Safety voltages: ELV, SELV, PELV, and FELV

As an ex rock climber, I always liken the system of safety voltages (ELV, SELV, and PELV) to the slightly opaque British Trad grading system for climbing (which I think should have been extended to include Tricky, Jolly Tricky, Bit Spicy That One, Whoops There Goes My Lunch, and Guaranteed Hospital Visit)

One effect of this is non intuitive nature is that people often say “SELV” when they mean “voltages too low to exceed the 50Vac / 75Vdc threshold of the Low Voltage Directive” or “a low voltage supply”.

This isn’t accurate, as one could meet the ELV/SELV voltage limits for a DC supply of 100VDC, which would fall under the LVD.

Importantly, these terms capture not only the voltage levels but the nature of the supply from mains.

  • ELV defines safe(ish) voltage levels for user accessible parts
  • ELV limits correspond to ES1 levels for AC and ES2 for DC from EN 62368-1
  • SELV, PELV and FELV levels do not exceed ELV limits, even under no-load conditions (a useful consideration when using an unregulated power source like a 50/60Hz mains transformer)
  • SELV indicates a double insulated mains supply (Class II mains)
  • PELV indicates a single insulated with earth (Class I mains)

One thing I do like about EN 62368-1 is that it skirts around this non intuitive terminology and makes voltages and insulation much easier to understand.

A breakdown of the terms can be found below:

Intialisation ELV SELV PELV FELV
Meaning Extra Low Voltage Safety Extra Low Voltage Protective Extra Low Voltage Functional Extra Low Voltage
Electropedia Definition 195-05-24 195-06-28 195-06-29 n/a, defined in BS 7671 wiring regulations
Voltage Limit
(Conductor-to-Conductor or Conductor-to-Earth)
50Vac/120Vdc 42Vac
50Vac/120Vdc with no load
42Vac
50Vac/120Vdc with no load
42Vac
50Vac/120Vdc with no load
Insulation to Hazardous Mains n/a Double
Reinforced
Basic + earthed screen
Double
Reinforced
Less than Basic
Earthed n/a No Yes Yes
Can be Accessible? Yes Yes Yes No
Can exceed voltage limits under conditions:
Normal No No No No
Single Fault No No No No
Earth Fault No No No No
Example ELV just defines acceptable voltage levels Class II a.c. mains with un-earthed output e.g. typical USB phone charger Class I earthed a.c. mains suply with low voltage outputs e.g. desktop PC power supply Low voltage that is not separated from a.c. mains e.g. voltage for SMPS controller primary side not accessible to user

.

failure of a series power switch under single fault conditions

Material Flammability Ratings – Comparative Reference Table

Flammability ratings of different materials can be a bit confusing. For instance, UL 94 V-0 vs V-1, which is more flame retardant?

We’ve pulled this together into one table to make referencing between the tests and standards easier for you.

Material performance increases as we read down the table so HBF is worse than, not equivalent to, VTM-0.

 

Test Classification

Test

Material Performance Worst to

Best

UL 94 Horizontal Burning Foamed Material
ISO 9772

Worst

HF-2 HF-1

HBF

UL 94 Thin Material Vertical Burning
ISO 9773

VTM-2 VTM-1

VTM-0

UL 94 Horizontal Burning
EN 60695-11-10 Method A

to HB-75

HB-40

UL 94 Vertical Burning
EN 60695-11-10 Method B

V-2

V-1

V-0

UL 94 5V Vertical Burning Test
EN 60695-11-20 Method B
Best 5VB

5VA

Spring or Star Washers for Earthing Stud?

Introduction

This article started with a simple question: what is the correct washer to use to secure a ring crimp terminal on a threaded bolt?

I have seen either spring/split washers or internal/external star washers being used.

I asked on LinkedIn and found some good advice, some received wisdom and “we’ve always done it this way”, but not much in the way of citeable standards or references from technical authorities.

 

Goals of Earthing / Bonding System

The fundamental goals of the electrical fixings in the protective earthing / bonding system are:

  • Provide (at assembly and maintain during use) a low resistance, potentially high current (tens/hundreds of Amps depending on supply) electrical contact
  • Not corrode or loosen under the normal environmental operating conditions to the point where the resistance goes out of specification

In reality there are many factors that one could worry about:

some considerations for protective earthing conductor connection to metalwork

 

Common Safety Standard Review

A review of the more frequently used safety standards for electronic products yields the following clauses.

