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Heating and cooling: central heating - mixer valves

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    • CommentAuthorfuncrusher
    • CommentTimeMay 22nd 2012
     
    Anyone with experience of fitting a mixer valve to a heat-store central heating system? Heating systems are not efficient unless parameters are controlled. For central heating that includes controlling the the temperature of the circulating hot water, because that determines the heat from the radiators. With a boiler you control the fuel consumption via a thermostat linked to oil or fuel supply. With a heatstore that is not possible. So there are two alternatives: either you vary the flow rate through the system, or you control the inlet temperature by blending cooler return water with very hot water from the heatstore vis a mixer valve (aka tempering valve). This allows the flow water unto the heating circuit to be at a constant temperature until the heatstore is exhausted. Without it, the radiators would be too hot at first and gradually decline in temperature as the water circulates via the heatstore. It doesn't create more heat of course, it just provides evens it out better, and when you switch the pump on you get the same pre-set water temperature eve if the temperature of the heatstore is very high.

    So what valves are available and what recommendations are there? Most mixer valves are designed for domestic hot water, so are designed to be restricted to temperatures which are far too low for heating (say 50C not 95C). Also, heating circuits operate at high flow rates and low pressures and often contain sludge debris etc.
    • CommentAuthoralec
    • CommentTimeMay 22nd 2012
     
    I think you are mixing lots of concepts up!

    modern boilers with compensation controls vary the radiator temperature by varying the flow temperature.

    Varying the flow temperature matches the heat output of the radiators to the heat loss which varies as a result of out door temperature.


    what I suspect you want is a compensated mixing valve to mix the return water with the flow to produce the right temperature for the radiators.

    Esbe from Essco controls make such a valve...
  3.  
    Hi,
    Like wise ACASO or Thermomix etc all are motorised 3 port valves that blend in some of the return water to ideally take only a trickle of hot water from the top of the store. The set point is the delivery temp (say 65 deg) it will mix to maintain that downstream of the valve. These can be either set at the valve or remotely via a controller. When the set point is adjusted automatically in line with outside temp it becomes a weather compensator. But you can do it manually by simply dialling the delivery temp up/down by your perception of how cold it is outside.
    The motorised 3 port valves can be used as a loading valve instead of laddomat type valves so there is quite a bit of info in threads.
    Word search threads for ACASO.
    Cheers Mike up North
    • CommentAuthorborpin
    • CommentTimeMay 22nd 2012 edited
     
    Previously I had a simple mechanical 3 port blending valve that did exactly what you want. Mixed the cooler return with enough of the feed to get the desired temp. No fancy electronics to break - just not needed.
  5.  
    Posted By: borpinPreviously I had a simple mechanical 3 port blending valve that did exactly what you want. Mixed the cooler return with enough of the feed to get the desired temp. No fancy electronics to break - just not needed.

    Manufactures name and valve type ????
    I presume it worked OK - so why does everyone seem to use / recommend motorised valves now??
    • CommentAuthorborpin
    • CommentTimeMay 23rd 2012
     
    Posted By: Peter_in_Hungary
    Posted By: borpinPreviously I had a simple mechanical 3 port blending valve that did exactly what you want. Mixed the cooler return with enough of the feed to get the desired temp. No fancy electronics to break - just not needed.

    Manufactures name and valve type ????
    I presume it worked OK - so why does everyone seem to use / recommend motorised valves now??
    Don't know and don't know! They came with my UFH system. Cast aluminim (? silver) body with a black knob on top like a large TRV.
    • CommentAuthoralec
    • CommentTimeMay 23rd 2012
     
    precision and reliability is why you use electronic mixing valves now...

    manual valves only allow for fixed flow temperatures, when in reality varying the flow temperature is a necessary to match heat output of an emitter to the heat load of the rooms...

    if you have several of them the heat generator can always provide the lowest demanded temperature...

