Power requirements for external swimming pool and pool house

[Thorfun]

thinking ahead here......

 

....we have planning permission for a pool house and swimming pool. I'm currently digging a trench for an SWA cable for the new chicken house and figured I should probably run a cable now in the same trench for the potential pool house and pool. After speaking to our electrician he said he needs to know the requirements before he can recommend a size of SWA cable.

 

so, does anyone have a rough ball-park figure for power requirements for a swimming pool equipment (including ASHP) and pool house (fridge, lights, tv and whatever would go in a pool house!)

 

sparky has said 10mm cable should give us 50A but wasn't sure if that would be enough for a heated pool.

 

anyone any experience on this please?

[Ferdinand]

You need to read @AliG's swimming pool thread.

 

He talks abotu his house attached pool, but discusses lots of numbers and how to save energy etc.

[Thorfun]

3 minutes ago, Ferdinand said:

You need to read @AliG's swimming pool thread.

 

He talks abotu his house attached pool, but discusses lots of numbers and how to save energy etc.

I have previously! but his pool is indoors and also substantially bigger than I think we'd ever build. 😉 

 

but, I will re-read it to refresh my memory as I'm pretty goldfish these days

[billt]

We have an outdoor pool that came with the house. The filtration pump uses a maximum of 800W (about 3 amps) and the ASHP a maximum of 3kW (about 12A). The other things are likely to be trivial. This is for a pool of about 76 cu.m. volume, 10m x 5m area, with a safety cover which reduces evaporation and hence heat loss.

 

The size of the pump and the heat pump depend on the volume of the pool, the bigger the pool the more water you have to pump round and the more energy you need to heat it. The heat pump we use has a nominal (i.e. exaggerated) output of 21kW. That takes about 10 days of continuous operation to get the pool to 26-7C at the start of the season. Once it's up to temperature it can run for a shorter time at lower output.

[Thorfun]

2 hours ago, billt said:

We have an outdoor pool that came with the house. The filtration pump uses a maximum of 800W (about 3 amps) and the ASHP a maximum of 3kW (about 12A). The other things are likely to be trivial. This is for a pool of about 76 cu.m. volume, 10m x 5m area, with a safety cover which reduces evaporation and hence heat loss.

 

The size of the pump and the heat pump depend on the volume of the pool, the bigger the pool the more water you have to pump round and the more energy you need to heat it. The heat pump we use has a nominal (i.e. exaggerated) output of 21kW. That takes about 10 days of continuous operation to get the pool to 26-7C at the start of the season. Once it's up to temperature it can run for a shorter time at lower output.

thanks. very useful information. 👍

[AliG]

50A should be plenty.

 

My pool has around half the volume of @billt's and so the filter pump uses about half the power.

 

The main use of power would be the ASHP, even a 5kW ASHP is only 21A.

 

The power use in the pool house is going to be relatively minor, I guess you might want an air heater which might be 3kW.

 

Showing the difference in heating costs for an indoor and outdoor pool. My pool uses around 40kWh a day for heating, call it 1500kWh for the year, we use gas. It is set at 29C all year round. @billt is quoting that it takes (assuming a COP of 4) almost 3000kWh over 10 days to get his pool to 26-27C.

 

On the other hand, I have a dehumidifier as the pool is indoors and that uses around 2500kWh a year. However, 1/4 of that is on cheap overnight electricity. The filter pump uses around 2000kWh with 40% on cheap rate.

 

An outdoor pool also requires a lot more cleaning and chemicals.

 

 

[billt]

The maximum input to the heat pump is 3kW and when the water's cold it takes less than that. 3 x 24 x 10 is 720kWhr. This year the total consumption was 1245 kWh - we don't use the pool much. When we bought the place we were going to get rid of it but decided to keep it for a while.

 

I have a large PV array and only run the heat pump when the sun's shining so it has zero running costs.

 

If you keep the pool covered most of the time I doubt that there's that much difference in chemical use (reducing evaporation reduces the chlorine requirement) and if leaves etc aren't blown into the pool there won't be much more cleaning to do either. You're right if it isn't covered.

[Thorfun]

thanks guys. great information and I definitely agree with you @AliG that 50A (so a 10mm cable) will be sufficient for all our pool needs. Will run it by the electrician and get it ordered and laid!

