SteamyTea

what size is your DHW cylinder?

Whoops, 0.00027778 (fat fingers on a small screen) Whoops again, autocorrect.

There is a bit of terminology to learn. Energy is measured in MJ (megajoule). A joule is the standard unit for energy and when converted to base units of kilograms, metres and seconds is very small. Why the M for 1,000,000 is added at the front. Now no one, apart from us nerdy scientists, use MJs, and domestic energy is metered and purchased in kWh. MJs can be multiplied by 0.0007778, or divided by 3600 to end up with kWh. The k just means 1000, W is watt and h is an hour, which is 3600 seconds. Power (W) is the rate that energy is used. You can think of this as your miles per gallon in your car, with energy being how many gallons are in the tank. If your car does 40 MPG at 60 MPH, and your tank has 8 gallons in it, you can drive 320 miles over 5 hours and 20 minutes. A unit of power is called a watt, which is actually a J/second. Again a small unit, so a k is added. A k is 1000. This gives the more normal kW for a power rating. Boilers, heat pumps and even wood burners all have a maximum kW rating i.e. 6 kW. Radiators, UFH and fan heaters also have a power rating. (This can get confused by some people talking old imperial units of BTU and BTU/h, but we went metric in ,'73, so tell them off) Where it starts to get confusing is a house will need a varying amount of thermal power to keep it at a steady internal temperature. This is caused by external temperatures rising and falling during the seasons and even during the day. This can be overcome in a number of ways. The easy way, and the way old heating systems were set up, was to fire up a boiler at full power, heat some water, pump it around the house to all the radiators, which then heated the air. When the house was up to temperature, the thermostat turned the boiler off. When the temperature dropped a few degrees, it turned the boiler back on. These days we are a bit more sophisticated and try to deliver enough energy to match the losses. This keeps the house at a steadier temperature, and used less energy overall. You will almost certainly read on hear about weather compensation (WC). This is just a basic feedback system that knows what the outside temperature is, how much power is being delivered to the house and for how long it may be needed. All that can be boiled down to a few numbers. The main numbers you need to know are the thermal losses for each room. Once those are added together, you get a number for the whole house. It is usual to size for a worse case i.e. -10°C outside. This gives you a maximum power requirement (heat source kW). Most of the time, you will be heating the house when it is way warmer outside, so the second number you need is about how much the heat source can be turned down internally. This is called modulation. Gas boilers have quite a high ratio, sometimes 10 to 1 i.e. 12 kW down to 1.2 kW. Heat pumps are not, generally, so good and are often in the range of 3 to 4 to 1. There are ways around this, but that is for later. The other thing that is important is domestic hot water (DHW). There are two ways to do this. Heat water only when it is needed (instantaneous), this requires a lot of power, often over 25 kW. Or Heat and store in a cylinder. This method takes longer for the same amount of delivered hot water, but used less power, often in the region of 3 to 6 kW. If the heat source is delivering both central heating and DHW, then this needs to be taken into account. With modern combination gas boilers, they are sized to deliver enough hot water, and rely on boiler modulation to deliver lower power for the space heating. Heat pumps, generally, rely on being only slightly oversized (which improves efficiency most if the time) and run a space heating time slot and a DHW timeslot at different temperatures and different times during the day. There is a lot of detail in heating design. So questions to ask are. Maximum house losses. Room by room heat losses. DHW reheat times.

Is it (expletive deleted)

I am sure mine does that, easily, since I put a RamAir sticker on the back.

That is a proper price. Gets the dirt off just the same as a £10k one.

I have no idea what that is, looks like an car.

FFS that system seems to be a disaster waiting to happen. Way to many stages and attention to detail, especially when you are up on a roof in a 30 MPH breeze, which is pretty normal down here.

Bit of a tricky one. At work, I often hear the therm 'I don't get paid enough to do this'. I pointed out the other day that if they were working at their peak performance, extra money could not make a difference. I feel the same about expensive items, which to me are generally add ons, not fundamentals. An example of this is car tyres. I can get a Goodyear for £170, or the ones I have, for £60. There may be a difference at the very extreme of performance, but as the ABS and stability control both work, I won't see the difference. I feel the same about a bathtub, or a kitchen work surface (I use a chopping board anyway). Maybe @Nickfromwales can join in as he often mentions the high spec places he works on.

