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    I have been asked to advise the trustees of a local community building on reducing energy costs. They spend around £10,000 a year on gas for heating and hot water. Majority is for space heating. Cavity walls appear to be insulated, and there is near 100% new double glazing.

    The building has six large rooms, including a '2 storey' hall with stage. Radiators (up to 10 in a room) are supplied by Ideal Concord CX mains gas boiler and nearly all are fitted with individual TRVs. The rads all appear to be on one circuit.

    A clear problem is that the TRVs are the only mechanism to control heat to individual rooms, and reportedly they are nearly always turned up to maximum from October to May, regardless of occupancy and outside temperature. Windows are opened by occupants if too hot and can be left open - with rads blasting away - after the meeting / bridge session has finished.

    Admittedly the first step is to get the building manager to ...manage the situation better. But to help I was thinking about an arrangement where the rads in each large room are controlled as a zone with a room thermostat linked back to the managers office , so he could set rooms on and off and control the temp. (a room being used by Scouts could tolerate a lower temp than one being used by bridge players). Would a scheme like this make sense, and are wireless-linked zone controls feasible to limit the amount of wiring needed?
    TRVs can be slow to operate so can frustrate users. If the system is all one loop then breaking into separate zones with individual zone control might not be possible. There are quite a few radio controlled "radiator" valves around now which would achieve this rad by rad (so is the same as many many zones). Some can be bound together and controlled as a zone, others will be programmed separately.
    Aside from temp control if you can simply program time limits for each radiator to be on then that will help.
    The advantage is that if you get some unexpected occupation then you can simply press an override or boost function that will open them up. Then on the next time segment it will revert.
    You can get tamper proof TRVs but some overall control would be good.
    Definitely worth investigating in detail – I’m sure lots of info will follow

    Cheers, Mike up North
    • CommentAuthortony
    • CommentTimeJun 8th 2012
    Management is needed and your input will be invaluable, go for commission on the savings now!

    Change the boiler for two or three new condensing ones.

    Fit a draught lobby

    Add zones and chronostatic control. or programmable room stats linked to each zone valve.

    It might be possible to use radio linked TRV,s to control the rooms.
    • CommentAuthoralec
    • CommentTimeJun 8th 2012 edited
    the most straight forward and cost effective would be a weather compensated boiler, correctly set up.

    TRVS never tell the boiler about the actual heat demand, at least with an out door sensor the boiler wont be thrashing away when its not so warm...

    Viessmann vitodens 200 with weather comp would be ideal, depending on the kw heatloss...do you know this...
    I think where they will take this will depend on whether they want to make a capital spend for boiler etc etc, or if they want to make improvements under ongoing maintenance. Once zoned properly it would (ideally) require a modulating boiler to deal with the variable load. If they have TRVs on all rad i would assume a by pass is fitted (??), so if all zone/rad valves close this would be the same but quicker - boiler would stop firing on high stat temp. Obviously moving to a modulating condensing boiler would help. I assume someone has looked up the boiler mentioned.

    Cheers Mike up North
    • CommentAuthorDaveS
    • CommentTimeJun 10th 2012

    I can highly recommend the Honeywell CM zone system - i have had one for 4 years controlling 4 zones in a large house. There are two main benefits - you can control each zone remotely (wireless valves on each radiator group) and they use a fuzzy logic thermostatic control to maintain a very accurate temperature in each room sensed from about 1-2 metres away from the radiator - when the room is up to temperature the valve adjusts itself to maintain the selected temperature from the remote controller which can be 20 metres away - or more depending on how many walls etc. Each radiator valve communicates with the boiler control which replaces the conventional room stat. So each individual radiator can call for heat when required even if the others in the room have shut down.

    The radiator valves replace the body of a traditional TRV - 5 minute job. If you think carefully about the system you can save costs by only fitting valves to selected radiators (for instance in common areas) where they will not be fiddled with and where heating is on at a lower temperature than the rest of the building.

    There is a slight noise when the valve adjusts itself or switches on or off.

    I change the batteries in the valves as a precaution every 2 years.

    I am really pleased with my system which has saved a lot of money by zoning and accurate maintenance of temperature - they are not cheap but are a great investment.

    • CommentAuthorCWatters
    • CommentTimeJun 10th 2012
    The stats are the easy part. There are plenty of programable wireless room stats that could do the job. However in order to have one room calling for heat and others off the plumbing will need to be partioned into zones. Typically each with a zone valve connected to the room stat/programmer. Find out how easy/hard that will be first as it depends on the pipe layout.

    One problem I noticed with a community building is this... People arrive for an activity and if the room is cold they turn up the stat. That's usually a mistake. Turning up the stat does not make a room warm up any quicker. The room is invariably cold because nobody arrived an hour early to turn the heating on. The end result is the stat gets turned up to 28 or something silly and the room reaches 20C just as everyone is leaving. I reckon you should see if there is a way to cure this problem. Perhaps link the heating to the room booking system? eg making a computerised booking also reconfigures the heating so that it's warm by the time the room is needed and goes off before the end of the booking unless there is another one following.
    • CommentAuthorGaryB
    • CommentTimeJun 10th 2012
    Exactly my experience Colin - hence in the larger projects with BEMS control systems, there is no user adjustable thermostat but just a sensor. Only the Building Facilities Manager can adjust it and hopefully he/she knows what they are doing.