Standard Clause Clause Text
EN 62368:2014 4.6.1 “parts fixed by means of screws or nuts provided with self-locking washers or other means of locking are not liable to become loose or detached
NOTE Spring washers and the like can provide satisfactory locking”
EN 61010-1:2010 6.5.2.2 c) “Screw connections shall be secured against loosening”
EN 61010-1:2013 6.5.2.3 k) “The contact pressure required for a bonding connection shall not be capable of being reduced by deformation of materials forming part of the connection”
EN 60335-1:2012 28.4 “Screws and nuts that make a mechanical connection between different parts of the appliance shall be secured against loosening if they also make electrical connections or connections providing earthing continuity. This requirement does not apply to screws in the earthing circuit if at least two screws are used for the connection or if an alternative earthing circuit is provided.
NOTE 1 Spring washers, lock washers and crown type locks as part of the screw head are means that may provide satisfactory security.”
EN 60335-1:2013 27.2 “27.2 The clamping means of earthing terminals shall be adequately secured against accidental loosening.”
EN 60730-1:2016 9.3.6 Clamping means of earthing terminals for external conductors shall be adequately locked against accidental loosening.
EN 60730-1:2017 11.2.2 “parts fixed by screws or nuts provided with a locking washer are regarded as not liable to become loose”

(note clause not specifically related to earthing)

 

Typical Locking Fixings

The below image shows a variety of locking methods that I would consider acceptable for this purpose.

a table showing locking nuts and washers

Conclusions

The standards are not prescriptive about the type of locking washer to be used.

Spring washers, lock washers and threaded fastener locking features are all valid approaches.

No washer is also an acceptable method provided there is a locking nut of some kind of suitable locking adhesive used.

Two independent fixings are considered to be acceptable in some standards.

 

Testing Testing Testing

In all cases, conformity with the standard is checked by inspection and/or appropriate testing. Testing is key.

Testing the protective earthing / bonding system includes measuring the resistance and/or measuring the current handling capability of the connections.

If you are the manufacturer and wanting to use a non standard fixing method then it may be acceptable. Any non-standard or atypical methods would need adding to the product compliance risk assessment.

The testing specified in the standard is the bare minimum and additional testing may be required to demonstrate that everything is indeed safe. Testing could include extended high humidity environmental testing to check for corrosion and representative vibration testing to make sure that loosening does not occur in use.

Selecting suitable environmental test levels for your product can be based on your experience as the manufacturer with typical operating environments, or perhaps using the ETSI EN 300 019 environmental engineering standards.

Of course, the simplest way is to just use a standard washer to reduce arguments.

 

 

Not Covered

Like all simple questions, there is a surprising amount of depth and possible considerations, including:

  • Corrosion, plating, passivation, surface oxide layers, dissimilar metals. This is a book in of itself!
  • Considering the current path. Using a locking washer with a small surface contact area in the primary current path can increase the resistance. Aiming for a larger surface area with a good quality connection would be optimum
  • Surface preparation: clearing paint, anodising, rust, or oxidation.
  • Minimum fixing size. Some standards call up a minimum 4mm diameter and number of threads engaged for certain types of screw fixings. This is not universal across all standards. If in doubt, selecting all threaded hardware to be at least M4 in diameter seems like a sensible option.

 

Your Thoughts

I would be very interested to hear of studies, standards, procedures, reports… indeed any published material that covers this topic of washers and fasteners specifically for electrical connection.

 

References & Links

  1. My original question posted on LinkedIn asking about washers
  2. NASA fastener design manual, page 10 has details of locking mechanisms
  3. The always amusing and informative AvE
  4. NordLock brand washers under the Junker test

 

 

 

comparison of weee crossed out bin logos with and without bar (simple graphic)

WEEE Symbol With Or Without Bar?

To Bar, or not to Bar, that is the question:
Whether ’tis nobler in the regulations to suffer
The affixing of a line under ones bin of marking,
Or to add the date of manufacture to ones label…

Hamlet, Act 3, Scene 1 (an early draft)

 

Two symbols walk into a bar…

The “crossed out bin” logo of the WEEE Directive 2012/19/EU is a common sight on electronic equipment to denote that these should be separated from regular waste for recycling.

