Design question

[safedepth]

Afternoon all,

My apologies if this is simple one.

Here is the scenario,

The customer owns a very old pub/hotel circa 15th Century. Looking at some of it the place was wired very shortly after!

Main supply is to a 3 phase board, 100 A per phase. A sub main from this supply's the bar area amongst others. An old metal Wylex board. This is fed via a 16mm Twin and earth. At least I think it's 16mm.

This sub main has a further sub main from it to a small modern distribution board via 10mm T&E feeding the landlords accommodation area, electric shower @ 40A, 2 16A radials for sockets and 1 6A lighting cct. Shower is on a RCCD, rest is MCB's only.

The old metal Wylex, also supply's the 4 hotel rooms.

Here's the thing, the customer wants to install new electric shower in one room plus saniflo. This board is directly below that room. Can I Henly off the 16mm to a second board, with RCD etc to supply that room. It would require 50A for the shower, 20A radial for sockets and 6A lighting cct. The main supply is some way off and I can't get an earthing conductor back to it. Will I need to install rod for it's own earth? That would mean separate means of earthing for supply's to that room only. Is that possible?

Sorry it's such a long winded one but I'm struggling.

Thanks in anticipation,

Fitz

 

[ProDave]

My only concern is you will have two electric showers on that submain with a 16mm feed. If they are both 7.5KW you might get away with it, but if they are both 10KW it won't be up to the job. Thinking about it, you are talking about a 50A circuit for the shower, so must be talking 10KW, so it's not really up to the job.

Of course the best option is another submain from the 3 phase box, but you seem to have ruled that out. Are you sure you can't find a cable route to lay a new submain in?

 

[safedepth]

Dave, That's a concern of mine too. Yes she does want a large shower. I have advised her to go for a conventional shower as she's having a new unvented system in to replace the existing boiler and tank combo. Her plumber said go for electric it'll be cheaper. Since he's installing plumbing for a sink and the shower I don't know what he's thinking of. I am tempted to push her along the non electric shower route. That would certainly ease the load.

 

[Tooold]

Pretty sure you are not meant to mix types of earthing in the same property. Two showers off the 16mm sounds like a lot of load, would have to be some cable calcs done as it sounds like a long run. If you could use a smaller shower and put a 45a in the wylex to supply a small board. If they are planning a lot more work that also needs to be thought about. I have done small hotels/b&b's but put small db's for each room. That doesnt sound like much help to you though

 

[ProDave]

Definitely advise a thermostatic mixer shower from a mains pressure water tank. Much much better shower with enough force to push you into next week, compared to the dribble you get from an electric shower.

How can the plumber say it's more expensive? if the mains pressure HW tank is there anyway, then it's two pipes and a mixer shower, compared to the cost of an electric shower and all the works needed to get an adequate feed to it.

If she does opt for the mixer shower, your job becomes much simpler, and I would think along the lines of upgrade the metal wylex board to take existing circuits + new circuits, but do some testing first to make sure the existing circuits are okay to be on an RCD.

 

[SPECIAL LOCATION]

Dave, That's a concern of mine too. Yes she does want a large shower. I have advised her to go for a conventional shower as she's having a new unvented system in to replace the existing boiler and tank combo. Her plumber said go for electric it'll be cheaper. Since he's installing plumbing for a sink and the shower I don't know what he's thinking of. I am tempted to push her along the non electric shower route. That would certainly ease the load.

Ask the plumber for his cable calcs and costs???

Work out the proper price for a full new circuit back to the main incomer..

then see which option is cheaper?

UNLESS they will go with 7.5 KW...

Personally I can never see the point of going up th 50amp for a shower!!!!

OTT! or what

9500KW ia a 40A @ 240v (manufactures guidance)

 

[safedepth]

Cheers Dave,

I think a PIR would be called for before I interfered too much with this lot. As I say some of the existing stuff looks very old, and there are lots of add ons dotted around the building. The main intake is some distance from the submain I'm looking at. A 15th Century building is a new one on me and throws up all sorts of it's own challenges.

Fitz

Toold, I agree about the earthing arrangements sounding wrong but haven't yet found any written evidence to back up my thoughts.

In view of the other issues I may just propose a fresh start anyway and look at other options, couldn't see any last time though!

Fitz

 

[safedepth]

Ask the plumber for his cable calcs and costs???Work out the proper price for a full new circuit back to the main incomer..

then see which option is cheaper?

UNLESS they will go with 7.5 KW...

Personally I can never see the point of going up th 50amp for a shower!!!!

OTT! or what

9500KW ia a 40A @ 240v (manufactures guidance)

I wouldn't go with 7.5Kw, especially on this one. The room is a lovely old room, 4 poster bed, loads of character and history. She wants to charge good rates for it and needs more than a dribble from the shower.

 

[SPECIAL LOCATION]

I wouldn't go with 7.5Kw, especially on this one. The room is a lovely old room, 4 poster bed, loads of character and history. She wants to charge good rates for it and needs more than a dribble from the shower.

Therefore needs to pay good rates to get it kitted out IMHO?

