Boiler efficiency in the real world - old WB vs new Intergas

[vulcancontinental]

My personal view is that there's combustion efficiency, thermal efficiency and system efficiency all separate but linked. Boiler manufacturer's figures are unrepresentative but are what the installer has other than personal experience and observation. I think the jump from standard efficiency to any high efficiency boiler results in somewhere between 10 and 14% real world, if the boiler is operating at condensing temperatures you might get a couple of % more occasionally. Not sure whether Wiser is OpenTherm which I'm told works well with Intergas but it would be a small advantage if any as that would depend on how you operate the system and the property. Whatever high efficiency boiler you choose you'll get a saving which I have found is often pleasing to the user first year but as many people, almost subconsciously, heat to their budget it tends to diminish afterwards as they increase comfort levels subsequently.

 

[StuB]

My personal view is that there's combustion efficiency, thermal efficiency and system efficiency all separate but linked. Boiler manufacturer's figures are unrepresentative but are what the installer has other than personal experience and observation. I think the jump from standard efficiency to any high efficiency boiler results in somewhere between 10 and 14% real world, if the boiler is operating at condensing temperatures you might get a couple of % more occasionally. Not sure whether Wiser is OpenTherm which I'm told works well with Intergas but it would be a small advantage if any as that would depend on how you operate the system and the property. Whatever high efficiency boiler you choose you'll get a saving which I have found is often pleasing to the user first year but as many people, almost subconsciously, heat to their budget it tends to diminish afterwards as they increase comfort levels subsequently.

The Wiser system is OpenTherm compatible.

I also appreciate that there's more to heating than just the boiler however I'd be happy with a 10% - 14% improvement.

As for turning the heating up afterwards, that's a separate question

 

[Nintendofan]

I'd spotted that the Xclusive modulated down to about 4kw instead of the 7kw+ of the Eco RF.

@Razor900 I have the Eco RF and when my Opentherm connected Nest requests a low CH water temperature (and the house is getting up to temperature) I presume the demand is less that the minimum power output the Eco RF can supply, so my question is: in the real world is there much difference between a constant flame at 4Kw against say 5 minutes at 7Kw and then 5 minutes of operation 1?

 

[StuB]

@Razor900 I have the Eco RF and when my Opentherm connected Nest requests a low CH water temperature (and the house is getting up to temperature) I presume the demand is less that the minimum power output the Eco RF can supply, so my question is: in the real world is there much difference between a constant flame at 4Kw against say 5 minutes at 7Kw and then 5 minutes of operation 1?

This is what I'm experiencing as I think our old boiler only goes down to about 10.5kw.

My understanding is that it removes the purging before and after the boiler fires which is good which helps a little however it seems that the actual answer is, as with a lot of things, it depends. This has some interesting reading https://www.hpacmag.com/features/boiler-modulation-better/

 

[Razor900]

In your car which uses more fuel over a mile, repeatedly starting accelerating and stopping or just cruising at a steady speed?

 

[Nintendofan]

In your car which uses more fuel over a mile, repeatedly starting accelerating and stopping or just cruising at a steady speed?

I’m not sure that’s why I asked.

Using your analogy of a car, if you let the car ‘coast’ the mile only loosing a few miles an hour until you apply power again I’d say there would be very little in it, so would this not be the same with heating water?

 

[ericmark]

How do you measure efficiency?
1) Heat lost to outside to heat delivered it inside.
2) Time an area is heated compared to time area used.
3) Amount area is over heated to maintain minimum target.
4) Energy used to produce the fuel.
5) Energy used to supply the fuel.
6) What it costs to heat.
7) Something else.
If you look at a caravan or car, the heat is delivered with a fan, it heats up quickly and cools down quickly so you only have heat when required, you could do same with house using the Myson ivector radiators however most people want cheap installation costs so we look as a cheaper option.

However speed is still important, if we can switch on the heating when we arrive home, or when we use a room, then it is going to be cheaper to run the faster it heats up unless running 24/7.

This means what is good for me, retired and at home most of the day may not be best for you. When I fitted electronic TRV heads I found the IFTTT apps are being released every week, so some thing you could not do yesterday you may be able to do today.

The problem it seems is mixing digital and analogue systems, the whole idea of a digital thermostat with a boiler that simply runs or does not run is easy to understand. However where the boiler is designed to modulate, then the old controls could mean the gains from a condensing boiler are lost.

And this seems to be the real world, analogue boilers have inappropriate digital controls, the new "Wave" thermostat may work with Worcester Bosch boiler connecting to boiler bus, but it only measures temperature in one room, and Worcester Bosch is not OpenTherm so limited options, even with OpenTherm Nest can follow or be followed by Energenie MiHome electronic thermostats but that means every room at same temperature and whole idea it to have each room independent.

It seems some systems the OpenTherm is added extra and it as standard still uses a mark/space ratio.

Even the building regulations seem not to have worked out how a modulating boiler works, with zone valves being fitted which are digital not analogue.

