JohnMo

I am in the camp, you change stuff at the planning stage, never ever after you start construction. One small change leads to 10 unforseen changes, each adding cost and delay. So my answer is follow the plan. Not sure that is correct, your plans when approved form what is legally agreed scope of work. Any deviation needs some approval, your planning agreement will say that. So minor or major change requires, a document trail, possibly revised approvals.

Think if you mix with Agar Agar, the solidification process becomes more repeatable and repeatable over time

Not a good material, as when in a saline environment 316 or 316L suffers pitting corrosion especially at or close to 60 degs. So you really need super duplex or even titanium. So not cheap.

As you say you can't help some people, they are on a path of knowing all, while knowing nothing. He possibly will get a prorated bill (for his time in the flat) based on his future usage, back dated to the time took over. That will teach him!

No not correct. You can get long cycle times, but you have to run it differently. Long runs will decrease gas consumption considerably. You need to think of using your floor more as storage heater. You fill it with energy then switch off the heat source, allow energy to deplete then recharge. That is what a simple thermostat does. Your smart stat may do that for you, but suspect it won't as it will want to run in TPI mode, not in hysterisis mode. This is what my heat pump did last night (boiler does the same but cannot give a pretty image). It was supplying around 6kW against about 1.2kW heat demand. It ran for a long period, because I had allowed the floor to deplete it's energy. All controlled by a simple thermostat. The yellow bit is kW, the red line is flow, green line return. Purple is outside temp. The long green line after the yellow is the combined flow and return (pump stays on). The spike is DHW at about 6.30am. The gap in data was the modem rebooting. Previous night for reference

You need UFH or fan coils

Heat output is related to overall floor surface temp and room temp. The close they get the lower the floor output. Further apart they are, the more the output. I run the circulation pump all the time 24/7. But control the heat input so the boiler or heat pump can cope. I have both and both, and both are oversized for heat demand - just like @Super_Paulie boiler is. That fine, but if the boiler output minimum is more than that, the boiler cycles. @Super_Paulie changes flow temp, boiler runs until floor is heat soaked. Boiler has little or no space to add more heat. Runs a short period stops a short period repeat, as boiler tries to stuff more heat in, but cannot. Imagine the floor is a battery, stick on charge, charger runs for a long period to get battery in a charged state. Then blips on off all the time it's connected. If your floor isn't giving off the heat equal to heat supply it's just the same. Messing with flow rates isn't going to make it better, you need to allow the floor to dump some energy then recharge it..repeat. At the moment the boiler is trying to do that, but not doing very good job. It needs assistance and a simple thermostat is needed or use what you have, bring thermostat down to 21 and see what it does.

I've a strong suspicion you are just going around in circles. You change lots and still have shortish cycles as you dump more and more heat into the floor. You need to allow the floor to buffer heat, then STOP adding more heat. Your current approach is like driving a powerful car against a speed limiter. I'm My approach is set thermostat at 21 to force start boiler. Let it run chasing 21 for about 4 hrs, then reduce thermostat to 20.5, for an hour or 2. Most the time the boiler switches off when the thermostat is moved to 20.5. Then set to 20, boiler switches off. Once set to 20 the floor stabilises and you get some overshoot as the floor releases it's energy. Our heating stopped at 7.30 this morning and by 11 the house was sitting at 20.7. Depending on heat loss, area and depth of screed you may need to heated once or twice a day heats. But it gives a huge heat sink for the boiler to work against. In reality excluding solar gain we have less than 0.5 Deg fluctuations in temperature.

Get some solar PV, they will supply the energy for free during most days

Your treatment unit would become a storage tank. The system uses aerobic digestion, switch off the air it would go anaerobic. So you have turned your unit into a sh@te storage tank, not a treatment plant. Would likely get carry over, of untreated sewage to soak away.

Yes - most the noise is pushed forward by the fan. You don't want to install with air pushing towards a wall. You get air recycling of cold air coming back round and that reduces CoP and changes the defrost onset temperature for the worse

Obviously your boiler link will be deleted following ASHP install. I would heat from borrowed house circulation water. Let thermostat open valve only but not call for heat. Or you will end up having a small zone dominating how the heat pump runs, which isn't good.

I really wouldn't go more than 15mm, you just don't need any bigger.

This is what they have said 3x If you are unable to obtain an MCS certificate for your installation, we will not be able to offer you an export tariff at this time. We are in the very earliest stages of trialling a solution for non-MCS customers. If you'd like to hear when this is available, pop your name and email down here: https://octopus.typeform.... Not sure if it's an issue with a smart meter that has no signal? Or another issue. Have used the link they provided each time and it's just repeat conversation.

