Gas Hot Water question

[Carl Inglis]

I've been troughing round the net trying to find an answer to this, or at least some clues as to how to work it out for myself, but I haven't been able to find anything of use. Pointers to useful information would be much appreciated.

We rent our property, so there's not a lot of scope for changing plumbing, insulation and so on. My wife has been told that one way we could save on the gas bill is to run the hot water system 24/7. This seems counter-intuitive to me, but the source of the information was apparently a British Gas chap.

Our setup is a gas powered Baxi Solo 2 50 RS, feeding an insulated hot water tank (airing cupboard) and the radiators. Each function is on a seperate timer. The boiler was recently gas-safety checked and is functioning at 74% efficency.

I'd appreciate any information that the group my be able to share that will allow me to prove/disprove this idea.

Thanks in advance.

Carl

[Roger Mills (aka Set Square)]

Running your how water system 24x7 will use *more* gas than timimg it to co-incide with your usage - though probably not by very much if the cylinder is well insulated.

As any schoolboy (or girl!) familiar with Newton's Law of Cooling will tell you, the heat loss from a body (for a given standard of insulation) is proportional to the temperature difference between the body and its surroundings. So if the hot water tank is hotter than it needs to be for a lot of the time, you will waste more heat.

Consider the scenario where you have a bath last thing at night, using most of the hot water, and will not require any more hot water until you get up at (say) 7am. In this case, it makes far more sense to allow the cylinder to remain cold overnight - bringing the boiler on at (say) 6am to ensure that you have hot water when you need it. If the system is running 24x7, the boiler will fire up to re-heat the water unnecessarily as soon as you run the bath.

As long as your water using habits are reasonably predictable, you should be able to heat the water for 3 short periods each day and have all the water you want when you want it without wasting gas.

It goes without saying that you should make sure that the cylinder is as well insulated as you can possibly make it.

[John]

".

It is also relevant to check that the tank has a thermostat and tells the boiler that the water is up to temperature. Some older installations relied upon the boiler stat and will keep firing even though the tank is hot enough.

John

[Carl Inglis]

[snip]

A very valid point. I've just gone and looked at the tank and there's a large pipe going in at the bottom, another one just over 1/3rd of the way up it and a smaller one coming out of the top. The only other connection is the immersion heater in the top (which we never use).

With that in mind, it seems very likely that adding another insulation jacket to the tank (which only has some blue foam with the makers labels on the outside) and changing to a timed system would be a great benefit.

I think my wife's informant was probably either trying to increase gas usage to profit his employers, or was talking about a very specific setup.

Thanks for the advice.

Carl

[Carl Inglis]

On 2006-03-18, Roger Mills (aka Set Square) wrote: [snip]

[snip]

Since we have had a shower fitted, it seems very likely that our usage will become much more predictable (electricly heated shower - landlord's choice, we didn't have a say).

Thanks for the information, I'll go and start working out the best time(s) to set it for.

Carl

[Geronimo W. Christ Esq]

This is the cylinder coil. Your boiler and pump circulate hot water through this to heat the water inside the cylinder. It's just a loop of copper pipe going around and then out.

A cylinder stat attaches to the side and controls a motorized valve, which allows your boiler to concentrate on heating your radiators whenever the hot water has reached the required temperature. Without a cylinder stat, the boiler will always try to heat the hot water whenever your timeclock is set to do so, even when it is hot enough. The cylinder stat is really an efficiency measure.

Do you know what motorized valves are on your system ? They just look like metal/plastic boxes hanging off the pipes.

Hot water comes out to this to your taps/shower etc.

Maybe not, but it's handy if the heating fails and you need to have a shower.

Others will be along to comment on this, but I think it is highly unlikely that adding a jacket to this will help much. Is there much ambient heat in your hotpress when the boiler has been running for a few hours ?

My cylinder has a jacket on it, but that's because it isn't sprayed with the foam that you're seeing. The foam is much more effective than a jacket.

[Carl Inglis]

[snip]

See below...

There certainly doesn't appear to be one of those.

I can't see any. All the valves I can see are the standard stop-c*ck type; but I can't see what's within the boiler itself. There's one big pump-like object just underneath the boiler, but that's about all there appears to be.

That disagrees with the diagram on the side of the foam...

According to the diagram the top pipe is a "vent" pipe, the pipe at the bottom is /to/ the boiler and the pipe a bit further up is /from/ the boiler.

Oh indeed.

It's warm, regardless of the room/outside temp.

In that case, I'll save myself the cost of the jacket! :-)

Thanks for your thoughts.

Carl

[John]

Even without motorised valves a cylinder stat can be used to shut down the boiler when the cylinder reaches the set temperature. I added one to my first house that had a back boiler and a very basic system. It saved me loads of money.

John

[mogga]

Ask your landlord about insulating the place if it needs doing. If he's reluctant then find out if there are grants in your area and offer to pay half of any amount (or 1/4 etc) to get more insulation. Try to convince him its a selling point for future tenants? EST link on

switching electricity company too.