[AliG]

1 hour ago, billt said:

The maximum input to the heat pump is 3kW and when the water's cold it takes less than that. 3 x 24 x 10 is 720kWhr. This year the total consumption was 1245 kWh - we don't use the pool much. When we bought the place we were going to get rid of it but decided to keep it for a while.

That sounds about right, I was trying to get an equivalent figure for an ASHP versus gas so multiplied it by the COP. If it is free PV then it doesn't matter.

 

Similarly I have the filter sumo set to come on at 1130pm when my Intelligent Go starts and it runs to 6 in the afternoon. So I get much of my filter and dehumidifier electricity either at cheaper overnight rates or on PV during the day. So I would guess of the 4500kWh I quoted you are talking 1400kWh at the cheap rate and maybe another 1500kWh from PV. Running them in the winter though you have to pay!

[Carrerahill]

2 hours ago, Thorfun said:

thanks guys. great information and I definitely agree with you @AliG that 50A (so a 10mm cable) will be sufficient for all our pool needs. Will run it by the electrician and get it ordered and laid!

 Hang on a minute, how long is the cable? What is the route? 

 

Do you have a proper load analysis for the pool house?

 

Lighting, heating, water heating, pumps, small power, ventilation, any other electrical loads, then realistic diversity added.

 

Post up some details and if need be I can run a cable calc for you.

 

 

 

 

 

 

Edited September 23, 2022 by Carrerahill

[TonyT]

Run a duct and install a draw rope aloes for future proofing.

also let’s civils get underway without having full electrical design

[Thorfun]

1 hour ago, Carrerahill said:

 Hang on a minute, how long is the cable? What is the route? 

 

Do you have a proper load analysis for the pool house?

 

Lighting, heating, water heating, pumps, small power, ventilation, any other electrical loads, then realistic diversity added.

 

Post up some details and if need be I can run a cable calc for you.

 

 

 

 

 

 

the problem is I don't have any details. tbh, we'll probably never build the pool but I'm currently digging a trench for a different cable and am just looking to try and future proof as much as possible. so, whatever cable I choose to bury now may not end up being enough but it also might! and so it could save much disruption further down the line. so I just kinda wanted a ball-park figure rather than doing tons of research. but, in answer to your questions, I would hazard a guess at the following:

 

Lighting: Minimal as it'll be LED. maybe 100W - 200W all in with a few spots and LED strips?

Heating: Shouldn't be any in the pool house as it'll be well insulated and mostly used in the summer months anyway. 

Small power: small drinks fridge, LED TV (maybe), Sonos speakers or stereo, maybe a fan or two if it's really hot in the summer.

Ventilation: Doubt much will be needed

Other electrical loads: ASHP for pool (3kW), filter (800W as per @billt), electric pool cover (small motor would presume)

 

anyone think of anything else? we're not talking a big building here! permission is for a 5m x 3m pool house.

 

distance will be approx 50m from CU in the plant room in the basement and SWA cable will be run underground. so, that can't be more than 5kW. even if we put 7.5kW load into this voltage drop calc (https://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html) it comes out at 6mm and 40A max cable load. a 10mm cable will give me up to 11kW (51A max cable load). that's gotta be plenty!? if I'm going to build something that needs more than that then I'll just dig up the garden and run a new cable but will I really need more than 11kW to run a 5m x 3m pool house and pool designed and permission granted at 9m x 4m?

[Thorfun]

9 minutes ago, TonyT said:

Run a duct and install a draw rope aloes for future proofing.

also let’s civils get underway without having full electrical design

and I have considered this but I've only dug a narrow 70mm trench using a tooth on my digger. so I 'could' fit a 54mm ducting in there if I really wanted to and maybe I should and this is most likely the best idea but it seems to be spending money of duct when I could just lay the cable underground now. although, I guess if I get the cable wrong now I've wasted money on that anyway!

[TonyT]

I hate mucking about with anything less than a 100mm duct, for power runs to unknown equipment.

but I don’t do domestic work so client are happy to fork out for ducting and drawpits.