    We have also used tamperproof stats where the cover plate has to be removed with a screwdriver or special tool - a more simple solution but equally as effective.
    • CommentTimeJun 10th 2012
    Indeed: had to explain to staff at the school that turning up the TRVs does not heat the room faster, just makes temp overshoot. Maybe you can lock the stat not to go above (say) 22C which reduces any overshoot at least. Maybe have some small radiant IR heaters linked to a separate thermostat and PIR movement detectors that come on when room is <17C and there are people. Shouldn't use much extra juice, may add to comfort and reduce temptation to fiddle with other stats. Indeed, 'setback' stats with PIR detectors may generally be part of solution.

    (Yes, I dislike resistive heating, but here is a case where a small amount may pay off, in money and carbon terms.)



    many thanks for your considered and valuable comments, which I will need to digest for a day or so, and give Google a workout.

    I too had thought of 'reverting' back to wall mounted radiant heaters like the ones that inhabited bathrooms in my youth. At least you get near-instant heat and a feeling that something is happening when you switch them on. My local railway station has manually controlled heaters on a 5 minute timer in the waiting room which seem effective and reliable. Adding motion detectors for a larger setting sounds interesting.

    The building, its finances and its management are frankly in a bit of a state, and any large capital spend will need fundraising. There is nothing remotely like a computerised booking system, it's best copperplate script on paper!

    Developing a plan which will make a decent and long term difference is going to take time. I think the way to make progress is to address management practices first, then change the technology.
    • CommentTimeJun 10th 2012
    Well then a PIR-plus-set-back system that keeps room from dropping below (say) 5C out of hours, 14C in hours, and triggers radiant heaters and/or rads when people are in the room and gets to (say) 20C might work well, and with no visible stats.

    Something like this at the most basic (without clock, and thus possibly set to a lower-setback temp therefore):


    or this:




    The thing to remember to distinguish between the types of “modern” TRV is if they can or cannot call to the boiler for heat. There are some which give time and local temp control – these act like a normal TRV except that instead of turning the top, you simply button press like a digital timer. You set time and temp and that’s it. It’s all provided the boiler is on.
    The other type such as the Honeywell can communicate that demand back to the base and thus the boiler. There is a limit to how many channels – so for a largish application you can have 10off separate rads. What you do is create zone by binding 2 or 3 together on one channel and so forth. So 10 rad might be 4 channels = 4 zones. These can open the rad to the position dictated by the temp and as not satisfied by the heat command the boiler on.
    So when investigating the various systems check which ones do/don’t have the boiler control (communication)
    For example there were some in screw fix a while back for £39ish these don’t control the boiler they give a digital / time version of a conventional TRV – but that’s it.

    Cheers, Mike up North
    • CommentAuthorDaveS
    • CommentTimeJun 11th 2012

    Just to add a bit on the Honeywell - it really is worth a look for your installation. Although say a 4 zone system would cost around £1500 controlling 20 or so radiators given you have a £10000 heating bill there is a lot of scope. You may get payback in a year or less by accurately controlling the temperature in the individual rooms and stopping people meddling with them - there is no need for a plumber or any pipe zoning.

    I am controlling 12 radiators in three zones and an underfloor heating system - the manager either programs the controllers or manually sets them. You can select temperature in the rooms in front of the radiator group to .5 of a degree from up to 30 metres away. if the area of room in front of the radiator is not up to the selected temperature the valve signals by wireless to a boiler controller up to 30 metres away and this switches the boiler on - when the temperature is satisfied to that part of the room the signal is dropped and the valve closes. This reduces the heat load and when the room is up to temperature all valves shut and the boiler is switched off. I have found this a substantial heat saving over TRVs and a very stable heat management system in the room. You can have a substantial number of radiators in a specific zone.

    I agree that its better to preset or manually control to get the room up to temperature before occupation - once up to temperature keep it on until all occupancy is finished - don't be tempted to switch on and off between sessions.

    You could try it in a couple of zones for about £500 and see if it works for you.... I hasten to add I have no connection with Honeywell I am just very pleased with my system which has saved me money and improved control no end.

    I'm using a few of the Conrad FS20 wireless radiator valves. At under £100 for a network of a programmer and 2 valves, they are more at the cheap and cheerful end, and so the energy savings will pay back (for my situation at home) within two years. I'm not sure theyre the answer for professional/public installations, but for interested DIYer they are a cheap way to 'try it and see'.

    If you are keen, you can expand the network to turn the boiler on/off, turn down the heating when the windows are opened, interface with weather sensors, turn the lighting on/off, control the temperature from your iphone, etc etc. I havent tried any of this yet. Some enthusiasm and a German phrasebook may be required.
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