Upgrade boiler in new house to Combi?

Albermarle

Steveotwo said:

ic said:

Have you checked the details of your boiler?  Whilst it might not be condensing, given its age it could still be pretty efficient - and might be B or C rated.  You might find yourself spending £1000s on an upgrade that might never pay for itself - especially if you might then move to a heat pump within the next ten years anyway.

Simple stuff like flushing the system, fitting TRVs if they're not present, upgrading the controls, insulating the tank and pipework to it could offer a far better return.  Also all the usual stuff - is the loft insulated, cavity walls, doors and windows draught proofed?

Its a baxi solo (2004) 80% efficent at the time maybe its running at 70 now?

Lets say it is running at 70%
 was looking at a viesmann combi with 98% efficiency for around 3k
That figure is probably difficult to achieve in real conditions, so lets say 94%.
So over a year in theory you should use 24% less gas. 
A typical household uses 11,500 KWH a year, so you will save 2,760 KWh of gas a year = approx £165.
If your house/household is bigger then maybe £200 a year. Not much compared to £3K.....

Steveotwo

Albermarle said:

Steveotwo said:

ic said:

Have you checked the details of your boiler?  Whilst it might not be condensing, given its age it could still be pretty efficient - and might be B or C rated.  You might find yourself spending £1000s on an upgrade that might never pay for itself - especially if you might then move to a heat pump within the next ten years anyway.

Simple stuff like flushing the system, fitting TRVs if they're not present, upgrading the controls, insulating the tank and pipework to it could offer a far better return.  Also all the usual stuff - is the loft insulated, cavity walls, doors and windows draught proofed?

Its a baxi solo (2004) 80% efficent at the time maybe its running at 70 now?

Lets say it is running at 70%
 was looking at a viesmann combi with 98% efficiency for around 3k
That figure is probably difficult to achieve in real conditions, so lets say 94%.
So over a year in theory you should use 24% less gas. 
A typical household uses 11,500 KWH a year, so you will save 2,760 KWh of gas a year = approx £165.
If your house/household is bigger then maybe £200 a year. Not much compared to £3K.....

This is exactly what I needed to understand, thank you for doing the math's for me here. I guess I should keep it for as long as possible than reassess the options at the time.

ThisIsWeird

Steveotwo said:

Thanks I know this is the right answer, Im just nervous about my energy bill spiking this winter when compared to my last home which was a little smaller and had a greenstar bosch combi

Are there any rooms in yer hoosie that you don't use, or don't need to use over winter? If so, shut off the rad in there, and crank open the windows to 'vent'. Keep the door closed.

Old heat-only boilers like yours are very simple machines, essentially a water case with a gas fire underneath it. About the only control is a temp-control thermostat, and an overheat one. Very little to go wrong, and usually very simple and cheap to fix.

If it's running reliably, then let it run...

jennifernil

We replaced our boiler a couple  of years back with a Viessmann 100 -w heat only, keeping the existing HW tank etc, I would not consider moving to a combi an upgrade!    I prefer  to have HW always available by some means, but would not want electric showers, so stuck with tank that has immersion for back up.

The old boiler was a Potterton, really solid, 34 years old and still working fine, though not particularly efficient.  Never needed any repairs in all that time.  Our engineer’s  previous advice was to leave it alone until it died as it would have taken many years to recoup the cost of a replacement in savings on gas.

It was still working well when removed, but we decided that the increased cost of gas merited replacing it on efficiency grounds, and doing that while new gas boilers were still permitted.

We also fitted a tado control system soon afterwards, which gives us good temperature control for every room individually, so difficult to know exactly what the new boiler has saved us, but overall we are now using around 35% less gas.    Will still take many years to recoup all the costs!

Steveotwo

jennifernil said:

We replaced our boiler a couple  of years back with a Viessmann 100 -w heat only, keeping the existing HW tank etc, I would not consider moving to a combi an upgrade!    I prefer  to have HW always available by some means, but would not want electric showers, so stuck with tank that has immersion for back up.

The old boiler was a Potterton, really solid, 34 years old and still working fine, though not particularly efficient.  Never needed any repairs in all that time.  Our engineer’s  previous advice was to leave it alone until it died as it would have taken many years to recoup the cost of a replacement in savings on gas.

It was still working well when removed, but we decided that the increased cost of gas merited replacing it on efficiency grounds, and doing that while new gas boilers were still permitted.

We also fitted a tado control system soon afterwards, which gives us good temperature control for every room individually, so difficult to know exactly what the new boiler has saved us, but overall we are now using around 35% less gas.    Will still take many years to recoup all the costs!

Is your replacement non combi anymore efficent than your old one do you find? Can you not keep conventional style showers when you upgrade to a combi? 
Thanks

jennifernil

Yes, the new boilers are much more efficient than a 35 year old one, something like 90% compared to 65%.

And yes, a conventional mixer type shower can be used with a combi, but using more than one shower at a time may not be satisfactory.

We have 2 showers, 1  bath, and 3 basins, plus the kitchen and utility room to supply with hot water, so considered a combi unsuitable for our needs.   Our tank is a vented type, but the cold water tank is in the loft, the living rooms on the first floor, and the bedrooms and bathrooms on the ground floor, so showers have good pressure.

We also have a “granny flat” on the upper floor, with its own boiler and tanks, and it still has a good shower as we choose one suitable for low pressure, as the others are too.