[Carrerahill]

58 minutes ago, Thorfun said:

the problem is I don't have any details. tbh, we'll probably never build the pool but I'm currently digging a trench for a different cable and am just looking to try and future proof as much as possible. so, whatever cable I choose to bury now may not end up being enough but it also might! and so it could save much disruption further down the line. so I just kinda wanted a ball-park figure rather than doing tons of research. but, in answer to your questions, I would hazard a guess at the following:

 

Lighting: Minimal as it'll be LED. maybe 100W - 200W all in with a few spots and LED strips?

Heating: Shouldn't be any in the pool house as it'll be well insulated and mostly used in the summer months anyway. 

Small power: small drinks fridge, LED TV (maybe), Sonos speakers or stereo, maybe a fan or two if it's really hot in the summer.

Ventilation: Doubt much will be needed

Other electrical loads: ASHP for pool (3kW), filter (800W as per @billt), electric pool cover (small motor would presume)

 

anyone think of anything else? we're not talking a big building here! permission is for a 5m x 3m pool house.

 

distance will be approx 50m from CU in the plant room in the basement and SWA cable will be run underground. so, that can't be more than 5kW. even if we put 7.5kW load into this voltage drop calc (https://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html) it comes out at 6mm and 40A max cable load. a 10mm cable will give me up to 11kW (51A max cable load). that's gotta be plenty!? if I'm going to build something that needs more than that then I'll just dig up the garden and run a new cable but will I really need more than 11kW to run a 5m x 3m pool house and pool designed and permission granted at 9m x 4m?

Go 16mm² 2 core SWA XLPE.

 

Don't trust the TLC calculator it doesn't add in enough variables, only volt drop in clipped direct installs. 

 

 

[Thorfun]

10 minutes ago, Carrerahill said:

Go 16mm² 2 core SWA XLPE.

 

Don't trust the TLC calculator it doesn't add in enough variables, only volt drop in clipped direct installs. 

 

 

wouldn't I need 3-core? one for earth?

[Carrerahill]

42 minutes ago, Thorfun said:

wouldn't I need 3-core? one for earth?

Use the armour - up to about 95mm² SWA you can use the armour, over 95mm² the cross section is usually not sufficient unless a very short run. Very rare to see a SWA cable core used as an earth commercially. 

Edited September 23, 2022 by Carrerahill

[AliG]

If you put in a pool they will put in an earth rod as understandably they want to make sure no one is accidentally electrocuted.

[Thorfun]

17 minutes ago, AliG said:

If you put in a pool they will put in an earth rod as understandably they want to make sure no one is accidentally electrocuted.

already got one of those as we've got a TT system. but I presume another rod wouldn't hurt and they're dirt cheap!

Edited September 23, 2022 by Thorfun

[joth]

15 hours ago, Thorfun said:

already got one of those as we've got a TT system. but I presume another rod wouldn't hurt and they're dirt cheap!

 

If it's a TT system with local earthing rod on an outbuilding, you specifically do NOT want to bond the earth back to the main building, it needs to be isolated.

(The SWA armour should be earthed at the main supply end only, to protect the cable itself but not the outhouse).

 

Earthing rods are cheap, but testing the quality of the earthing and moving it around if it's in a poor location can become an expensive job. 

[Thorfun]

9 hours ago, joth said:

 

If it's a TT system with local earthing rod on an outbuilding, you specifically do NOT want to bond the earth back to the main building, it needs to be isolated.

(The SWA armour should be earthed at the main supply end only, to protect the cable itself but not the outhouse).

 

Earthing rods are cheap, but testing the quality of the earthing and moving it around if it's in a poor location can become an expensive job. 

cheers. and great info. but I'm happy to leave that sort of stuff to my electrician who I trust!

[Onoff]

Knock the earth electrode through the bottom of the pool once finished. It'll keep the soil nice and damp and make for a nice low Ra

 

Or not... 😂

[SteamyTea]

15 hours ago, Onoff said:

Or not

Will work well for a week or so.

 

Leaky pools are such fun to deal with.

[Thorfun]

I've quite enjoyed this data gathering mission but I've decided to be sensible and stick some 50mm ducting in and be done with it for now.

 

chances are by the time we get around to building the pool house cable prices will have dropped enough to have paid for the ducting in savings over today's cable prices! even if they haven't it's £250 or more in cable that I don't have to buy now and it's not like I haven't got enough other stuff to think about and organise and get done! not sure why I want to keep adding stuff to my already full plate. must be a self-builder.