    If you want to buy the TMVs they still exist and can be used on heating...but just think of all that heat you are wasting...
    • CommentAuthorborpin
    • CommentTimeMay 23rd 2012
     
    Posted By: alecmanual valves only allow for fixed flow temperatures, when in reality varying the flow temperature is a necessary to match heat output of an emitter to the heat load of the rooms...
    I'm not sure I would agree with 'necessary'. I had one on my UFH supply and another on the DHW to mix it down. Horses for courses. Having re-read the initial thread though, you are correct in this case.
  9.  
    Hi,
    Its probably something from Reliance Water (RWC) from the Heatguard range or very similar form many others basically a version of the DHW mixing valves for controlling tapwater temp. These will maintain a set point set on the valve with the adjuster on the top. The problem with these will be finding one that has a high enough delivery temp. The UFH ones and DHW sre settable in the 25 - 35 maybe 40 deg range (for obvious reasons). If you wanted rads at that temp? So you would have to find one with say 50 - 80 deg range.
    Thats why units like the ACASO Automix controller http://www.acaso.se/en/LK-Acaso/Products/Heating-Controls/Automix-CT--CTR/ are used to control the motorised 3 port valve eg Termomix http://www.acaso.se/en/LK-Acaso/Products/Mixing-Valves-of-brass/Termomix-mixing-valves-DS-and-CS/

    As mentioned above when this is coupled to weather sensors that compute the heating / cooling curve of the building then it automatically adjusts the delivery temp. The above controller is a half way house in that you the "driver" can dial up any desired delivery temp and it will controll to match that.

    It really depends if you want to have 1) no control, 2) some control with user interventions or 3) totally controlled automatically.

    Hope that helps

    Mike up North
    • CommentAuthorbillt
    • CommentTimeMay 23rd 2012
     
    It's rather ironic that, on a forum that will debate the finer points of window construction (effect on fuel consumption marginal), people seem to be willing to consider heating systems with no, or inadequate, controls - effect on fuel consumption potentially very large.

    Posted By: borpinNo fancy electronics to break - just not needed.


    Point of information - electronics are exceptionally reliable, if designed and manufactured correctly. I think the most unreliable heating components will be diverter valves (very clever design, but built down to a price) followed by pumps; both mechanical.
    • CommentAuthorCWatters
    • CommentTimeMay 23rd 2012
     
    Remember to size the rads for the lowest temperature from the store ?
    • CommentAuthorowlman
    • CommentTimeMay 23rd 2012
     
    Diverter valves billt, like their electronic controllers are only as good as their design and manufacture. Circulating pumps generally are quite good and the modulating ones perform very well indeed.
  13.  
    Hi,

    Like anything else there will be levels of quality in all aspects of the design and manufacturing and you will get what you pay for – as they say.

    As to sizing the rads they would be sized to suit the nominal flow temp conditions, the lowering of the delivery temp in line with warming internally/externally will reduce the power from them accordingly. The power rating of rads is standard at “delta-50” meaning water in at 75 deg out at 65 deg thus mean = 60 deg which is 50 deg above a nominal 20 deg room.
    So at 75 deg delivery from store @ 80 deg this would only be slightly tempered down. So the bulk of flow would be from the store. So the key is to get the store a as hot as possible and use the lowest delivery you can get away with say 50 deg, that way the store is only supplying a smallish stream of very hot to top up what’s been dissipated by the heat systems.
    Another advantage with the lower delivery temp is that lower temp water is returned to the store (at the bottom), if you want to avoid mixing up the store, then the turnover wants to be as small as possible. The returned volume has to equal the delivered volume which is hopefully small. This can be further achieved by increasing the temp drop through the rads (but not as easy as it sounds).

    As to heating (if required) control is a very key part. I’m not totally comfortable with fully automatic systems, I do like to tweak things, I’d like not to need the heating, and I can manage pretty much without it (not others).

    Cheers, Mike up North
    • CommentAuthorborpin
    • CommentTimeMay 23rd 2012 edited
     
    Posted By: billtIt's rather ironic that, on a forum that will debate the finer points of window construction (effect on fuel consumption marginal), people seem to be willing to consider heating systems with no, or inadequate, controls - effect on fuel consumption potentially very large.
    Posted By: borpinNo fancy electronics to break - just not needed.
    Point of information - electronics are exceptionally reliable, if designed and manufactured correctly. I think the most unreliable heating components will be diverter valves (very clever design, but built down to a price) followed by pumps; both mechanical.
    The only bits of the heating system that broke in 14 years was the electronic circuit board on the boiler and the micro switches on the motorised pumps. mechanical is almost always more reliable than electronic!

