I need help choosing correct shower and assessing cabling!

[LJDIYs]

I have a combination heating cylinder with a disconnected eco 7 option, and the "normal" elec running the other immersion.

I thought when i first purchased the flat several years ago that there was a New Team power shower installed, as i remember pressure being high, and there were selections on the unit which affected pressure, though i suppose his could have been a high kw electric unit, with selectors affecting how much water was heated and therefore how quick throughput was.

I rented the flat out and a pluber was called to replace the faulty New Team unit. He told me the cabling was insufficient to cover more than an 8.5kw shower. I have recently got back the flat from rental and the replacement shower has minimal pressure. It has a single feed from the mains cold water, but i was surprised to find that there is a twin and earth cable, which appears to be relatively substantial - white cable enclosing brown and blue cable, and a yellow and green earth cable (though this could have been sheathed). Each of these three cables is made up of 3 cables of approx 1mm diameter.

I don't know how to get more pressure. I don't have a separate cold tank, and can't install one, suggesting the original shower was not power unless it used the small cold water tank of the combination cylinder, and i have no room for a pump, so although i do not need water to be heated, i think i am stuck with an electric shower. My hot water pressure is very low, however my cold water pressure is very high - i am considering buying a high kw electric to see if i can up the flow, but i'm not sure if the cable is big enough from what the plumber fitting the replacement said, and not sure if this will fix the pressure problem. i now wonder if original shower was perhaps a 10.8kw or something...

The double pole is in the room backing onto the shower, which is incidently next to my RCD. I imagine from shower unit to pole switch is max 2m, if not 1m.

Any advice?

 

[ColJack]

get a sparky in to consult..
have a close look at the cable and see if it's got anything printed / embossed on it.

measure the outer sheath dimensions and then look in the wiki which gives approximate dimensions for T+E cable sizes ( in the electrics section )..

 

[Whitespirit66]

If your plumber said that the max KW shower you could have with your existing cable is 8.5, then its likely that your cable is 6mm twin and earth.

As a rule, the higher the KW of the shower, the higher the flow of hot water from the shower will be. A 10Kw will give a better flow than your 8.5 KW, especially if you invest in a good make, eg. Mira, Triton. However, a more powerful shower will require a 10mm twin and eath cable all the way back to the consumer unit, instead of your 6mm. An electric shower will always be a comprimise, as the throughput of water needs to be slowed for the shower to be able to heat it.

If you have poor flow, first check that the stop tap is fully open , and that any isolation valves on the cold supply to the shower is fully open. Also, clear any scale out of the head and ensure that the hose isn't kinked.

 

[LJDIYs]

I think perhaps replacing with a 10mm is the only option, and getting a 10kw electric.

In terms of my options for a power shower, could the cold part of my combination cylinder run a power shower as i have no separate cold tank, or would it run dry too quickly and cause an airlock...the total height of the whole hot and cold cylinder is about 4.5ft but not sure of the volume as can't find it quoted or see the make... its bright turquoise if that helps.

Would 10mm T+E be sufficient for a power shower - i know i need 3 core...is that actually T+E?

Thanks

 

[JPC]

if its a normal combination cylinder with cold storage on top of the hot storage...u have no chance of running a power shower from it

 

[LJDIYs]

I suspected as much - essentially ruling out options of power shower and pump (which there is no room for anyway). presumably nothing has changed and you can still not pump mains water?

Means only option is upgrade cabling and use cold mains feed already there, but with a higher kw electric shower.

Only other thought - will a mixer shower work? i am assuming with high pressure cold and very low pressure hot, a mixer shower will either regulate down to the hot water pressure, or if it doesn't regulate, will produce a pretty luke warm shower, though perhaps better pressure - that's if mixer showers can be connected to mains cold and cylinder hot?

Thank you

 

[Whitespirit66]

Think electric is your only feasible option with your combined 'Fortic' type tank.

A mixer wouldn't work, as the hot and cold supplies to it need to be balanced pressure. The high pressure cold could even force the low pressure hot back down its pipe.

 

[LJDIYs]

Thanks Whitespirit.

If i went with the not very promising sounding mixer idea:

a.) could i put in a regulator of some sort to regulate the cold/ hot pressure imbalance (which i would get if i used cold mains and cylinder hot)...mind you then i'm back at the pressure from the hot water part of the cylinder which is very low....

or b.) could i actually just use cold from the cylinder and hot from the cylinder that would then be equal pressure...or would the cold run out in the same way it would with a power shower?

i guess either way i'm back at the low cylinder pressure, and in fact changing cabling....looks like a post is neededin the electricals part so that someone can explain the difference between t+e and 3-core, and also will an electric run off 3 core in case i change mymind in the future and have to install a pump somewhere....?

 

[JMLanders]

Google "venturi" showers. May be what is needed.

Bit like this

 

[LJDIYs]

If mixers aren't going to work either, a venturi might... that's a good call... they look difficult to get hold of... looks like the trevi boost is less unit based, but the newteam jetstream is unit based...are there others on the market...where would be the best place to buy one... a lot of places do not stock any venturis...

 

[JMLanders]

If mixers aren't going to work either, a venturi might... that's a good call... they look difficult to get hold of... looks like the trevi boost is less unit based, but the newteam jetstream is unit based...are there others on the market...where would be the best place to buy one... a lot of places do not stock any venturis...

Just a quick search yielded this

May seem expensive, but given that you (probably) won't need an new cable run for a new powerful electric shower (with possibly a new RCD protected outlet etc etc), then I suspect the overall cost won't differ too much.

The thing that may cause a problem is the requirement of 300mm of head of cold water tank above the shower head. From the sound of it, your combination tank is putting a bit of a kybosh on this (the only possible way round this would be to bodge a higher cold water tank within the airing cupboard and bypass the one that's integral - sounds messy )

 

[LJDIYs]

Yes, i spotted the head bit, and actually no sure that i could get tank any higher than the cold water part of the combination tank, it is on a platform raising it to the ceiling, but with the shower on a slightly raised tray...thinking there might be a problem here.

Any sparky/plumbers in this forum know the difference between 3 core and t+e?

Everyone has been really helpful, thank you very much.

 

[JMLanders]

Any sparky/plumbers in this forum know the difference between 3 core and t+e?

Am a bit confised by your terminology. Earlier, I think you said that each cable was made up of 3 cables; whereas I believe you meant 3 strands.

 

[LJDIYs]

Hi

I meant that each of the sheath within the twin and earth is made of 3 cables - so the earth wire for example is 3 strands of copper, each approx 1mm thick, twisted together and sheathed in green and yellow, which then with the other two cables, each also made up of 3 copper strands each and sheathed, are sheathed together in a white cable.

i just wondered what makes 3 core different from twin and earth?... which i am assuming mine by the look of it.

Thank you

 

[simond]

Twin and earth does not have a insulated earth conductor within the white sheath, it is bare. The bare conductor is sleeved at the point of termination to prevent accidental connection with phase conductors.

Most sizes of T&E also have a smaller earth continuity conductor than the phase conductors.

Three core cable is not generally used/available, 3 core flex is more common (commercial applications excluded). This has insulation and sheathing. The three cores are the same size and current rating.

Flex is not generally permitted for permanent house wiring where it can be damaged eg: in the garage, or where it cannot be inspected, eg: under the floor.