Vaillant weather comp - lower heating curve = less gas used?

[ChrisR]

there is no economic functioning of an on-off thermostat.. it has to over heat rooms to shut down, and then when every thing has cooled down it has to work pretty hard to replace lost heat quickly...

Shows very basic misinformation and misunderstanding which have been pointed out to this troll severall times.

It's Alec's nonsense, yet again.
Overshoot is less than half a degree if it's working properly. The last one I measured was much less than that. The boiler cycled with the stat at minimum modulation, as expected.

Remember that the seasonally adjusted efficiency of a fully weather compensated system is only 2-3% better than a plain condensing boiler. That's accepted by even the most ranting manufacturer.
That assumes it's set up perfectly, which very few are, which is why there's a long history of weather compensated systems being disabled, or maladjusted so that they run just the same a non-compensated system would. That's the most common set-up, unfortunately.

Alec repetitively tells fairy stories to support his irrational obsession.
Unfortunately he doesn't seem to understand much about how many heating systems are controlled.

Several of us have tried to educate him but he doesn't learn, or pretends not to. It doesn't suit his mantra, or the way he flogs boilers.
We have to assume the misinformation is deliberate, he can't be that "limited".

 

[ALEC1]

Compensation controls do turn things off too, but wind down the heat output of the boiler as they approach room set point..

I have seen too many savings when upgrading controls from on-off to compensation controls to take a different view I am afraid Chris..

The 4% is a low saving based on boiler efficiency, but usage patterns, and necessary system enhancements all contribute to make these figures higher...

 

[scoobydo123]

I am with Chris on this one, WC for Vaillant is far to expensive. Cannot see how your money can be re-couped. I have WC but not installed due to the continued woes of my 4xx boiler.Luckily I only paid £70 for the full kit so if it worked it would be worth it. Viesmann have priced correctly last time I looked


A lot can be said however for a decent stat that will keep the flow down to less than 55. I have had very good success with a Myson MPRT as have others with the honeywell range with proportional control and TPi. My myson has 3 set temps that you can set for 48 time periods per day with a 1hour boost very useful in my H.M.O.

 

[Agile]

Those are two different arguments being expressed!

There is the basic question of what savings can be achieved using WC. I subscribe to the 3-6% viewpoint.

Stupidly some manufacturers quote 15% but their small print can say thats compared with a non condensing boiler and on/off stat.

The whole point of WC is that it controls the flow temp to achieve the required internal temp. Thats only possible if the boiler is correctly sized and has a good turn down ratio.

Then there is the financial cost of providing WC. With Viessmann, Intergas and some Biasi, all thats needed is the sensor costing less that £19. Even less if you know how to fit the component yourself.

Then there is the Vaillant and Worcester WC controllers costing £130-£230. Its very questionable quite how long its going to take to get that cost back from the saving!


SSSSSh... you can provide the benefits of WC without any controls if you are there just by adjusting the flow temp manually! But dont tell Alec!

 

[JonCa]

Bit of a question, surely the boiler is able to regulate its burn even with a simple thermostat (ok perhaps not so efficiently) OR is it utterly dependent upon the thermostat/programmer for economical functionality?

If its the thermostat/programmer that's doing the work then who makes the best/better ones, and can one rely on a good level of inter-working between a.n.other boiler and the thermostat/programmer? Presumably the inter-working will be via Open-therm.

OK so WC improves a little on a plain condensing boiler and putting a wooly jumper on helps to BUT does all this intelligence live wholly in the programmer/thermostat or would the boiler do its best to be efficient without the new fangled all singing and dancing controller (with WC )

Must admit IMVHO I thought the boiler had the fundamental capability and the controller added the finesse.
SO
Is there a best controller both for functionality and expandability i.e 6 plus time steps and adjustable temps for each time across a day while also supporting a number of zones (say 5 + H/W) Is it just the likes of HomeTronic things.
OR
Should large installations (say htg load 40kW plus) be reduced to a single heating zone? As that seems to be the preferred capability of the main manufacturers products?

I'm coming from a direction of "I want to know more "

 

[JonCa]

SSSSSh... you can provide the benefits of WC without any controls if you are there just by adjusting the flow temp manually! But dont tell Alec!

Isn't there the cost of a comfy chair and window (by the boiler) to be considered or can you get wireless temp adjusters too

 

[Agile]

You cannot ask those questions without being specific about the boiler make and model!

Different makers have different ideas on what they think is best.

Only a very few room stats have a proportional control to a suitable boiler.

Most are still just on/off. Some pulse the boiler on/off for short periods as they get close the the room set point.

Tony

 

[JonCa]

You cannot ask those questions without being specific about the boiler make and model!

