Choice of intelligent switches ?

zeupater

zeupater wrote: »

... 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) ...

Hi

Just been checking this out ... basically, the test criteria is 65C in the cylinder with a 20C ambient. The cylinder is tested with an electric immersion which raises to temperature to 65C and maintains the temperature at that level for the duration of the test, beginning with a 24hours thermal soak before a 72hour test cycle starts - the standing heat loss equates to the metered electrical energy required to maintain the temperature at 65C over the 72 hours which is then divided by 3 to give a kWh per 24hours standing heat loss ...

Great for printing on a label for comparing one cylinder's relative efficiency with another, but as a reliable source for calculating actual heat loss in real world conditions, especially ones where the DHW temperature is allowed to vary, possibly over a number of days, it's more than a little flawed ...

HTH
Z

Cardew

zeupater wrote: »

Hi

Just been checking this out ... basically, the test criteria is 65C in the cylinder with a 20C ambient. The cylinder is tested with an electric immersion which raises to temperature to 65C and maintains the temperature at that level for the duration of the test, beginning with a 24hours thermal soak before a 72hour test cycle starts - the standing heat loss equates to the metered electrical energy required to maintain the temperature at 65C over the 72 hours which is then divided by 3 to give a kWh per 24hours standing heat loss ...

Great for printing on a label for comparing one cylinder's relative efficiency with another, but as a reliable source for calculating actual heat loss in real world conditions, especially ones where the DHW temperature is allowed to vary, possibly over a number of days, it's more than a little flawed ...

HTH
Z

Presumably that is the measuring data from the old? British Standard? The kWh loss in 24 hours @ 65C was stamped on the tank. With my new tank just the kW loss is given.

Agreed it is flawed as a measure 'for calculating actual heat loss in real world conditions, especially ones where the DHW temperature is allowed to vary' .

However in your situation with a lower water temperature and the HW tank in a small cupboard with a high ambient temperature, the heat loss will be even less.

It is also pertinent that for much of the year, this 'heat loss' warms the fabric of the house; so is not a loss. Indeed there is an argument for those with an Immersun type device, to remove insulation from the HW tank and allow the tank to act as a 'solar heated radiator'

P.S.
Have you read this?

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/198850/hot_water_cylinders_buffer_tanks_heat_pumps.pdf

Dave_Fowler

orrery wrote: »

An extra question...

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

Neither!

It's not as sloping as it looks in the picture, as there is a 3D effect. The pipe on the left is further from the camera than the one on the right and the picture is taken from a height which is higher than the pipes.

There is a slight slope, but that's just due to my varifocal glasses distorting the image when I was cutting the pipes.

Dave F

zeupater

Cardew wrote: »

Presumably that is the measuring data from the old? British Standard? The kWh loss in 24 hours @ 65C was stamped on the tank. With my new tank just the kW loss is given.

Agreed it is flawed as a measure 'for calculating actual heat loss in real world conditions, especially ones where the DHW temperature is allowed to vary' .

However in your situation with a lower water temperature and the HW tank in a small cupboard with a high ambient temperature, the heat loss will be even less.

It is also pertinent that for much of the year, this 'heat loss' warms the fabric of the house; so is not a loss. Indeed there is an argument for those with an Immersun type device, to remove insulation from the HW tank and allow the tank to act as a 'solar heated radiator'

P.S.
Have you read this?

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/198850/hot_water_cylinders_buffer_tanks_heat_pumps.pdf

Hi

"old? British Standard?" ... I don't believe so as our current cylinder is Part L compliant and states the standing energy losses in kWh/24hrs, simply dividing this by 24 gives the thermal losses in kW so I don't see an issue .... the test procedure is as per current standard HWA001 (your stainless steel) which in turn relates to current copper cylinder standard BS 1566, after all, when comparing storage heat losses, why would anyone sensible (so obviously excluding DECC, BRE etc) use different test procedures ?

Regarding the DHW being stored in a small cupboard, almost every domestic property with a cylinder I've ever been in has it in a small cupboard, usually using the raised heating levels for airing, so I doubt that a 20C ambient is anywhere near representative ....

Anyway, looking at the referenced link it seems to just be another example of why DECC is being axed. The report carries over flaws for test procedures and then makes them worse ... simply look at the test methodology, particularly the test-bed timescales .... then there's the 'field' test which doesn't account for site variables (primary circuit lengths etc). DECC are (/were) always being criticised for commissioning hugely expensive research with little regard to practical follow-up projects. Effectively, the report tells me that heating a cylinder from the bottom is preferable, stratification is good, the bigger the cylinder the greater the standing heat loss and that a considerable amount of heat is lost through uninsulated primary circuits ( :think:Wow, as if!! ... :wall::whistle:) - however, the cross relationship of stratification to heat-loss is totally overlooked, as is the ability to reduce primary circuit losses by simply reducing the frequency which they are used and netting that off the cylinder losses ..... I simply wonder whether the research led to the conclusions, or the conclusions came first and the research was specifically designed to support them in order to satisfy the DECC funding criteria ...

HTH
Z

adampv

Not meaning to hijack but has anyone else with an Immersun device noticed the monitoring service has now been shut down after 4eco went into insolvency?

Anyone managed to get into the data logging and read direct?

orrery

zeupater wrote: »

...and states the standing energy losses in kWh/24hrs, simply dividing this by 24 gives the thermal losses in kW so I don't see an issue ....

Maybe they assume that the loss reduces as the water cools so measuring it as kWh/24hrs would be correct, but this wouldn't equate to a constant rate in kW ... ?

danesol

Don't worry adampv, it maybe soon back up Immersun has just been acquired by another leading company in this field :-)

pinnks

For most of us it is back up and running. see the thread on "Own consumption v export" for details of how to get back in

mickyduck

My solarimmersion has started to play up.. in the last couple of months it has randomly stopped diverting power to the immersion. Factory reset has so far fixed it for a while.. I have raised a ticket with their support I will let you all know of the outcome.

mickyduck

Looks like I will have to return it.. repair will be £55 +VAT.. unless I want to "upgrade" to Mk IV where I will get a small discount on the new price.....
3 years in and faulty, probably not a good ROI