Beelbeebub

I think you might be the architect of your own downfall here. The installer might have concluded there is insufficient system volume based on your reports of noisy defrost. The original installer might have calculated there was enough system volume based on the assumption the user wasn't surreptitiously turning radiators off. Hence no buffer or volumiser needed. The new installer would look at the system on his visit and think "hummm... there should be enough volume according to the calculations and my inspections yet the defrost is still behaving like there isn't enough.... There must be something we are missing, best be cautious and stick a big buffer in to make absolutely sure we won't have this problem again!" If you insist on operating the system in a way it's not supposed to be, it's not surprising it misbehaves and if you don't tell the installers you have been doing that, it's unsurprising they struggle to rectify the issues.

The best approach woukd be to "suck it and see" Install it and see how much the sound bounces about. Having worked with noise attenuation (from roads and industrial sites) itvs really tricky. Sometimes barriers can make things worse! It may be the noise is perfectly acceptable with no barrier, then the issue is simply visual.

That should be shutting various rads..... 👀😁

All fair points, especially splicing in an inline mechanical meter then shitting various rads. My musing was more a simple first take device. Before any major work is done, to aid with the quote process. If the pipe work needs lots of upgrades it will.add to cost and upheaval and might male the job less attractive. Better to find out before install starts!

I'm sure it is in a lot of cases. But there is the persistent assumption that you need at least 28mm thought your 1 bed flat to go with a couple of 2000x800 triple fin rads per room (not to mention a 150l buffer to go with your 18kw heatpump). Being able to stick a gizmo on the flow pipe of your booker and go "yup plenty of flow, no need to rip UK the floor or repwmce any pipes" would be a big time saver and eliminate a potential cause of poor performance.

Yeah, something like that and i'm sure there is all sorts of clever magic going on under the hood. If they could make a £100-200 unit, maybe some bt sensors that link to your smartphone like the bt temperature clamps, so you could just clip it on and hey presto you've got the flow..... That would be really useful. Be great for tuning the emmiter output too.

Yes that's exactly what I'm talking about. You could use the table but that only gives you a rough estimate. You might have 28mm pipes heading out of the boiler, but they drop down to 15mm in some boxing before meandering about all over the place. Or, as has happened to me on a boiler system, you think the issue is the pipes are 15mm but it turns out it's actaukky 22 all the way to just before it pops up above the floor and you're fine. Measuring the actual flow has to be the gold standard.

Pretty much. Length of pipe and number and type of bends are the most important. A long straight pipe may have less pressure drop than a short length with multiple 90 degree elbows. Valves that aren't full flow will also have a big effect.

Yeah, but you'd have to cut into the circuit with all that entails. And would only give a single point measurement. For example you could tell you had enough flow in the system but maybe the flow to upstairs was too low. If this could be fitted to any exposed pipe you could go from rad to rad and measure the actual flow availible to each rad. Might only take half an hour to survey a house and say "yeah this pipework is fine" which could cut a load of work out of the job. I did see clamp on no invasive heat meters. These would be really good if it integrated with some room and outdoor sensors. You could basically measure the actual heat demand of the house over a few days and if you got enough temp variance about automatically generated a demand curve.

In a closed loop (like a sealed heating system, the static head due to the height difference between the bottom and top of the system, isn't relevant for the flow head. For example, if you had a 30m loop of pipe from the output of the pump back to the input. The flow rate for a given pump pressure will be the same if the loop was horizontal or if it went up 15m and back down 15m.

I was having a think and one of the issues with retro fitting HPs is "oh you need to replace all your pipes for bigger ones" This is apart from upgrading the radiators. That can be relatively simple, in some cases a straight swap from a singkenoanelnradnti a double or even triple finned rad. Pretty quick and easy. But if you have to start ripping floors up etc it gets costly and disruptive quickly. The key thing is the flow rate. If the pump can push the required flow at a velocity that doesn't cause problems you're fine. So, when a plumber comes to a job it would be great if they know what the pipework is capable of flowing at the moment, it might be enough. Which is where non invasive flow measurement comes in.... The kit is as low as a few hundred £ (though can be more). Plumber could come in, stick the boiler pump on full power and measure the system flow at various points to see if any pipes need replacing. Anyone aware of this happening?

External copper pipe diameter. Plastic pipe has a smaller bore and more pressure drop for fittings. I think you nearly halve the capacity for plastic pipes.

Here's the heatgeek cheat sheet for pipe sizes. 32mm should be good for 15kw, so plenty of margin as long as your pipe run doesn't look like a kids balloon animal....

