Help with understanding my indirect hot water system, and whether it is efficient for my needs?

QrizB

haste said:

The current arrangement means that the hot taps take a long time for the water to run hot - I would guess 60 seconds on average.

That will be the time taken for the water to flow from the tank to the taps.

haste said:

I am pretty sure the boiler we have is a combi boiler. Would it be a big job to set it so that it's this that produces the hot water, and not stores it in the tank? 

It would be quite unusual to have a combi boiler and a hot water tank, but it's also quite unusual to have an uninsulated hot water tank (not least because the energy-saving properties of HW cylinder jackets have been well publicised for the past 40+ years).

Exactly what make and model of boiler is it?

haste

QrizB said:

haste said:

The current arrangement means that the hot taps take a long time for the water to run hot - I would guess 60 seconds on average.

That will be the time taken for the water to flow from the tank to the taps.

haste said:

I am pretty sure the boiler we have is a combi boiler. Would it be a big job to set it so that it's this that produces the hot water, and not stores it in the tank? 

It would be quite unusual to have a combi boiler and a hot water tank, but it's also quite unusual to have an uninsulated hot water tank (not least because the energy-saving properties of HW cylinder jackets have been well publicised for the past 40+ years).

Exactly what make and model of boiler is it?

I am doubting my self now whether it is a combi boiler. I cant figure it out. 

Worcester Bosch Greenstar 8000 Life GR8300iW 50 R NG 

Verdigris

I would investigate fitting a new, foam lagged, cylinder somewhere between the bathroom and kitchen to reduce the "dead leg" in the system. You clearly need that size of boiler to heat such a large property but is is immaterial to water heating, which only requires a small proortion of the maximum output.

tim_p

So is this uninsulated hot water tank just bare copper?

haste

tim_p said:

So is this uninsulated hot water tank just bare copper?

I think so?

It's this:
It's a Joules Indirect Cylcone CY250L, with nothing wrapped around it. 

doodling

Hi,

There are several issue, not all related:

The first is how quickly the water runs hot when you turn on a tap.  This is generally unrelated to whether you have a combi or a traditional hot water cylinder but is more determined by the length of pipe between the source of the hot water (i.e. the hot water cylinder or a combi boiler) and the tap.  It sounds like in your house there is a very long pipe run.  It may be that the plumbing is poorly arranged, or simply that the hot water cylinder has been installed a long way away from the taps.  Fixing that might involve re-plumbing, moving the hot water cylinder to the same space as the boiler or replacing the boiler with a combi (because the boiler is close to the taps).

The second is the rate at which you use hot water.  A hot water cylinder (once it has warmed up) can deliver a lot of hot water very quickly, limited only the size of the pipework.  This means that a bath can be filled really quickly or that several showers can be used at the same time.  The rate at which a combi boiler can deliver hot water depends on how hot the cold water is when it comes into the house and how powerful the boiler is.  For example, a 40kW combi boiler could heat around 16 litres a minute from 5 degrees to 40 degrees C, whilst a hot water cylinder could deliver 50 litres a minute or more.  There is no universal agreement as to what constitutes a decent shower but 10 litres per minute is probably satisfactory to most people.  bear in mind that an electric shower (12kW) will achieve around 5 litres per minute under the same circumstances.

The third is that the combi has the advantage that it never runs out so whilst the combi can deliver its 16 litres per minute forever, the 200 litre hot water cylinder can only deliver its 50 litres per minute for 6 minutes (assuming for ease that water is stored around 58 degrees, incoming water is 5 degrees C and therefore to get 40 degrees C water you mix two parts hot to one part cold).

The fourth is the rate at which you use water generally.  If you have very poor mains pressure or flow then filling a bath might take a long time or a shower would have low pressure and you might want to store water (e.g. in a tank in the loft) so that you can fill a bath quickly and/or use a pump to boost pressure.  Combi boilers are not designed for systems where cold water is stored (i.e. is not at mains pressure).

The fifth is efficiency.  In general heating water on demand is more efficient as it doesn't get a chance to cool down.  In many properties that doesn't make much difference in winter as the cooling down is heating the rest of the house although in your case that might not be true.  Having said that, a properly insulated hot water system shouldn't lose that much heat.

The sixth is the future.  Instant hot water heating is incompatible with heat pumps, the governments preferred future heating technology.  Be aware that whilst a combi might be an option now, you will be putting a hot water cylinder back when we reach the point that gas boilers are no longer socially acceptable, this might be 20-50 years in the future though.

doodling

Hi,

haste said:

tim_p said:

So is this uninsulated hot water tank just bare copper?

I think so?

It's this:
It's a Joules Indirect Cylcone CY250L, with nothing wrapped around it. 

Unless the insulation has been deliberately removed then that tank is delivered covered in insulation.  Are you sure you aren't mistaking the thin metal outer cover for the tank itself?

That is also an unvented cylinder so your hot water is (presumably) at mains pressure?

tim_p

haste said:

tim_p said:

So is this uninsulated hot water tank just bare copper?

I think so?

It's this:
It's a Joules Indirect Cylcone CY250L, with nothing wrapped around it. 

My moneys on it being insulated. Can’t believe it isn’t. 

haste

doodling said:

Hi,

haste said:

tim_p said:

So is this uninsulated hot water tank just bare copper?

I think so?

It's this:
It's a Joules Indirect Cylcone CY250L, with nothing wrapped around it. 

Unless the insulation has been deliberately removed then that tank is delivered covered in insulation.  Are you sure you aren't mistaking the thin metal outer cover for the tank itself?

That is also an unvented cylinder so your hot water is (presumably) at mains pressure?

 Ohhh I see! It does have a metal covering that must be covering the insulation. Okay you are filling in gaps in my knowledge, thank you. I will cancel my order for insulation jackets.

I did think it was really odd it was not insulated, especially as it is quite new.

Yes I believe we are at mains pressure. The cold water is very powerful, so I do not think we have an issue with pressure generally. 

QrizB

haste said:

Worcester Bosch Greenstar 8000 Life GR8300iW 50 R NG 

That looks to be a 50kW regular boiler (the Combi model number ends "50 C NG").

https://www.worcester-bosch.co.uk/products/boilers/directory/greenstar-8000-life-regular