Query: Gas central heating & hot water...

whowants2brich

Hi there!

We have an old-style timer for our gas central heating and hot water (all in one, but obviously at this time of year, we have all the heaters turned fully off), so we're just heating the water in our storage tank. I'm not talking about the central heating element of it, because I know that that's a whole different ball game...

My scenario is simple:

We have the gas on for an hour in the morning and an hour at night (at a setting of 1.5 on the gas boiler), and have enough hot water. I don't know if there's a separate thermostat on the water heater, but I don't think I can move it - it's not moving! I can't set the timer to be on any less time than this, without manually intervening. I can't help but think that we could have the gas on for shorter because it's heating more water than we need, but there's not much I can do about it.

Our gas heater has a thermostat thing between 0 and 6, to control the flow of gas and power that is pushed through the system. I think that 6 heats the water much faster, 0 is hardly any gas at all...

The question:

Is it better (cheaper, use less kWh) to have the gas system heating water at a lower setting (say 0.5-1) for a few hours, or at a higher setting (3/4/5) for a shorter space of time by manually activating it as and when we need it?

Or would it be better (cheaper) to manually use our immersion heater, and not use the gas at all in the summer?

I look forward to hearing your comments, and apologies if anyone else has already asked this question...

Thank you!

espresso

whowants2brich wrote: »

Our gas heater has a thermostat thing between 0 and 6, to control the flow of gas and power that is pushed through the system. I think that 6 heats the water much faster, 0 is hardly any gas at all...

The thermostat on the boiler does not affect the gas flow, it's either burner on of off dictated by the water temperature, which is controlled by the thermostat setting. Usually 0 - 6 equates to approx 55C - 85C (130F - 185F)

The question:

Is it better (cheaper, use less kWh) to have the gas system heating water at a lower setting (say 0.5-1) for a few hours, or at a higher setting (3/4/5) for a shorter space of time by manually activating it as and when we need it?

It won't have much effect on the time taken to heat the water as long as it's set to a high enough temperature to obtain the required hot water setting on the tank stat.

Or would it be better (cheaper) to manually use our immersion heater, and not use the gas at all in the summer?

No, standard rate electricity is at least three times more expensive per kWh than gas.

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whowants2brich

espresso wrote: »

.The thermostat on the boiler does not affect the gas flow, it's either burner on of off dictated by the water temperature, which is controlled by the thermostat setting. Usually 0 - 6 equates to approx 55C - 85C (130F - 185F).

Does this mean that a setting of 0 on the boiler is 55C and 6 is 85C ? If so, setting the boiler would mean that the water is heated to 55C and therefore use less gas than heating the water to 85C?

If we have the boiler on for 1 hour at a setting of 0 (55C) that should be more than enough to heat the tank only? I hate the idea of paying to heat up the water, only to find it's too hot and that we have to add cold water to it to cool it down...

Thanks!
Richard

Sponge

Don't forget your hot water really needs to be heated to, and stored at, at least 53C (I think it may even be 60C) to prevent Legionellas.

Edit:

How water temperatures affect Legionella (temps in C)

70-80 Disinfection Range
66 Legionella die within 2 minutes
60 Legionella die within 3 minutes
55 Legionella die within 5 to 6 hours
20-45 Legionella multiply
<20 Legionella are dormant

So as you can see, simply increasing your water storage temperature from 55 to 60 dramatically reduces the risk from Legionella.

How the above is of some use.

espresso

whowants2brich wrote: »

Does this mean that a setting of 0 on the boiler is 55C and 6 is 85C ? If so, setting the boiler would mean that the water is heated to 55C and therefore use less gas than heating the water to 85C?

It depends on your particular boiler so RTFM. 0 may well actually be OFF and 1 - 5 may equate to approx 55C - 85C

If we have the boiler on for 1 hour at a setting of 0 (55C) that should be more than enough to heat the tank only? I hate the idea of paying to heat up the water, only to find it's too hot and that we have to add cold water to it to cool it down...

If you have it on the lowest setting, then the water in the tank can never get hotter than that setting can it and 55C is below the recommended temperature for domestic hot water. You should have a separate adjustable thermostat located on the hot water storage tank, which will shut down the boiler when no more heat input is required, irrespective of how long you have the boiler timed to come on.

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