Choice of intelligent switches ?

zeupater

phsci wrote: »

... My guess is that firing the boiler up just to maintain a supply of hot water was very wasteful! ...

Hi

Agree ..... If you have the DHW storage capacity to not need to fire up the boiler every day you can hugely impact on the seasonal efficiency. Of course, this not only depends on the volume of DHW, but also the level of insulation and the functionality available on a heating programmable controller (unless DHW is controlled on a manual basis as required).

For example, as short winter days approach our solar thermal system moves from providing all of our DHW, through needing a manual boiler 'top-up' about once/week, through to having two 'burns' a week in December/January .... unless we experience an extended period of consecutive dull days, even in deep winter the thermal system usually provides some heat to the cold fed water at the bottom of the cylinder which, although not enough to heat the DHW to usable temperatures, still reduces the GCH fuel demand ...

HTH
Z

silverwhistle

phsci wrote: »

The installation of the Intelligent Immersion seems to be saving significantly more gas annually than the 1000 or so kWh diverted. <SNIP> My guess is that firing the boiler up just to maintain a supply of hot water was very wasteful!

Interesting. You should have a discussion about this with Cardew of this parish: he has some interesting views on the matter...

My experience, with just me and occasional guests, is similar to Zeupater's although I suspect I might get up to three manually controlled blasts of gas water heating a week. I do like a long, deep bath when I get back from Sunday football games as I tend to play in goal for my women's team and get very cold! My savings amount to about 1100kWh a year diverted with a normal, pre-existing tank.

Actually, I've a question: my diverter reads 'HOT' very early in the day at the moment, as you'd expect. Does drawing a little hot water off cause any turbulence within the tank to affect stratification, to thus allow a little bit more energy to be taken on board? In other words, like the situation above, is there any multiplier effect over and above the loss of energy of the actual hot water drawn?

Apologies, but physics wasn't a choice at 'O' level with my options, and sometimes here I really notice my lack in this area. :-)

orrery

Dave_Fowler wrote: »

Here's a picture of the de-strat pump ...

An extra question...

The pipe run appears to be slightly 'on the cant' - is this an optical illusion or deliberate?

EricMears

orrery wrote: »

No sleeve on mine but that's not the point.

orrery wrote: »

No, the thermostat is inserted into a sleeve in the immersion assembly

I'm confused !

orrery

EricMears wrote: »

I'm confused !

Ah yes, I see the confusion!

Some immersion have a cylindrical sleeve around the element, presumably to funnel the water and force it to circulate (discuss). Mine doesn't.

So, the immersion has an element which hangs below the gubbins at the top, plus a sealed narrow tube also hanging down from the gubbins at the top which is separate, and contains a slide-in thermostat.

Well, it makes sense to me.

Cardew

zeupater wrote: »

Hi

Agree ..... If you have the DHW storage capacity to not need to fire up the boiler every day you can hugely impact on the seasonal efficiency. Of course, this not only depends on the volume of DHW, but also the level of insulation and the functionality available on a heating programmable controller (unless DHW is controlled on a manual basis as required).

For example, as short winter days approach our solar thermal system moves from providing all of our DHW, through needing a manual boiler 'top-up' about once/week, through to having two 'burns' a week in December/January .... unless we experience an extended period of consecutive dull days, even in deep winter the thermal system usually provides some heat to the cold fed water at the bottom of the cylinder which, although not enough to heat the DHW to usable temperatures, still reduces the GCH fuel demand ...

HTH
Z

Interesting. You should have a discussion about this with Cardew of this parish: he has some interesting views on the matter...

Interesting??

I have recently(April) had a new gas boiler and converted to an Unvented(Pressurised) system with a 180 litre Gledhill cylinder see:
http://www.gledhill.net/pdf/Spec%20184%20StainlessLite.pdf

The brochure gives the heat loss as '54 watts' and there is a label on the cylinder to that effect. However nowhere does it state the period over which that heat is lost or at what water temperature. I assume that the 54 watts loss is each hour making 1.3kWh a day.

I have been trying to measure the gas consumption and as I have been home alone for 2 weeks I put Hot Water on 24/7(continuous) - obviously heating off - and took an accurate gas meter reading on Sat 09 July and again today(12 days)

I have had 12 showers with a large shower head with a real torrent of water, my daughter and partner were here at the weekend and had 4 baths. Water temperature set to 60C.

With that and some water for washing up(most is done in dishwasher) in 12 days I have used only 69.3kWh.(6.188 metric gas units) which will cost less than £2.

Without measuring, I suspect the cost of water is more than the gas.

Bearing in mind that I don't wish to compromise on my shower length or temperature, I wonder how much would be saved by Zeupater's method of a minimum period of heating every x days?

