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Another big issue with gravity arrangements is that the T blocks up with crud where the F&E (small plastic “Feed and Expansion” tank in the attic) T’s into the heating system. This prevents the feed water topping the system back up, but the tank stays full and you don’t think there’s an issue with it filling itself up ‘automatically’. Every single time I did “old to new” conversions, someone was tasked with popping as many floorboards as was necessary to find the T in question, and every single one got cut out, and replaced with a straight section of new pipe (lazy plumbers just cap the 15mm pipe off and bin the F&E tank ( @SimonD will know what state these get into ). The F&E tank can be full to look at, but be sat there not actually feeding back into the system, so the entire first floor of rads would often be less than half full of water and doing diddly-squat as no new ‘feed’ water getting into the system as needed. It doesn’t take much of a blockage to stop this. Seeing as this thread was just moving sideways, the next thing to do is reverse fill the system and then I think we’ll get some results. As the system refuses to get itself going after the pump change, and the topology makes me think it should, then this is what I think is going on. @jfb, you will need to get a hose on an outside tap and bring it inside. Q: can you find a drain off cock down as low in the system as possible. Let us see a pic of the pumps and motorised valves etc, wide angled if possible so we can see the pipework etc, and under the pump or near one of the downstairs rads is where you should find a drain off. You need a +1 and a +2 ideally for the reverse full up btw, so bribe a mate with beer and send them up the attic with a torch. They need to monitor that tank without deviation. Put the hose onto the drain off and use a suitably sized jubilee / hose clip to secure it on tight as feck. You do not want this coming off ‘mid whoosh’, ask me how I first found this out…… So. Once the hose is on, and you’ve secured it, and it’s connected to the outside tap (or a mains cold washing machine tap) you now have the mother of all balancing acts to perform. You will need to open the outside tap just a half turn or so, so you can see the hose filling with water pressure. It’s not advisable to let this fully equalise with the cold mains as that’s when the hose and clip are going to want to shoot off. The idea is to get this to have more ‘head’ / pressure than the heating system. This is usually noted when the hose on the drain off starts to swell up and start to look like it is about to go pop. Then you open the drain off cock and let cold mains enter the system from the bottom up. Now the fun begins. Have the heating turned on and running, so the motorised valve is energised and open, and the pump is running on its highest setting. You then need to have the attic victim on high alert. You will be back filling the system so the thing to go wrong here is to be filling up the system unaware that the F&E tank is now about to overflow and puke out into the attic. This balancing act is controlled by attic person and hose / outside tap person being on their phones all the way through this purge process, so the moment the F&E tank starts to fill up, the person on the outside tap can speed up or slow down to stop the F&E tank overflowing. It’s fine for the water to get up to the overflow and some escape down it, but this needs to be”live communications” for obvs reasons. If it gets to the overflow, tap person shuts off the cold mains and stands by. Now rope the wife in. Whilst this is going on, you need to vent the rads on the first floor and see if they start letting air out. If the F&E tank T is blocked, then you may not see the water level begin to rise in the tank immediately, so be prepared for that to go pop all of a sudden (as the crud gives way) and then tap person needs to be told to slow down or stop with a bit of gusto. Once rads are confirmed as full of water, and the F&E tank has raised / lowered at least once, then you turn off the outside tap, close the drain off, and go see if all is now working as it should. If this doesn’t get the system working, I will eat everybody’s hats. Issues to avoid: Blasting cold mains water clean out of the F&E tank. Please video this for our entertainment if so. Letting the central heating water get down the hose and back into the cold mains pipe work via the outside tap. Likelihood is that the cold mains pressure will mean this cannot happen, but one to consider. When you’ve finished doing this purge, run lots of clean water through the hose to make sure it’s not contaminated, eg with inhibitor etc. After a day or two of normal operation, you can look at treating with inhibitor and booking a holiday. Hows that sound? One for today and then you’ll be up and running I reckon.

Came very close to fitting 2 in my office and "clean room" in my workshop. Well, the propane filled ones, so no need the an F gas person. Sadly, my "electricity supply" issue means that ill need to go oil for that too. Lots of second hand boilers around at the moment for bugger all money. And easy to DIY. Which is a shame, because this would have been much simpler.

Cheap but noisy, and easy to fit, but just for one room. But buy in southern Spain (prob france too) and they are much cheaper...and noisier. If that was running off solar and battery that shouldn't take long to pay back.

That's the loneliest place in the world . You (we, I) have been told / made to understand that self-building is a privilege. Given to few. And we should be grateful - stop moaning and "JustBloodyDoIt." Self-building is as big a character test as doing a PhD, or handling a long-term relationship break down, or surviving a major operation. A full-on build's knackering. You're among friends here. Don't ever forget that

Ha! Yeah, but prettier obviously. What is that product? I wonder if you could get around the big box of an outdoor unit with a large black roof/wall mounted panel

Quick. Ring up the Guinness Book of Records. Make your claim to be the first person to lower BP by consuming alohol. Hic! 😳

It is on here, if not for any other reason than to get @SteamyTea hot under the collar 😁. But on a tangent, I was talking to my son the other day and I was winding him up by using the term phase change where he insists it's state change. I then explained to him that during school I had 2 physics teachers. One was adamant that centrifugal force did not exist and said the only force was centripetal force and the other would repeat that centrifugal force did exist and it was fine to use the term as long as we knew what centripetal force was. Hope this doesn't now cause a 55 page discussion of the reality of force.

