Beelbeebub

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.

And there will be an internal cutout that kills the burner if you get more than 95C, say there was a glitch with the control system, or maybe the pump failed. Point is it is highly unlikely a gas boiler will boil an UVC. If your expansion vessel was dud and the pressure relief failed (or was capped) the worst that would happen is the tank would split and leak hot water. It's unlikely to be a huge split leading to a tsunami, more of a crack and a big drip. The myth busters style steam explosion and ballistic tank (which would be very bad) is only possible if you superheat the water beyond 100C so you get a lot of water flashing to steam upon pressure release.

The newer boilers really don't like boiling, it can damage the heat exchangers. I don't think the old cast iron jobs cared. They just kettled away. But because the new heat exchangers are so thin thry could locally overheat if they boiled so the manufacturers put high limit cutouts, normally at 90/95C in the heat exchanger. Given the design philosophy of gas boilers is usually to fail safe ie if a sensor breaks stop working, i'd say there is very little chance of a gas boiler ever being able to output a flow of more than 95C and hence being able to boil the UVC. Only if an immersion heater is fitted to the UVC is there a possibility of boiling. And to be fair, immersion heaters sticking on is not that uncommon.

Crikey! In which case you would need to look at the max output at - 10C 😁 and possibly some extra woolly jumpers!

where were they for, the top graph seems to be from somewhere pretty chilly! but in both cases time below -5 is much less than time above 10C

i'd say the chances of a gas boiler being able to boil the UVC are pretty minimal. As a gas appliance they have multiple safety features and sensors and are more likely to shut themselves down than run away uncontrollably. The only things that could boil a tank realistically are a solar system and an immersion. Yet we have to have G3 even for an UVC just on gas. In all honesty I think the UK is a little *too* careful with them, other countries seem to get away with much less installation regulation (as opposed to design and manufacture regs which do need to be tight) I kinda wonder if it has some bias in the fact it was a "foreign" and "European" system and therefore automatically inferior to the good old british vented cylinder.....