HughF

I only pressure tested it because I could... a vacuum down should be quite OK if you're not messing about and modifying the linesets.

I used welding argon and a ‘borrowed’ nitrogen regulator to pressure test mine, before vac’ing down to 500 microns (I’ve got a testo gauge) I don’t think anyone should be doing mini-splits, f or non-f gas, without these basic tools tbh.

If you’re in Dorset, I’ll lend you my gear to vac down and test. You can buy r290 off eBay.

C20 for my 9kW unit. Stuff it on a c32, it’ll be fine. I ran mine on a 13a plug for a few days so it’s hardly a big deal 🤣

No such thing as a half day job.... unless you're a plumber or electrician.

Time and materials, It's a days work, £350/day is going rate...

I've patched the cracked asbestos with sealer for now, and the water is no longer coming in... Box profile seems a sensible option, or even regular corrugated. I expect I'll have to run anything past the landlord to get their approval. Ice and water shield is a self-bonding roofing felt underlay that's used in the US underneath felt shingles. Usually on the first few feet of roof, to prevent ice dams forming. It's like incredibly sticky, super wide, super flexible, flashband. https://gcpat.uk/en-gb/solutions/products/grace-ice-water-shield

I'll try and calculate it once I've measured my pipe length inside the house. I know I've got 15m of twin 32mm underground, so that gives 25ltrs ish... Probably close to 50ltrs I expect?

The background: I've lived here all of my 40yrs, my dad built it in '72 from demolition materials. Parents had an agricultural tenancy under the '87 act, without succession rights. They died last year. I've been there for a year on an eviction notice, now have a new 3yr lease to allow me to stay and carry on tidying up the 10 acres of scrap that my dad accumulated, and I'm obliged to clear as executor. In the meantime, I need to re-roof the house, as the old roof leaks, and I'm responsible for repairs. The requirement: Cheap, fast to fit, light weight, good for a shallow pitch The options: 1. Box pan tin in ral7016, over battens, new felt. 2. Sark the roof with OSB, get torch on felt applied. 3. Go straight over the rafters with insulated box pan tin. 4. Sark the roof with OSB, apply grace 'ice and water shield' to the whole roof, apply felt shingles. I've used 'ice & water' before and it's amazing stuff. What would you do? My concerns are that option 1 would be too noisy in the rain.

That makes sense, but also sounds like a complicated plumbing mess that I don't have time for at the moment. Struggling to keep on top of the rest of this renovation project, day job, and clearing a 10 acre site of scrap...

Delta-t 5, pump pwm set to auto. I don’t get a delta-t on heating as my connected emitter volume is small compared to the size of the heat pump, it’s short cycling the compressor quite a lot (probably 20% duty cycle), but it’s not costing a fortune and the rads are always warm. A combination of a couple of fan coils being out of circuit, and the ufh not hooked up yet.

Same as my setup, rads sized for 45deg, open loop, pump runs whenever there is a call-for-heat. Thermostat does a nighttime setback, rest of the time it’s a hi-limit stat which with the current weather comp settings, it never reaches. I’m short cycling like mad, but it’s not costing me the earth and the house is warm. Shame the heatpump doesn’t have a wider modulation ratio.

DHW update, the 1m2 coil is no issue whatsoever. I can recover the bottom half of the tank from 20-48.5 in about 20 mins, whilst pulling around 2.1kW off the mains. Getting good delta-t across the coil.

If you ever want to cool in the summer, you should definitely have your pipework insulated.

I Insulated all the primary pipework to the cylinder cupboard, and will continue to insulate as much as I can whilst the ceilings are down. Fully insulated from the ashp to the cylinder now, close to 25m of pipework.

Just done a retrofit in our 100m2 end of terrace, 1946 build, replaced a 40yr old baxi back boiler with single panel rads. Sized the rads for 45deg@-4, so far so good. We’re upgrading the windows to 3G, insulating the suspended floors and doing some IWI on some troublesome walls. Early days yet but so far so good. Should work out a bit cheaper than gas I expect, as we were running about 65% efficient before on the old back boiler.

Siemens programmable room stat has been in for a week, 17 deg setback from 23:00-06:30, 21 the rest of the time. weather comp is 37@15, 47@0 Seems to sip electricity in this damp but not too cold weather and the residents haven’t frozen to death. UFH to get running in the extension now, currently just running a few rads and a couple of fan coils.

Ok, this seems a reasonable strategy as I’ve already plumbed up the system and didn’t think to add any zone valves in the already cramped airing cupboard. I’m thinking ufh stat with a slab sensor, driving the mixer pump and a relay to short out the call for heat. Then the rads will come on with the ufh, but not the other way round (because of the lack of a zone valve on the heating circuit)… set the blending valve to a sensible low figure and just let it slowly charge up. I’m planning on going to octopus on their HP tariff.

Yeah, different set of regs iirc…

I tried to push my wife into having air-air but she wasn’t having any of it and wanted to stick with radiators…. I think she was put off with how noisy my cheap r290 mini split is at another property we stay at.

My friend (m&e project manager on the embassy refurb teams) has just done his f-gas as he’s basically spending half the year doing daikin related stuff. He’s got an engineering degree but no other vocational training (nvq etc). If you get the c&g one, it doesn’t expire. Only really required if you want to fit splits, or air/air… Monobloc air/water doesn’t require it, obvs.

Weather compensation set, timers set, analog stat wired in (for now)….. we have heating and hot water. Once my programmable stat gets wired in then I’ll switch the timers off and use the stat to take care of things. Doesn’t seem to be running up my smart meter too fast, even with the short cycling that I’m experiencing in this mild weather, with only 5 rads in circuit and the bottom of the weather comp curve set to 37… It’s probably a bit too big by a kW or so, but I guess it’s better for it to be ticking along in the middle of it’s modulation curve than running flat out. Tech note, if you plan on using it like a system boiler and just rely on the pump in the unit, without a buffer or header, you need to change the pump settings from ‘demand’ to ‘normal’ , otherwise the pump will stop when the buffer/flow sensor reaches temperature.

Yeah, I’d advise going for two ducts if you ever decide to do something like this…

And fitted…. Not yet wired as the electrician is doing his thing. They have a thermal switch that turns the fans on at 37deg flow, should work just fine as the bottom end of my curve is 38 degrees iirc.