Crofter Posted April 25, 2017 Author Share Posted April 25, 2017 Thanks as ever Nick. Can I really run 3x5kw loads simultaneously off a normal domestic supply? I thought you were normally capped at 80A so there's not much left there in case someone puts the kettle on, or in the fairly likely event that the heated towel rail is on at the same time. Twin 6kw should be safer perhaps? I presume the use of E7 swings the balance towards a larger tank heater mostly at off-peak times. But of course a larger tank costs a few hundred more so you start looking at payback times, as well as space issues. Link to comment Share on other sites More sharing options...
Nickfromwales Posted April 25, 2017 Share Posted April 25, 2017 5000w / 230v gives just short of 22A so ~66a of your domestic 80a supply gone. 6000w / 230v gives just short of 26.1A Theyre resistive loads so you'll be able to allow for diversity but others on here will know more about the specifics of that rule than me . @ProDave / @Steptoe ? 2x 6kw sounds the better option TBH, with a boost control which feeds the E7 immersion with grid electric. You can use one of these with a changeover contactor. Link to comment Share on other sites More sharing options...
Steptoe Posted April 25, 2017 Share Posted April 25, 2017 12 minutes ago, Nickfromwales said: 5000w / 230v gives just short of 22A so ~66a of your domestic 80a supply gone. 6000w / 230v gives just short of 26.1A Theyre resistive loads so you'll be able to allow for diversity but others on here will know more about the specifics of that rule than me . @ProDave / @Steptoe ? 2x 6kw sounds the better option TBH, with a boost control which feeds the E7 immersion with grid electric. You can use one of these with a changeover contactor. That's pretty good One thing a lot if people seem to not realise is that An 80a fuse won't simply blow at 81amps, Depending on fuse type etc, it may well hold in excess of 100amps for some considerable time, 5-10minutes, or more. Sub main at my house is protected by a C50 iirc, 9.5kW shower, 20a welder, oven on and wife boiling kettle when the 2kW compressor kicks in, not had the C50 trip yet. Obviously the 2x6kW immersions will be your largest continuous load, (no diversity for water heating iirc) , any other significant load is going to be short period, so I wouldn't worry too much. Link to comment Share on other sites More sharing options...
Onoff Posted April 25, 2017 Share Posted April 25, 2017 46 minutes ago, Steptoe said: That's pretty good One thing a lot if people seem to not realise is that An 80a fuse won't simply blow at 81amps, Depending on fuse type etc, it may well hold in excess of 100amps for some considerable time, 5-10minutes, or more. Sub main at my house is protected by a C50 iirc, 9.5kW shower, 20a welder, oven on and wife boiling kettle when the 2kW compressor kicks in, not had the C50 trip yet. Obviously the 2x6kW immersions will be your largest continuous load, (no diversity for water heating iirc) , any other significant load is going to be short period, so I wouldn't worry too much. Do you mean a Crabtree C50 type breaker or another make's Type C 50A? My whole board is C50s. Do they ever trip? Link to comment Share on other sites More sharing options...
Nickfromwales Posted April 25, 2017 Share Posted April 25, 2017 4 minutes ago, Steptoe said: (no diversity for water heating iirc) See, always best to check. My mates just done a 4 storey student digs and had to have another phase brought in for the 7 or 8 electric showers. I was sure he said they'd allowed diversity on the showers ?. I have slept since then though ? Link to comment Share on other sites More sharing options...
Nickfromwales Posted April 25, 2017 Share Posted April 25, 2017 22 minutes ago, Onoff said: My whole board is C50s. Do they ever trip? What? Are you serious? Link to comment Share on other sites More sharing options...
Onoff Posted April 25, 2017 Share Posted April 25, 2017 52 minutes ago, Nickfromwales said: What? Are you serious? It's OK it has got a single up front RCD! Not at all inconvenient! .....which was as far as I got with upgrading it all. Keep putting it off changing it as I want to move the board position...which means bricking a door up.....and cutting through for another door. My chippy mate used the phrase "mechanics car"... Has to happen soon though. Link to comment Share on other sites More sharing options...
Nickfromwales Posted April 25, 2017 Share Posted April 25, 2017 Do you not have 6a lights / 32a ring etc? Just 50's? Link to comment Share on other sites More sharing options...
Steptoe Posted April 25, 2017 Share Posted April 25, 2017 2 hours ago, Onoff said: Do you mean a Crabtree C50 type breaker or another make's Type C 50A? My whole board is C50s. Do they ever trip? My bad,,,, 2 hours ago, Onoff said: Do you mean a Crabtree C50 type breaker or another make's Type C 50A? My whole board is C50s. Do they ever trip? 2 hours ago, Nickfromwales said: What? Are you serious? C50 is a 'make' of breaker, as opposed to a 50a type C My upfront is a 50amp type C, C50 breakers are notoriously unreliable, ie, they never trip,!!!!!! A 6a could probably hold in at 80amps,! Link to comment Share on other sites More sharing options...
Steptoe Posted April 25, 2017 Share Posted April 25, 2017 2 hours ago, Nickfromwales said: See, always best to check. My mates just done a 4 storey student digs and had to have another phase brought in for the 7 or 8 electric showers. I was sure he said they'd allowed diversity on the showers ?. I have slept since then though ? Showers are a bit different, You can 'assume' a shower wouldn't normally be on for more than 15mins, an immersion heater could be on for hours. Link to comment Share on other sites More sharing options...
Nickfromwales Posted April 25, 2017 Share Posted April 25, 2017 Cheers for clarifying Link to comment Share on other sites More sharing options...
