Radian

Your autocorrect drives me nuts 😆 Do you mean you got a new feed from cold storage tank to make the pressure for H & C the same?

I don't know how familiar you are with gravity fed domestic water systems but vented HW cylinders tend to be paired with bathroom cold taps of the mixing variety fed from the same gravity source otherwise the differential pressure can be a problem. Every house I've ever been in with gravity fed water systems have had cold taps fed from the storage tanks on the top floor, which has been standard practice up until the advent of UVC's. It might be said that cold water taps would be better if fed from the main when a UVC is used but this would nearly always be the case anyway. Presuming it's a condensing boiler then it's certainly not working efficiently. At 54°C return flow, under perfect testing conditions, the boiler is only up to 87% efficient. In practice it will be significantly less.

Just resuscitating this topic because I'm trying to increase the efficiency of my condensing boiler and while the radiator sizing for space heating is such that I can just about operate with a flow temperature of 60oC the hot water can't reach 55oC as I currently have it set. Because of the limitations of the boiler in question I have to work with just a single fixed flow temperature. Ideally I'd like to set the HW to 47oC which experimentation shows is all that's needed for washing and has the benefit of protecting from scalds (as others have discussed here) and can be achieved with a flow of 60oC. I have taken on board the opinions that legionella is not a real concern but I am, by nature, risk averse. However, when I think about it logically there's plenty of places where water accumulates at lower temperatures. For starters, all the pipework between taps and cylinder would need purging to ensure there was no contact with water left at lower temperatures. And then there are those occasional events where the tank is not timed to be used yet water is still drawn off, or when all the HW has been used yet more is demanded for an ultimately disappointing shower. But even more confusing is the cold water! Again, this is talking with respect to taps supplied by a vented storage tank situated in a loft. It's always been my understanding that you don't drink from such sources and neither would I want to given the appearance of a typical tank after accumulating decades of crud. But this water routinely ends up in showers and baths, on hands and faces, etc. Is it supposed to be too cold for harmful bacteria? At 20oC it is around 18oC away from body temperature so about the same margin as the recommended HW temperature (I understand that it's keeping the operating zones between humans and bacteria sufficiently separate that makes things safe rather than killing bacteria) but in hot weather the cold water storage tank can reach much higher temperatures - i.e. I measured water coming out of 'cold' taps at over 26oC last month. It therefore seems to me as though the official advice of keeping water above 55oC has to be flawed because of all the exceptions I've been listing here.

Good. Now can we get back to talking about video games with pussies? Oh wait, that was in another thread...

Not sure how to accurately convey the actual feelings I have about this. I'm not grumbling, or annoyed about it - but It's not such a simple matter as that. Anyone at any age can drop dead at any moment but anyone under 35 might be able to expect another 35 years without being too wishful. Your assumption that you’d not worry about any ROI time knowing your time is limited could do with being upgraded to include the life expectancy. That's all I'm pointing out really.

I'm lucky that I've got a HW immersion. Could you not preheat the cold feed into the combi with a smallish tank? Compared with batteries water is a very cheap energy store. However, I'm also keen to do some small scale off-grid storage to be used as a 'glorified' UPS. I think a <£1500 investment in battery and charger/inverter could make sense in this role.

OK, just picked up on this... Not everyone necessarily has 5 or 15 years Maybe it's part of a calculation about how to maximise your enjoyment of the life you've got left.

Amen to that.

It may be too late in the day for you but you could get a CT clamp meter (emonpi or homebrew something else up with an ESP?) and have all the resolution your heart desires. I measure real power over every mains cycle (for a PV divert) and update a database 10 times a minute (to see things like kettles going on and off). Admittedly this doesn't help with the PV database but things move at a more stately pace in the sky.

Oh, so what happens when you put on the kettle and the oven at the same time? Your PV clips out at 3kW so you're not necessarily seeing full utilisation even though the half-hour averages make it seem like you are.

Judging to a landscaper I was talking to, People are trying to improve their own places and staying there.

Does today's price cap announcment mean something in the region of 36p per kWh for the next two years? Or have I done the sums wrong.