 

[Hot&Cold]

StuB,we all like to consume less gas. Manufactures have the right to publish their efficiency results,great but consider its a guide. Something to remember is the test facility will not resemble your own property.

Your current boiler is gas thirsty during hot water draw off you have not mentioned how many hot water draw offs you have,its old tech but good old tech and easily repaired.

Tbh if i had a 35cdi i would keep it but when it needs exchange where there are multiple hot water draw off's i would fit an unvented cylinder with a suitably sized intergas system gas boiler.

 

[StuB]

StuB,we all like to consume less gas. Manufactures have the right to publish their efficiency results,great but consider its a guide. Something to remember is the test facility will not resemble your own property.

Your current boiler is gas thirsty during hot water draw off you have not mentioned how many hot water draw offs you have,its old tech but good old tech and easily repaired.

Tbh if i had a 35cdi i would keep it but when it needs exchange where there are multiple hot water draw off's i would fit an unvented cylinder with a suitably sized intergas system gas boiler.

The house has two bathrooms and there are two adults and one child in it generally having one or two showers a day each (rarely at the same time) and the usual washing up. The pipework between kitchens and bathrooms is quite short.

Based upon the summer and winter bills I'd guess across the year it's about a half and half split between CH and DHW.

I appreciate a combi isn't suitable for everyone but we've found it suits us quite well and it makes the showers work well. The lack of space used for a tank is a bonus.

Over the years the 35CDi has only needed a secondary heat exchanger and a capacitor for the pump so has been quite cheap to run.

 

[vulcancontinental]

In your car which uses more fuel over a mile, repeatedly starting accelerating and stopping or just cruising at a steady speed?

That's an analogy I used to use Razor and it's logical; then I worked an example which proved otherwise (if you accept the situation I created) comparing a constantly running boiler in condensing mode against a condensing boiler operating at higher temps, cycling and not condensing.

The condenser running hotter, not condensing, not modulating as much and cycling is cheaper to operate

Did the same with supposed component life as well.

So much depends on boiler design and user patterns.

 

[OvertonPlumber]

Wave doesn't work with that many Worcester boilers either.
The Xclusive is nice, i saw the one with the clear body. I probably have 50 Intergas boilers out on the patch, oldest is 9 years.
A few pressure sensors have gone over the years had to descale another on the domestic circuit after 6 years. They really need a polyphosphate doser like combimag on main and change cartridge yearly.
Water is very hard here "Surrey". Probably why we have the Harvey factory in Woking.
Went and commisioned a LPG Worcester 35 CDI exactly 12 months ago.

"We’ve got a boiler that you converted to LPG last year. We’ve a couple of issues - one room the underfloor heating doesn’t seem to be running at full heat, and the boiler seems to cut out when heating the hot water (making the shower rather bracing!)."

Good old Worcester!

 

[mrbrunes]

What did the OP go for in the end? I'm in a very similar situation - old WB Highflow 400 looking at an Xtreme or Xclusiv with Drayton Wiser. Only the one bathroom but I like a decent shower which the Highflow was very good at. I've only experienced older combis with not very good DHW flow rates though, so not sure if I really need a Xclusiv/Xtreme 36 (13.5/15 li/min @ 35deg rise) or if a 30 would do (12.2/13.3 li/min).

 

[ianmcd]

Not loads at about £550 to £600 a year but if it makes £60 or £70 a year difference then over 10 years and with not having the the repair costs of the WB then it starts to make more financial sense.

I'd spotted that the Xclusive modulated down to about 4kw instead of the 7kw+ of the Eco RF.

Remember that no matter which new boiler you fit, it will have to be serviced and the service record updated every year for the warranty to be valid

 

[StuB]

What did the OP go for in the end? I'm in a very similar situation - old WB Highflow 400 looking at an Xtreme or Xclusiv with Drayton Wiser. Only the one bathroom but I like a decent shower which the Highflow was very good at. I've only experienced older combis with not very good DHW flow rates though, so not sure if I really need a Xclusiv/Xtreme 36 (13.5/15 li/min @ 35deg rise) or if a 30 would do (12.2/13.3 li/min).

Sorry for the delay replying to this. We've held out so that the change could be done in the better weather and it's always easier to book an annual service at this time of year rather than in winter.

Anyway we've gone for an Xclusive 36 as the DHW specs are similar to the old boiler and we''ve always been happy with those flow rates.

We didn't go for the Xtreme as while it's a couple of percent more efficient it only has a 7 year warranty instead of the 10 of the Xclusive, presumably it's more complex inside and is also a few hundred pounds more.

It gets installed tomorrow so I'll report back in a week or so after we've used it for a while as to how well it works.

 

[Gasguru]

Wise decision...top spec boilers from any manufacturer are best avoided as it's often a test bed for new technology which you the customer will be trialing and that can mean crazy priced repairs when the warranties are voided. AFAIR the Xtreme has a really backward pump design whereby a failure could also take out the main boiler pcb...the control electronics has been split from the pump.