Boiler control

[Andrew Gabriel]

No, the pump runs continuously, with the water going round the internal bypass loop.

The instructions recommend fitting a roomstat, in which case the pump won't run continuously.

[John Rumm]

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"

[dennis]

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.

[Doctor Drivel]

The Bxi/Pott boilers that had the flow switch were advertised as being capable of have TRVs all around. Maybe another boiler.

[Doctor Drivel]

Stick to electronic toys, heavy jewellery, tattoos and bull terriers.

[Doctor Drivel]

There isn't. There are a number of ways of doing. it. Do not comment, as it know it all, on topics you know little.

[Dave Plowman (News)]

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 modern boiler.

[dennis]

But never repay the costs.. either in cash or CO2.

[Alan Braggins]

[...]

A zone stat will include a switch to signal demand, a TRV doesn't. (Yes, you can get programmable TRVs with radio switching - that's just sticking the zone state in the valve head.)

[Dave Plowman (News)]

The way gas prices are going I wouldn't be too sure. What is your annual bill?

[YAPH]

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.

[Dave Plowman (News)]

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.

[John Rumm]

If that is what does it for you, then be my guest. I will pass if you don't mind, you are definitely not my sort of style icon.

[Doctor Drivel]

I have the brochure on the HE plus range in pdf. It states

"Flow switch fitted as standard - Part L compliance via flow switch for fully TRV'd systems, which means no room stat or bypass required."

It is clear this boiler can have TRVs on all rads and no central room stat. You have the wrong boiler.

[Alan Braggins]

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).

[Doctor Drivel]

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.

[Andrew Gabriel]

I didn't say it didn't. I described how it works if you do that.

You seem to have imagined something I didn't say. I read the installation instructions, where it describes in detail how it works. Also clearly states it's more efficient if a roomstat is used (although it's not essential).

[Doctor Drivel]

You clearly implied it couldnot TRVs all around.

Read what you wrote again.

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.

[John Rumm]

For goodness sake dribble, work "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 direction etc).

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 hot air.

[John Rumm]

Could we have that again in English please?