If staying electric then I think you have already sussed you need some serious cable work. :| :C

 

[safedepth]

Therefore needs to pay good rates to get it kitted out IMHO?If staying electric then I think you have already sussed you need some serious cable work. :| :C

Spec Loc,

Yes, I think she will be shocked to discover what she may have to pay for this work. A new cable run is potentially very expensive but the only way to go. All the electrics on that side of the building are from this wylex metalclad, and all in need of work. Any work planned on the remaining three rooms will only add to the load. Also, the whole bar area is on that board. Any faults discovered could seriously affect her income.

Thanks for your help everyone.

Fitz

 

[kmaccui]

hi just a quicky if you are interested you can ask the guys at niceic,eca or select about the earthing part of your problem.

they normally get back to you the same day.

http://www.voltimum.co.uk/consult.php?universe=consult.index

 

[ProDave]

Just another thought, you say there are other rooms needing work. So is she thinking of upgrading all the rooms to en-suite, i.e adding more showers in the future?

If so, she seriously needs to plan ahead, and forget any notion of electric showers. The only way to go for several, decent showers is a decent capacity unvented hot water tank feeding thermostatic mixer showers.

I note her plans were only for an "unvented" system. I do hope she is not planning just a combi boiler with no hot water storage tank. Definitely a bad move and she will be disappointed with the hot water flow and / or temperature, particularly if trying to run more than one shower.

Surely the plumber should have advised her of that? or do plumbers just like fitting combi boilers because they are easy, even though the hot water performance is often little better than an electric shower.

 

[sparkytim]

Had a job last year wanted three 8.5 kw on 100 amp single phase supply.

Installed changeover switch for 2 of them so only 1 could be used at once

Would this work for you?

 

[batty]

Had a job last year wanted three 8.5 kw on 100 amp single phase supply.Installed changeover switch for 2 of them so only 1 could be used at once

Would this work for you?

Not good in a hotel if the shower does not work customer would soon be downstairs kicking up a fuss.

 

[sparkytim]

Give guest room priority and Landlord only use when Guests out

Simples

 

[safedepth]

Sorry, been out for some dinner.

From what the customer explained to me she is having a new combi boiler with unvented storage system. Just as she should. This is why the plumbers comments surprised me.

The changeover switch would not be an option for the reasons Batty pointed out.

I will follow up on the earthing issue with nicey.

She has not specifically said the other rooms will be upgraded but if they are in the future these problems will rise again so I will be pushing the new submain route. If she has the money and the foresight she will go that way. If either is missing though, well, we all have wishes without funds!

 

[ProDave]

Sorry, been out for some dinner.From what the customer explained to me she is having a new combi boiler with unvented storage system. Just as she should. This is why the plumbers comments surprised me.

You need to clarify that.

A combi boiler has no hot water storage, it heats the water on demand in real time, just like an electric shower does. They are just about okay for 1 shower, pathetically slow at filling a bath with hot water, and no good for 2 showers at the same time unless you get a really large one. Then there's the situation where someone turns on the kitchen hot tap while you are showering and your shower goes cold.

IMO a combi is great for 1 person living alone. For a familly, let alone a hospitality business they are rubbish.

If there's a hot water storage tank (preferably unvented for decent flow and presure) then it's heated by a conventional boiler, NOT a combi boiler. Providing the tank is big enough these will give a really decent shower and will fill a bath in just a couple of minutes. Far Far better.

There's also a third option of a "heat store" it works a little different, you heat a tank of water with the boiler, but the tank is only at low pressure. You don't draw the water directly from the tank, but mains pressure water enters a heat exchange coil, and comes out the other end heated from the water store. Some people like these as they don't have the (very small) potential hazards of high pressure hot water storage.

 

[safedepth]

You need to clarify that.A combi boiler has no hot water storage, it heats the water on demand in real time, just like an electric shower does. They are just about okay for 1 shower, pathetically slow at filling a bath with hot water, and no good for 2 showers at the same time unless you get a really large one. Then there's the situation where someone turns on the kitchen hot tap while you are showering and your shower goes cold.

IMO a combi is great for 1 person living alone. For a familly, let alone a hospitality business they are rubbish.

If there's a hot water storage tank (preferably unvented for decent flow and presure) then it's heated by a conventional boiler, NOT a combi boiler. Providing the tank is big enough these will give a really decent shower and will fill a bath in just a couple of minutes. Far Far better.

There's also a third option of a "heat store" it works a little different, you heat a tank of water with the boiler, but the tank is only at low pressure. You don't draw the water directly from the tank, but mains pressure water enters a heat exchange coil, and comes out the other end heated from the water store. Some people like these as they don't have the (very small) potential hazards of high pressure hot water storage.

Thanks Dave,

I will. I must admit I thought it was still a combi simply replacing what had been drawn from the unvented tank.

Cheers,

Fitz

 

[mercurystar999]

Any nice hotel room would need a decent shower. Even the Mira advance which imo is the best you can buy is pathetic in comparison to a power shower fed from a tank. Plumber seems to not have a clue from the sounds of it.

 

[kme]

There is another issue here, SD:

load balancing.

I`ve just been doing a similar pub, with similar(ish) leccy. No hotel rooms, though.

They had single phase subs everywhere, we`ve run TPN to the kitchens and cellar, and SP submains from there.

Customers average phase loading before we started:

L1: 34A L2: 8.4A L3: 83A

And he had 3 X 60A BS88s up front - had WPD out to replace L3 fuse twice in one week.

I haven`t metered it since we reworked the distribution, but his monthly leccy bill has dropped from ~