Three phase vs single phase underfloor power track

[MagicalArmchair]

My office is moving premises to a larger office of circa 8,000 sqr feet. The old Britway power track under the floor is obsolete and thus the landlord is paying to get it replaced. We are an office type company of around 40 people and our projections show us growing to over double in the coming years. Our power requirements are moderate, we do have lots of higher spec computers with high (ish) wattage PSUs, all desks have two monitors, a raft of white goods, big tellies on the wall and we have a small number of servers.

The two electrician companies I had initially quote for floor power track quoted on three phase rather than single. The landlord suggests this is overkill and add that their own electricians thinks its balmy putting three phase track into an office environment. I am inclined to believe the professionals who quoted me, who tell me in offices of this size single phase just isn't installed any more and three phase will give much better fault resilience.

What is the accepted standard on power track for commercial premises from you great electrical jedi? Am I being up sold by my electricians something I don't need and will never see the benefit of, or is my landlord trying to duck the higher cost of the three phase track?

 

[Simonslimline]

Money will always factor for the person responsible of managing the finances. Why employ electricians if you dont trust there proffessional advice on the most suitable system? Have you had just the one spark advise?

 

[Sparkie30]

3 phase mate, 40 people at the moment and will double that in coming years as you said. Spend extra now and you covered in future me think. You call anyway.

 

[telectrix]

if the option is there, then 3 phase every time.

 

[Darkwood]

The landlord will probably be wanting you to use his budget electricians and 3phase probably scares them or he is pulling their strings here, the fact they advised against 3ph shows a lack of competence in electrical design IMHO.

 

[Pete999]

Don't think he means 3 phase track mate, he is IMO saying as you are a growing company with future expansion, a 3 phase system may suit your needs better by this he means splitting the outlet circuits over 3 phases, your outlets will still be 230 Volts A/C

 

[Deleted member 26818]

Are you sure that they are refering to 3phase track?
I would think they are more likely refering to single phase tracks spread across 3 phases.

 

[Darkwood]

Would it matter how we interpret the OP- 3ph track or single phase track across the phases would still be the better option than all on one phase.

 

[Brightspark2]

Definitely better with the load spread over 3 phases...

 

[Deleted member 26818]

Well 3phae track would be more expensive than single, and I'm not sure such an animal even exists?

 

[Darkwood]

Same plane as yourself, not sure it exists either but I would suggest that 1 X 3phase track is deffo cheaper than 3 X 1 phase track, although the cost benefits would be subject to layout and whether 3ph track could cover a smaller footprint thus savings been made... if I had time I would look it up but the pub quiz be calling

 

[MagicalArmchair]

Firstly, thanks for taking the time to respond. In response:

Are you sure that they are refering to 3phase track?

Quite sure. Currently the premises has three lots of obsolete single phase track for which parts (tap offs etc) can no longer be purchased. Both sets of quoting sparks are quoting on installing three phase track. They suggest that this is the standard now in offices of this size and would give business continuity if a phase was dropped. Check out here for details of Electrak 27 (3 phase) https://www.legrand.co.uk/media/4572/electrak-underfloor-to-workstation.pdf

Money will always factor for the person responsible of managing the finances. Why employ electricians if you dont trust there proffessional advice on the most suitable system? Have you had just the one spark advise?

I had two sparks quote independently and they both recommended 3 phase, and I do trust them both frankly, however I have never had any work done by either company in the past. Caveat Emptor and all that...

 

[Richard Burns]

For almost any office situation, especially one that is changing and expanding, where there is a three phase supply it would be a very good idea to make use of that supply as effectively as possible. This would mean utilising the three phase supply with loads across different phases.
If you were to install a single phase arrangement then in practice it would be inconvenient to spread the loads across phases as there would only be one phase available in any one area and would lead to grouping of loads, which while certainly possible to do is not an ideal arrangement.
Any modifications would also be limited to the phase available in the area if there were no major upheaval undertaken.

Having three phases available in all areas provides flexibility and load balancing opportunities that would not be available with single phase systems.
The initial cost would be higher but the long term maintenance and modification costs would be reduced significantly.
Therefore one can see why the original supplier would want to minimise his costs while effectively moving those costs down the line to you at a later date.

 

[Deleted member 26818]

Not knowing the shape or size of the area which you intend to supply doesn't help.
However in all the offices I have worked in, I have never seen anything other than single phase track used. I was not even aware of 3 phase track.
My main concern is that having equipment across different phases in close proximity will double the prospective fault current between such items.
Other concerns:
Linking IT equipment which is fed from different phases may cause data transmission faults, monitors may flicker, lines could appear on screens, printers could produce poor quality copies, etc. (I would check with equipment manufacturers first).
When connecting floor boxes to the track either a specifically manufactured single phase plug and lead will be required, or a 3 phase plug and lead will have to be modified to remove the extra two phases which would void the manufacturer's warranty.
(With Legrand equipment, conductors are soldered to the plug pins. BS 7671 requires single phase conductors to be identified as brown. When making modifications compliance with BS 7671 would require the black and grey conductors are removed and the brown conductor re-soldered to the appropriate phase).
If maintenance requires the track to be isolated, with 3 phase it may be that three times as much equipment will be switched off. (Not sure whether single phase MCBs can be used with 3 phase track? Would need to check with the manufacturer).
As for versatility:
With for instance 3 separate single phase tracks, any floor box can be moved to any track without having to worry about which phase the plug and lead have been configured for. If each single phase track has the same number of items connected, loading across the phases should be the same (or at least similar).
With three single phase tracks spread over an area, shorter leads can be used to connect floor boxes.
With a single 3 phase track covering the same area, correspondingly longer leads will be required. (Normal length for leads is 3 or 5m. Longer leads can be obtained.)

It may well be in your particular instance, 3 phase track is the best option, however as already pointed out, I have never seen it used. (Not sure as to why).

 

[MagicalArmchair]

Thanks for the responses.

I suppose that illustrates the trouble - two of the forums trusted professional members with opposite opinions. I have had about 75% of electricians telling me 3 phase track is the better option, and 25% telling me I'd be as mad as a box of frogs to go for 3 phase track.

So is the consensus that there IS no consensus? No standard for a commercial office fit out as to which track to use?

 

[Richard Burns]

As you can see there are positive and negative aspects to three phase supplies.
If you get the electrician to design the installation taking account of the problems identified by Spinlondon then you should be OK.

The layout of the building and areas of use and their loading would be a key aspect in choosing the most suitable arrangement, if you have all the IT equipment at one end of the building and all the distribution and loading equipment at the other end then maybe three single phase tracks for IT and one three phase track for the heavier loading but lower earth leakage.

Probably your best answers are going to come from someone on the ground who can adequately assess the situation.

It does occur to me that if the installation was fully equipped with three single phase tracks at each location, but the tracks are assigned to specific items with a schedule of permissible modifications then this would probably resolve the problems in all cases, but could be initially costly and have a lot of redundant track in place,