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I've no questions, but with much thanks to those who documented their own Willis-based UFCH and in the hope that it may be of interest to someone else, here's a photo of my Willis heater UFCH which is now up and running on a temporary supply here in France. Sadly, due to French liability laws, I had to resist installing it myself and use a local plumber, in order to obtain a 10-year warranty. I'm not sure if it was the Willis heaters or the concept of 15mm pipe (unknown in France) that intrigued him most. The pipe disappearing top right heads to an expansion vessel. The insulation will be redone and completed more tidily once the room is finished. Once the electrical install is finished later this year, the heaters will be controlled primarily by Node Red running on a Raspberry Pi, via a Shelly Pro 4 PM which will also double-up as a backup controller in case the Pi goes down. The Shelly will in turn control the contactors that will switch the power, via a Hager 60060 load-shedder. The load-shedder will temporarily switch out the heating (and, if necessary, the hot water) when the total load approaches the 52A supply limit, which is likely when cooking.

It's been a while since I was here. "Life issues"...! Been using the willis heater set up for a couple of years now, and it's proven somewhat more expensive than anticipated, partly down to the electricity price rise fiasco. So I'm now looking to replace the 2x 3kW willis heaters that I had set up feeding the manifold for 150sqm of UFH. More here on my setup: 1) Presume the feeds from ASHP will be plumbed in directly to the manifold feed and return pipes, i.e. no buffer tank? I may leave the willis heaters in-situ as a backup. Probably looking at running the temps between 30-40c for 2-3hrs per day (bit more when it's really cold). This is current setup: 2) Siting the ASHP - the closer the better, but as I'm probably looking at around a 11kW unit, these can be the 'double stacked' types like this, and rather obtrusive to have this next to my front door (closest to plant room). I could site it a bit further out (approx 9m away from entering house) out of view and lay the pipework in the french drain surrounds the whole house - If I had additional insulation to the already insulated pipework would that be an option to consider for an quicker and easier install or would the heat loss still be an issue? 3) Can't afford to buy a new ASHP, so looking to get a used/reconditioned one. What are the best places to look at apart from ebay? There are some installers who are selling older but new models that come with warranty still, but any other sources I could consider? 4) What should I look out for in a used system? Obviously need to ascertain whether it still works, why it's being sold etc. Ensure that there are no refrigerant leaks, pump works, control board works... 5) How much should I look at for an install? I'm happy to dig any trenches, get cabling in by my electrician and do any preparation work to minimise cost. Thanks in advance for your feedback/suggestions!

I’m confused by the data that my Shelly 1PM’s are giving me. Today we have used around 36kWh of electricity, the vast majority on the Octopus 5p rate between 00:30 and 04:30 as you can see from the images below. The bulk of that consumption was the Sunamp: and the Willis heater: According to the Shelly app the Sunamp consumed 13.32kWh but the Willis heater consumed 14Wh. I’m assuming the 14Wh should be 14kWh. Does anyone know why this isn’t showing correctly or is something else afoot?

Right, so following on from my blog entry here where I discuss using Willis heaters to heat up my UFH (https://forum.buildhub.org.uk/blogs/entry/680-temporary-heat-source-for-ufh-willis-heaters/ ) I'd initially tested them earlier in the year when I'd set them up and then only in the past 4wks really started to use them for some evening heat in the house and they did their job pretty well (not turned on all the loops yet as there are some rooms that aren't completed yet (north colder part of house). So only switched them on manually for say 2-3 hours each day. Yesterday one of the heaters started 'making noises' that he was not happy, so I switched that one off and left the other one to run. Then today the other one also decided it was not happy. Video below, with aforementioned Willis...'making noises'. 20201112_164008_001.mp4 To me it sounds like a kettle that's trying to boil/simmer with not enough water. I'm suspecting it's scaled up already in this short time. There's no heat coming from the outlet pipes at all and the heaters themselves don't feel warm either. I still have pressure (1.5 bar) so I don't think I have a leak anywhere and no water in pipes. The manual bleed valves indicate there's water in the manifold at least. Any other ideas before I start dismantling the buggers as there's at least 4 compressions I have to bugger about with which were a pain to seal initially? Resident willis heater experts @Nickfromwales, @TerryE ? :-) TIA!

After much heart ache, time and tears I'm looking for some advice from you guys regarding my heating system, which is completely separate from DHW. I plan to directly heat my slab with ASHP using Willis heaters as back up. Hydraulically does this look ok? Input much appreciated.

