

Change over switch ive been looking at is 100 amp or 125 amp, think 100amp is more than suitable given 80amp DNO fused supply, I understand and take the point of ensuring garage earthing and DNO supply earthing is indeed separate I'm going to test this separation today, ill also do clamp test on DNO earth to rule out any other issues, thankyou that's a good point you highlighted.

With ref to "diverted neutral currents" from DNO this was my reasoning in switching the DNO earth given intention of back up generator is provide power during DNO power outage 99% of time i due to a fault on the DNO network/grid rather than planned maintenance. If I use a  double pole line and neutral isolated bypass (break before make) but with this there is potential for DNO diverted neutral current through the DNO earth and at same time If I tie to DNO earth with generator running and i have a fault my end fault current could potentially be introduced to DNO network.

AJJewsbury said:

The usual approach is you use a DP change-over switch (for single phase) and have Earth solidly connected to both a local electrode and the DNO's earth. In Grid mode it's then TN-C-S as before, and TN-S in generator mode.

This is my concern if I'm using generator the DNO supply will be off line likely due to a fault and if I've all earths tied to DNO earth and ive a fault at my end will this not sent fault current through the DNO Earth/neutral onto to network?, my other thought on this is the stipulation in G99/NI (as id replied to gkenyon if you could review my reasoning on application of G99/NI and indeed ESQCR ) .  

Find out more about the Distribution Code for Northern Ireland | Northern Ireland Electricity Networks

section 7.4.1.4 The Power Generating Facility shall use an earth electrode independent from the Distribution Network.

AJJewsbury said:

Maybe one option to consider is to make both the house and workshop one common earthing system - TT in grid mode and TN-S in island mode.

Would this not mean in grid mode having the DNO supply N-E link disconnected? ,    this would remove my thought and need for 3 pole bypass but at same time would need to have new earthing cable runs from garage esco/earthing electrodes back to the house. Appreciate that  the TN-S in "island mode" is in ref to the neutral earth link in generator winding/centre tapping.

For completeness in generator terms, im use to referring to island mode = floating neutral at generator (no neutral earth link or tie) in this format is advised small output generators are only used for one item of class 2 equipment. If more than 1 item of any equipment or indeed hook up to property or building then neutral-earth are to be "tied" in alt winding and earth electrodes used. would you believe I've heard of and seen people linking neutral earth in the plug lead or actually linking in winding on some duel voltage (110v and 230v) generators where the 110v is generated from 55v centre tapping .

Appreciate any and all feedback and advice, I'm no expert by any means but like to fully understand and indeed question myself so im grateful for any discussion and direction to this end.