Hello Folks,
Further to my Gas Bill question last week, I have realised that I really need to have my radiators coming on at different times. TRVs which are adjustable by time and temperature seem like the logical choice, but I can't find that they exist. All I can find is a Honeywell RF system that have two zones that you time from a central "hub". Is there something else that anyon knows about?
Cheers Mike
========================================= I was toying with the idea of doing something like this using standard components but decided it might be too complex. My plan was to fit a two way motorised valve close to each radiator controlled by its own room thermostat - no TRVs. Each valve to be further controlled by a small dedicated timer. Grasslin is one example of timer. These basic components would be quite easy to do on their own. Problems would arise in co-ordinating the operation of the various controls to ensure that each produced heat only when required without interfering with other components, especially the boiler.
You might like to play with the idea for yourself unless somebody suggests an off-the-shelf solution, which would probably be very expensive if it exists.
Cic.
I found this a while ago. The author did a lot of experimentation.
It's easy enough to create an S++ system - with one zone per room - if you wish, but it starts to get expensive!
All you need is a 2-port zone valve per room, controlled by a programmable thermostat in each room. As with all S-Plan systems, the secondary contacts on the zone valves are all wired in parallel to control the boiler and pump. So the boiler will fire when any one (or more) room requires heat.
Another poster has cited an article about modifying TRVs by heating their wax elements electrically to enable each radiator to be controlled remotely. I'm sure that valves are available commercially which work on this principle - but I can't remember who makes them. [The late - and much missed - Andy Hall was an expert on such things]. I'm not sure though whether they had any secondary contacts for controlling the boiler, and you'd still need a (preferably programmable) room stat[1] so such a system may not be any cheaper than using zone valves, although it may be neater (I don't think you can get 15mm zone valves and, even if you can, the actuators are going to be the same size as 22mm valves).
[1] If you use a PC or PLC to control the whole thing you'd only need a temperature sensor (rather than thermostat) in each room - but it's then starting to look pretty non-standard when you come to sell the house.
I am fitting this at the moment. You can (allegedly) have up to four of the controller doohickies interfacing with the part that is wired to the boiler, so you can in practice have 8 zones. If you want more, you can have a component of a more complex system which talks to the rad stats.
As another poster has said, there is a solution that uses wired rad valves that just heats the control when the stat is 'on', but I didn't want the wiring, so I didn't pursue that one and have forgotten the manufacturer (but I think it was one of the usual suspects in the heating control world).
HTH
Pete
Pete
I've been looking for a good choice of these for years. Danfoss make some actuators that fit their ordinary TRVs, but they are absurdly expensive.
lists these thermohydrolic actuators, and something I've not seen before for "direct digital control". I've also seen some thermohydraulic actuators made by someone else that were cheaper, but I can't find them again.
Neither of the actuators mentioned above have.
I find it rather sad that I can get something as complex and precisely engineered as a hard drive for about £50, and yet a wax filled piston with some resistance wire wrapped round it costs £100.
That was me :-). I've still got some of the modified Honeywell TRV heads (the bodies have started going unreliable and I've been replacing them with Drayton RAS-C2s) but I never got round to doing a control system, and to be honest I wouldn't bother now. My view is that applying loads of energy to heating a place is, in engineering terms (given the planetary ecological issues), a bodge, and doing it with radiators is a worse bodge! I reckon if I have Tuits to spare I'm better off improving draughtproofing and insulation first, putting in UFH, and possibly zoning off upstairs from downstairs. (I've already replaced the dinosaur boiler with a condensing one, and if I ever get round to building an extension will put in ground-source.)
m
I stumbled across this german product. It looks like a programmable TRV replacement (with optional RF master unit) .. what do you think?
========================================= You can improve the performance of your TRVs by fitting them remotely like this:
It looks as if the Danfoss valve you referenced could be fitted in the same way.
Cic.
Fan control of rads
It struck me that I dont need the full range of temp control, ie from stone cold to over 20C, for each individual room or rad. What I was looking for was just to be able to vary the temp a couple of degrees from the average system temp. And doing that can be achieved in a simpler way, and one with advantages too.
