The problem with your system is that it requires a reasonably sentient being to operate and adjust it, which makes it fine for someone such as yourself who understands the interactions between the various valves and temperature sensing devices and knows not to fiddle after it is set up.
For an installation by an engineer for your average spod with no understanding on how central heating and TRVs work, it would be hopeless. The first thing most people do with TRVs is set them to 30C when they feel cold, as they think they are on/off/power switches.
Fine if you want the same temperature all the time the heating is on, but most don't.
I have a programmable stat in the living room which has no TRVs. Every other rad has. The house comes up to the morning temp set by a combination of the room stat and TRVs - obviously the room with the stat mustn't be the first to reach its set temperature - and when the later daytime lower temp switches in the whole house drops pretty consistently, and maintains that new temperature. Similarly with the higher evening temperature - and much lower nighttime one if I leave it on 24 hours as I do in very cold weather.
Exactly. Because you are a prat was the instant assumption....:-)
Er, but it DOESN'T DO THIS. The primary circulating water, being nice and lagged, stays hot for a LONG time, and the boiler stat has hysteresis in its thermostat, so it may take up to an hour before the little tiddy bit of water looping around gets cool. IF you have the system on, and it doesn't need ANY heat input in an hour from the rooms, might I suggest you switch it off anyway?
It makes NO sense to have a house stat.
Nothing in the system I am proposing wastes heat, or short cycles the boiler. It is merely - and without actually reading the regs in full detail, I can't even be sure - a TECHNICAL INFRINGEMENT. Not something that wastes power - which is after all the spirit and purpose of the regulations.
Ad the average bozo can just about understand turning up the room TRV's to get warm, and does so, and then calls in the plumber cos the rads are cold. Right. Been there, done that.
(hint. I have done this for some considerable time. The boiler doesn't short cycle at all. Only in the case of very poorly insulated CH pipes and a fairly warm set of rooms, and very cold spaces through which the pipes run [almost impossible to achieve together with fairly warm rooms] do you get teh '5 minute burn, five minute idle' sort of cycle. You MAY get this with a fully TRV'ed system with a bypass buit even then its unlikley. The water has to cool down quiet a lot to overcome boiler stat hysteresis, and in that time its almost certain that one or more rads will have opened up the TRV's a tad and be calling for heat anyway. )
What is wrong with letting the CH return stat do this?
That is the point.
I ran a system fuly TRV'ed with the house stat turned flat out for several years. The boiler neither short cycled nor ran continuously. It cut off when the TRV's had had enough. There was a single unregulated radiator in a well insulated airing cupboard.
I have a system now that in part is functinally equivalent, in that I have room stats on fan blown rads. Plus a few TRV equipped rads. The pump runs continously, The water circulates continuously, the fans come and go, and the boiler does the same. It burns a few minutes, and then shuts down.
Every room is set to the temperature requiertd. I don't have to mess with heat leaks - which anyway would never work, because there is no simple place to put a zone stat on this little lot. Dowqnstais hall ae on a different zone (UF) and upstairs halls/landings are unheated as they take heat from teh UF system by convection.
I beg your pardon. All boilers cycle under normal usage. They get the water up to temperature in the primary HW or CH circuits, and then shut down. That is what they are designed to do for gawds sake!
I don't think YOU do then.
No, you are confuding 'cycle' with 'short cycle' and also if yopu read back on all posts, I never said that all rads were TRV'ed without at least a bypass loop. The point is that short cycling happens when there is NO flow. With ANY flow the boiler cuts out, and the hystersis of teh boiler stat means the water cools several degrees before the next burn comes along to raise it again. Unless you have a stalled pump, that takes several minutes and more likely up to half an hour.
How quickly it heats up again of course depends on boiler stat hysteresis and how much water is actually circulating. Obviously if you stick a bypass loop by the boiler its not a huge amount. However, in my case a long pipe run to a small radiator in an airing cupboard was more than enough to mean a 2-3 minute burn was required at the minimum. And frankly, any house that has its heating on, and requires no heat input for half an hour, is wrongly timed anyway. I have been sitting here for the duration of typing this, and my boiler has not fired up, yet the pump is running all the time in the evening.
Ok, at what point will a system with all TRV'ws and a master stat become exactly the same as a system with no stat and all TRV's?
Easy. When the stat is turned up beyind the ability of the TRV'd rads to flip it.
Result, one user adjustable contol that all by itself, renders the house essentially exactly the way I ran mine. Statless.
Guess why they have stats in the boilers chaps, and make them cycle...
No. I still don't see it.
On an ALL TRV'ed system, I'll buy that a poorly designed system equipped with a very short bypass COULD in theory - but rarely in practice - short cycle. It will NOT run the boiler continuously tho. If it does the bloody thing wil explode.! Thats why teh boiler has its stat... Equipping the house with a stat does NOTHING to remedy that in my opinion. Either the stat is set too low and the TRV's never do their work, or the stat is set too high, and might as well not be there at all. Finding some arbitrary finely tuned position and temperature setting for the stat is completely beyond the average home owner, and is far more likely to result in over use of energuy as he rams the stat open in frustration, and then faffs around with his TRV's.
A non statted sytem that detects a stalled pump is good, except how does it detect a stalled pump when the pump is off? It can't. So instead of boiler short cycling we have pump short cycling.
The answer os simple. All TRV's no ghouyse stat and one radiator that is not TRV'ed that has sufficient thermal inertia and water capacity to stop short cycling. Or simply put a bypass right across the longest pipe run. Sure, the pipe run is contributing to heatinbg teh house, but the situatin where th ehouse is warm enough, all rads are shutdown and teh bozo still runs his heating every day all day seems rather remote.
Most users can cope with the 'its bloody hot today, sparrows are wilting in teh park, I'll turn my central heating off'.
The iedal is obviously a separet zone in every room coupled back to the pump and boiler. TRV's are almost that, the only difference is that you have to rely on return temperature to tell the boiler its not needed anymore.
Well in my house its even easier. If its cold upstairs I switch the heating on. When I go into a room, I set the wall stats (TRV equivalent) whilst I am in it, and when I am done I turn it down again.
Bedrooms that are in use are set to a preset setting that is comfortable, as are bathhrooms.
If the weather is wearm, I switch the whole zone off. In between times I have a timer that does the switching on and off for me.
The boiler does not short cycle. Neither is it always on (Except under full demand when heating first comes on or severe winter weather, when it can take a LONG tome for the underfloor to come up to temp...
Asd fars as I can tell the regulations merely say that you need some system to stop teh boiler running continuously, and that is amply provided for by a single unregulated branch in the CH system, and the boiler stat itself.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.