Many people love zoning, but from an installers perspective there is no way to integrate zoning on small projects (less than for example 35kws) to a boiler other than on-off controls which open and close valves. Thats all very well for the heating system but its not very kind to the boiler as these require pretty well constant flow through them, and do not tolerate the variable flows created by zoning very well. Indeed to do properly you would need a Low loss header to separate the boiler Constant flow from the heating circuit (variable flow). All this adds to the install cost with no research to suggest there is any benefit...

Weather compensation and indoor compensation offer a useful alternative at a much lower cost. And any house under 35 kws is going to be consistently used throughout so no real benefit to zoning..

The apparent absence of products on the market that vary the heat output of the boiler to match prevailing load conditions rather suggests that there are no benefits to zoning. Indeed weather compensation controls supplied by viessmann and vaillant rather suggest that temperature profiling ( that is not turning the system off, rather lowering the temperature for set back) is the optimal way to use the technology and probably increase efficiency.

Stable state of a regularly occupied building with temperature profiling seems to be the optimal way to run boilers...indeed my experience is showing that this way is a win win situation for installers (simplified install ) and users (stable temperatures and increased reliability)

well I was really thinking about when you have a room thermostat in each room...

From the Roll-your-own UFH thread:

Zoning is a different issue. Which needs a different solution for every building. When we fitted the Mk 1 version of Honeywell's CM programmable stat range back in the late '80s, they produced research, aided and abetted by the government's own, now-famous, DOE research (1 deg C drop in temp saves 10% of your fuel bill) which said that their machines, avoiding the hysteresis caused by the on-off cycles you mention, could save upwards of 15% if used sensibly. My experience with customers ever since makes me agree.

Note caveat about different houses needing different solutions, so no right or wrong answer. However, to pick up on a couple of points: Optimising/weather compensating controls are fine, if the customer understands them. Which, picking up on Paul's point about end-users not understanding them, may be why, when we first fitted two gens of these control in the late '80s/early '90's, the complaints came thick and fast.

As far as flows go, modern boilers modulate for a number of reasons, and those include reducing output to match demand. No after-market black box required, though you will find several, including Danfoss' BEM 5000, but these have reduced in popularity, though NatWest fitted many to their boilers. Some solutions to flow issues: By-pass radiators (sep zone?), pressure-differential by-pass valves or open loops are just three ways of overcoming the problem of low flow.

Honeywell aside, as far as research goes, I have monitored my own customers' installations over many years to see the effect of zoning. I cannot isolate zoning as a sole ingredient in savings, nor quantify the %, as we offered many solutions including BEMs and weather compensating systems, but zoning is certainly one factor in the mix achieving reductions of 35-40% plus. (Google Ben Shirley CAT 2008). When we won an award from WILO pumps in 2011, it was for achieving savings of 55%, including 6 separate zones, in a terraced, sub-30KW/h house. The customer is very chuffed and certainly doesn't think it an expensive waste...

PeglerYorkshire suggest savings of 30% - their own research using their itemp programmable thermostatic radiator valve, a zone-per-room set-up.

Perhaps I should point out that, contrary to catholic procedure, wherever possible I do not connect boiler directly to radiators or UFH, which overcomes your flow objection. Why not? For the simple reason that direct connection allows only THAT boiler to heat those radiators (low loss headers are a limited exception to this, with very limited benefit). I prefer to be able to harness 'free' heat like solar, or off-peak sources with heatpumps, and integrate these into heating whichever part of the house I shall be inhabiting at a given time.

So I am clearly from a different school of thought. Doesn't make me right or you wrong or vice-versa, but I must beg to differ in the eating of this particular cake. A single slice will do me fine - I don't want to eat the whole thing.

Paul: What reliability issues did you have in mind?

The best way to lower the return temperature is of course to lower the flow temperature to the minimum required...thats what compensation controls actually do, espceially weather compensation when the outdoor sensor is acting on the burner through the boiler.. (not with a mixing valve!)

I am finding the condensing boiler (when installed with compensation controls, which after all it has to accept as part of EU legislation) surprisingly reliable... the oldest I know is 12 years old with very limited maintenance...longer running pump times, lower average operating temperatures and constant flow seem to keep the boiler well happy..

That compares favourably with on-of controls (of which zoning would be one) that suffer from all manner of reliability issues if you listen to domestic installers....

I do make a point of using compensation controls...because reliability and efficiency is a big issue for my clients...I am open minded to zoning...whats needed of course is zone controls that calculate optimum heat output of boilers according to requirements... probably exists in open therm versions in Germany...not yet in the UK!

well I am looking to be convinced about zoning! People love it and it does seem to offer savings, but I only see pitfalls especially after installing so many compensated boilers...which offer the same savings but at lower cost!

I have recently been called to one to replace a grundfos pump after 4 years of use... the cause, almost certainly the zoning controls that mean the fixed head pump has worn out prematurely..

the problem with thermal stores and condensing boilers is that the turbulence mixes the water in the store to such an extent that the return doesn't stay low... great in theory but not so good in practice...

alec,
you've been a strong voice for weather compensation on a number of threads, and I keep meaning to get myself gen'd up on their ins & outs - I'm guessing there are others similarly ignorant. Rather than me googling my way through stuff, could you perhaps point me to a couple of useful sites?

Thanks in advance.

this is the best I can find:

http://www.pmengineer.com/CDA/Archives/cdd55d5472298010VgnVCM100000f932a8c0

Outdoor reset is the american for weather compensation and it refers to standard efficiency boilers.

I agree there is little on the web about weather compensation, but it seems to be sensible to install boilers in the way they would be installed in Germany, as out door sensors are mandatory there...

the most proactive manufacturer is Viessmann on there website there is a document about weather compensation...and they also have one that explains the benefits of this control strategy to enhance boiler efficiency...

Couldn't have put it better myself Seret. I like sunshine in my UFH. And that's a pretty well no-carbon heat source.

Anyone imagine how they would run district heating schemes (see concurrent thread) without zoning?

Easy indeed, mine work somewhat differently. Perhaps I should have included the words 'effective and efficient' in my last sentence...