Beelbeebub

Yes, too early in the morning!

I think so. My guess is that vailant are a boiler company so that thinking is sort of built in to how they view things, and the (electrical) energy consumed by a boiler is not really relevant to the final heat output.

Or simply cop=yield+1

Good point about the mice. We are 5 floors up in an attic, but the little blighters do get about.....

I know everyone says "don't use speedfit/Hepco plastic pipe because it restricts the flow, use copper" But if I was going to use 22mm copper for the primary feeds, what about using 28mm plastic. The internal diameter of the 28mm plastic is a little bit more than the 22mm copper. 22mm copper is about the same per meter as 28mm plastic but I may have some long and difficult to access routes where pulling though a (pre insulated) length is pipe is easier than jointing then insulating 3m lengths in somewhat awkward conditions. Any thoughts? Should add, I was planning on doing the final runs off the primary in copper, 15 or 22mm to suit. This is just for a run from the unit outside through a loft space and possibly down a stairwell.

Which is why mixers should only be installed as a last resort. The only reason to have a mixer is having two zones that need to run simultaneously and one is significantly higher temp than the other. The classic example being UFH downstairs and Rads upstairs. Hence my musings about multiplexing.... does it allow for "seamless" switching between the flow temps? I seem to remember someone saying their HP would stop and then restart at the changeover. If it simply ramped up or down then it might work. You could mod your current setup by fitting a 2 port valve on both the rad and ufh loops (or a 3 port depending on your pipework). Then setting your blending valve to be the maximum safe temp. In UFH mode, the low temp is output, the valve to the UFH is opened and the pump is turned on (this bit is optional, might not be needed). The blending valve will go 100% hot trying to achieve it's set temp which is lower than the flow temp so you will effectively have an open loop. When you switch to Rads, the UFH loop is closed off and the rads opened. Just kicking ideas around! not actual advice!

I'e be really interested if it was possible for HPs to time multiplex output temps for two zones (UFH and rads). If the system simply switched output temps setpoints in synchronization with a 3port (or 2x 2port) valves that diverted between the two zones I don't see a technical reason why it wouldn't be possible efficiently. I also wonder if you could do defrost cycles by switching to DHW coil. As long as you had a bottom biased coil, you would steal a few degrees from the probably already cold bit of the dhw tank. You would then replenish the heat as the last part of the defrost cycle as you rampee back up to temp.

Yes, you would need a direct UFH mainfold without the mixer and pump or at least a minimum sized always on zone

Agreed, but I don't think the minimum volumes are as high as people think. Irrc grant/Chofu are happy with a 30l volumizer regardless of the size of the rest of the system, which implies the min volume is around 30-40l. 15mm UFH pipe laid at 200mm centers is about ½liter per m2 So a small house with a 60m² footprint and UFH only on the ground floor would be nearly 30l before you look at upstairs rads, primary pipework etc. Unless it's a very thin system, UFH adds considerable thermal mass as well

but also more water volume for defrost so less need for a volumiser!

We had a high pitched wail, loud enough to be clearly heard inside behind double glazing, from a nearby school boiler (actually the blending valve) for about 3 years. It was loud enough to be annoying to people living 200m away. Initially it was whenever the heating was on - so almost constantly over the depths of winter. They progressively managed to reduce it until by the 3rd winter is was a "honk" when the system started up. They seem to have finally sorted it as it's been quiet since. But the fan exhaust is clearly audible outside when it's going full blast.

Is there much of a downside to having too much UFH pipe? The capital cost is fairly negligible.

I'm shocked the Telegraph would twist the facts to suit it's agenda Shocked!

Exactly, unrealistic noise requirements are a defacto ban. Maybe you should set up a speaker and run it with white noise at the noise level the HP will generate and see is anyone complains. Then when the planning objection is "it will be too noisy and disturb people" you can say "it hasn't yetx 😁

I think there is a public perception they are noisy. Maybe they are refering to objections to planning that cited noise concerns? Noise is almost always mentioned, along with they don't work when it's cold. There are aspects of the "culture war' bleeding into this. A well know YT building channel is not keen on them and recently visited a terrible install that was making a racket. It was down to a failed bearing due to poor installation and maintenance and was obviously not the normal noise. Yet he did a YT short "people tell me heat pumps arent noisy! Well listen to this!". And underneathg5the fist comment was about HPs being for "the woke". It's almost like the Trump supporters proudly tuning their trucks so the can be "rolling coal to own the libs"

Lifting the size restrictions would help with noise reduction. Getting rid of the boundary requirements is also sensible. Maybe some sort of scheme where the noise aspects are waived if the unit has a pre-approved certification. That would involve testing the units in a set of scenarios (including worst case situations with reflective surfaces) so it can be deemed to be acceptable in any installation. If a HP only punts out 35db at full chat then it can't really be an unreasonable nuisance.

