Heating water in summer months

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PC100

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Just wondering can a modern gas boiler heat water for showers, etc more efficiently than turning on the immersion a couple of times a day.
We have what I think is fairly common boiler (Gloworm Flexicom 24hx) for 4 bed house. Is it possible to turn off the radiator heating and just heat water using the boiler and am I correct in thinking that just turning off all the radiators is inefficient.
 
I thought it fairly typical modern controlling thermostat has 2 zones, one for heat and one for water.


I don't know about efficiency re: turning off all rads.
 
I'd be interested in the responses to this also. We have an oil fired boiler. In the summer we turn it on for an hour in the mornings but with all the thermostats turned down. Not sure if this is the most efficient way of doing it.
 
Like Odyssey06, I would have thought that all modern heating systems would have at least two zones.

I turn off the radiator zone in the summer and heat the water for two half hour periods, morning and evening. It has the advantage, (in my mind) of cycling the boiler as opposed to having it lie dormant for a few months, only to pack up at the start of winter when it's needed again.
 
I asked this question recently as we got a new Vokera boiler in. The answer was that gas is cheaper than electricity to heat an immersion. But....we have a very old solar panel set up - nearly 15 years old and that does all our hot water from April to end of September. Rarely would we use immersion in theis period. Well worth it.
 
The SEAI produce an energy cost comparison, while its focus is space heating it is useful to water heating too. Gas or oil is significantly cheaper where you have the ability to isolate the water circuit or turn off all rads.
 
I have an old system that I can't zone. But even with turning the rads off and using gas to heat the water, it's still cheaper than using the immersion.
 
If you were on the BG EV plan with has a night rate of 10.40c between the hours of two and five in the morning
Would it then be cheaper to use the immersion compared to gas at 12.71c??
 
Last edited:
Cervelo said:
If you were on the BG EV plan with has a night rate of €10.40 between the hours of two and five in the morning
Would it then be cheaper to use the immersion compared to gas at €12.71??
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€10.40/€12.71 per kWh/unit?! :eek:
I presume that you're out by two orders of magnitude there?

Anyway, the respective unit rates and the number of units used by each method in a particular installation determines the answer to your question.
 
Cervelo said:
If you were on the BG EV plan with has a night rate of 10.40c between the hours of two and five in the morning
Would it then be cheaper to use the immersion compared to gas at 12.71c??
Click to expand...

Yes in that case immersion would be cheaper, also keep in mind the immersion is 100% efficient and the boiler can be anywhere from 60-90% depending on age so this need to be factored in to the calculation too.
 
Buddyboy said:
Like Odyssey06, I would have thought that all modern heating systems would have at least two zones.

I turn off the radiator zone in the summer and heat the water for two half hour periods, morning and evening. It has the advantage, (in my mind) of cycling the boiler as opposed to having it lie dormant for a few months, only to pack up at the start of winter when it's needed again.
Click to expand...

2 x 0.5 hr periods ? we're a family of 4 and need 2 x 1hr periods.
Click to expand...
 
And wouldn't you know it, the boiler is on it's last legs and we're investigating replacing it what an air to water heat pump. Luckily we have UFH and new rads, so it might not break the bank.

I'll start a new thread on the process/cost when we get the ball rolling rather than derail this tread.
 
Even with a zoned system we would use the immersion to heat water in the summer because it's much faster than using oil, and by a considerable margin.
 
demoivre said:
Even with a zoned system we would use the immersion to heat water in the summer because it's much faster than using oil, and by a considerable margin.
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That might point to an issue with the coil or water heating circuit affecting the efficiently of the transfer of heat. 30 minutes twice a day is all we need to run our oil burner to heat all the water we need for power showers, general use and the occasional bath.
 
For 3-4 months during every summer I do a scheduled immersion heat up using a MyEnergi Eddi and then during the day if there's any excess solar this also gets dumped into the hot tank before being exported. I turn off the Gas Boiler during this time.
My Gas boiler stopped working today so I made the switch a few days early. I've a day/night meter so I time the morning boost to finish before the day rate kicks in.
 
Interesting thread, we have the choice of either but typically stick with gas throughout the year.

Our night rate electricity is cheaper, so on paper it is the better option. I did think though there was (probably?) a benefit keeping the gas boiler in daily usage, rather than leaving it sitting idle for 4 months of the year.
 
I use the immersion during the months the heat isn't on, old gas system so don't have the option of just heating water and can't be bothered going around to turn off all the radiators! Only need a tiny bit of hot water anyway to wash up usually. Never gave a thought to the idea that leaving the boiler off for months was an issue, it's lasted 32 yrs so hasn't done it any harm yet!
 
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