jpadie

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!

superb. will look out for them and maybe even swap them out the next time I have a free Sunday. I didn't like the jaggedy edges of the last lot either!

job is done, but i am eager to learn - what pattresses (for surface applications) are less hated?

Hello all I have a small mini-split R290 heat pump in Surrey. No heat being expelled at the indoor unit but the larger hose leading from the outdoor unit is warming. Probably to c 35C - I will measure today. I don't often use the heat pump after commissioning before the Summer (it worked then) but have needed some heat the last few days! I'm not sure what the pressures should be with R290. Compressor off I am measuring 5bar at ambient 9C. Compressor on after 5 mins, the pressure is 5.2bar. After 60 minutes the pressure increases to 8.3 bar. the vendor support has been less than marvellous and ducks the questions about target pressures, recharge steps (i.e. into vacuum or not) etc. the total charge is 0.32Kg for a 4.5m hose run (each way). can anyone help with the diagnostics? My guess is low charge as one of the flare joints is greasy (the propane odorant perhaps) - however the flare joint is supposed not to be torqued up too heavily and it is pretty tight (no movement with a. 10" wrench and moderate force). and if this is a low charge scenario can anyone help with target pressures at ambient and other info useful for recharging? I could vent the propane and recharge based on weight of propane but that seems unnecessarily wasteful. lastly (for a non HVAC engineer) I'd appreciate some guidance on how to "unleak" flare joints! These are factory made joints by the way. thanks in advance Justin

I'm using some Screwfix surface mounted pattress boxes to add some sockets to a ring main in the garage. These are they. The manufacturer data that came with them says to use rubber grommets for the knockouts. But LAP don't make any such grommets and I've not idea how they would fit to the knockouts for flat cable. Any thoughts on these? Are they a regs requirement? Could I just fill the 1mm gaps around the cable with silicon or another filler? I think the plastic is far weaker than outer insulation on 2.5 t&e so I can't see abrasion being a big issue.

I am still on the fence about this! I started building a bigger door out of ply and found that every board had warped beyond where it would straighten up if clamped to a straight edge, glued and pinned. So off to Wickes to buy a cheap premade door. Which obviously cannot be matched for the small cupboard. So 'sameness' is no longer a criterion. I'm thinking next of maybe making a hidden door with double usage as a book case.