    Edit - oh and the pump motor x2
    • CommentAuthoralec
    • CommentTimeMay 23rd 2012
     
    pump life is compromised significantly by TRVS, two port valves and by passes, all giving variable loads...if given free reign i.e. constant flow, variable temperature they will last much longer...

    One british boiler manufacturer put their PCBS on the top right hand corner next to the heat exchanger and all the PCBS failed pretty quickly not helped because everyone oversizes boilers anyway even to this day......

    Decent boilers have countless alterable parameters to enable people to match the boilers to the heating system and building...sadly the importers are not so keen on assisting installers or the public in understanding them...
    • CommentAuthorborpin
    • CommentTimeMay 23rd 2012
     
    Posted By: alecpump life is compromised significantly by TRVS, two port valves and by passes, all giving variable loads...if given free reign i.e. constant flow, variable temperature they will last much longer...
    One of the pumps that failed was on the boiler loop so no TMV. The other was on the DHW / towel Rad loop with a TMV.
    • CommentAuthoralec
    • CommentTimeMay 23rd 2012
     
    what do you mean a boiler loop, feeding a header?

    also the high temperatures that we love to run all our heating systems at compromises component life...
    • CommentAuthoralec
    • CommentTimeMay 23rd 2012
     
    its actually much more sensible to run a boiler and heating system as hot as it needs to be...with the right controls!
    • CommentAuthorborpin
    • CommentTimeMay 23rd 2012
     
    Posted By: alecwhat do you mean a boiler loop, feeding a header?
    Boiler to Thermal Store.
    • CommentAuthoralec
    • CommentTimeMay 24th 2012
     
    well no surprise there then the either... thermal stores are really hard all the components due to the high temperatures required by the heat exchanger for hot water...
  21.  
    Hmmm, I use a mechanical valve to mix my radiator water down to 55 deg or so and TRVs on all my radiators (with a mechanical by pass valve). I use a mechanical (centrifugal) filter before the tank and and another after mixing on the flow. I use a Grunfos Alpha adapt which uses 15-20 watts most of the time and if it drops to 14w I change it to low using 5/6 watts. (wood burner, 2000 ltr tank-in-tank, massive house, lots of solar). All the important bits are Caleffi and clearly I like to snog. My solar controller has over 70 settings God knows what most of them are for.....

    I love my Grunfos because I can watch the pretty little green watts number vary telling me all about my house and the weather. It all works marvellously and so far no probs; of course it wouldn't work in a lightweight house.

    My valve is peculiar; it is a 2 way valve (a big TRV really) with a remote sensor in the upstream flow and a carefully adjusted bypass valve in return - it works but was a bit tricky to set up and wanders for a while when the flow changes. I think I would just use a 3/4 inch caleffi solar 3 way valve if I did it again - like the one I use to mix down my DHW (from the tank inside my 2000 ltr tank).
  22.  
    Hi, yes the 2 port version is like a big TRV it will just throttle the flow acording to the downstram temp prob. Any valve driven by a sensor bulb acting on the valve stem (like a trv) woll be fairly slow to respond (so ok for steady state applications) and needs to be paired with something the Grundfoss alphas to modulate flow down as it closes in (like a TRV).
    A example is the Danfoss AVTB (closes on risng temp) - the other way would be opens on rising temp for cooling applications (AVTA)
    btw you can use the AVTA as a 2 port loading valve (in place of thermovar/laddomat types) between a boiler and a thermal store. The valve is placed on the inlet to the store, preceeded by a branch down to the boiler reurn with a bypass valve. Put the AVTA sensor not in the forward flow but in the thermal store return line down from the by-pass. When the boiler is initially coming up to temp it is short circuited as the AVTA is closed as the boiler comes up to temp the return water temp rises and the AVTA opens allowing flow to the store. Effectively what the chartridge in the bottom of the laddomat is doing.

    Cheers, mike up North
  23.  
    Posted By: funcrusherAnyone with experience of fitting a mixer valve to a heat-store central heating system?