This is commonly seen both with and without the solid black bar underneath the bin. But which is correct?

Unsurprisingly the answer is “it depends” (I swear I’m capable of giving an answer that doesn’t begin with this phrase, honest)

comparison of weee crossed out bin logos with and without bar (simple graphic)

Directive check

Article 14

Information for users

4. With a view to minimising the disposal of WEEE as unsorted municipal waste and to facilitating its separate collection, Member States shall ensure that producers appropriately mark — preferably in accordance with the European standard EN 50419 (25) — EEE placed on the market with the symbol shown in Annex IX. In exceptional cases, where this is necessary because of the size or the function of the product, the symbol shall be printed on the packaging, on the instructions for use and on the warranty of the EEE.

Article 15

Information for treatment facilities

2.   In order to enable the date upon which the EEE was placed on the market to be determined unequivocally, Member States shall ensure that a mark on the EEE specifies that the latter was placed on the market after 13 August 2005. Preferably, the European Standard EN 50419 shall be applied for this purpose.

 

Seems pretty clear – some kind of mark should be applied to denote manufacture after 2005 (that’s a loooooong time ago now) and the PREFERENCE is to use the methods given in EN 50419.

 

EN 50419 breakdown

Summarised, clause 4 (marking) of EN 50419:

 

4.1 Requirements of marking

a) Identify the producer of the WEEE (brand name, trademark, company name/number). Name to be consistent with name used to register WEEE producer with the authorities

b) equipment [placed] on the market after 13 Aug 2005 shall be identified by EITHER

1) the date of manufacture in text form

2) marking as shown in Figure 1 of the standard

4.2 Design of the marking shall consist of a solid bar with dimensions shown in Figure 1 (shown below)

 

EN 50491 figure 1 bin and bar dimensions

 

Summary

It’s pretty simple, either

  • Apply the bin only logo (Option A) but make sure you have date of manufacture clearly shown on the product label
  • Apply the bin-and-bar logo (Option B)

 

 

 

Graphical Guide to EMC: Near Field Probing (free eBook)

 

You can download our free eBook on Near Field Probing here

I have a love / hate relationship with textbooks.

They are thick, have lots of words, make me feel clever, and stop my bookshelf from floating away. They often have the one thing that you are looking for.

On the other hand, they have far too many (big!) words, too many equations with no context or explanation. I find it very difficult to sit, read and quickly gain an intuitive understanding.

 

I prefer to communicate with pictures. This is why my presentations are image heavy and text light. I’ve sat through (and slept through) far too many “PowerPoint Karaoke” sessions where the presenter reads the words on the slide.

Also I love the format of cartoons and graphic novels, but you rarely see them outside of the fiction sphere. I’ve recently been thinking about what a combination of a graphic novel and a text book would look like.

 

With the recent acquisition of an e-ink tablet with drawing stylus to replace my 74 + 5/8 different notebooks and notepads I started sketching out some ideas for a guide to using near field probes. A subject that I’m often asked about and is complementary to our free Pocket Probe Set that we give away at shows and to customers.

One thing turned into another and once I started drawing I couldn’t stop.

 

You can download our free eBook on Near Field Probing here

 

 

 

I’ve released this under the Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0) license. This means you can share or adapt this work but you must provide a credit / link back to the original source (here). Any adapted work must be shared with the same licence terms.

 

I’d be interested to hear your feedback on the format and content of this mini eBook – please get in touch and let me know!

Thanks and happy probing!

James

 

 

self interference demo USB3 and 2.4GHz

2.4GHz Intra-System (or Self/Platform) Interference Demonstration

In this blog we are going to take a short look at noise and interference in the 2.4GHz band. Our example victim is a Zigbee controller and the sources are nearby USB3.0 devices and Wi-Fi sources.

 

Background

One of our customers makes these rather useful USB Zigbee Coordinator sticks, frequently used for controlling smart home or IoT devices like light bulbs.

These devices operate at 2.4GHz, a very crowded frequency band with Wi-Fi, Bluetooth and Zigbee all fighting for a narrow, congested slice of spectrum.

One of the common issues faced by users of this band is that of intra-system interference, sometimes referred to as “self” or “platform” interference. This is where components in the same system interfere with each other, primarily due to their proximity.