Fair point and the one over which I'm stumbling.

I look at boilers and the own brand controllers. They don't seem to do what I feel I want/need. Often its only by reading the IM that you find they do a controller. Intergas come to mind here.

If I find what seems like a suitably functional controller, its like as not they don't appear to make boilers. At least I've not seen a Honeywell branded boiler yet.

 

[Agile]

Honeywell only make controls. Also gas valves and other internal boiler components.

But boiler makers dont use a simple single communication protocol and in fact make it as difficult as possible to use other makes of controllers! I wonder why!

Could be wrong, but I am not aware of any Honeywell controls which are designed to modulate the flow temperatures of boilers by directly interfacing.

Tony

 

[JonCa]

Currently I have Honeywell CM67NG controllers with associated HC60NG relay box and the destruction's state that the CM67 can instruct for % burn. but as my Potterton Osprey does not support anything less than "foot on the floor economy style" I have not looked further. I believe that their HR80 electronic TRV's support % burn
In both cases it does not indicate whether burn is % of on time - or - % of max gas.

As for modulating flow temp ???

My parents have just had new boiler WorsterBosch Greenstar24i with Honeywell ST9420C1008 wireless programmer DTS92E1020 digital room stat CS92A1007 tankstat; Honeywell words make no suggestion of flow temp management in this instance.
However the WB boiler can be managed for flow temp and does seem to spend a lot of time running while using very little gas, also flow pipe temps (at boiler) are often low enough to touch despite being set on the manual temp control to 4 (out of 6) suggesting that the boiler has the inherent ability to modulate flow temp on its own. My impression may of course be well wrong.

 

[ALEC1]

Honeywell have a large range of open therm controllers that they do not sell in the UK...

Open therm if people don't know is a bus communication protocol between all parts of the heating system to maximise boiler efficiency...

So yes Honeywell do make controllers to modulate flow temperature.

There are definitely different ways of compensating boilers...but only three can do it on the outdoor sensor only...Viessmann 200s and 300s, all vaillants, and worcester bosch CDIs.

On all these you can have room sensing too..and on the worcester bosch and viessman you can vary the proportion of "room influence"

and as JohnCa says you can vary the flow temp manually, as many people do...but you won't get all the swanky algorithms that force the boiler to be as efficient as possible all the time...

 

[Agile]

Open therm if people don't know is a bus communication protocol between all parts of the heating system to maximise boiler efficiency...

So yes Honeywell do make controllers to modulate flow temperature.

Yes, but which boilers say they will accept a generic open therm instruction from a control not made or marketed by them?

Or/and which ( UK ) boilers will acccept the Honeywell opentherm instructions?

Tony

 

[ALEC1]

generally dutch boilers as all boilers have to accept OT controls in Holland...

Vaillant, viessmann etc make converters to converte OT to ebus, and km bus...

its all possible but in the UK we lack the will for change...

 

[JonCa]

and as JohnCa says you can vary the flow temp manually, as many people do...but you won't get all the swanky algorithms that force the boiler to be as efficient as possible all the time...

Alec, what I meant to convey was :- despite the manual control setting the WB boiler appears to be modulating the flow temperature of its own accord, with only a simple on/off controller.
Having looked at the WB "gas boiler wiring guide", it would appear that for any configuration all the boiler requires is a switched live and it will do the rest. IM is much briefer.
Wiring guide on this page http://www.worcester-bosch.co.uk/installer/boilers/gas-boilers/greenstar-24i-system

I am not sure about

" but in the UK we lack the will for change.. "

I believe it is more about there being available clear detailed information about enablers to change. Often technical information is no better than the advert that says its good for me which does not help; one needs to know practical detail about what it does for me yet so often these things are so very hard to find out about

For example WB do a controller with WC, its the FW100 - try finding out about what it can do for you things like :- zone control, (how many); on/off times per day (how many); temp settings (how many); is it configurable ......

 

[ALEC1]

well I find most of the information I need from the instructions..of both the boiler AND the controllers books. Viessmann vitodens 200 books are great, vaillant's not so great, but all the equipment does the same thing, with the same limitations....

That said you do need a modicum of understanding as to what these controls are trying to do an why....(use just the right amount of gas to maintain a stable programmed temperature)

Ironically all this stuff was developed at Glasgow university and then sold to a consortium of heating manufacturers in 1986...the return journey seems particularly fraught I must admit!

FWIW I also think that the technology is far adopted in places like germany (outdoor sensors have been mandatory for over 20 years) that they don't see the need for the basics to be explained... and then again there is a reluctance of any exporter to dictate to any importing country...either way the manufacturers could give better and more concise information