    I have a Sonnenkraft PSR350 thermal store with a heating circuit with mixer driving nine radiators. This heating circuit has a flow temperature sensor; Wilo Stratos Pico pump and an ESBE Series VRB140 4-port bivalent valve and rotary actuator (ARA600?). The three inputs to this valve are from the return; store middle and store top. It is controlled by an extension module for my Viessmann Vitodens 200-W system boiler. All seems to work fine.

    Plenty of useful documentation on the ESBE website (http://www.esbe.eu/gb/products/?prodid=4043).

    The idea behind the bivalent valve is that to satisfy the target flow temperature it adjusts the blend first between the return and store middle then between store middle and store top. If the heat demand is relatively low then the heat in the store top is saved for DHW which requires the higher temperature.

    The controller driving the actuator doesn't know nor care if it is driving a 3-port or 4-port valve. With a 3-port valve the blend would be between the return and a single level in the store.

    My system also uses a relay on the solar thermal controller which when energised switches in a couple of resistors which increase the apparent temperature of the boiler controller DHW and heating sensors in the thermal store. This stops gas being burnt when solar thermal is available. Fairly crude but effective.

    At present, the radiators have TRVs. I plan to investigate a more sophisticated alternative next winter.

    Hope that helps.
    • CommentAuthorowlman
    • CommentTimeMay 27th 2012
     
    Posted By: john_connett...........At present, the radiators have TRVs. I plan to investigate a more sophisticated alternative next winter.

    Is your CH zoned?
  25.  
    <blockquote><cite>Posted By: Mike (Up North)</cite>state applications) and needs to be paired with something the Grundfoss alphas to modulate flow down as it closes in (like a TRV).</blockquote>

    with mine though, a second bypass valve opens up as the big TRV closes so mixing return water and maintaining the volume being circulated, the pump only changes as the TRVs on the radiators operate. In a high mass house, with heating on 24/7 I struggle to see why rad TRVs are 'unsophisticated' John C, am I missing something?
  26.  
    Posted By: owlmanPosted By: john_connett...........At present, the radiators have TRVs. I plan to investigate a more sophisticated alternative next winter.

    Is your CH zoned?


    It's a single heating circuit through the nine radiators with TRVs. There is an "indoor temperature" sensor in the control panel in the living room and a wired outdoor temperature sensor on the north exterior wall. I suppose it depends on your definition of zoned. The top floor is a shower room and spare bedroom and I have adjusted the TRVs to frost when they are not occupied.

    Posted By: GotanewlifeIn a high mass house, with heating on 24/7 I struggle to see why rad TRVs are 'unsophisticated' John C, am I missing something?


    I didn't say or intent to imply that "TRVs are 'unsophisticated'"! What I am considering is wireless radiator valve actuators and sensors. My technology of choice is EnOcean and I particularly like the look of the Kieback & Peter MD10-FtL-HE as described on page 34 of:

    http://www.enocean.com/fileadmin/redaktion/pdf/perpetuum/perpetuum_01_2012_en.pdf

    As far as I know, this is the first wireless, battery-less device. Earlier devices from K&P and Thermokon have batteries.

    The advantages are convenience and flexibility. If I decide to go out for the day I could go round and adjust the TRVs before I go out and again when when I get home but I suspect most people wouldn't! With a suitable control system it should be possible to set the house to "standby" and perhaps use my mobile 'phone to reset it to "home" so that it would be comfortable by the time I returned.

    Not sure how much energy could be saved. I should really try modelling the thermal performance of the house to see what strategies would be most effective. It may be that keeping unused rooms warmer it would reduce energy use as the insulation between rooms and floors is less than the external walls ...

    One frustration is that although it should be possible to collect temperature or valve position data from the actuators I haven't found a way of communicating this demand back to the boiler controller. Viessmann have an EnOcean module (Funk-Basis) but At the moment, Vitotrol 200RF and Funk-Basis are not able to interact with other EnOcean-products. They use the EnOcean standard, but it's coded.

    Other possibilities are using the next day's weather forecast to estimate the likely performance of the solar thermal system (cloud cover, temperature, precipitation?).

    I suspect it might be difficult to justify the cost for an individual house so this would probably fall somewhere between hobby and eco-bling.
  27.  
    Posted By: john_connettI am considering is wireless radiator valve actuators and sensors. My technology of choice is EnOcean ...

