Economy 7

[hard-work]

No, it is not new, it's an old idea

I explained to you where it is new, but your know-it-all-ness gets in the way. Half a century ago no such cylinder control system existed. I do not plug, which is your sneering fallback to veneer your lack of understanding. A bit of a knowitall, who knows far less than he thinks.

MOD Please refrain from personal insults.

 

[JohnW2]

I know the exact cost of my gas usage in summer when the CH is out of use. It is negligible. What's yours?

To be fair, I suppose it depends on what one is comparing with what.

I'm sure that, in a 'standard house' (I don't know about 'super-eco' ones), DHW heating is a fairly negligible proportion of the total DHW+CH energy usage. In my case (albeit different fuels for DHW and CH, and a very big house to heat), over a year my energy usage for DHW heating is about 5% of the total DHW+CH usage.

I would also think that the absolute cost of DHW heating is so modest that any 'saving' due to the use of some new-fangled (and expensive to install) system would take an unrealistically long time to 'pay back' the capital cost of the 'new-fangled' technology. Using E7 electricity for DHW, it currently costs me a little under £200 per year. If some new-fangled system could, say, halve that (and ignoring cashflow downsides and/or notional interest) it would take 10 years to get back each £1,000 of initial 'investment' - and I suspect that, within a decade or three, that 'initial investment' will need replacing, starting the calculations all over again - I am therefore far from convinced that there would ever be an overall true 'saving'.

Even if (obviously not going to happen), some system could reduce my DHW heating costs to zero, it would still take 5 years per £1,000 'investment' to even get my money back, let alone making a 'saving'.

Kind Regards, John

 

[SimonH2]

No. Look it up yourself, as I do not tell lies. If you were well up on these matters, which you are not, you would know that.

I am not the one making claims about this miraculous new technology - you are. Yet you expect people to sit through long videos because YOU don't care to back up your claims. As teh saying goes, put up or shut up.

It is to do with economics of fuel use, not down to developers working on the "how can we shave 2d off the build cost". It has to be economical enough to run to sell the house. Selling points of electrical heating is that few need any annual servicing.

It is everything to do with shaving costs off the build. Developers really do not care about liveability and running costs, and few buyers are in a position to assess running costs. Developers know that it's a sellers market as there's a housing shortage - that's the only reason they get away with selling poorly thought out shoe boxes.

I explained to you where it is new, but your know-it-all-ness gets in the way. Half a century ago no such cylinder control system existed.

Actually the control system DID exist many decades ago - in the form of E7 (and similar) tariffs and radio teleswitching. I don't know when radio switching came in, but I do know that it was common by the end of the 80s. As I said, the ONLY new thing about this thing you are pushing is the "with added internet and an app".
Those are the facts, whether you like them or not.

 

[JohnD]

In my case (albeit different fuels for DHW and CH, and a very big house to heat), over a year my energy usage for DHW heating is about 5% of the total DHW+CH usage.

...for water heating. In summer, ours uses 0.6 cu.m/day. That's about 6.7kWh. Our current price is 2.62p plus 5% VAT. So a usage cost of 18.4p/day

 

[JohnW2]

...for water heating. In summer, ours uses 0.6 cu.m/day. That's about 6.7kWh. Our current price is 2.62p plus 5% VAT. So a usage cost of 18.4p/day

Energy-wise, that's almost the same as me - over a year, it averages at just under 7 kWh/day. The difference is that I am using cheap-rate E7, so that at current prices (7.844 p/kWh, incl VAT) that equates to around 54.9p (including VAT) per day (or, as I recently wrote, around £200 per year) - i.e. almost exactly 3 times what you're paying with gas. (if, as I could, I used LPG, at current standard prices that would be a similar cost to cheap-rate E7 electricity).

As I said, in my case, the fact that I have a very large house to heat means that DHW represents only about 5% of my total DHW+CH energy uses (the total of which is of the order of 50,000 kWh/year). Since I imagine that most people, including yourself, probably have a much lower total usage than that, I imagine that your DHW energy usage is probably a fair bit more than 5% of the total.

Kind Regards, John

 

[hard-work]

I am not the one making claims about this miraculous new technology - you are.

Stop whining on like an old woman. Find out.
Actually the control system did not exist for the Mixergy cylinder decades ago. This cylinder can be used as a stand alone or controlled via the grid. It is a convergence of technologies, which some were not available decades ago.

MOD You have been warned about personal insults. No further reply from yourself will be allowed in this thread.