Useful info. I will havea play over the weekend. Is that a thing - Steamy will be along shortly, no doubt, with his cosh.

Exactly the same a solar assist heat pump outdoor condenser, but indoors

The pump is in the hot water cupboard upstairs and I’m pretty sure it is higher than the bleed point on the rads.

Just been told that this is the actual product... fqml1.5m10m6mm---ybs---product-guide-1671023508.pdf Apart from the acousitcs I remain unconvinced of any benefit. (except maybe for stopping the screed from falling down any perimeter gaps) Am I crazy to think no insulation is actually better anyway?

Ok, then the rads upstairs must be where the system shunts air to, and then you bleed these off. That suggests the pump and valves etc are all lower than the first floor rads, and therefore you may not need an auto air vent in the system.

Just had this same enquiry with a project where the clients went with Nordan. They had options for bottom handle, top hinged etc, for folk who are less abled, so I would expect most of the big hitters are able to accommodate this requirement / request.

Clicked the button on the wilo. It made some different sounds for the duration (the display said it was doing the auto bleed). Eventually I stopped it after 15 minutes. Did it a couple times. no automatic air vents on the system as far as I know

Ben I'm interested if you learnt anything about "accessible" windows, designed for wheelchair users, and have any comments. Whilst you were looking into the design, did you come across anything with the handles at the bottom (rather than half way up) to be easier to reach?

Ok. The auto bleed function on a pump is usually just it pulsing / stop-starting to ‘bump’ air around and out of the water circuit. To clarify, an automatic air vent is a piece of equipment that’s installed at the highest point of each circuit, which allows air to be released in your absence. Air comes out, and they they do a little ‘spit’ and then no more water comes out. When you auto-bled the pump, what exactly did you do?

Not quite. Curves for radiators and ufh are different - the output factor of each is calculated as to the power of 1.3 for rads and 1 or 1.1 for ufh, so neither are linear and so heat pump curves aren't either. With the curves, you'll general have a default curve and then you adjust this with a heating curve shift. Usually, a heat pump manufacturer will supply a heat curve chart which provides you with the initial basis of your settings - this can be in the manual or just on screen on the main controller. Against this curve, all you need to do is draw from the x and y axes,which tell you the outside air temperature (usually on x-axis) and flow temperature (usually on y-axis), until you meet the curve that matches your heating system design flow temperature and corresponding design outdoor air temperature. Fire the system up and wait at least 24 hours, or if the house is cold and has lots of thermal mass, it could take weeks for the house to thermally balance out. Then you can look at how the system behaves as outdoor temperature fluctuates which will then tell you what adjustments you need to make to the curve and shifts.

I get that. The indoor units aren't great and people on the UK aren't used to warm air heating. I did wonder if it woikd be possible to make a "radiator" - basically an aluminum plate with fins on the back and the gas/condensate tube sandwiched between. So it would look and act exactly like a radiator (no fans etc) but have the working fluid running through it instead of water. Could be cheaper as it would be a dumb unit but manufacturing volumes would be an issue.

Good point, thank you.

Once compacted it's just very thin insulation, with same thermal properties as thin insulation - it has zero reflective properties without an air space to reflect into. Would use any other insulation than this. If it's first floor just 25mm EPS or XPS.

No practical experience so hopefully someone with some will be along but fill the gaps with foam? I guess you'd want something with a little give in it to allow for movement.

Yes, if by grouted you mean filling the gaps between slabs with dry-mix concrete. That was done a long time ago, and before blocks were laid above FF. Sorry, I should have been more specific, the gaps of concern are around the perimiter, where the slabs run in the same direction as the walls. There is maybe a cm or two gap in places. To my lovely plastered walls below. Not having done this before, I imagined the sreed to be liquid enough to run through the gaps, maybe it doesnt?

That's a good call on both counts. My recommendation is also to have a serious look at the tools out there available - as well as rigs you can knock up with spare timber - that can make your life easier to move and fit materials. One of the things I've noticed is that the trades and builders generally are really bad at thinking things through like this and will scoff at stuff that makes life easier - as a consequence we unconsciously follow those practices. Building on your own takes a very different mentality than a testosterone filled building site with lots of labour available or those who are willing to harm their bodies (I once got laughed at by a builder for putting on some chain saw trousers when I was about to chop down 3 trees). One very small example is atool I bought several years ago was this: https://grabo.com/ It turns lifting plywood, plasterboard, windows, paving slabs, you name it, into a one person job and means you can hold a sheet up to a wall single handedly with putting in a screw with the other. When I first started using it I got giggles from staff in the builders merchants about how I'd just got the vibrator out. Then that turned into how they wished the company would buy a few in for them. I had no idea how much I'd end up using it.

Have the precast slabs already been grouted? I thought the screed layer was often used as grout to tie everything together on precast? (Depends on how it's specified).

WC only sets the ASHP flow temp, and I'm pretty sure it does so using only the exterior temperature. When running perfectly, the higher flow temperature completely cancels out the increasing heat loss as it gets colder outside. Once WC is properly set up, interior temps are solely a function of whatever thermostatic feedback you implement. For example, I have a 10 year old Panasonic Aquarea. I only have the dumb controller without a thermostat. All interior temperature sensing is handled by my home automation system, which controls a relay across the relevant switched live contact. The ASHP knows literally nothing about the internal temperature of the house other than indirectly via switched calls for heat.