I have seen the title term used, as well as similar terms like 'high end'. To me they just seem like marketing puff, and have no real meaning. If I was building a good house, it would have thicker walls, floor joists, stairs that bear onto a concrete floor. Basically things that give a very solid structure. What I would not consider is anything that is easily replaced, bathrooms, kitchens, doors and windows, which are nice to have, but do not really add real value in my eyes. A decent heating and ventilation system is important these days, but assuming the basic design is right, the replaceable heat source or MVHR unit is a bit of irrelevant as it can be changed. What do others think constitutes 'quality'?

I would hope so. (May have to check my figures as it seems wrong to me that they all have such similar volumetric expansions)

Was not argon filled anyway. I have always suspected that gases, even atomically large ones, get out over time though normal expansion and contraction. The volumetric thermal expansion of argon, oxygen, nitrogen and air, at STP, are all pretty similar at 3.4 x 10-3 K-1.

I have just remembered something from 40 years ago. I had a misted up DG unit that got cracked. The misting vanished. I wonder if a small drill hole in the edge (that pane separator bit) may cure the problem. May give it a go.

I think it is to allow a neutral at the switches when 2 or 3 way switching is wanted. Usually the neutral is up in the ceiling rose and only live and earth are at the switch. Sometimes not even an earth.

And some will be bolts.

Data is so useful, so much better than guesswork. I am quite impressed with the efficiencies, what are the two different methods you use?

When I changed my glazing units, the supplier offer a 1 year warrantee with timber frames (which I have) and 5 years with plastic frames, 7 years in they installed them. Most now need changing after 20 years, so may go and see if he is still in business.

Yes, was a while back, so they may have started to inject them. One can usually tell by the trimmed edges and any 'swirl' patterns on them. Would need a very large injection moulding machine. The formula is F = A x P x SF Where F is ton A is area P is injection Pressure SF is safety factor A flat sheet would need a huge machine compared to a similar amount of material injected into a a thicker, but smaller area area i.e. a plastic bin shape. There is also the speed that it can be injected, though multipoint injection alleviates this a bit, but these are niche mouldings, so would be hard to justify the costs of machinery and tooling for a few thousand parts per year, vacuum forming would be much cheaper. So they may well be injection moulded, but I would be surprised. I was only peripherally involved in the injection moulding side, but my Mathematics Lecturer in the early 1980s was John Dunhill, of the cigarette family, who worked on the Topper Dingy design back in the mid 1970s. The Topper was, at the time, the largest single moulding every made and was only possible because it was a development project, backed by industrial (ICI and Rolinex) and some government money, Ian Proctor could never have afforded to develop it and would have stuck to the cheaper GRP mouldings, which I seem to remember were lighter. Was a long time ago in my personal history, but interesting times.

Well what a surprise. Every time you double insulation thickness, you halve the power though it. So an inverse rule. But this is really looking at the problem from the wrong point. The overriding idea is to reduce total losses, and that depends on the relative ratios of surface areas. So a building with 50% glazing would benefit more than a building with 20% glazing by having lower overall U-Value windows. It will cost more to build (usually), but that is when you create a spreadsheet and work out the lifetime costs. The last 4 years should have shown that energy prices can be very volatile, even with government support (even though domestic spend is still around the long term average of 5% of household income).

The ones I saw were vac formed.

They are vacuum formed, so apart from the offcuts recycling value, there is extra pattern/tooling work and then extra trimming. It is a case of an extra quid to not have a hole, 2 quid to have one.

Interesting the in-roof panels and PV panel size mismatching. My roof is 4 meters wide, and it would be nice to fit 8 990mm by 1600mm panels in portrait. When I last looked, there was not an in-roof system that could do this. As the house is terraced, I could slip a bit of a tray under both neighbours tiles, which should give me enough width for bolts and panels. I do wonder how hard it would be to make my own from GRP, which I can do myself. When I look at the design of the GSE ones, I do wonder why the have a large hole, in the middle, moulded into them, is it just for roof ventilation and cable access?

Why surprised, it is the amount of trapped air that does most of the insulating.

but the sheep can escape the worrier.

They will float if mixed with a fluid that has a greater density. I have recently, out of curiosity, been reading up on foaming concrete. With suitable reinforcement and on site quality control, it seems to me that this could be a very useful product.