 

[ban-all-sheds]

it seems to be a case of "everyone other than hard-work" (I wonder how he got that name?!),

You really have chosen a very apt user name.

 

[JohnW2]

Where is Lectrician, I wonder?

 

[ban-all-sheds]

IIRC from what you've written you don't have a combi, so probably aren't familiar with some of their drawbacks.

The thing is, what's a chap supposed to do when he has no space for a cylinder (without re-carving out a chunk of bathroom where it probably used to be), and radiators sized for non-condensing boilers and the whole system just one zone?

Looking for a combi with a high modulation ratio (e.g 10:1) seems the only practical solution.

This can amount to several gallons of wasted water and (I've timed it !) over a minute waiting.

Despite what you say above, and previously, I have never experienced these long delays you mention - never more than a small number of seconds, at most, before (usually 'too'!) hot water appears at a tap when it is turned on. In fact probably no more delay than one experiences in getting hot water to a tap which is a significant distance away from the DHW storage cylinder.

Well, actually...

I did a quick'n'dirty test the other day, just using the sweep hand of my watch for timing.

After 30s the water from the hot tap in the kitchen was 40°, so it would have taken < 30s for it to be OK for handwashing or to start filling the sink. After 60s it was at about 55°, which is uncomfortably hot for handwashing.

With only a measuring jug to hand to measure flow rate, I timed 1l in 6-7 seconds, so 30s would have seen 4-5l flow, and 60s 9-10. Technically gallons, not sure if "several" would be correct.

Boiler is in the kitchen, probably 3-4m of pipework to the taps. I suspect distance is the main factor, and as you say, things are unlikely to be significantly better with stored hot water, particularly if it is used to heat water, rather than directly.

 

[SimonH2]

The thing is, what's a chap supposed to do when he has no space for a cylinder (without re-carving out a chunk of bathroom where it probably used to be), and radiators sized for non-condensing boilers and the whole system just one zone?

Looking for a combi with a high modulation ratio (e.g 10:1) seems the only practical solution.

Indeed, if that's the set of constraints then you have to do the best you can with them. In the case of new builds, they build these constraints in as a way of scraping every last penny from the job.

I did a quick'n'dirty test the other day, just using the sweep hand of my watch for timing.

After 30s the water from the hot tap in the kitchen was 40°, so it would have taken < 30s for it to be OK for handwashing or to start filling the sink. After 60s it was at about 55°, which is uncomfortably hot for handwashing.

With only a measuring jug to hand to measure flow rate, I timed 1l in 6-7 seconds, so 30s would have seen 4-5l flow, and 60s 9-10. Technically gallons, not sure if "several" would be correct.

Boiler is in the kitchen, probably 3-4m of pipework to the taps. I suspect distance is the main factor, and as you say, things are unlikely to be significantly better with stored hot water, particularly if it is used to heat water, rather than directly.

Yes, distance (and pipe size) is a big factor - but so is the state of the boiler. What you don't state in the above is how the boiler was at the start of the test.
As I've mentioned, there are different modes, and some boilers allow the user to select the mode. If you start with the boiler completely cold - main and DHW HEs both cold, then it can take quite a while before hot water even reaches the pipework - I've have timed this at about a minute with one boiler. But if the boiler is already hot then obviously you have a head start.
Our shower will fill a 2 gallon (or larger, there's no size marked on it ?) bucket before the shower is hot enough to use. However, part of that is the fact that most of the run is still (completely unlagged) 22mm pipe from when it was a gravity fed system - which is another advantage of main pressure hot water. 22mm (or 3/4") pipe was only used to get enough water flowing with the low pressures available. With a few bar behind it, you get enough flow rate with 15mm pipe and so less cold water to flush before the hot comes through.

But with stored hot water, but only a small number of combi boilers, you can recirculate the water with a bronze pump and have "instant" hot water at the tap. Obviously then you do need the pipes to be well lagged or they'll act as a radiator whether you want heat or not.

EDIT: Replacing that 22mm pipe with insulated 15mm (as well as tidying up some of the other stuff) is on my "round tuit" list which is quite long for this house

 

[ban-all-sheds]

What you don't state in the above is how the boiler was at the start of the test.

Cold. As in hadn't been used for a time measured in hours.

But if the boiler is already hot then obviously you have a head start.

Not really - what I find is that if DHW has been recently used then you get a burst of very hot water out of the tap (more than hot enough to really hurt) very soon after turning on, but then you still have to wait for the same amount of time for normal performance to be established.