The point was that it can be fitted with TRVs all around. I can't see where
it is more efficient. I detect rear end covering by them. TRVs are the
scourge of the boiler manufacturers. They like high flows through the
boilers. TRVs reduce flow. That is where heat bank/thermal stores score
over direct rad systems.
For goodness sake dribble, work on your comprehension a bit. Its bad
enough we have to teach you about heating systems (something you claim
to know about), but do we have to teach basic reading skills as well?
"No, the pump runs continuously, with the water going round
the internal bypass loop."
This was in answer to Dennis' question about how it recovers from the
situation where the flow switch has tripped out the burner.
He also said "The instructions recommend fitting a roomstat, in which
case the pump won't run continuously."
Since this is a way to achieve a proper boiler interlock.
Yup, just did, and you definitely imagined it.
Not running the pump unnecessarily for starters... If you are running
against significant back pressure from an all TRV system, then you also
trap most of the residual heat from the last combustion cycle primarily
in the boiler, rather than being able to allow the pump overrun to
dissipate the heat in the bypass rad, and hence into the house rather
than allowing more to escape from the flue.
So TRVs all round *may* make boiler cycling _less_ efficient than it
otherwise would be. (this assumes that you ever get the system well
enough balanced in the first place to have all the TRVs restrict at once
- in reality this is probably impossible to achieve all the time since
if it works one day, it won't the next time the wind is in another
This is where a heat banks et al *used* to score over direct rad
systems. Time to update another bit of your old plumbers folk law, and
drag it into the modern age. As previously explained, there is little
improvement in efficiency to be had these days. A bog standard
modulating condensing boiler can archive >90% efficiency driving the
rads directly. Boiler cycling is not the demon it once was. Add weather
compensation to that, and you claim the lions share of any further gains
available. So basic maths alone should tell you that no matter what you
do next, the most you could achieve is going to be well under a 5% gain,
and the second law of thermodynamics probably robs you of half of that.
So all the flannel about ideal hydraulic environments, smart pumps, and
buffers etc adds up to a couple of percent overall system gain if you
are lucky. Certainly not enough to repay the capital costs of a heat
bank if you don't need it for a worthwhile reason.
So thermal stores etc can do several things for you;
1) They are great for combining heat sources such as solar, wood burner,
biomass etc with that of a boiler.
2) They are good for running split temperature heating systems that need
rad circuits and UFH circuits.
3) They are great for getting a decent flow rate "instant" water heating
system (yes we know that "high flow combis are available" - for smallish
values of "high" at least),
4) They are good in commercial installs where they can allow a smaller
boiler to better cope with peak transient loads.
5) They *might just* be worth having if you have a tiny heating load
(i.e. well below the minimum modulation range of a small boiler) for a
significant part of the heating season.
If you expect us to believe that they are going to save you loads of
money however, you are going to have to some up with some compelling
numbers. Otherwise, you are like many a vented heating system - full of
I would go with the prog stat and one non TRV rad (TRVs elsewhere),
since without it you lose the ability to preselect different
temperatures during the day, and also the ability to tweak the
temperature should you feel too hot/cold.
If the system is well balanced then its not really a problem.
You can get wireless stats if you are afraid of wires.
I have explained the stat/progs to you on other threads. Read them again.
To the others. This boiler is one of the few that can cope with TRVs all
around and no nuisnace central stat. I doubt he knows that. If Baxi had a
good reputation for reliability, they would sell a lot of these boilers.
Cheap and quick to install and the customer satisfied as TRVs all around.
Yes, it helped me realise that you don't really understand them...
This would be the nuisance that lets you vary the house temperature to
suit your requirements without needing to go around adjusting all the TRVs.
I think that dribble sometimes looses sight of the fact that we don't
all sit their all day in our wing backed chairs with the nice woolly
blanket tucked over our laps by matron - never moving but to change
identity in between posting to one forum and the next. In real houses,
people will have differing levels of activity (and occupancy) throughout
the day, that will require different room temperatures to remain
comfortable. They might also have family gatherings or friends over that
again change the required temperature. Scooting off to twiddle a bunch
of TRVs - many obscured by furniture, or using the brute force approach
of turning the heating off altogether does not really cut it. Especially
when compared to a nice conveniently placed prog stat that can deal with
the anticipated day to day routine without any need for intervention,
and can also allow for unscheduled tweaks with the push of a button or
turn of a knob.
This is the consensus among the members of your elite club called "One
more TRV please!" no doubt? Now recruiting new members with the slogan:
"We desperately need one extra TRV, and we don't like prog stats - the
nasty electronic new fangled things"
There is only one proper way to control wet CH and that is zone timer+stats
and valves in the correct places.
All the others like a room stat + trvs, "plans" with three way valves, are
compromises that work OK in some circumstances but are less efficient.
My five zone 28 year old system runs on less energy than most (same sized)
modern systems with their condensing boilers and TRVs ever will and it runs
at the time and temp I want. You don't even need to switch it off in summer,
it does that all by its self, *if* it needs to.
TRV are just a bodge intended to be retro fitted but some fool has decided
they should be fitted in place of a proper control system just because
plumbers can't do proper systems.
The only difference between a zone for each room and using TRVs is how
accurate the temperature sensor is in each case. And a single sensor is
never going to give an accurate temperature for all of a room.
BTW - if your system is 'efficient' at moment, it will be more so with a
*If a mute swears, does his mother wash his hands with soap?
Dave Plowman email@example.com London SW
On Sun, 18 Oct 2009 20:53:41 +0100, dennis@home wrote:
I think if you do the sums you can repay the costs of going from a
dinosaur boiler with a standing pilot light and SEDBUK of about 65% to a
modern high efficiency boiler, at current gas prices and interest rates,
for fairly normal houses and consumption patterns. Of course you're still
taking a punt on interest rates not going up and/or gas prices going down
during the payback period, but then just about every decision you make in
Real Life (tm) is a punt of some sort ....
CO2 is probably a harder one to account for.
John Stumbles -- http://yaph.co.uk
Thesaurus: extinct reptile noted for its extensive vocabulary.
You site the main house stat in the area of most demand.
I can see zoning being useful in commercial premises but not really worth
the bother in the average house. Unless it's set up to alter temperatures
in each area automatically. And you have door closers everywhere.
*Do infants enjoy infancy as much as adults enjoy adultery? *
Dave Plowman firstname.lastname@example.org London SW
I can't imagine anyone bothering with zones but not bothering with
programmable ones. Most people are capable of closing doors themselves
(especially people with pets they don't want everywhere in the house).
If there is TRVs all around people will tune off rads, because of the big
knob - as peopel turn off gas fires in rooms. They will use it even more,
if the TRV is set off the rad using extensions. People don't like their
knuckles sraping the rad as the turn the knob.
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