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

haste

We have moved into a large, old house and the bills are very high - currently £400 a month for gas and Elec with Octopus. 

I'm trying to figure out the most efficient way to manage the hot water, amongst other cost saving measures. 

In the cellar is an Indirect Hot Water cylinder, controlled by a Honeywell Smart thermostat, and powered by a relatively new 48kw Worcester boiler.

The current schedule has the hot water on for four hours in the morning, and four in the evening.

In my previous home I had a combi boiler, so hot water was produced only when It was needed. In the current system, hot water is being heated and stored whether it is used or not, and I'm trying to figure out if this is more efficient, or even why this was chosen over a normal combi boiler.

We are not a high usage household - but the home is big so maybe it's a way to get hot water around the property?

If I set the hot water schedule to be off entirely - am I right in saying that the immersion heater in the hot water cylinder will heat the water? Is there any way that would be more cost effective for us than heating an entire tank of hot water?

Would I be better moving to a combi boiler system? 

BUFF

What capacity is the cylinder & how well insulated is it? Might be useful to also know manufacturer & model.
What temp is the cylinder thermostat set for?

Do you have E7 electricity? Presuming it's a gas boiler then electricity (other than a heat pump) is usually a much (3-5x) dearer way of heating than an efficient modern boiler.

Verdigris

Is the cylinder foam lagged or does it have "jacket" insulation? If the latter it will lose lose heat more quickly. It won't take 4 hours to heat the cylinder but the boiler may be firing again, if the water cools off in the set period. See how long it takes to heat an full cylinder from cold. Then you can start to work out how long to fire it to meet your particular needs.

I run my boiler for 6 minutes, in the summer, which gives me enough water for a shower. I run it a bit longer if there's washing up to do. In the winter I have haot water all the time because the boiler satisfies the DHW load befoire the heating, but the heat loss from the cylinder warms the house, so no real loss.

haste

BUFF said:

What capacity is the cylinder & how well insulated is it? Might be useful to also know manufacturer & model.
What temp is the cylinder thermostat set for?

Do you have E7 electricity? Presuming it's a gas boiler then electricity (other than a heat pump) is usually a much (3-5x) dearer way of heating than an efficient modern boiler.

It's a 250l tank, and it is not insulated at all right now. I have just bought a set of insluation jackets that will arrive this week, so I can at least rectify that.

As for what temp it is set for - I do not know. I can't find that particular setting anywhere. On the immersion heater (I think thats what it is) in the boiler it's self, which is a Thermowatt alloy, the dial is set all the way to the right - which I persume is max.

My Honeywell smart home system reads the tank at 54c when the hot water is On, but I again I can't find where I could increase or decrease that. 

haste

Verdigris said:

Is the cylinder foam lagged or does it have "jacket" insulation? If the latter it will lose lose heat more quickly. It won't take 4 hours to heat the cylinder but the boiler may be firing again, if the water cools off in the set period. See how long it takes to heat an full cylinder from cold. Then you can start to work out how long to fire it to meet your particular needs.

I run my boiler for 6 minutes, in the summer, which gives me enough water for a shower. I run it a bit longer if there's washing up to do. In the winter I have haot water all the time because the boiler satisfies the DHW load befoire the heating, but the heat loss from the cylinder warms the house, so no real loss.

The Tank is in the cellar, so it's certainly not heating the house much, if at all. 

What I am trying to figure out is why I have this system in the first place, rather than use the Worcster boiler just to produce hot water as we need it? Can you shed some light on that at all? 

Verdigris

What I am trying to figure out is why I have this system in the first place,

It is what was the norm before combi-boilers became prevalent. The advantage is that you get a much faster delivery of water. Horses for courses.

haste

Verdigris said:

What I am trying to figure out is why I have this system in the first place,

It is what was the norm before combi-boilers became prevalent. The advantage is that you get a much faster delivery of water. Horses for courses.

Annoyingly, the hot water takes 60 seconds or more to run hot. I'm not sure if that's because its traveling a long way through the pipes, or because it has to be heated in the tank before coming out. 

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? 

matelodave

Reduce the time that you are heating your hot water - we get away with around 1-1.5hours a day, in the morning just before we get up so it's nice and hot for ablutions and there's still plenty left for a bedtime shower.

Secondly put as many insulating jackets on it as you can manage and it would be worthwhile putting some insulation over the hot pipes that leave the tank to reduce heat losses by conduction.

Lastly turn the tank temp down to around 60 degrees - the hotter you keep it the more heat it loses and there's really isn't a lot of benefit in keeping the tank hot during the day or overnight unless you are using vast quantities of hot water during those times. Bear in mind that the boiler will keep firing and circulating hot water around the system to maintain the temperature.

You can reduce the heat losses by reducing the number of times you draw off hot water. Use cold where possible (from the cold tap) rather than wasting half a gallon or so of cold water down the sink until the water runs hot and then leaving half a gallon or so of expensive hot water sitting in the pipework to get cold.

Likewise, use a bowl or dishwasher for washing up rather than letting hot water run down the drain whilst washing and rinsing stuff.(including your hands and face)

QrizB

haste said:

We have moved into a large, old house ... in the cellar is an Indirect Hot Water cylinder, controlled by a Honeywell Smart thermostat, and powered by a relatively new 48kw Worcester boiler.

48kW is huge for a conventional domestic boiler, most normal-sized houses have boilers one-third to one-half that size. If your new house needs a boiler 3x the size of a typical one, I would expect your bills to be 3x the size too.

doodling

Hi,

How big is the house, does it have more than one bathroom?  Does it have a bath?  How far from the point at which the hot water is used is the boiler?

Whilst combi boilers are great if the maximum rate at which you consume hot water is limited (e.g. you are never using more than one shower at a time), they will struggle to keep up with supplying two or more showers (especially ones with relatively high flow rates) at once or filling a bath at a sensible speed.

If the house is really big (does it have wings?) then the use of a hot water cylinder permits an arrangement where hot water is circulated by a pump such that there isn't a delay whilst hot water finds its way from a cylinder to the tap.  I have no idea if your house is sufficiently big for this to be an issue.

There is also a matter of expectation - as an example, I am aware of a row of Victorian villas which are effectively 7 bedroom, 3+ bathroom properties.  People in the market for that kind of house would be disappointed to discover it had a combi because they know that it wouldn't deliver what they expect if all the bathrooms were in use.

haste

doodling said:

Hi,

How big is the house, does it have more than one bathroom?  Does it have a bath?  How far from the point at which the hot water is used is the boiler?

Whilst combi boilers are great if the maximum rate at which you consume hot water is limited (e.g. you are never using more than one shower at a time), they will struggle to keep up with supplying two or more showers (especially ones with relatively high flow rates) at once or filling a bath at a sensible speed.

If the house is really big (does it have wings?) then the use of a hot water cylinder permits an arrangement where hot water is circulated by a pump such that there isn't a delay whilst hot water finds its way from a cylinder to the tap.  I have no idea if your house is sufficiently big for this to be an issue.

There is also a matter of expectation - as an example, I am aware of a row of Victorian villas which are effectively 7 bedroom, 3+ bathroom properties.  People in the market for that kind of house would be disappointed to discover it had a combi because they know that it wouldn't deliver what they expect if all the bathrooms were in use.

Hi Doodling.

The house is quite large - It's a listed 5 bedroom property spread over what you could call two wings. But there is only one bathroom. The boiler is currently in an outhouse that is right below the bathroom, which does have a large freestanding bath.

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.