So, again to be clear, the existing "split" system has been removed? Or is it still in situ pending the approval and sign off and install of a monoblock system? If it is in situ, you could look to simply having an electrician rewire the boiler and HP seperate. The other alternative, is the HP system must be linked in some way to the boiler, ie the control system decides which heataouece to use depending on the circumstance. It follows there should be a way in the control system to effectively command the system to not use the HP, either explicitly or by setting the parameters such that the HP never actually activates This swap seems to be causing you a lot of angst, and maybe the easiest way is to avoid the swap in the first place As an aside, the buffer vessel itself should be silent, it's just a tank of water. There may be (depending on layout) a water circulation pump on or near it (or it may be elsewhere). These are standard units, the same as used in boilers and other wet heating systems thought the land. They are generally very, very quiet. The exceptions would be if thet are running flat out and the pipe work has kinks and restrictions that cause noise, but that is not a heatpump issue, it's just bad plumbing.

Can i get this clear? You had a gas/oil/lpf boiler that was knackered. You had (on some sort of scheme I assume) the chance to have it replaced and have an ASHP installed as well You are complaining that the ASHP installed (a split unit) is noisy inside and vaillant will replace with a monoblock but insist on putting a large buffer unit inside. The stress of the situation is causing you ill health. If you don't intend to use the ASHP, and have a boiler, why not just turn the ASHP off? It'll be super quiet then, no big buffer required, not extra.work? Why put yourself thorough stress to install a thing you don't want to use?

That sounds better. The vaillant machines look really good anyway.

That seems to indicate you system under read the heat delivered, unless your heating demand for the last winter was drastically less than usual. If you did in fact use 8,000kwh last heating season your Cop would be a bit above 3, which would be much more plausible.

How many litres of buffer/volumiser do you need? Grant do a nice small unit, about 11liters (tho g on the left) If you already have an indoor hydro unit, you coiod replace that with 2 or 3 of those for 35l or so. It has an immersion backup as well. With regards to the buffer not being in the loft. If the only objection is "it needs to be in the insulated envelope" (which sounds like an excuse) then slapping an insulated box around it would be pretty easy. Grant make a volumiser tank specifically for external mounting.

Can you not get the buffer stuck somewhere out of the way a garage, loft, wherever. They insist on having one, but you can indicate where it can go. Maybe if it's too much of a ball ache to fit (say loft), they will delete it?

Aren't you looking to put your HP under a window? The diagrams show exclusion to the side, in front, behind, but not above the top of the HP. R290, propane, is heavier than air. The worry is any leak might allow propane to sink down and flow into the house, say through an air brick or pool in a light well or drain gully. It's not going to float up into a window.

As you were using electric heating before, the 13,000 reading will be the absolute accurate measure. The question is how much of that is hot water. If you take 20% as typical your annual heating demand was about 10,000kwh, which would be typical for a house you described. Though we are not a full year, we are mainly through the heating season. If you actually used 8,500kwh and the 6,500 is an error due to the flow meter problem, then your Cop would be closer to 3, which would be more in line with your flow temps. I'm not saying your system is perfectly set up, but it may not be as bad as the figures you posted suggest. I've been tricked in the past (not with heating systems) into long and complicated programs of improvements which were actually down to a measurement error in the first place.

what type of house do you have? 6,500kwh for space heating seems a bit low? For example the average UK household uses closer to 10,000kwh for space heating. That figure seems to tally with a well insulated new house or maybe a flat or terrace. If you had problems with the flow sensor over winter, not only might that cause inefficient running, but it would also affect your heat out readings as they are a product of the temperature difference between flow and return and the flow rate. Do you have any annual heating estimates from before you fitted the HP (often on your bill somewhere)? Does 6,500kwh tally with what you were using before? What happens to the CoP if you assume you used the assumed consumption from you bills?

Yeah, I guess that's one area a water (and particularly UFH) system would have an advantage. Maybe it could do clever stuff about blowing the air away from people.

Sorry, I meant the minimum heat requirement for the house (aka 0kw heat demand) will be around 15C and at that point the minimum the HL can output is around 3.4kw so the HP will have to be cycling. I don't know how much of an issue that will be from an efficiency, longevity and comfort point of view. If there are huge issues there, then oversizing might not be bad idea.

I have a feeling you might struggle to get that through. It's arse covering. A sensible approach would be all UVC have to be certified (made by registered manufacturer, clearly marked etc) but they can be installed by anyone as as long as there is no immersion (big sticker on side, immersion boss either missing or blanked off with dummy immersion covered in warning tags if one is fitted). Updating the info plate to show the coil area would be a useful thing too.