Our daughter has a large flat, with a sprawling layout, and a combi boiler that was there when she bought it, she dislikes it intensely.    Her previous home had a unvented tank system which was excellent.

She has 4 showers,  but only 3 that are used frequently.  Only one  shower is run off the  combi,  the others are electric.  Originally they were all electric, she connected one to the combi when re-doing their en suite.   Electric ones are better than they used to be, but expensive to run.

The boiler  is at one end of her flat,  near the utility room and 3 of the bathrooms, but the kitchen and the 4th bathroom are as far from the boiler as they could be, so it takes ages to get hot water in the kitchen and the bathroom wash basin, which is far from ideal.   When she replaces that bathroom, probably in a year or two, she will install some sort of instant HW system for the wash basin.

Will be many years before she can afford to replace the kitchen, but I would think she will install a Quooker type HW tap there instead, and do away with the long HW pipe runs.

Steveotwo

jennifernil said:

Yes, the new boilers are much more efficient than a 35 year old one, something like 90% compared to 65%.

And yes, a conventional mixer type shower can be used with a combi, but using more than one shower at a time may not be satisfactory.

We have 2 showers, 1  bath, and 3 basins, plus the kitchen and utility room to supply with hot water, so considered a combi unsuitable for our needs.   Our tank is a vented type, but the cold water tank is in the loft, the living rooms on the first floor, and the bedrooms and bathrooms on the ground floor, so showers have good pressure.

We also have a “granny flat” on the upper floor, with its own boiler and tanks, and it still has a good shower as we choose one suitable for low pressure, as the others are too.

Our daughter has a large flat, with a sprawling layout, and a combi boiler that was there when she bought it, she dislikes it intensely.    Her previous home had a unvented tank system which was excellent.

She has 4 showers,  but only 3 that are used frequently.  Only one  shower is run off the  combi,  the others are electric.  Originally they were all electric, she connected one to the combi when re-doing their en suite.   Electric ones are better than they used to be, but expensive to run.

The boiler  is at one end of her flat,  near the utility room and 3 of the bathrooms, but the kitchen and the 4th bathroom are as far from the boiler as they could be, so it takes ages to get hot water in the kitchen and the bathroom wash basin, which is far from ideal.   When she replaces that bathroom, probably in a year or two, she will install some sort of instant HW system for the wash basin.

Will be many years before she can afford to replace the kitchen, but I would think she will install a Quooker type HW tap there instead, and do away with the long HW pipe runs.

Thanks for the detailed response, I have no idea how to tell if its vented or not. Im leaning towards just upgrading to a modern system boiler now

BarelySentientAI

Steveotwo said:

jennifernil said:

Yes, the new boilers are much more efficient than a 35 year old one, something like 90% compared to 65%.

And yes, a conventional mixer type shower can be used with a combi, but using more than one shower at a time may not be satisfactory.

We have 2 showers, 1  bath, and 3 basins, plus the kitchen and utility room to supply with hot water, so considered a combi unsuitable for our needs.   Our tank is a vented type, but the cold water tank is in the loft, the living rooms on the first floor, and the bedrooms and bathrooms on the ground floor, so showers have good pressure.

We also have a “granny flat” on the upper floor, with its own boiler and tanks, and it still has a good shower as we choose one suitable for low pressure, as the others are too.

Our daughter has a large flat, with a sprawling layout, and a combi boiler that was there when she bought it, she dislikes it intensely.    Her previous home had a unvented tank system which was excellent.

She has 4 showers,  but only 3 that are used frequently.  Only one  shower is run off the  combi,  the others are electric.  Originally they were all electric, she connected one to the combi when re-doing their en suite.   Electric ones are better than they used to be, but expensive to run.

The boiler  is at one end of her flat,  near the utility room and 3 of the bathrooms, but the kitchen and the 4th bathroom are as far from the boiler as they could be, so it takes ages to get hot water in the kitchen and the bathroom wash basin, which is far from ideal.   When she replaces that bathroom, probably in a year or two, she will install some sort of instant HW system for the wash basin.

Will be many years before she can afford to replace the kitchen, but I would think she will install a Quooker type HW tap there instead, and do away with the long HW pipe runs.

Thanks for the detailed response, I have no idea how to tell if its vented or not. Im leaning towards just upgrading to a modern system boiler now

Do your hot and cold taps seem to be about the same pressure?

Often, same pressure = unvented, cold has lots more pressure = vented.

jennifernil

If it is a vented system there should be a large cold water header tank somewhere, to both feed water to the cylinder, and,  ideally to the bathroom cold taps and toilets, ours is in the loft.    This equalises the hot and cold pressures .These days, certainly here in Scotland,  only the kitchen cold water is direct from the mains.  So if we have a water mains problem, at least we can still flush a toilet and wash hands.

Also, the HW cylinder in a vented system is much simpler than in an unvented system, as the latter is pressurised.

Steveotwo

jennifernil said:

If it is a vented system there should be a large cold water header tank somewhere, to both feed water to the cylinder, and,  ideally to the bathroom cold taps and toilets, ours is in the loft.    This equalises the hot and cold pressures .These days, certainly here in Scotland,  only the kitchen cold water is direct from the mains.  So if we have a water mains problem, at least we can still flush a toilet and wash hands.

Also, the HW cylinder in a vented system is much simpler than in an unvented system, as the latter is pressurised.

Ahh ok, I dont have a header tank so I guess unvented water pressure is great though