Part G of the building regulations - section 3 applies to all hot water storage systems now, not just unvented cylinders like it did in the past. (partly influenced by the energy efficiency requirements introduced elsewhere).
In reality most of the requirements impinge on the design of the system, and its installation. The servicing requirements are fairly trivial. (and I expect in the majority of cases ignored!)
I've been re-insulating pipes this week, doing the job properly clearing up after our heat pump installation muppets. One thing they left was a 1 foot piece of pipe uninsulated at the top of the hot water tank. Putting decent insulation on that has made a noticeable difference in the water temperature (the water is heated to 55C).
The reasoning I suspect is that, while water isn't flowing in the pipe, it's part of a convection cell. Hot water collects at the top of the tank, and that's conducted to the pipe. The pipe surface cools the water, which means the cool water falls, being replaced by fresh hot water.
Result is that the surface area of the pipe, while small, is constantly being supplied with the hottest water, even when no water is running. That explains why the airing cupboard has been hot and the water not quite as hot as it now is.
It is surprising how common it is to have an insulated tank but no insulated pipes.
Theo
Thanks very much. One thing I don't know is whether the off-peak heating (i.e. overnight) is meant for those people with different off-peak tarrifs (to save money), or whether it's meant to reduce demand at times when the grid might otherwise be struggling (to be 'socially responsible'). I also don't know why one heater is designated as the 'off-peak' one, since I'm sure that one heater would serve both purposes. My guess is that when a boost is needed, the heaters are activated in parallel (which your reply seems to confirm, but which I haven't seen explicitly stated anywhere). Since I believe that the mains supply in our airing cupboard comes simply from the upstairs ring main, I'm wary of drawing more than 3kW from it. And I'm not going to assume it would be any help to stick a higher-rated fuse in our old consumer unit :-)
I'll take a look at the heat bank link, too.
Almost exclusively for people on reduced night rate tariffs like Economy
7 etc. Usually people with electric space heating.I doubt many people give it any consideration (yet) since it has "always worked" in spite of dire warnings of how close it came last winter etc.
One is positioned lower in the cylinder, so that it can heat the full volume of the water. One placed higher up will only tend to heat the water above it, and stratification will tend to stop the upper and lower sections mixing.
Boost is normally just a top heater - designed to heat a smaller volume of water to a decent temperature at minimal cost (since boost would often be used at peak rate times of day for those on split rate tariffs)
There are cases where a cylinder has multiple heaters, but the intent is not boost or overnight so much as "more power Now!" - i.e. to do a full cylinder reheat faster when electric heating is the only source of heat.
My boiler will do the bulk of the cylinder recharge at close to full output (the cylinder will take 22kW or so). You will have difficulty getting close to that with immersion heaters, since many properties only have a 24kW rated electrical feed.
If it is on a ring then it is normally suggested you don't stick single point, long term loads with a rating of more than 3kW on it.
One immersion on a 7.2kW ring that is otherwise lightly loaded (as many upstairs socket circuits often are) would no be a problem. However if you need multiple immersions, then a dedicated circuit would be at least preferable if not required.
Is that primary circuit water or DHW that is heated to 55?
If DHW, then that is a bit risky since it is not hot enough to sanitize the water, and legionella etc.
(lifting it to 70 once a week is usually considered adequate if it is normally cooler)
Well part of that you typically want some heat to leak into the airing cupboard... A more controlled way of doing might be preferable though.
Our tank barely leaks enough heat to be able to call our cupboard an “airing cupboard”. I’d be really surprised if a double jacketed jacket performed anywhere near as well as a foam insulated one.
How long and at what times of day do you heat yours for?
Tim
Does this stratification involve physical separation, or is it just hot water rising wanting to get to the top?
Yes, our rings have 30A fuses, and my grammar school 'watts equals volts times amps' tells me this is 7.2kW. There are three PCs on full time up here (each 500W max), plus the occasional use of the Henry (800W, I believe). Two 3kW heating elements is, I guess, sailing a bit too close to the wind.
But if I stick it in the loft, where the cold water header tank would (I'm assuming) no longer be, a dedicated circuit may be easier in the future. At the moment, I imagine that all the floor boards (and laminate flooring, etc.) would need to come up. But maybe I'm exaggerating what would be needed to put an extra circuit in.
DHW. I'm rejigging the controls so I can reduce the temperature for improved efficiency.
There are separate controls with a timer to heat it with the immersion once a week. This is standard fit on ASHPs.
That depends whether people actually use their airing cupboards for drying things. Often they don't (in our case, it's a store for random junk). IMHO it's more efficient to run a heat pump tumble dryer than have a place whose purpose is to make moist warm air inside the house. Or at least put a dehumidifier in the cupboard, that collects the water to drain it away.
Theo
Check the cylinder is large enough, since you will be using it without adding much cold.
That should be ok then.
Yup a dehumidifier is a better way to actually dry stuff...
But then again, airing cupboards were never designed for drying as such
- just a final "airing" after ironing etc, plus a bit of linen storage. They in effect came free of charge since there would (historically) have been a poorly lagged hot water cylinder somewhere, and the space around it was going to get warm)
It is just natural gravity separation - it quite pronounced - especially in slimmer thinner cylinders.
Some heat bank type cylinders designed for pumped circulation include some baffles near the return connection to stop pump circulation from "stirring" it too much since you want hot water coming out into the primary side of a PHE and not water that has been mixed down to "warm".
Probably less of a problem with internal coil style heat exchangers.
In load probably not - you can allow a bit of diversity of the other loads (e.g. PCs will not spend much time using 500W - and probably never at the same time unless you are crypto mining or having a LAN gaming party).
