and I can't see any obvious snags on their website - except I never heard of them before, but got nothing against dutch kit in principle. It does seem to have all the bells and whistles.
This compares to 2x £652 (£1304) for the Worcester-Bosch 24i from my local PlumbCentre.
Vailent ecoTEC plus 624 looks very expensive.
But then I found a Glow-worm 18HX £ 480 plus a 24HX at £499 (£979) also at
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- and this is a better match to the existing
41kw chaffateaux, although it does not give quite equal redundancy, 44% vs 56% worst case failed output compared to the 41kw assumed requirement.
I don't consider weather comp necessary at all, and as per my response to Ed, it does seem possible to work with no sequencer at all, though may not be ideal.
I do mean output (from each boiler) which when fed into a sequencer will decide whether to switch the other boiler on. Your syxthsense man says he thinks WB have that, I havent asked WB themselves as yet, and as said the data on their site is pathetic.
The alternative it to measure common return temp in the LLH.
Ideally they would be, but the main CM67 is a wireless one on a side wall - has been moved several times to find an optimum position, whilst the second boiler one is a wired one where the original stat was. The override one is programmed on a rough and ready basis.
is
One was an extra pipe stat on the low-loss header that kept the second boiler off until the first was hot, abandoned because a failure of the first meant the second never fired, and one was an extra room stat in an unheated area that kept the second boiler running on the coldest days regardless of inside temp (which in practice on such days would struggle to get to the desired).
My impression (perhaps wrong) with our Kestons was that this strategy doesn't work very well as the boiler just modulates down as the set temperature is reached - you're more likely to see two boilers running with 1 or 2 lights (of 4) running
You are obviously not technical enough to understand it.
If you want a highly efficient system running at maximum economy then weather compensation you do need, especially when burning so much gas as you will be. I don't think you understand what it does and what it gives. It will not cost much to do. It keeps the flow temperature as low as possible promoting maximum condensing efficiency. You don't fit two condensing boiler and try to sequence them using simple stats.
What do you want? A simple boiler sequencer? Then just fit the Warmworld model and keep the boilers on maximum temperature. You will then only be doing half the control setup, leaving out weather compensation.
I think the best thing for you is to drop the two boilers idea and fit one boiler with integral weather compensation, as I doubt you will control the two of them properly or efficiently.
I have seen so many systems working inefficiently because of poor control.
Sequencers do not work that way. They control "both" boilers and it decides when to switch them in. On cold start, both boilers will be on full. As the setpoint temperature nears, the lag boiler will be switched out, then the remaining boiler will modulate on itself until setpoint is reached and then the sequencer switches that out. On commercial systems, each stage will modulate the burner of each boiler, so both on full, the lag boiler modulates down, then off, the lead boiler modulates down until off.
I think what you are after is a boiler that says I am on full and gives a signal saying so which switches in the lag boiler. When on less than full burner rate the lag boiler is switched out as it is not needed. This is simple and simple for the makers to put into a pcb, and would eliminate a sequence controller. I know of no open who does it. If you find one let us know.
No. As I understand control.
I am not aware that any OpenTherm protocol boiler accepts a 0-10v signal that modulates the burner. If so, the two controllers I gave, would be ideal. The weather compensator gives a 0-10v output signal into the sequencer, which in turn outputs 0-10v into each boiler which uses the signal to modulate the burner.
The Broag is a quality model with a far superior OpenTherm control system - the Dutch invnetd the condensing boiler and most quality models are Dutch, like Atmos. It has: Gianonni heat exchanger, Grundfos pump, Dung gas valve, etc.
The Glow Worm HX is a open vented heating boiler (no pump) The SX is the system boiler. The Flexicom range I think are cast off Vaillant models. The better GlowWorm range is the Ultracom.
Look at a the Broag Avantapluc 39C combi. A few kW below your old boiler - a good match. You then don't need to connect the water section and just use the CH side. It is well priced and has the weather compensation control. It is £917 inc VAT, that is very well priced for a 40kW boiler. If you need the water part in the future you have it. Or connect it up and isolate the DHW section and use as backup only.
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at the combi options pages 17 to 21. The outside senors etc, are extra.
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Broag 28kW combi costs less than the 24kW system boiler, because of bigger sales, competition, etc. A combi is a system boiler with a water section. You do not need to use the water section.
It's the return temp that you need to keep down, and a stat on the heating return achieves just that. BRE reckon that weather compensation will improve a gas system's efficiency by 2%, but of course this is only
2% of the heating (not DHW) cost, so on smaller or well insulated properties it is not cost effective.
But not very well or efficiently and it will use more gas.
As many boilers come with weather compensation as standard it is highly cost effective indeed. Even a BIASI model has integral compensation. Danfoss and Honeywell have dropped their stand alone weather compensators as they do not sell enough as integral compensators have stolen their market.
BRE tests. Where they using OpenTherm control types where the burner modulates to the demand? I doubt it. In this case where 40kW is being burned it makes lots of sense.
What he is referring to is a backup boiler rather than a lag boiler. If a boiler locks out it brings in backup. Different to lead-lag boiler sequencing.
Quality modern boilers with integral weather compensation are very reliable and not complex in controls terms. All this came from the commercial sector which has had this for many decades. Well proven.
You could have two Broag system boilers or two combis versions which is cheaper and bigger kW, and don't use the water sections. Use the integral weather compensation for both (two outside sensors). Just adjust the compensation control slope on each boiler so one boiler is always lagging the other. Setting up the compensation slope is easy on the Broag Avantaplus. That is a very cost effective way of getting what you want.
Presumably, yes, though - like most current generation combis - they use a hall-effect turbine to sense DHW flow, rather than a diverter valve with a diaphragm that's prone to splitting. But even allowing for them being less reliable in total, including the DHW function, the space-heating function should be no less reliable. And if you have (and keep) a conventional DHW system as well the total set-up should be /more/ reliable by giving you 3 separate sources of DHW!
I've heard of them (Remeha), but not heard much. One of the guys on my recent ACS reassessment seemed quite keen on them, and he seemed a clueful sort of person. I know he put one in on a job I passed to him because I couldn't fit it in, but of course it's only been running a few weeks.
Another thing I heard about them (though from a general builder with FA^-2 heating knowledge :-)) was that they had (past tense, at least) had a poor reputation for reliability.
Funnily enough their premises are across the road from the gas training centre we did our ACses at, in Wokingham.
£584 + VAT (for the 24i Junior combi) from PlumbNation - who actually buy and get deliveries through PlumbCentre, so if you talk to the manager at your PlumbCentre and show him the PlumbNation prices he should be able to match or beat them.
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