After various delays, the time has come to get some heat into the house, and as there have been a few on BH that have gone down the route of Willis, thought I would give it a go as well. Hopefully others will find the blog entry also. Background: Renovated (3G passiv-rated windows, 120mm EPS EWI, 400mm loft insul, MVHR - not tested air leakiness yet) / extended (175mm SIPs) south facing detached house, East Kent 156sqm of wet UFH in 100mm concrete (with circa 300-375mm EPS insulation) 130L in UFH Wunda 12 port manifold (The heating valve on the manifold operates in the range of 30-70oC) Wunda wired room thermostats for each room (but probably won't use for this temporary setup now) 12Kw eDual for DHW (not to be included as part of Willis setup) 12Kw Sunamp for DHW/UFH (not to be included as part of Willis setup) 3.8Kw PV (potentially have further DIY grid implemented later on) Not looking to cater for worst case low temps as at these times will just plug in some extra heaters: I originally ordered 2x 12Kw heat batteries for DHW and UFH. Total reliance on the PV in summer and then off-peak grid in the winter. An all electric approach initially without ASHP. Not keen to spend £8-10k on an MCS installed heat pump to get back an estimated / possible £8-10k. Installers seem very vague on the RHI returns and if I have read correctly, I will have to be metered in order to qualify in any case (as have not lived in the property previously). Since the house will be far above buildreg stds (but below PH level), I simply won't be using the amount of expected input that the installers calculate - hence I won't be getting back the cost of the ASHP supply and fit install. So most likely won't go down the MCS route, and if I were to install an ASHP, it would be a cheapy from fleabay. Having excluded using an ASHP, I learnt that Sunamp were testing various units late 2019. But typically with Sunamp, after continued confusion on their part as to what ASHPs they may have tested/not tested/will be testing soon, I've made the decision that I can't want any longer on their input. So for now I will leave the ASHP option until later on and perhaps consider a propane unit (e.g. Vaillant ) when they come online on a non-RHI basis if I can get a decent install cost. Willis Heater approach So therefore looking to heat the UFH with 2x 3Kw willis heaters in order to progress with the internal house work. Thought I'd add some info on here as a lot of people like myself aren't familiar what they are. They originated out of Ireland and still much in use over there. They're essentially external immersion coils and instead of sitting inside a tank are simple external electric units - AKA "Willis jacket", "standard sleeved immersion heater"," inline electric heater". Googling should get you something like this: Item Weight 1.15 Kg Product Dimensions 30 x 9 x 9 cm I have tried to get plumbers interested in rigging this up, but they're either not interested or have told me it's not possible/don;t know what a willis heater is. I've managed to plumb in all the Hep2o in the house, so hopefully this won't be too much of a bodge. @TerryE has kindly discussed his set up which is pretty impressive with his DS18B20s set into the walls etc. I'm no programmer and my javscript is mainly simple web stuff and wanting to get heat into the place ASAP, I just want a KISS approach for now. Perhaps later I will think about having some of it programmed using Terry's Node Red option which makes for interesting possibilities. Get a feel for Terry's approach here: But as I've said, I'm after a bog standard dummies approach to this - seriously KISS: So rather than wiring up room thermostats to the wiring centre, I will for now simply use the Willis inbuilt thermostat and set that to gradual increasing temps from 10oC up to a max of 25oC. A gradual heat increase seems safer in my mind. My only concern is if the Willis thermostat fails and carries on beyond 25oC - up to max temp. Obviously I will have the manifold mixing/blending valve that should restrict temp flow into the UFH also, but is there a further failsafe to consider? Dummies layout. Eventual Sunamp units (for DHW) will be located on left of manifold so having to locate Willis heaters to right and expansion vessel top right: FYI: The immersions need to be turned the other way (so colder water enters the side) Parts list: 15mm copper pipe. The Willis heaters are 15mm so I presume plumbing them into the manifold with 15mm would be okay? 15mm plastic pipe for cold return should suffice I presume? Bottle vents - automatically release any trapped air (like this one). Do I need any and if so where do I place them? Willis heater (ebay has the cheapest) Expansion vessel - 8litres sufficient for total UFH volume of 130L? (like this one) 20A DP switch outlet (for each willis) from a 16A MCB (like this one) . Probably one for each willis Immersion timer (like this one) to be added possibly when I change over to E7 low tarriff rates Will get an electrician to wire it all in for me! Be grateful for comments, suggestions and any answers to above questions! FYI: I'm no way the first person to install a Willis, so here's a list of other users on BH that have gone the Willis way and will know more than I do: @dpmiller: photo / details here @TerryE @vivienz @CC45 @chrisb here @Gav_P - here (Any pics?) Willis instructions: schematic

Currently have a 300 litre UVC ready for a heat pump to handle hot water + heating at a later stage but in the meantime like several others on the forum I would like to add a Willis heater between the manifold flow/return to run our UFH system. System is 3 x 100m loops all to be run as one zone in a 100mm screed. Wunda manifold is installed minus a pump at this stage. Wiring wise 3 core + earth from the stat is in place and power can be added from the plant room board easily. I would like to finalise and order the necessary components so if someone could advise if I've missed anything it would be greatly appreciated... Wilo manifold Pump from Wunda + Isolators Digital room thermostat (recommendations?) Willis jacket + immersion Timing Switch to ensure E7 use Electricians will fit all wiring and controllers but I supply everything. Possibly a 2 port valve as per @Nickfromwales recommendation in this thread but not sure if this is necessary? Trying to keep it as simple as possible at this stage.