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

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?

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.

please forgive me for back-tracking slightly, but there's a subtle yet important point about the supply regs (ESQCR and equivalent). the OP is absolutely right, micro-generation isn't classed as a "generator" under the regs. However, many of the requirements about generation apply not to "generators" but to "any person" with a genset. this is how you "may be caught" by those requirements 

Hi Dave, Your quite alright and thankyou for contributing to the discussion.

gkenyon has be really good throughout this discussion highlighting and pointing me in the direction of different regs etc below is a part of that discussion relating to what you have kindly contributed. If you could if you've time to review below inno it regs and long and tedious but think the thread/content is helpful . Hopefully you can see my reasoning within it. Any and all thoughts and feedback are welcome, maybe bias but I'm of the thinking what I'm suggesting doing is permitted after regs review and again further review to regs  gkenyou directed me to. Feel free to disagree / query /question any and all it helps the discussion from multiple view points.

Kendo51 said:

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 . 

thanks

yes, there are some excellent points about G99 and ESQCR that have been made by more informed commentators than me

my minor point doesn't affect any of that, it just creates the link from your installation through the supply regs to the wiring regs. specifically, reg 22 of the supply regs covers "Where a person operates a source of energy" and reg 23 covers "a person who installs or operates a source of energy". you'll see that regs 22 and 23 don't apply to "generators", they apply to "person[s]"

Fair enough.

I'm not sure you should include the 0.8 power factor when converting kVA to amps.  Maybe someone more knowledgeable will chip in, but as I understand it Amps x Volts = VA, regardless of power factor, but VA may not be equal to Watts.

Hi Simon, you are correct in your point you highlighted ref calculations as we apply them

With caveat not all generators voltage is fixed at 240v, some are 230v some even 220v. In saying that I take reference/lead from manufacturers figures, this manufacturer for example for DHY8000SELR-T claim max output is 6.9kva 5.5kw peak with a constant at 6.3kva 5kw  (page 21)

DHY6000SE_DHY8000SE_DHY8000SELR-T.pdf

Dave Miller said:

"generators", they apply to "person[s]"

For the purposes of ESQCR, 'generators' are 'legal persons' not pieces of equipment.

Dave Miller said:

"generators", they apply to "person[s]"

For the purposes of ESQCR, 'generators' are 'legal persons' not pieces of equipment.

gkenyon said:

For the purposes of ESQCR, 'generators' are 'legal persons' not pieces of equipment.

Specifically:

“generator” means a person who generates electricity at high voltage for the purpose of supplying consumer’s installations via a network; 

(See Regulation 1 Citation, commencement and interpretation)

This is the nuance with discussion that helps us all understand better. Thankyou gkenyon  

Quite so, but is this topic not about low voltage (< 600 V phase to earth AC).

So the OP's generator isn't a generator.  And the OP isn't a generator either, because their generator (that isn't a generator) doesn't run at high voltage.

Simple!

Chris Pearson said:

Quite so, but is this topic not about low voltage (< 600 V phase to earth AC).

Indeed ... that means that if you provide generation at 'low voltage' (such as many solar farms on the AC side), you might not be covered by the term 'generator' as defined in ESQCR ... but more pertinent to this discussion, it also means that if you are a 'prosumer' you are also not a 'generator' as far as ESQCR is concerned.

Simon Barker said:

generator (that isn't a generator) doesn't run at high voltage.

I would perhaps say that the AC side of their generator doesn't run at high voltage, but that's perhaps another debate which is not, perhaps, completed.

the OP's generator isn't a generator.  And the OP isn't a generator either, because their generator (that isn't a generator),,,

And that, ladies and gentlemen, is the sort of thing that happens when you let the legal chaps draft anything technical, and then let politicians edit it. Too many holes.

What for example if I had an LV generator and stepped it up to HV to run the length of a large farm and then stepped it back down to LV before it was used to supply any loads ?  (I am aware of at least one of these in the UK )  

So it is far more important that this installation is safe for its users, and can not damage  the DNO network, or rely on it when it may not be there for earthing, than agonising over which bit of legislation is or is possibly not appropriate, though it is quite fun.

Unless the OP refers himself to the police, who probably won't be interested anyway, we'll never know.  The only time such laws are tested in earnest is after there has been a serious accident and then some sort of inquiry, and the trick is to avoid that under all circumstances.

Mike.

yes, there are some parts of the supply regs which apply to legal entities who are "generators" as defined in the regs. however, there are other requirements (including regs 21 & 22 of the supply regs and regs 22 & 23 of the statutory rules for Northern Ireland) which apply to any person:

• reg 21/22: Where a person operates a source of energy as a switched alternative to a distributor’s network, he 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.
• reg 22/23: (1) Without prejudice to regulation 21[/22], no person shall install or operate a source of energy which may be connected in parallel with a distributor’s network unless he—
  (a) has the necessary and appropriate equipment to prevent danger or interference with that network or with the supply to consumers so far as is reasonably practicable;
  (b) has the necessary and appropriate personnel and procedures to prevent danger so far as is reasonably practicable;
  (c) where the source of energy is part of a low voltage consumer’s installation, complies with British Standard Requirements; and
  (d) agrees specific requirements with the distributor who owns or operates the network.
  (2) Sub-paragraphs (b) and (d) of paragraph (1) shall not apply to a person who installs or operates a source of energy which may be connected in parallel with a distributor’s network provided that sub-paragraphs (a) and (c) of paragraph (1) are complied with; and
  (a) the source of energy does not produce an electrical output exceeding 16 amperes per phase at low voltage;
  (b) the source of energy is configured to disconnect itself electrically from the parallel connection when the distributor’s equipment disconnects the supply of electricity to the person’s installation; and
  (c) the person installing the source of energy ensures that the distributor is advised of the intention to use the source of energy in parallel with the network before, or at the time of, commissioning the source

you will observe that these key requirements (including preventing danger and complying with the wiring regs when in scope) apply to any person with a source of energy. reg 22/23 is so important that it applies retrospectively, which isn't generally the case when new rules are introduced

I agree that what matters most is that the installation is safe, but I think that understanding the legislation does matter too. I'm sure that there's something in UK-SPEC about understanding relevant legislative and regulatory frameworks, so you don't have to take my word for it.

There seems to me to have been some confusion in this discussion about which rules apply where, so I want to avoid people thinking that certain rules don't apply to their installations because they've seen what appears to be a loophole but the parliamentary draughtsman has been smarter than they may have been given credit for. the key rules apply to any person who operates a source of energy

Dave Miller said:

you will observe that these key requirements (including preventing danger and complying with the wiring regs when in scope) apply to any person with a source of energy. reg 22/23 is so important that it applies retrospectively, which isn't generally the case when new rules are introduced

and similarly Regulation 21 (22 in NI) if the generator operates as a switched alternative, this needs to provide safety for those working on the distribution network, and BS 7671 is to be used.

Interesting with these two Regulations in ESQCR, it is the 'person' who 'operates' the generator (that could be, again, a 'legal person' as an entity), not the installer, who has the duty under the Regulations, and might be proceeded against under the Regulations (unlimited fine I believe).

However, that would not stop the 'person who operates' being able to take action against an installer if the installer were the designer recommending the change to the electrical installation.

I imagine that there's a CDM angle to this, where ultimately the client is responsible for appointing the right people to do the right things