A vacuum is a fairly short term load. (much the same as adding an extra
3kW for a kettle onto a kitchen ring that is already running at full capacity has no real effect - 45A for 3 mins will not bother it!)You would need to take more care that you are not putting that load on a single point, unless you are sure it is close to the (electrical) centre of the ring so that the two legs are well balanced.
You would also need to make sure there are no other de-rating factors on the cables, and this is where airing cupboards can be difficult, since one of the big de-rating factors is ambient temperature.
TBH, if I were doing two 3kW immersions, I would run a dedicated circuit (which could be also be a ring if you wanted)
OOI, there is a worked example on doing the calcs for a pair of immersion heaters here:
There are usually ways and means of getting cables through without nearly as much disruption as you expect.
Discussed in some detail here:
Or once my next door neighbour wanted a shaver socket in his bathroom, but could not see how to run a cable to it since it was fully tiled. So I cutout a neat rectangle of tile with a multimaster, sunk a box with the SDS, then drilled through to the other side of the wall (which was in an adjacent room and just painted), chased that up to the loft and ran the cable there!
Fredxx snipped-for-privacy@spam.uk wrote
It doesn't REQUIRE annual inspections, f****it.
Pity that one doesn't REQUIRE annual inspections, f****it.
Pity that one doesn't REQUIRE annual inspections, f****it.
You never could bullshit your way out of a wet paper bag.
No point because that STILL doesnt produce any UK regulation that REQUIRES annual inspections, f****it.
so the cable was on the bedroom side of the wall whereas the electrical accessory box was on the bathroom side of the wall?
I always thought that if the cable was not within 50 mm of a corner, that it had to have visible electrical accessories so that people "in the know" would avoid accidentally drilling/screwing/nailing vertically or horizontally from the visible electrical accessory?
yup, inline with an exiting double socket.
150mm from a corner (internal or external), and within 150mm of a ceiling.Mostly true, although there is scope where both sides of a wall are visible (say from a doorway), and there is an accessory visible on one side, and the wall is only 100mm or less, then you should assume the zone passes through the wall:
See:
If I stick it in the loft (and I'd have to give it a lot of thought, but the extra storage space left behind would be nice), the airing cupboard would be no longer be so warm. Actually, the airing cupboard location provides a better route to the downstairs ring, since the connecting block used for the HW/CH is already located there, although this might confuse future owners. Our electric load downstairs is certainly lower than upstairs, disregarding an induction hob on its own 30A circuit (we must hope that we never put all inductors on their 'P' setting, and then turn on the oven, at the same time).
We have a suspect length of 15mm cold water copper tubing which has developed a few pinholes recently, and I have had on several occasions to cut holes in the downstairs ceiling to locate and repair the affected pieces; so I do know that some things can be done that way. Sadly, the beams in the void go in a direction that makes this sort of thing harder than I would like it to be :-)
I am glad to say that my pipes are definitely insulated. I did it years ago, when installing a shower and switching from a pair of motorised valves (hot water and central heating) to 9 of them (one per room, all individually controlled).
I'm not completely sure. We heat it in the morning for us all getting up and in the evening from when we are all getting in, but I'm not sure how long it actually heats for, as the thermostat cuts the heating and will only come back on if we use a lot - which can occasionally, but rarely happen if we've done a lot of cleaning and taken a number of showers (there are 5 of us).
I was judging the double jacketed against the pre-insulated tank based on how warm the water is after going away for a weekend and switching the hot water to "holiday mode", where is remains off while we are away.
So you’re heating it at least twice a day at times just before you want hot water?
Try running your water heating for two hours from 23:30 to 01:30 only and
*then* tell me that your tank keeps your water piping hot all day long. At present with two heat input cycles you’ve no idea.I’m not suggesting that 23:30 to 01:30 is in any way optimal BTW, it’s just that 01:30 is when my cheap electricity stops.
Rather depends what “holiday mode” is. It it simply “off” or is it cycling the boiler?
Tim
It is heated twice a day, because with 5 of us, once a day simply doesn't always provide enough volume of hot water and we don't have the space in that location for a larger tank.
My comparison between double jacketed and pre-insulated was based purely on being away for bank holiday weekends.
Holiday mode simply doesn't heat the tank at all for a selected number of days. So going away on a Friday night, after work and setting 3 days, doesn't heat it again until Monday night. Which means that having got back before the evening heating time on Monday, the remaining hot water is from Friday night - so a pretty good comparison.
We are also planning on replacing our vented cylinder with an unvented (mains pressure) one.
The new cylinder will primarily be heated indirectly (via the coiled loop) by the boiler. It will also have a single direct heat source (immersion element), like the old cylinder, which will be used as a backup in case the boiler fails. This will also give us the option of feeding excess energy from the solar panels to heat the water.
The benefit of having an unvented cylinder is that it will allow us to get rid of the shower pump. It will also solve (so I am told) the low hot water flow rate to the kitchen tap. The con is that it needs yearly servicing. I have been warned that the additional pressure to things like taps and toilet cistern ball valves can sometimes be a problem, requiring them to be replaced.
The only thing I wasnt too sure about is that our cold feed from the incoming mains is 15mm. All of the cylinders I have looked at state a 22mm feed. The plumber I have spoken to said that 15mm will be fine as long as I am not expecting to run multiple showers at the same time.
I dont know what our water pressure is (I dont have a pressure gauge) but a crude test the other day showed around 20l per min flow rate.
Alan
No it does not in reality. Works fine without that.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.