Crofter Posted October 4, 2017 Author Share Posted October 4, 2017 Looking at the space where my UVC is going to go. What are the rules/guidelines for siting the expansion vessel? I've got a 554mm wide tank and a 1300mm wide space, but I'm putting the washing machine in there too. So the expansion vessel can't just go at the side, like in the diagram. Likewise, the PRV gubbins that has to be within 500mm- because of the way the tank is laid out, if I put these fittings in clear space, the immersions will be against a wall and you'd be unable to change them out without totally disconnecting the tank and rotating it on the spot. So I'm hoping that I can simply put an elbow in place and run the control group off at a tangent to the tank's circumference, if that makes sense. I'm also not really sure how much space I need to leave for all the runs coming back to this point. Obviously I'm not actually plumbing this in myself but I'd like to be fore-armed with enough information to at least have an informed discussion with the plumber- and also I need to make sure I don't inadvertently put anything in the way of where the expansion vessel will end up. Experience of trades so far is that they'll do whatever is fastest and easiest for them on the day, and sod the next guy who comes along and has to work around it Link to comment Share on other sites More sharing options...
PeterW Posted October 4, 2017 Share Posted October 4, 2017 Check with @Nickfromwales but consider using flexis to connect the tank. As long as they are full bore it will give you some room for manouvre Link to comment Share on other sites More sharing options...
Nickfromwales Posted October 4, 2017 Share Posted October 4, 2017 (edited) Why not run a pipe up to the attic space above ( iirc your only part-vaulted ? ) and put the EV up there? You need to allow your plumber to answer the final fitting questions TBH, ( G3 regs will apply even though your not getting a BR certificate if you want a warranty ) but iirc D1 can have a bend horizontally before dropping to the tundish as long as you can get 2-300mm of vertical D1 pipework before the tundish ( to take the swirl out of the flowing water ) as otherwise it goes everywhere except into the ( open sided ) tundish. You then also ( iirc ) need a minimum of 400mm vertical dropping D2 leaving the tundish before the next horizontal / invert. The control group does indeed need to be within 500mm of the UVC. Edited October 4, 2017 by Nickfromwales 1 Link to comment Share on other sites More sharing options...
Crofter Posted October 4, 2017 Author Share Posted October 4, 2017 OK that's useful- thanks. I couldn't see anything about positioning of the EV but it could quite happily go up in the loft space if that's allowable. There should be space to simply run the discharge pipe down through the floor, with the tundish part way down- this puts it between the washing machine and the cylinder. I guess you end up with a bit of heat loss via the copper pipe which is open to the air. I've done a bit of Google image searching and it looks like everything should be doable- the EV was the main thing I was concerned about. Now to track down that plumber.... I'll hang around the local pie shop and take it from there Link to comment Share on other sites More sharing options...
Nickfromwales Posted October 4, 2017 Share Posted October 4, 2017 Take D2 into a Hotun waterless trap and then to ground. Ditch the tundish but keep all the pipework in copper. Link to comment Share on other sites More sharing options...
Nickfromwales Posted October 4, 2017 Share Posted October 4, 2017 3 hours ago, PeterW said: Check with @Nickfromwales but consider using flexis to connect the tank. As long as they are full bore it will give you some room for manouvre I'd shoot anyone plumbing in the entire UVC on flexis TBH, but you NEED rigid pipework for the control group anyhoo plus rigid for the D1/D2 so you wouldn't be saving much imo. Link to comment Share on other sites More sharing options...
PeterW Posted October 4, 2017 Share Posted October 4, 2017 More thinking boiler / ASHP feeds @Nickfromwales Telfords aren’t the easiest with the HP coil as the outlets are set as 150mm apart and level - makes for interesting pipework ..! All the other connections are relatively simple with rigid pipes. Control set can nearly drop straight onto the top of most of the cylinders. Link to comment Share on other sites More sharing options...
Crofter Posted October 7, 2017 Author Share Posted October 7, 2017 On 4 October 2017 at 16:29, Nickfromwales said: Take D2 into a Hotun waterless trap and then to ground. Ditch the tundish but keep all the pipework in copper. Just got round to looking this up and it answers one of my major concerns: the open pipe from tundish to outside. Could see a lot of heat loss through that. Unless you're allowed to put a u-bend in it? Still haven't got hold of the plumber I'm hoping to use (it's good that he's busy, right?) and need to get a move on with things. Should I just pair everything up for h/c for each run and bring them back to the tank? What about the cold runs (wc etc)- can these tee off the cold feeds to the taps, or do they need to be dedicated runs? Link to comment Share on other sites More sharing options...
Nickfromwales Posted October 7, 2017 Share Posted October 7, 2017 1 minute ago, Crofter said: Just got round to looking this up and it answers one of my major concerns: the open pipe from tundish to outside. Could see a lot of heat loss through that. Unless you're allowed to put a u-bend in it? Still haven't got hold of the plumber I'm hoping to use (it's good that he's busy, right?) and need to get a move on with things. Should I just pair everything up for h/c for each run and bring them back to the tank? What about the cold runs (wc etc)- can these tee off the cold feeds to the taps, or do they need to be dedicated runs? No need for dedicated runs because the hut ( lol ) is small enough not to worry. 15mm pipework throughout will suffice, with everything teed off as and when to suit. . Link to comment Share on other sites More sharing options...
Crofter Posted October 7, 2017 Author Share Posted October 7, 2017 1 minute ago, Nickfromwales said: No need for dedicated runs because the hut ( lol ) is small enough not to worry. 15mm pipework throughout will suffice, with everything teed off as and when to suit. . Yay, that's what I wanted to hear. The shower won't have anything teed off since there's no need, but if I can have a single cold to the kitchen that will save a lot of hassle. Link to comment Share on other sites More sharing options...
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