EricMears

Cardew wrote: »

The brochure gives the heat loss as '54 watts' and there is a label on the cylinder to that effect. However nowhere does it state the period over which that heat is lost or at what water temperature. I assume that the 54 watts loss is each hour making 1.3kWh a day.

The brochure is using the correct unit. Anything losing heat @54W would indeed lose 54Wh per hour or 5.4kWh per 100 hrs.

I agree it should make it clear at what water temperature and outside temperature the loss has been measured but it would perhaps be impractical to print that on a label. No doubt it will be spelt out in great detail on page 85 of its user manual but I think you could safely assume they're referring to the water temperature being at its maximum designed figure and the outside temperature at 20 deg C.


HTH

EricMears

orrery wrote: »

Ah yes, I see the confusion!

Some immersion have a cylindrical sleeve around the element, presumably to funnel the water and force it to circulate (discuss). Mine doesn't.

So, the immersion has an element which hangs below the gubbins at the top, plus a sealed narrow tube also hanging down from the gubbins at the top which is separate, and contains a slide-in thermostat.

Well, it makes sense to me.

Can't say that I've ever seen a 'large sleeve' as described.

As I started by saying, thermostats are usually slipped into a sleeve (call it a 'pocket' if you prefer) which is a lump of metal joined to the metal heating element casing. By the very nature of conduction through metals, that pocket will always be very close to the temperature of the actual element. Indeed, thermostat length isn't quite as crucial as one might expect since it's quite hard to get a significant temperature gradient along a piece of metal.

zeupater

Cardew wrote: »

Interesting??

I have recently(April) had a new gas boiler and converted to an Unvented(Pressurised) system with a 180 litre Gledhill cylinder see:
http://www.gledhill.net/pdf/Spec%20184%20StainlessLite.pdf

The brochure gives the heat loss as '54 watts' and there is a label on the cylinder to that effect. However nowhere does it state the period over which that heat is lost or at what water temperature. I assume that the 54 watts loss is each hour making 1.3kWh a day.

I have been trying to measure the gas consumption and as I have been home alone for 2 weeks I put Hot Water on 24/7(continuous) - obviously heating off - and took an accurate gas meter reading on Sat 09 July and again today(12 days)

I have had 12 showers with a large shower head with a real torrent of water, my daughter and partner were here at the weekend and had 4 baths. Water temperature set to 60C.

With that and some water for washing up(most is done in dishwasher) in 12 days I have used only 69.3kWh.(6.188 metric gas units) which will cost less than £2.

Without measuring, I suspect the cost of water is more than the gas.

Bearing in mind that I don't wish to compromise on my shower length or temperature, I wonder how much would be saved by Zeupater's method of a minimum period of heating every x days?

Hi Cardew

As you are aware from previous discussions, I don't really have much faith in many of the test procedures & related calculations which the BRE build into SAP because they don't represent what really happens ..... this is a just another example.

The DHW cylinder heat loss is calculated on a standing loss basis - that being the energy lost over time (ie kWh/24hrs) whilst maintaining a standard water mass temperature (60C ?) with a standard Delta-T to the house temperature (as per heating) ... see the issue yet ?

Our cylinder is highly insulated, but above that it's also (like most others) in a very small cupboard, which is also insulated ... the temperature in the cupboard is (almost) always warmer than rest of the house ... I've just checked and the wall temperatures inside the house are currently 22.4C, but inside the 'airing cupboard' they're 39.2C, so the Delta-T in this case would be around 17C overstated which would result in the standing heat-loss being considerably lower than the manufacturer's declared loss .... but it doesn't stop there .... we, like almost everyone else, don't maintain a standard 60C water temperature. Whatever the temperature in the cylinder, if it's higher than what we need at the taps, a TMV blends it with cold water - so as long as MrsZ's shower temperature is adequate we don't notice the water temperature falling over a number of days - and as you know, the lower the stored water temperature, the lower the Delta-T, the lower the heat-loss ....

There you go, logical reasoning to why & how the energy losses can & will be lower than one would expect if purely using SAP or the energy efficiency label on the cylinder .... but now for the obvious money-saving observation - if possible, fit flow restriction to the shower head, it'll save both water & energy. We used to have high-flow 'monsoon' shower heads - they were changed years ago ....

An obvious observation to wrap up with ... over the 12 day period you mention, we used no gas and paid nothing whilst you used 69.3kWh and paid considerably more than the £2 mentioned, more likely around £5 when standing charges are accounted for ....

HTH
Z

silverwhistle

zeupater wrote: »

An obvious observation to wrap up with ... over the 12 day period you mention, we used no gas and paid nothing whilst you used 69.3kWh and paid considerably more than the £2 mentioned, more likely around £5 when standing charges are accounted for ....

That reminds me: I asked on another thread what actual standing charge you pay. I'd be interested to know, as it has a big impact on us poor, low usage types. Thanks.