Did you get it working?

What do you structural drawings say?

If you are operating single zone why the actuators? You need a pretty dumb thermostat nothing with TPI control just on or off, ideally with adjustable hysterisis. With UFH the thicker the screed the smaller the hysterisis you need. Otherwise you get big swings in temps - under and over target room temp. If you need a thermostat at all depends on how you intend to operate. Weather compensation? Fixed flow temp? Batch charge during cheap rates?

Tried 3x with octopus without MCS just not interested, said bluntly no each time. Have full structural drawings, electrician sign off and MCS install cert for battery. Can tick everything box - but big NO. So don't bank on it, in any calculations.

There is a school of thought that ASHP should be sized at least 10% bigger than design required, just to help cope with defrosting. Living with a heat pump 100% oversized (I do) isn't an issue. You just operate as appropriate. Doing weather or batch charging, I have done both with zero issues. Most situations an ASHP is designed for -3 degs. So no where near the oversizing required for the top of Scotland, where you could be designing for -10. A larger heat pump also seems to bigger range of modulation than a small one from what I've seen. Not sure that is true. If you are air tight and can provide proof of it and proof of other improvements, not sure there is an issue. Most of the issues are down to assessors or so called designer with no clue. Or owner thinking they know better because they like a house at 16 degs. It's tax payer money (£7500) so needs to fit for purpose if you sell in two years time. Then there is homeowners wanting to operate as they did with the gas boiler, short on time control over multiple zones. Most the buying public really aren't ready for a heat pump, they have been fed on rubbish information for years, saying zones good, high flow temps and short operation windows are fine. So running at low flow temperature for long periods just sounds wrong (and so will be very expensive). Heat pumps as currently sold, are a rich man's play thing, even after grants, the prices quoted to install are in the general daft and well beyond the general person.h. Building well, in the first place, fixing issues with poor housing stock (insulation and airtightness or bulldozer) are the first fix. Second is education of installers and general population (most would have zero interest in both categories). As @Roger440 pushing people into energy poverty isn't an answer. Rant over

kw or more correctly kW. So say 2kW for 24 hrs is 48kWh, so a big uplift in cost. This also goes away from the statement of direct heating is rubbish. So if everyone goes this path, grid comes to standstill on a coldish day.

In 99% of households this just isn't required, just heat the water to 50, it's no longer an issue anyway. Most houses run on chlorinated water (like or not), if you have an unvented system also, how does legionella get in? Is that a real comment, add in loads of defrosts at anything approaching zero, sounds like a good system performance will prevail - NOT.

Some parts of UK cities provide distributed heating systems knot many), many countries also. A new housing scheme should be built around this approach, not some ad-hoc boiler or heat pump decision. CO2 charging mechanism already exist within the tax system and have done for a decades or so.

I just said a way So a new gas appliance has the same playing field as a heat pump. I would apply those limits to ALL heat pumps also. R290 can pump out 70+ degs, but at a CoP hit so why allow it.

Exactly, if you don't want people to use direct electric heaters or gas, slap 100% sales tax (plus vat) at point of sale on those commodities. Zero tax, at point of sale, on those items you want people to use. Scrap the grants. I would go further Force manufacturers to limit temperature output in heating mode to 45, and hot water mode to 60 for all heating appliances, sold to UK market. Stops use of S and Y plan overnight. Heating mode would made via Opentherm and/or weather compensation only, both methods are to be provided as standard, this would include all heat pumps. If manufacturer has their own version they can provide that as well as the minimum required standard of Opentherm and WC. Hot water cylinder below 180L minimum coil size 2.5m² and above that size a min 3m².

Cycling is part volume and the other more critical is having somewhere to take heat away - the heating system. An example is trying to push low flow temps through small radiators, they just don't have enough heat transfer area to transfer the energy generated to the room. So heat source cycles as that is all it can do. In this situation you would install radiators with about 3 to 4 times the surface area and the system works. Your system is having a first cycle helped by having to heat a bigger volume (volumiser). But you are not really dumping the heat to the house, I suspect the heat loading in the floor is running full, the house heat loss is way smaller than the continuous heat being supplied. The heat flow through your UFH is about 1.2kW per loop. But depending on room heat losses a lot of this will be recycled water, so may not all come from the boiler. So 4x loops at 2.5 l/min, so y The Salus actuator will target that dT. Suggested action Leave system as is Manually switch off boiler or UFH until house cools to about 20, then switch boiler or UFH back on again see what happens. If you get a long run your solution couple simply batch charge the floor - use as a storage heater.