BartW Posted February 22, 2023 Share Posted February 22, 2023 Hi, I am currently embarking on the installation of the heat pump, as part of the rest of the process of building my house A couple of questions for checking if I may: - single phase power supply is being planned to be a 6mm2 T+E. Total wire run is 13m. The pump is 7kW. THat's 30.4 Amp. Various sources stipulate different methods of measuring, thus establishing the cable size. I have been forever confused why installation method impacts the max cable Amperage. - In view of the above cable length, Vaillant suggest the T+E and Ebus cables should be separated if more than 10m in length. Would this be due to the main cable magnetic field that might affect the comms between the pump and the control unit? Anyone put this to the test and managed to get it trouble free when over 10m? - I am running all pipes in PEX (and variations of). 98% of the run is inside the building with only 200mm being outside (and inside the insulated Vaillant pipes). I have few bends to overcome. Are there any no-nos when it comes to using 90deg elbows? I suppose it would ideally be a single coil run, but I am not sure how easy a 32mm pex pipe would bend where needed. - anything else I should pay attention to, other than the obvious? Many thanks Bart Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 22, 2023 Share Posted February 22, 2023 Which model is it? 1 hour ago, BartW said: Anyone put this to the test and managed to get it trouble free when over 10m? Just use a screened cable, but yes, segregate them as I have heard of issues where there has been a loss of the comms signal on other HP's. 32mm elbows will be fine, as long as you're not fitting lots of them. Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 23, 2023 Share Posted February 23, 2023 1 hour ago, BartW said: The pump is 7kW. THat's 30.4 Amp. Nope. This will likely only need a 25a breaker and a 4.0mm2 cable. Most I can see in the spec is a bit over 20a inrush, but constant power will be 6-7a max, or lower if the heat pump is running at very low temps. Link to comment Share on other sites More sharing options...
Jenki Posted February 23, 2023 Share Posted February 23, 2023 (edited) 10 hours ago, BartW said: The pump is 7kW. THat's 30.4 Amp Surely this is the heat output? (I've not looked at the model number,) Power input will be way less. Edit: What @Nickfromwales says ↑↑↑↑ Edited February 23, 2023 by Jenki Link to comment Share on other sites More sharing options...
BartW Posted February 23, 2023 Author Share Posted February 23, 2023 Hi Both, Fair point. If I work on average SCOP @ 3 then this would be merely just over 2kW. So way less. Another thing to check, I could literally half the run if I run the cable / comms / pipes low level internally through the house behind the kitchen cabinets. Of course pipes would still get lagged, but they would otherwise be exposed. This would give me a pretty straight run with no elbows, bar one at the pump itself, which could be a sweeping bend. Good idea or bury it in the ceiling? Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 23, 2023 Share Posted February 23, 2023 24 minutes ago, BartW said: Hi Both, Fair point. If I work on average SCOP @ 3 then this would be merely just over 2kW. So way less. Another thing to check, I could literally half the run if I run the cable / comms / pipes low level internally through the house behind the kitchen cabinets. Of course pipes would still get lagged, but they would otherwise be exposed. This would give me a pretty straight run with no elbows, bar one at the pump itself, which could be a sweeping bend. Good idea or bury it in the ceiling? Good idea. Crack on. Use phenolic insulation and do NOT clip to the pipe. You need to have movement in the mechanical fixings so you don't get any creaks. Also, you do not want to clip to the pipe if using cooling, as the stalks of the clips will be condensation forming points of contact. "Go for it" 1 Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 23, 2023 Share Posted February 23, 2023 On 28mm pipe you can use 25mm wall insulation and then fix with a 3" waste pipe clip, with one every 400mm. That'll keep you nice and tight to the wall so you have less woodwork to do. If no appliances, use the plinth space and run them on the floor ( unless you bought your kitchen from a meat-ball vendor ). Link to comment Share on other sites More sharing options...
BartW Posted February 23, 2023 Author Share Posted February 23, 2023 52 minutes ago, Nickfromwales said: On 28mm pipe you can use 25mm wall insulation and then fix with a 3" waste pipe clip, with one every 400mm. That'll keep you nice and tight to the wall so you have less woodwork to do. If no appliances, use the plinth space and run them on the floor ( unless you bought your kitchen from a meat-ball vendor ). I make kitchens and other things so will defo have a plinth and some extra depth. Muchos grazias! 1 Link to comment Share on other sites More sharing options...
JohnMo Posted February 23, 2023 Share Posted February 23, 2023 16 hours ago, BartW said: 6mm2 T+E. Total wire run is 13m. The pump is 7kW. THat's 30.4 Amp. Just read the installer instructions, it should specify min cable mm2 for given max length. Link to comment Share on other sites More sharing options...
BartW Posted February 23, 2023 Author Share Posted February 23, 2023 3 hours ago, JohnMo said: Just read the installer instructions, it should specify min cable mm2 for given max length. I had done it before I posted. There is no mention of the pump cable. Only ebus @ 0.75mm2. Link to comment Share on other sites More sharing options...
