jpadie

I have a garden room with a cu fed from a time delayed RCD in the main consumer unit. The garden room CU is populated with rcbos. I was installing an isolator for a vmc this evening and when I came to turn the local rcbo back on (all circuits were turned off but the main isolator switch was not) I found that the RCD in the main CU had tripped. Any thoughts on why this happens? I've also had a recent experience where the RCD in the main unit tripped whilst none of the rcbos did. Related to a brief short to earth on a circuit in the garden room. All rcbos have tested good and earth is good, albeit the rod is much closer to the main house than the garden room. I'm swapping the main RCD for an mcb shortly so this is just trying to understand what's happening rather than looking for a solution

Hello I've had a fixed power gshp for 20 years and changed a couple of years ago to a 15kW DC inverter. I'm curious about what the relationship between pump frequency and output is. And what best practice might be. What I've found is that I don't see much benefit in terms of speeding up the ufh warming or maintaining the temperature when I let the inverter ramp up to max versus keeping it at 44Hz (which correlates roughly to 11 amps at 230v). To the contrary, the power draw is close to 6kW at that point. I'm also finding that in dhw mode the heat pump errors without a fixed max frequency as the outlet inlet delta t exceeds 10C. I think this is because the circulator used is the same for the dhw and ufh and is set too low for the short run to the water tank. It's not a PWM controlled pump but I could upgrade. For info UFH is buried in a big concrete screed with tiles on top. House is 22 years old and located in southwest France. Surface area of the ufh is 180sqm. Upstairs is heated by forced air and one coil from the heat pump and is very inefficient: takes hours and hours for a room to warm up). Thanks in advance Justin

following up here. I spent an informative hour with CEF in Horsham. bottom line is that they don't sell Wylex links and ... Wylex don't sell flexible links either. I can get them on eBay. I spoke to Wylex directly and they went further by saying that they could not condone adding an RCD to their consumer units (and they don't sell links or 63A MCBs). the DNO is coming next month to upgrade the fuse to 100A. British gas is coming in a couple of weeks to repair the smart meter that they've just installed and to add an isolator since they've put a seal on the DNO's fuse (fair enough, but there's not been one there for at least 13 years). there's insufficient space in the cabinet to put a second consumer unit there. Even a wee one. I've got perhaps 200mm of height. the isolator will give me the (safe) ability to install a henley block and split the tails but I think I'm in a bit of a pickle! Options seem to be: 1. swap out the current consumer unit for an 18th edition version from a supplier that has 63A MCBs and use RCBOs to gain some extra ways. This would be expensive (£400 worth of kit plus it's notifiable so that's another £600 for building inspection and almost certainly there would be insurmountable wiring issues to remedy given the change in regs and the fact that this is a 16th century cottage with a bix of early 60s and early noughties electrics) 2. abandon the idea of the MCB and instead split the tails into the existing CU and a switched fuse (like this or this). Ideally I can go straight into something like this with SWA. Even more ideal would be if horizontal mounting were permitted. 3. export the wiring a couple of metres and place a new mini CU somewhat out of the way. Downside is a significant loss of aesthetic. 4. use a 50A MCB in lieu of the 63A and add an interlock to make sure that both immersion heaters are not on at the same time (or a CT clamp to limit the amount an EV might draw from the circuit). Just to recap the sub distribution board powers a garden room that has a small ASHP, two 3kW immersion heaters and a 7.5kW EVSE, the two immersion heaters _should_ never be on at the same time and it's a small 120L tank, the ASHP is inverter driven and draws 750W max. If I used an interlock the max current draw should be 46A. a bit close to the bone but possible perhaps with a C curve MCB. the possible fifth option of replacing the cabinet altogether for a larger one is not practical due to other constraints. Have I missed any obvious options please?

thanks @ProDave yes - the electrician I had lined up could not do the job with me and recommended that I got the inspection done instead. so I am permitted to go Meter -> Henley Blocks -> Distribution Boards * 2? I thought I might be required to use particular tails to go directly from the meter to the distribution board without a break.

Hello all I'm wanting to export from the meter to a second distribution board in a garden room. Cabling is long since in (SWA) and the building inspector has been around. The BI's dominant issue relates to me taking the second supply from the main distribution board, downstream of the main breaker. The distribution board has three RCDs in it, two were factory supplied and serve the MCBs for the main house. The third is a time-delayed RCD taking the SWA cable for the garden room. Selected with the advice of this forum. the issue on the building regs report is that I should have either (i) used a 63A MCB with a bus bar; or (ii) used manufacturer links inside the distribution board (i.e. i've used different wires, same gauge, different flexibility, from the two RCDs that were factory supplied.). Two challenges I face: Wylex don't do 63A consumer MCBs; and don't sell separate links. I can find some on eBay. I wondered if it were better to put a second small distribution board for which I can get a 63A MCB. If so what are the rules for exporting to a second DC that's next to the first? can that be directly from the meter? via a Henley block or maybe direct links to the first DB? If the latter, do I then have the same problem in needing to match manufacturers? thanks in advance Justin

it's possible that there is a valve of sorts but if it is an NRV then it's pointing the wrong way! the allen key is used in commissioning. the commissioning steps require that the machine is left to sit for a while then a series of venting cycles via cracking the socket bolt. I pulled a vacuum down as low as I could last night, then turned off the valves. It was holding for a couple of hours but over 24 hours I am almost back to zero (still below). all the joints are as tight as I can make them and no visible loss via bubble tests. I added some leak detector a few days ago but I suspect it all got evaporated by the vacuum.

it was 1986 so not quite 40!

I remember the gas laws. Boyle and Charles ? A level physics nearly 40 years ago so I'm probably wrong.

thank you, I am used to recharging on the low side (for my GSHPs and car aircon) but in this case the only service port is on the high side (the low side does have an odd vent port too, you take the cap off and there's an allen screw underneath that opens the valve, like the back of a brake. No schrader here and too big a hole to fit one, it looks like). So my plan is to pull a vacuum and vent the current propane charge completely and then charge by weight. Annoyingly I only have long hoses, spanning 3m in total.

Thank you. I'm never really sure what those saturation charts mean nor how to use them. Is the relationship with the temperature of the gas or the temperature of the compressor? I assume it is the gas (ie ambient temperature when everything is off). It's also not clear to me whether this is like r12a and needs to be recharged via the circulation pressure rather than into a vacuum. It may not matter much given the boiling point is so low. I did try adding some r12a (isobutane +propane) using the same method as I use for that refrigerant (compressor on). However this just refilled the can! The vendor is unhelpful.

thanks dpmiller. there is no immediate surge of heat. it's a gradual warm up of the outflow pipe and nothing from the indoor unit.

have been running the compressor for an hour as a test. outlet temp is 30C. inlet temp is 15C. but nothing useful coming out of the indoor unit. so it seems the outdoor unit is doing "something". but perhaps not enough. and the indoor unit ... not sure what it is achieving!

perfect. many thanks!

very neat @joe90. in my garage the sockets are on the roof joists as the walls are all taken up with racking. wiring is stapled to the joists or through the air (above head height) when traversing.

thanks for that. v. interesting. when you say 13bar (hot) does this mean when the heat pump is set to heat mode? If so then the pressures I am seeing look more or less what would be expected. I will have a look at the compressor again but from memory the inlet valve has no service port at which I could test, so outlet pressure was all I had. appreciate that propane is flammable. the concentration has to be quite specific though: above/below the range it is not ordinarily flammable. from you last para do I take it that there's not likely to be awt wrong with the indoor unit? the outdoor unit is warming the discharge hose. feels like high 30sC cheers!