[Note: The counterpart to intra-system (within the system) in this context would be inter-system interference (between separate systems), which is what the conventional EMC test regime of radiated and conducted emissions and immunity seek to characterise.]

This common problem is something that our customer knows all too well from helping their clients integrate these Zigbee products into the end application.

So, during a recent visit to our lab for some testing on a related product, we spent some time investigating this noise on a typical setup.

 

Demonstration Setup

The setup in the below image is common to many users with a Raspberry Pi Model B and lots of stuff plugged in to the USB ports. In this case, a Zigbee adaptor (black case) and an USB3.0 SSD in close proximity.

These parts, including the spectrum analyser, is part of the customers in-house electronics development laboratory.

 

self interference demo USB3 and 2.4GHz

 

The effects of USB3.0 on the 2.4GHz spectrum are well known. A good example is this 2012 paper from Intel which

For this demo, we used a near field capacitive probe and a 2.4GHz antenna to measure noise in the 2.4GHz to 2.5GHz band local to the Raspberry Pi.

This demonstrated the degradation of the noise floor with various levels of system activity including

  • Measurement of system noise floor
  • Presence of a USB3.0 SSD running a large file transfer using the dd Linux command
  • Activation of the Raspberry Pi internal Wi-Fi

The below image shows three traces under these different conditions.

 

spectrum of 2.4GHz band showing ambient noise, SSD noise and Wi-Fi emission

 

Experiment Conclusions

The conclusions we can draw about the in-band noise are:

  • Noise from the SSD raises the noise floor by approximately 10-20dB (a factor of x10 to x100)
  • The Wi-Fi transmission from the Pi is 40dB above the local noise floor. This will mask any received Zigbee signals from a remote transmitter.

 

In-Band vs Out-of-Band Sensitivity

Well designed radio systems are generally very robust to out-of-band interference i.e. anything outside of the narrow radio band that it is tuned to. For instance, a Zigbee radio system set to channel 20 (2.450GHz) will reject anything below 2.445GHz and above 2.455GHz.

 

Intra System Interference Diagnosis

Advice on diagnosing these issues is mostly outside the scope of this short blog. Differences in systems, components and ambient noise levels makes it impractical to offer guidance for all situations. However, some generic problem solving pointers are presented below.

A systematic approach to isolating the problem is required.

One of the primary rules of problem solving is to change only one thing at once and observe the effects.

In EMC terms, it is possible to change several things at once without realising it. Cable position, the specific port that a device is plugged into, location of nearby equipment and cables, even how firmly a connector is tightened will all make small differences that stack up. (Don’t use anything other than a torque spanner on those SMA connectors though!)

Another key rule is if you think something has made a difference, reverse the change and see if the problem re-occurs. Unless you can achieve consistency then you might be changing something else unintentionally, or the problem is caused by something outside of what you are changing.

Correlating the problem against time can help. Does it happen when something else happens (other devices on, or off, or switching, certain configurations, times of day, etc.) This can give clues.

Lastly, we should be looking for a significant step change in improvement to identify the issue. Phrases like “I think it made a bit of a difference but I’m not sure” indicates that we are dancing around the issue and not getting to the heart of it.

Ultimately, for a detailed understanding, the spectrum analyser is a key tool in gaining a proper grasp of this issue.

 

Solutions

The solutions to the problem are simple yet sometimes difficult – a technical balance needs to be struck.

Use of Ethernet rather than Wi-Fi on the Raspberry Pi.

It is not practicable to synchronise transmission from the Raspberry Pi Wi-Fi with that of the Zigbee stick. The simplest way of ensuring the Wi-Fi does not interrupt the Zigbee transmissions is to disable the Wi-Fi and provide network connectivity via Ethernet instead.

Depending on the installation this might not always be practicable but it certainly is more reliable.

 

Separation of components

Moving the antenna away from the noise source is usually the best way to achieve increased performance.

In this instance, placing the module at the end of a USB cable and away from other electronic items is a good start.

Another option that is not as ideal: a good quality SMA extension cable could be used to extend the antenna away from the problem area. This introduces loss into the RF channel, reducing signal quality.  Measurements made in our lab on a cheap extension cable from RS show a power reduction of 6.5dB at 2.4GHz for a 5m cable. This equates to a ratio of around 0.25 meaning we are broadcasting and receiving a quarter of the power we were before.

