Upgrade boiler in new house to Combi?

RavingMad

Albermarle said:

Grenage said:

RavingMad said:

Given that you're already in the house, you must be seeing how much energy you're using to heat the tank? I only heat the water up to 45⁰ in the summer and it's about 4/5 kWh a day (30 mins in the morning) that does the 4 of us

Isn't that too low to kill bacteria?

The recommended temperature is 60 to 65 degrees ( depending in what you read) to kill all Legionnaire bacteria.
However Legionnaires disease frequency in UK is very low, and in a domestic setting where there is water flow every day the chances are even lower. Also temperatures lower than 60 still kill the bacteria, but more slowly.
Plus hot water at 65 ( even if it drops to 60) will scald your hands.
Personally I think 45 is a bit low but the risk at 55 is minimal. 

If the poster is worried about the cost of heating a tank, and the risk of legionella in this country is next to zero, then I think lowering the temperature is a handy tip. Plus you may end up using less hot water as you're adding cold to it

Steveotwo

Albermarle said:

Ectophile said:

I can't imagine the extra gas used by the existing boiler is going to cost £2000 over any reasonable time frame.

When I changed from non condensing to condensing and generally a more modern boiler, I saved about 15% in gas consumption. So about £100 then and about £150 now.

I'm nervous of the bills spiking from heating a water tank and not using all of the water that is heated

A lot depends on the hot water tank. If it is an old copper one, with some lagging around it, then it will be ineffecient and will cool down quite quickly.
If it is a new one with integrated insulation, any hot water you do not use will still be largely hot many hours later.

Thank you, is that a saving of £150 a year or month? I think its more of a modern one with green foam insulation

Section62

RavingMad said:

Albermarle said:

Grenage said:

RavingMad said:

Given that you're already in the house, you must be seeing how much energy you're using to heat the tank? I only heat the water up to 45⁰ in the summer and it's about 4/5 kWh a day (30 mins in the morning) that does the 4 of us

Isn't that too low to kill bacteria?

The recommended temperature is 60 to 65 degrees ( depending in what you read) to kill all Legionnaire bacteria.
However Legionnaires disease frequency in UK is very low, and in a domestic setting where there is water flow every day the chances are even lower. Also temperatures lower than 60 still kill the bacteria, but more slowly.
Plus hot water at 65 ( even if it drops to 60) will scald your hands.
Personally I think 45 is a bit low but the risk at 55 is minimal. 

If the poster is worried about the cost of heating a tank, and the risk of legionella in this country is next to zero, then I think lowering the temperature is a handy tip. Plus you may end up using less hot water as you're adding cold to it

The risk isn't "next to zero" though, and one of the reasons why cases in the UK are relatively low is because most systems are designed/installed to reduce the risk as much as possible.

When people go off-piste and modify systems without full knowledge of the risks involved they can place themselves (and their family) at much higher risk levels than the national average.

This is a moneysaving site, but taking unnecessary risks with people's health to save a few pennies is not a good idea.

Albermarle

Steveotwo said:

Albermarle said:

Ectophile said:

I can't imagine the extra gas used by the existing boiler is going to cost £2000 over any reasonable time frame.

When I changed from non condensing to condensing and generally a more modern boiler, I saved about 15% in gas consumption. So about £100 then and about £150 now.

I'm nervous of the bills spiking from heating a water tank and not using all of the water that is heated

A lot depends on the hot water tank. If it is an old copper one, with some lagging around it, then it will be ineffecient and will cool down quite quickly.
If it is a new one with integrated insulation, any hot water you do not use will still be largely hot many hours later.

Thank you, is that a saving of £150 a year or month? I think its more of a modern one with green foam insulation

If 15% saving = £150 a month, then it would mean my annual gas bill was £12k !

It is per year for a 4 bed older house that is not that well insulated. If you had a more modern 3 bed semi, probably the saving would be more like £100 a year.

Steveotwo

Albermarle said:

Steveotwo said:

Albermarle said:

Ectophile said:

I can't imagine the extra gas used by the existing boiler is going to cost £2000 over any reasonable time frame.

When I changed from non condensing to condensing and generally a more modern boiler, I saved about 15% in gas consumption. So about £100 then and about £150 now.

I'm nervous of the bills spiking from heating a water tank and not using all of the water that is heated

A lot depends on the hot water tank. If it is an old copper one, with some lagging around it, then it will be ineffecient and will cool down quite quickly.
If it is a new one with integrated insulation, any hot water you do not use will still be largely hot many hours later.

Thank you, is that a saving of £150 a year or month? I think its more of a modern one with green foam insulation

If 15% saving = £150 a month, then it would mean my annual gas bill was £12k !

It is per year for a 4 bed older house that is not that well insulated. If you had a more modern 3 bed semi, probably the saving would be more like £100 a year.

Sorry you caught me early after the bank Holiday 😅
Yeah 4 bed reasonably insulated. if the annual saving is only going to be around £150 I think ill take the family on holiday instead with that money

Steveotwo

FreeBear said:

Albermarle said:

Ectophile said:

I can't imagine the extra gas used by the existing boiler is going to cost £2000 over any reasonable time frame.

When I changed from non condensing to condensing and generally a more modern boiler, I saved about 15% in gas consumption. So about £100 then and about £150 now.

I'm nervous of the bills spiking from heating a water tank and not using all of the water that is heated

A lot depends on the hot water tank. If it is an old copper one, with some lagging around it, then it will be ineffecient and will cool down quite quickly.

With my old non-condensing Baxi back boiler, I had been using around 8000kWh per year. Several measures were put in place to cut gas consumption (turning gas off during the summer, using a programmable thermostat). This reduced consumption down to around 5000kWh/p.a.. Latest figures with the new combi suggests 3500kWh/p.a. or 30% saving. Cutting the gas bill by £75, I'm never going to recover the investment, but having a warm home and instant hot water offsets the cost somewhat. Also don't have to argue with a GS engineer when it comes to getting a Gas Safety certificate.

Yes I think not worrying as much when the heating is running about inefficient usage will put my mind at rest a bit more
 

Martyn_H

There's only the two of us in our house but our gas consumption for a non combi boiler is a rather high 15000 kWhs per annum. Having said that, our dual fuel direct debit is only £145 per month.

Steveotwo

Martyn_H said:

There's only the two of us in our house but our gas consumption for a non combi boiler is a rather high 15000 kWhs per annum. Having said that, our dual fuel direct debit is only £145 per month.

Do you think it would lower much with a combi?

Eldi_Dos

Martyn_H said:

There's only the two of us in our house but our gas consumption for a non combi boiler is a rather high 15000 kWhs per annum. Having said that, our dual fuel direct debit is only £145 per month.

You might be able to lower that consumption by installing a more modern boiler control/thermostat at not too great a cost.

ThisIsWeird

Steveotwo said:

Martyn_H said:

There's only the two of us in our house but our gas consumption for a non combi boiler is a rather high 15000 kWhs per annum. Having said that, our dual fuel direct debit is only £145 per month.

Do you think it would lower much with a combi?

I suspect it depends on what the main gas use is? Is Martyn's house particularly hard to heat, do they like it proper-warm, or do they just have lots of soapy baths? 
Tbh, in neither case will a combi make a significant difference, as the current usage will remain the same.
If it's a poorly insulated house, then that's the solution, as it would be with any boiler.