    As far as I know, this is the first wireless, battery-less device. ..

    With a suitable control system it should be possible to set the house to "standby" and perhaps use my mobile 'phone to reset it to "home" so that it would be comfortable by the time I returned.

    Not sure how much energy could be saved. I suspect it might be difficult to justify the cost for an individual house so this would probably fall somewhere between hobby and eco-bling.


    John, do you have a price for the enocean valves?

    I have some Conrad FHT wireless programmable radiator valves. They have gone one winter so far on the set of AA batteries that came with them in the box. At £63 per room it was much cheaper than retrofitting wired zone control, so plenty left in the kitty for rechargable battreies... but the enocean ones do look neat.

    http://www.conrad-uk.com/ce/en/product/646463/Conrad-Radio-heat-thermostat-FHT-80BTF-saving-set/?ref=detview

    They apparently can be re-programmed in clever ways from a PC or mobile phone but I havent tried that. They can also interface with a relay that switches pumps or the boiler on/off (havent tried that either).

    I used them to make the living room into a separate zone from the bedrooms/bathroom/kitchen. The living room is now programmed to: unheated overnight, 14deg in the day and 19deg on weekends and weekday evenings, whereas previously the TRVs were set at 19deg all the time.

    This reduces the heat losses and consumption in the living room, so the FHTs should pay for themselves in 2 years, but obvs this depends on how much heating you were using to start with, and how fast your room heats/cools.

    The thermostat unit can be mounted on the wall somewhere remote from the radiator, this was why I first got them as the TRV was getting confused by draughts.

    Downsides are that the manuals are in German (but english translation of sorts on the web)
    The motorised valves do make an audible noise, is OK in living room but not in bedroom.

    If you keep one room warm and another one cool, you might get condensation in the cold one.
  28.  
    Ahhh I understand where you are coming from now. Of course in my massive house I don't get the option of 'playing around' like that as the house takes at least 24 to even begin to react to change in the TRVs and 3 days to warm up from cold! I guess you have a 'lightweight house' or rather the bit you keep warm is not massive and so it reacts quickly enough for it to be worth at least exploring 'nouveau verde bling' :wink:
  29.  
    Posted By: WillInAberdeen
    John, do you have a price for the enocean valves?

    Not current ones. However, EnOcean stuff is typically priced for the professional building automation market and can be eye-wateringly expensive! However, some products aimed at the (German) domestic market are starting to appear such as the curiously named Telefunken Joonior (http://www.telefunken-sb.de/en/home.html). If they are pushing into the mass domestic market there is a chance that might lower prices.

    The Joonior radiator servo control is made by Kieback & Peter and is probably a very close relation of the K&P MD15-FTL actuator. Both use 3 x AA alkali batteries for a service life of around three years.

    The other player is Thermokon Sensortechnik with the SAB01 wireless valve actuator. That uses 2 x AA alkali batteries.

    I heard from the UK distributor that the battery-less K&P MD10-FtL-HE isn't yet available. My hope is that as 10 is less than 15 the MD10-FtL-HE might be less expensive than the MD15-FTL. However, what is described as a low-cost investment for energy-efficient room temperature control for the luxury German market may translate to something very different in the UK!

    I will probably get an EnOcean starter kit to experiment with the technology while keeping an eye on developments from K&P, Telefunken and others.

    I have not noticed any condensation problems. As it is the top floor that is typically cooler quite a lot of the heat from the to floors below takes that route to the outside world anyway. My MVHR has a humidistat which might catch some potential problems. As a mid-terrace I probably "steal" some heat from my less energy efficient neighbours too.

    This Englishman's house isn't a castle but is of brick construction with insulated cavity walls and has a moderate amount of thermal mass. Certainly wouldn't take three days to get from cold to comfortable. What have you got, Gotanewlife, rammed earth like this?

    http://peasehouse2011.blogspot.co.uk/2011/09/rammed-earth-wall.html
  30.  
    Just a 50 year old Italian house with thick solid stone uninsulated walls (ground floor rear wall is fully underground), though I have insulated my roof...perhaps 3 days is an exaggeration and the last time is was properly cold I didn't have the capacity to pile heat into it that I have now.

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