I think this is important. I think historically alot of installations have defaulted to a large 4 port buffer to prevent the installer having to think too hard about the rest of the system. Whilst it does allow the HP to run even if you balls up the other side of the system the cost is the system will run inefficiently in all but perfectly balanced conditions - and if you can achieve those regularly, why bother with a buffer?

You can usually unzone UFH fairly easily by unclipping the actuators (normally on return). The zones are then always on. You can adjust the heating to each room by tweaking the flow rate. I unzoned my house (admittedly fairly open plan) and the UFH runs much better. Also a ceiling fan works well to move the warm air down to ground level. We havea 4.5m high lounge with a mezzanine. When we ran the wood burner we would hit 28C upstairs and 23 on the sofa. Now we turn the fan on and downstairs gets warmer immediately

It does need to be made clearer that "more efficient" doesn't necessarily mean "cheaper". Unless you HP install is terrible (and historically some have been) you will almost always be ahead in terms of carbon emissions. If your first priority is dropping those, then a HP will do that. But in order to actually be cheaper, especially with the higher up front cost of a HP, then your install does have to better than has perhaps been typical in the industry.

Most* monoblock HPs have a pretty powerful built in pump. For example the grant/chofu HPs have 10m or 12m head. It's unlikely he will need a additional pump, those are only needed for very big and complex systems. In fact if he has UFH fitted downstairs he may need to remove that pump and run direct. Historically, installers have often put big hydraulic buffer tanks in, which do need additional pumps, but the thinking now is to run the systems with a few "bells and whistles" as possible. The ideal is a single 3 port valve and no zoning. If (big if) his heating system was designed with a 55C flow temp, which was recommended in 2019 but not an actual requirement then the HP should be able to run at about 45C to give a similar output on those rads (the mean flow temp of a radiator spec'd for a boiler flow temp of 55C is 45C because they have DT of 20C across the rads. A HP has a smaller DT of about 5C so will have a Flow temp of 47.5C for the same mean rad temp of 45C) One test would be to turn his boiler flow temp down to 55C (or lower) and see how he goes. If his house is nice and warm with a 55C or lower flow temp, then he probably doesn't need any significant changes to his heating system. *I believe the Samsung Gen6 monoblocks use an external, customer supplied, pump.

I think it's inevitable we are going to end up with boxes outside our homes One interesting concept I've seen for high-rise properties is a central brine (glycol) water network drawing heat either from ground source or from big air exchangers in central location. This brine is piped to each flat where a small water to water unit does the actual heat pumping using the communal external heat exchanger. Sort of a hybrid between a whole building heating system with heat meters and the individual units with multiple external boxes

The capacity and efficiency of any HP is constrained by the airflow and the airflow is constrained by the noise. External HPs can flow alot of air at a low velocity (for low noise). The internal HPs are limited by the ducts. Drilling ever larger holes inthe wall becomes a problem. Even the 180mm ducts are a bit too big really. 150mm or even 125mm would be easier, but then the power or efficiency would be lower or the noise higher. Maybe if you could have a low powered, high efficiency device that was easy to install (say single 150mm concentric duct but only 1kw) and it was really cheap (say £250) you might have a situation where you just installed 2 or 3 in a room. Imagine this but with a small HP (and better looking)

I think by outside. They just defrost and the water falls out the bottom. If the outlet blocks it just overflows outside which is less of an issue than inside!

Yeah, but the condensate from cooling is a slow steady trickle. The condensate from defrost is a sudden high flow as all the condensate from the last 30mins or so is released at once. It's not an impossible problem, but I can see it being very tricky to handle, plus the a2a monoblock wouldn't have much stored heat volume. A a2w unit already needs a fair volume of water to store heat for defrost and this unit would have none. The defrost might have to be a straight up electric trace heater on the coil, which would impact COP. But you're right, the plumbing of a2a split units is a bit beyond the average DIYer simply because of the tools involved aren't worth getting for a one off job. That is the potential advantage of a2w based systems, they can be tackled with fairly rudimentary skills and the complex refrigeration side of things is compleatly "black box" sealed. The problem is the system design of water systems is more complex and even professionals cock up. Maybe if we used fan coils more. They would remove alot of the issues associated with too small emitters and are pretty simple devices themselves. If you could buy a 3kw fancoil for about the same price as a 3kw radiator that would be a big step forward.

I was thinking handling the melt water inside and having to drain it out through the wall might be problematic. At least moreso than simply letting it drop out of the bottom of the unit into a soak away.