Also, it is still possible for the noise to couple onto the nearby module even without the antenna attached meaning the problem does not get entirely resolved.

 

Better quality components

Sourcing a bunch of cheap-as-possible parts from Amazon or eBay is likely to bring problems.

Using devices from big name manufacturers and buying from reputable sources helps. But, even reputable components are designed to a price point and can still cause problems if the other points in this blog are not taken into account.

USB cables can be a big source of the problem. Unshielded back shells (the part between cable screen and connector body) compromise the shielding to the point where their performance at high frequencies is equivalent to an unshielded cable.

The only way to tell if a cable is good quality is to perform an autopsy on the ends and check on the cable shielding

Remember that Pawson’s Law of Cable Quality states that the EMC performance is inversely proportional to the physical appearance. Braided covers, shiny plating, metal connector bodies, transparent mouldings etc are all indications of money spent on the OUTSIDE of the cable. EMC quality comes from the INSIDE and is not visible.

shiny usb cable vs boring usb cable

 

 

Hope this was useful! See you soon.

James

 

 

 

V2 pocket EMC debug probe PCB - near field probe set - board front

Pocket EMC Debug Probe V2

A Bag of Water.

This is a very useful analogy to use when considering an EMC emissions problem, particularly true for radiated emissions in the (often problematic) 30MHz to 1GHz band.

 

Lets get squeezing.

Many of you will have experienced this before. Making a change to an emitting structure inside the equipment by changing the electrical connection between two points results in some emissions going down and some going up.

radiated emissions plot

Then you make another change and this has the opposite effect.

This is like squeezing our bag of water. We can move the water around in the bag much like we can emissions around in the spectrum. The harder we press down in one area, the more it pops up in another.

Emission goes up.

Emission goes down.

 

Reducing the volume

But unless we reduce the amount of water in the bag we will nearly always have a problem. The water is incompressible and it just finds new places to appear.

To achieve this in an EMC context we need to reduce the overall energy in the system.

This could be achieved either by keeping the energy controlled on a PCB away from the radiating structure or by adding lossy components (filters, ferrites, etc) to reduce the amount of energy coupling into the radiating structure.

Changing grounding and bonding within a system without reducing the energy is going to be an exercise in frustration and probably wasted time. Better to address the problem at source where possible.

 

Caveats inbound

There will always be a requirement for us to have to try and achieve the goal of “shaping” our bag of water to fit the radiated emissions limits.

A good example is a manufacturer that has already built a production run of units and needs a quick fix to get them onto the market.

Whilst this is often achievable, there are often significant rework / modification costs involved.

There is also the question of repeatability and consistency. If small changes in bonding of parts can make a large difference to emissions, how can you guarantee that each unit will be compliant? Testing multiple samples can help. As can having good production inspection points during the manufacturing process.

But common mode noise is a slippery customer and these kind of fixes should only ever be considered as temporary pending design changes to address the root cause of the issue.

 

A small plug.

Help is available.

We are really good at this kind of work

We’ve been through the cycle many many times with many many different products.

Using Unit 3 Compliance to help with your emissions problems gets you access to our years of accumulated experience.

Our on site test lab allows us to have a rapid cycle time between analysis of a problem on the bench, developing a fix, and testing in the chamber.

 

Hope this was interesting!

James

test report extract showing all tests passed

Thoughts: First Time Pass Rate

This question popped up on one of the email lists that I’m a member of.

“Calling all labs – In your experience how many products pass the Unintentional Emissions test first time?”

I thought I’d share my response:

 

Speaking from my own experience. Over the last four years of running a consultancy, pre-compliance and low cost test EMC laboratory I would (very roughly) estimate that around:

  • 50% of products pass their desired radiated emissions limits without any modification
  • 33% or less pass all of the applicable tests first time without modification

 

The major caveats and notes here are that

  • These figures are for customers products where the EMC performance is not known before testing. We do a lot of work helping people solve existing EMC problems but we are not counting this in these figures.

 

  • Most of my customers are smaller businesses that can’t afford to employ an engineer to just look after compliance. That job role is either split amongst several people or the engineer in question has to look after quality, manufacturing, sustaining, thermal, system, and everything else. Speaking as someone who has designed many products and systems in the past, trying to design for functionality whilst simultaneously considering best EMC performance is HARD.