It'd have to be fairly powerful to keep the wind out! The actual fan is OK as is, the usual type operated by the light switch - but modified by me to use a 140mm PC case fan after going through a series of noisy expelairs! Almost imperceptible now, instead of something that sounded like a food mixer.

I must fit some sort of active shutter to an extractor fan in our downstairs loo. I was puzzling over a uniform layer of dark grey dust on the lid of the toilet cistern when it dawned on me that the day before I'd been in the garden sanding a painted picnic table!

Just wondering how this turned out in the end?

Unless the roof has a breathable membrane between rafters and battens, but somehow I suspect we are talking about an older, bitumen based roofing felt here. Out of interest what alternatives to ridge venting are there?

Not sure about that. I know it's subjective but I feel anything in the 50's is going to annoy eventually.

Why do you want to put PIR against the rafters? You've effectively trying to convert a cold (ventilated) roof into a warm roof and that's not trivial. To achieve beneficial insulation for the house it's going to be far more cost effective and safe (for the fabric of the roof) to simply add insulation to the floor of the loft.

It's an estimate of the gas consumption. If the return was 55 then yes it should be in condensing mode but in practice (my experience) a 75 flow will result in a return over 60 and lose out on efficiency. Obviously there's a trade-off here somewhere but it'd take some finding. It's a Glowworm Flexicom 30hx The manual is very opaque on HW priority hinting that it all happens using auxiliary eBus control but I don't have that. Not unless I hack something together.

The best, home brewed

Oh that's very interesting. It implies a degree of 'dead reckoning' where a decision is made to energise the load for a certain amount of time based on previous measurements. Of course the loads in a house are dynamic so something else may energise and soak up the apparent excess. By then it may be too late to 'call off the dogs'. My diverter measures the power for every cycle and 'sees' the dump load along with everything else (including any other diverters) and reponds accordingly. If this isn't done then the dump load may be burning unnecessary power.

I started a new topic about this if anyone's interested...

I've been trying to reduce the flow temperature of our 30kW condensing system boiler to improve it's efficiency. The lowest I can practically operate it and have HW at 55oC, is with a flow temperature of 65oC. Any smaller difference results in extended running and short cycling. As this chart shows for the start of today, the cylinder temperature sensor governing the HW demand fell just below the overnight minimum setback temperature of 40oC and very briefly fired up the boiler at 4:56AM. The hysteresis is programmed at 2.5oC so the boiler demand ceased 8 minutes later at 5:04AM as the cylinder sensor reached 42.5oC Notice, however, that the temperature in the HW cylinder continues to rise to almost 50oC over the next 10 minutes which is how long the boiler overrun is programmed to be. This is another area that could do with more examination as it seems there was still plenty of energy to be transferred from the heat exchanger and pipe work. But the real issue comes at 7AM when the daytime temperature demand of 55oC kicks in. Initially the temperature rises quite quickly as it did earlier, due to the full 30kW being applied. But on reaching 51oC the boiler starts modulating and the rate of heating falls (as witnessed by the change in slope). When the cylinder sensor reaches 53.3oC at 7:33 the boiler switches off completely and commences to cycle on and off at 10 minute intervals at its minimum output of 10kW. This strikes me as being inefficient as it's only at 8:13, 45 minutes later, when 55oC is finally attained and the boiler demand is removed. From this it seems to me as if a HW temperature setting of 53.3oC would be about the limit of what the system was comfortable with - as this is where we get to when modulating reaches its limit and the boiler starts cycling off and on. If I drop the flow temperature below 65oC then this will push down the HW temperature by a similar delta. By inference from the numbers above, a flow temperature of 60oC would mean something in the region of a maximum HW setpoint of 48oC for sensible operation. I think this would be too low, yet people talk of boiler flows of 55oC! At the setpoint of 65oC the boiler flow itself reaches a self-reported peak of 68oC just as it clicks off. The actual return temperature at this point is 56oC also according to the boiler diagnostics menu. My cylinder sensor is typically three or four degrees lower than the return temperature which seems reasonable. Am I wrong to see on/off cycling as undesirable once the turn-down is insufficient to keep the boiler delta happy?

Smallest one is 5kW which is a bit too big for me without a buffer.

Have you identified a particular model? I was looking at this Trianco Activair have you seen any others?