Thanks. All this could have written up front to save hard work for Hard-Work. Avoid one liners.
All this gas been written before. Use the search box.
Intergas...but which...
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All this gas been written before. Use the search box.
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I do try the search box, but sometimes it takes a lot of searching and still failure.
To the topic under debate here. Interesting. The Intergas heat exchanger appears bomb proof. I assume they do not modulate the gas rate lower than they do because of:
1. The type of burner they use.
2. Efficiencies will drop off sharply when modulating right down.
I looked up the minimum modulated output of some boilers. The lowest output I found was a French boiler dropping to just under 1Kw which only went up to 10 or 12kW max output. I believe it is used successfully on UFH avoiding the cost of a thermal store. There may be other boilers around now than equal or better it.
The range of say 9kW or 11kW seems to tell me it is the heat exchanger design which matters rather than just putting in a wide range modulating burner/flue fan.
Will people on this thread stop the ad hom attacks please it clutters the thread.
That particular french boiler is an atrocious piece of equipment. We're planning to pull a pair out of respite home soon as the maintenence is ridiculous.
There are lots of things that dictate modulating ranges. Burner being one.
There are lots of things that dictate modulating ranges. Burner being one.
Thanks, that is interesting.
What is the Intergas modulation range compared to the competition? If there is less range, how much does this affect the efficiency?
I thought the whole idea behind modulation was to use the least amount of energy required for the specific output (or something like that, I am coming from a laymen perspective here).
Is this the trade off with the intergas design, more reliability less modulation?
Is that another reason manufacturers moved to their current designs, it gives more flexibility to control modulation but at the cost of reliability.
Sorry for repeat questions, just trying to work out all the pros and cons.
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I believe the fan is another. Makers advertise that a boiler has a max flue length of say 6 metres. That is a great selling point for versatility and should sell more kit. The fan has to be man enough to exhaust the gasses out of the flue pipe at minimum fan speed (assuming the fan does modulate) and maximum flue length. That may mean a burner's gas rate can be quite high. If they did not have extended flues they may get away with a fan that can run down to a very low speed giving a very low burner output. As you say lots of points dictate this. But a variable burner and fan designed for all flue lengths and associated controller may be just too expensive for a domestic unit. They may need models only for long flue lengths, by inserting a beefier fan.
I really can't see why all boilers cannot go down to 1kW these days. I looked 15 years ago and not much has changed in the lowest outputs. The lower the modulating output the more expensive the boiler.
Domestic boilers are clearly built down to a price. Many now are expendable products like washing machines. Once the drum bearings are gone on a washing machine and it is 5 years old it is cheaper to replace it and another 3 years warranty to be thrown in.
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Intergas are about 4 to 1.
No. It effects the amount of stop start operation during marginal heat demand periods.
No, it's about matching as closely as possible, the heat output with the heat demand.
No.
No, in fact wooshitter and iirc Faillant have both tried to buy the rights to the Intergas hex design.
To add to Dan's excellent reply. Constant on-off operation is inefficient. It wears out the controls more. There is a lot of inefficiency on the start up of a hot boiler. The start cycle purges the burner chamber with cool outside air ensuring no gas is hanging around, as it does this it extracts heat from the heat exchanger with the cold air moving over the heat exchanger via the fan dumping it outside, until the burner lights up.
In a condensing boiler the lower the flue gas temperatures the more efficient the operation, so lower modulation has real advantages.
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Many thanks. Most informative.
So I presume combis are at their most inefficient when people use the hot water tap for short hand washes?
So I presume combis are at their most inefficient when people use the hot water tap for short hand washes?
The modern boilers premix gas and air like a carburretor, the fans can run at low speeds of course but the volume of flow drops with velocity. As the gas is 'pulled' from an 'open' gas valve through a restrictive injector the gas and air have to be kept in proportion and there's a limit to this as the injector is a fixed size. A very expensive way is to put a motor on the gas valve and control it over a greater range with sophisticated software, one boiler can acheive 20:1 in this way, many have recently acheived 10:1. It's complicated and expensive to repair.
20:1 is admirable but if you have a max heat load of 15kw it's unlikely a property's loss would ever be 0.75kw.
One brand can achieve 10: 1 with an ordinary pneumatic gas valve and a simple variable venturi which they've patented, been around 6 years, no problems, have one myself.
Informal tests were carried out with two boilers runing the same program, one 5:1 the other 10:1. The energy saved was calculated at 8% but that also included electricity consumed as the 10:1 boiler had a modulating pump that adapted to the system load.
Less start stops mean less rejected energy through pre and post purge but I'm not sure it lengthens component life, the old Apollo's and Fuelsavers would fire and stop every few minutes and I have seen some over 27 years old.
Modulation is good as in driving to Scotland 0 to 80 then braking and repeating it all the way up - say 6 hours. Same car, steady 40 same six hours but less acceleration decceleration losses. crude analogy but viable.
20:1 is admirable but if you have a max heat load of 15kw it's unlikely a property's loss would ever be 0.75kw.
One brand can achieve 10: 1 with an ordinary pneumatic gas valve and a simple variable venturi which they've patented, been around 6 years, no problems, have one myself.
Informal tests were carried out with two boilers runing the same program, one 5:1 the other 10:1. The energy saved was calculated at 8% but that also included electricity consumed as the 10:1 boiler had a modulating pump that adapted to the system load.
Less start stops mean less rejected energy through pre and post purge but I'm not sure it lengthens component life, the old Apollo's and Fuelsavers would fire and stop every few minutes and I have seen some over 27 years old.
Modulation is good as in driving to Scotland 0 to 80 then braking and repeating it all the way up - say 6 hours. Same car, steady 40 same six hours but less acceleration decceleration losses. crude analogy but viable.
My investigations over the years has concluded that a modest family home has a background heat input of around 1.5kw when occupied, so, modulating range is great, but minimum output is the aim. Hence correctly sizing the appliance. And where combination boilers are inherently flawed.
As in most things though there is a compromise.
VC knows which of the two boilers he refers to I rate me highly.
And the relative cost makes it a no brainer. But I still favour the Intergas over both of them i'm afraid.
Did you get those emails the other day BTW?
As in most things though there is a compromise.
VC knows which of the two boilers he refers to I rate me highly.
And the relative cost makes it a no brainer. But I still favour the Intergas over both of them i'm afraid.
Did you get those emails the other day BTW?
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Yes Dan, I thought I had ticked the acknowledge receipt box. Actually I thought I wrote back and thanked you. Allow me to be formal and do it in public: thank you
Never be afraid to give anconsidered honest personal opinion.
Never be afraid to give anconsidered honest personal opinion.
well the way I see it OP if they have had a Vokera fitted in the prop for over 20 years ??
& it has given good service why not replace it with another vokera
They also make a Vokera with a 10.1 modulation ratio. Unica I . 28,32 or 36 Kw out puts & the Linea
& it has given good service why not replace it with another vokera
They also make a Vokera with a 10.1 modulation ratio. Unica I . 28,32 or 36 Kw out puts & the Linea
Interesting.
Is that 10:1 a veissman as that is anther brand I had considered.
The Vokera is an Option 24 CDI and it only just manages. I assume it has lasted this long because it is a non-condensing combi.
My other brother as a WBosch. It never seems to cope with anything. If I fill the bath, it seems to cut out heating the water like it cannot cope with the flow. You have to turn the tap down to a dribble for it to give hot again.
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