jack

This from the member who has needed more moderation for his shit-stirring than any other in the history of BuildHub. I'm clearly posting as a member, not a moderator. I'm pleased that your experience as a teacher has taught you not to let people's comments get to you.

Of course, it was my explanation that led you astray For someone who spends as much time as you do criticising the minor errors of others, you're hilariously thin-skinned when you get it wrong yourself.

Who said he was wrong about that? In any event, he just posted it to distract from the fact he used the wrong equation in the first place!

Absolutely not. It isn't a democracy! The only practical impact of lots of objections is that they may trigger the application being brought before committee. I think that happens in our area if you get more than 5 objections. Of course, I think counsellors are entitled to bring it to committee of their own accord, even without any objections having been lodged.

Larger pumps typically have a higher minimum output though, I believe. This can be an issue in a highly insulated house with an oversized heat pump, because the minimum output might be higher than is desirable. By way of comparison, I ran some figures a few years back when comparing a nominally 8kW unit against a nominally 5kW unit from a different manufacturer: At the conditions the ASHP would experience most of the time where I live, the 5kW unit had a comparable output at worst. No idea why the Nibe 2040-8 is considered an 8kW unit given it doesn't seem to ever output 8kW. Maybe there's some specific combination of exterior temps and production temps where it peaks at 8kW capacity?

It's kWh. Oh, wrong thread.

I initially read it as that, but talk of stepping it down suggests it's an actual pipe.

It's both of these. You could presumably tweak some of these factors one way or the other and balance that out by changing one or more of the others, but in essence you roughly double everything.

You're calculating cross sectional area, but the surface area of a pipe is circumference x length.

You sure?

Welcome. 50mm is bigger than you need, but the other issue is insulation. 50mm pipe has nearly twice the surface area of a 28mm pipe. Water will also be moving at a third the speed, so more time for it to lose heat. Have you insulated the pipe well?

I'm sure there're higher radiative losses via glass (less with low-e coatings) than walls, but I believe the perception of cold is partly convection-based drafts and partly the colder surface not reflecting back as much of your body heat as the warmer surface of a wall.

Yup, exactly this. It could be -1 or 10 outside and I can't tell from standing beside a window.

We get a breath of condensation on the bottom of our 3G windows in the bathroom when it's very cold outside and the shower's been on for a while. Even without boosting the MVHR, they clear within half an hour. I can't imagine condensation on the inside of our 3G windows so bad it forms droplets like that, so gut feel is that there's something wrong with the window itself. Is there any evidence of air leakage within the glazing units?

If it's usually only during short periods (eg, when it's cold overnight) that it's struggling, a buffer tank could help by allowing the ASHP to use its excess capacity to heat the buffer during warmer periods, for use during the colder period where it would otherwise struggle. However, this only works when there's enough time for it to catch up during warmer periods. During a long cold spell, it likely won't help much if at all.

I don't think you need aircon to get the benefits of running MVHR in summer. On a hot day when it's cooler inside than out, opening windows is just going to let the heat in. You're better off keeping the windows shut and the MVHR on (ideally on as low as setting as possible while keeping the air fresh) to maintain the temperature difference as far as possible. Once the temperature outside drops below the temperature inside, you can either open the windows (hopefully you have insect screens!) or turn on summer bypass if you have it.

I don't actually know whether that's the right term. I just mean trowelling on some sort of plastering product (could be lime, clay, cement-based, whatever) and flattening it as best you can while leaving some texture. A house I rented many years ago have this sort of finish over blockwork and I quite liked the effect. Cheap and easy to experiment with, at least.

If I ever build another house, I'd consider looking into some form of rough plastering, possibly using lime. I think a slightly imperfect finish looks great (better than the nearly-but-not-quite perfect a lot of plasterers will achieve), and unlike "proper" plastering is something you can learn to DIY reasonably easily. Materials are cheap too. This would potentially work well with woodcrete, although you'd need to think about how you'd run services.

I can't comment on the windows, but it sounds like something was going on here. No-one goes to this much trouble in broad daylight to break into a random house in a generally safe area unless they know something about who is living there (or what might be onsite). Could be anything - Facebook photos showing or discussing expensive watches or jewellery, eBay sales of similar, or possibly something more nefarious (doesn't take much imagination). Have a look at https://www.police.uk/pu/your-area/ to get an objective measure of the real risks in your area. That said, there's nothing wrong with getting things secure up-front.

Yes, exactly. Not sure whether it's worth going to the trouble of installing a full manifold at this stage - is there any way to just connect just the radiators of interest with new temporary pipework, ideally in a way that let's you continue to monitor flow rates? Also, I notice you have an IR thermometer. What's the temperature at the inlet to the problem radiators?

Can you run something temporary (and above-floor) to the distant radiator to see whether that improves things? If flow improved, it would at least suggest an issue with the pipework.

Hi George Welcome to BuildHub. I'm not an expert by any means, but a few things jumped to mind. How old is the pipework? If it's old, was it properly cleaned and flushed when you had the ASHP installed? If it's 22mm everywhere, I can't imagine you having much of a restriction based on furring up, but who knows what crud might have gotten stuck in it from old radiators over the years. Are the rads ASHP-compatible (i.e., designed to run at lower temps)? If they're old, were they properly cleaned when the ASHP was installed? Perhaps it isn't the flow, but that you're losing so much heat on the trip to the distant radiators that they just aren't capable of putting out much energy. 45°C isn't a lot of temperature to work with even with good ASHP-compatible radiators, so losing even a few degrees on a long, uninsulated copper run could make a difference. A bigger pipe is actually worse in this situation, because there's a larger radiant surface area, and the water is moving more slowly for a given flow rate, giving it more time to lose heat. I'm sure someone who knows a bit more about these things will be along soon. @Nickfromwales @PeterW @ProDave

Wrong part of the body, surely?

So do I.