 

  • The products that pass first time generally fall into one of three categories
    • Products that we have design reviewed before the design was finalised
    • Retests of products that have already been through our lab once
    • Products that are very simple in nature

 

  • Our hit-rate at being able to solve our customers problems is around 90-95%

 

  • The “ones that got away” where we were unable to help deliver a compliant include
    • No action taken: Products where it was deemed by the manufacturer not economically feasible to modify the product (e.g. product going end of life)
    • No further communications from the manufacturer so we don’t get to find out what happened next (no news is good news, right?)

 

I would echo the sentiments of others on this thread regarding the need to design in compliance from the start.

One of the problems with the field of compliance is that it is too often “learned through experience in industry” and not explicitly taught. When it is taught at academic level it is often a surface treatment with a theoretical look at shielding or maybe crosstalk with no other practical context or background.

 

The split between industry and academia is one of the possible causes. Yes, there are exceptions to this but they primarily remain exceptions. I had discussions with a local university about some guest lectures on compliance and the theme of the response was “it doesn’t really fit into any of our modules” and “we can’t have it as an optional lecture as none of the students will attend”.

The number of times I hear “oh, thanks for that. No one has every explained it that clearly before” is worrying!

 

That’s my rant, hope it was useful

James

 

 

 

Thoughts on In House Pre-Compliance Test Equipment

From an email sent to a customer who asked for some feedback on their list of proposed EMC pre-compliance test equipment.

 

“On the subject of equipment, sounds like you’ve identified a nice little pre-compliance setup there! I agree that investing in equipment is a much better long term view than just hiring some in (for the common tests at least).

Com-Power stuff is very good, I use some of their kit myself. The TekBox stuff is very reasonably priced for pre-compliance and again, I use some of their equipment in my test setups. If you are making conducted emissions measurements with a LISN you’d be wise to put a limiter in series with your spectrum analyser input to prevent costly damage. Armoured cable isn’t strictly necessary as it can be difficult to handle, just regular good quality coax is fine.

As a substitute for radiated measurements you can use a current probe around cables as these tend to be excellent emitters of radiated noise. It helps if you already know what the problematic frequencies are. Again, Tekbox make some very reasonably priced probes.

I would also consider the Signal Hound SA44B or BB60C (I have one and I really like it) spectrum analysers as an alternative to the Tektronix one. There’s quite an in depth review of the BB60C here. Their software is easy to use and crucially is free with an EMC pre-compliance option.

If you need test equipment support, I usually talk to Joy Torres at Instruments 4 Engineers in Stockport. She is very helpful and can often get you access to good prices. joyt@instruments4engineers.com. I know she represents Tek, Com-Power and Signal Hound.

The main downsides of making your own emissions measurements is the amount of ambient noise from other electronics, radio sources, reflections off nearby surfaces, etc. It is good for “is A better than B” testing, but it doesn’t really get you to a “but does it pass?” kind of answer. This takes some practice to get right and to get to know your equipment.

The question you could ask yourself is “do I have both the capital and the time to invest in this solution?”. I’ve talked to other companies about their setting up of pre-compliance facilities in house and their struggles tend to be:

  • Engineers lack time to work on the EMC project aspects as well as their regular project work
  • A lot of up front time required to learn the variables of the test setups and standards
  • How to make useful measurements and interpret the results
  • How to match the results from this testing to predicted test lab pass/fail results (spoiler: it is very tricky)
  • EMC knowledge is not well shared amongst employees or the engineer who has the knowledge is on holiday / off sick / unavailable / working on something else

None of these obstacles are insurmountable with good planning and management  🙂  but it is worth going in with eyes open.

In my experience, the best weapon in the EMC armoury is not a spectrum analyser, nor an antenna, not even a full test lab. It is a design review. When we design something we define its EMC characteristics. Getting this up-front bit right is the key to shorter design cycles, fewer prototype runs, reduced time to market and much less stress. Working together to catch the problems before they become problems gives experience in how to design for EMC and the lessons learned can be carried forward from project to project. We’ve helped many customers this way and we’d be happy to help out on your future product ideas.

Similarly, if you want to run quick checks on equipment that needs equipment that you don’t have then we are happy for you to send us the kit via courier and to run the tests on your behalf. I appreciate that our office isn’t exactly nextdoor so anything we can do to help minimise disruption to you and your team would be our pleasure.”

 

Hope some of this is useful

All the best

James