Radian Posted February 23, 2023 Share Posted February 23, 2023 23 hours ago, BartW said: Ebus Who ever came up with it should be taken out and shot. Single ended signalling is asking for trouble over distances when mixed with power switching cables. Someone retrofitting ebus controls is bound to want to use any T&E cable already buried in a wall for a dumb thermostat to hook things up but the chances are it'll be run alongside pump or other power circuit. So easily could have been differential and good for 100's of meters in any environment. 21 hours ago, Nickfromwales said: Just use a screened cable Screened twin with the screen tied to Earth at just the HP end should be OK. But good luck finding it in 0.75mm2 RS have this although I don't know why the photo shows three cores. Seems totally daft asking for such a big CSA when the whole bus will fall over if loaded by much more than 0.2A anyway. Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 23, 2023 Share Posted February 23, 2023 1 minute ago, Radian said: Who ever came up with it should be taken out and shot. Single ended signalling is asking for trouble over distances when mixed with power switching cables. Someone retrofitting ebus controls is bound to want to use any T&E cable already buried in a wall for a dumb thermostat to hook things up but the chances are it'll be run alongside pump or other power circuit. So easily could have been differential and good for 100's of meters in any environment. Screened twin with the screen tied to Earth at just the HP end should be OK. But good luck finding it in 0.75mm2 RS have this although I don't know why the photo shows three cores. Seems totally daft asking for such a big CSA when the whole bus will fall over if loaded by much more than 0.2A anyway. I use screened Cat5 and put on of the twisted pairs into a bootlace for each core ( so 4 connections per Cat5 cable over 8 cores ( 4 pair )) Link to comment Share on other sites More sharing options...
Radian Posted February 23, 2023 Share Posted February 23, 2023 1 minute ago, Nickfromwales said: I use screened Cat5 and put on of the twisted pairs into a bootlace for each core ( so 4 connections per Cat5 cable over 8 cores ( 4 pair )) Sounds fine. I doubt if would make a difference but I think I would treat each of the twisted pairs as one wire rather than split the two ebus lines across each pair. i.e. take two of the twisted pairs into one ferrule for one of the signals and repeat for the other signal line. Dammit, you can't even refer to an ebus wire as + or - 🙄 1 Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 23, 2023 Share Posted February 23, 2023 1 minute ago, Radian said: Sounds fine. I doubt if would make a difference but I think I would treat each of the twisted pairs as one wire rather than split the two ebus lines across each pair. i.e. take two of the twisted pairs into one ferrule for one of the signals and repeat for the other signal line. Dammit, you can't even refer to an ebus wire as + or - 🙄 Depends on how many cores you need, and how many cables you've run. One twisted pair per ferrule has been fine for everything I've done to date tbh, but I always segregate and never run signal and mains in parallel for any distance ( all squeezing through a shared transit is fine afaic ). Link to comment Share on other sites More sharing options...
Radian Posted February 23, 2023 Share Posted February 23, 2023 1 minute ago, Nickfromwales said: Depends on how many cores you need, and how many cables you've run. One twisted pair per ferrule has been fine for everything I've done to date tbh, but I always segregate and never run signal and mains in parallel for any distance ( all squeezing through a shared transit is fine afaic ). Seems like a nice quiet night to muse over the intricacies of such things. Cat 5e is specified to be ≤ 0.188 Ω/m per conductor so doubling up halves this to 0.094 Ω/m 0.75mm2 copper is around 0.023 Ω/m Will it crash and burn? I think not. Ebus @ 200mA over 100m would drop 2V on a twisted pair, x 2 for the round trip. 4V may start to be a problem, but 100m is unlikely. Worth bearing in mind though. Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 23, 2023 Share Posted February 23, 2023 Just now, Radian said: Seems like a nice quiet night to muse over the intricacies of such things. Cat 5e is specified to be ≤ 0.188 Ω/m per conductor so doubling up halves this to 0.094 Ω/m 0.75mm2 copper is around 0.023 Ω/m Will it crash and burn? I think not. Ebus @ 200mA over 100m would drop 2V on a twisted pair, x 2 for the round trip. 4V may start to be a problem, but 100m is unlikely. Worth bearing in mind though. I'm 4 IPA's in mate. You own this. The night is yours. I'll go open #5, and you work out the impact that CCA would introduce to the maths. I'll have @SteamyTea check this over and authenticate at 08:00, so use your best crayons please Link to comment Share on other sites More sharing options...
BartW Posted February 24, 2023 Author Share Posted February 24, 2023 I managed to run the ebus in standard 0.75mm twin. Totally along its own joist and away from anything so that’s sorted now Link to comment Share on other sites More sharing options...
markocosic Posted February 27, 2023 Share Posted February 27, 2023 Loads of room under IKEA cabinets for flat pipework unless you're a midget settings worktops at 850. Waste pipework on a fall less so. eBus (and the similar M+Bus) at the data rates they run at are idiot proof when it comes to noise IME. I would consider NOT insulating primaries under a plinth depending on heat loads in older builds. It's like adding a radiator without taking up the space of a radiator. Run hours in summer will be low (DHW only) and windows van be open if too toasty. In new build this insulation can be fairly pants too. (i.e. no phenolic) as the only job is to reduce gains in summer or avoid hitting condensation if used for summer cooling. Definitely don't insulate on the space heat side of the 3-port valve. You want all the emitter area you can get there. Link to comment Share on other sites More sharing options...
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