The method I went for was to use a small fan on the radiator. Its important it be silent. Now this basically switches the rads between 2 modes: standard convection and 20% boosted convection heating. Being able to switch between these 2 is enough to give the level of control I want.
The switching element is simply a bimetal stat: these are simple, reliable, long lived, and either cheap for new ones or free used. The stat feeds a wallwart that supplies power for the fan.
Such a setup enables balancing of a system that is inherently unbalanceable, even with TRVs. (TRVs fall far short of full thermostatic control.) And it enables the degree of room by room control I wanted.
Other advantages are that
A final note about fans, since there has been heated argument over this in the past. Only a minority of PC fans can run silently. These are a) ultra low noise fans b) low noise fans that will run reliably at reduced voltage, and quieten down enough by doing so
Most PC fans can't meet these requirements. Its easy to see which does if you can plug them in.
NT
X10 Home Automation, X10 thermostats, 2 way valves on each radiatior and something like an EeePC to control the lot.
-------------------8><
If you have intentions in this direction, it's worth discussing your requirements with Dorothy Bradbury. Extremely well informed, and very helpful:
:-)
I thought exactly the same! Not exactly a thing of beauty, is it?
========================================= Well, I did say that it is going to be tidied. Eventually the pipework will all be 8mm in conduit and thus almost invisible.
In any case I think that a fully functional item is better than a rather inefficient compromise like having the heat sensor directly attached to the heat source when it's intended to be sensing an average air temperature.
Cic.
Yeah, but judging by the horrid wallpaper & the unfixed cable, I doubt that would be an issue.
You can buy TRV's with remote heads (a very thin copper capiliary connects the head to the valve body).
However, I have found that self-heating the heads just doesn't seem to happen, although I did worry about it a bit when I installed my heating. When the radiator is on, there's a draft pulling room air in at the bottom, and there's no heating of the head by the radiator or pipework. I did install most of the TRV's on the return pipe, on the basis that it would be cooler and less likely to effect the head, but on reflection, that was unnecessary.
Another way is to mount the TRV under the radiator...
More interestingly, I found that if you did detailed heatloss calculations for all the rooms and accurately sized the radiators accordingly, the TRV's are actually completely unnecessary, but unfortunately still required by Part L. (Domestic heating installers don't tend to do accurate calculations though, so it's probably best if they do use TRV's.)
Isn't it better to oversize the radiators, now (if we have combi boilers who's output is chosen for their hot water flow), thereforme making the house heat faster with the higher output rads?
Toby...
But wouldn't it be simpler and tidier to use one of these:
?
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I was aware of the capillary tube connected TRVs but the tube appeared to be too vulnerable especially to users unfamiliar with its purpose. Cost was also a factor especially as I already had some TRVs bought over a year ago.
I decided to fit the standard TRVs whilst doing other work which required moving one particular radiator. I decided some time ago that the standard position, connected directly to the radiators, isn't very effective which explains why I tried fitting them remotely. Several manufacturers are now making TRVs with a simple 15mm compression fitting to attach to a straight
15mm radiator connector instead of the more usual mushroom shaped connector. This makes remote fitting easy as in my picture by using a standard 15mm compression coupling with a length of 15mm copper. The TRV valve body is then fixed to the end of the copper pipe in any desired position.My experimental version was intended to be positioned something like a room thermostat as far as distance from the radiator is concerned. I positioned it about 18" from floor level (rather than the recommended 5') which I expect to give a more useful measurement of comfortable air temperature. So far it's working well and generally appears to give quite a good comfort level although this isn't something you can actually measure. I'll leave them in their current position until the weather improves and then I might try them at different heights to see if there's any major difference in performance.
As far as actually being needed at all is concerned I tend to agree that accurately sized radiators should make them unnecessary although they do enable one to shut down a few rooms more or less permanently.
On the whole I think it's worth experimenting a bit to achieve any savings in view of the current high fuel costs, and these remotely fitted TRVs may be one way of doing so.
Cic.
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