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    • CommentAuthortopher
    • CommentTimeAug 20th 2015
     
    In October I plan to install a Honeywell Evohome system in my UK house. From my analysis is seems to be the best current offering, unfortunately the most expensive too. Would anyone be interested in reading my experiences?
    • CommentAuthorgravelld
    • CommentTimeAug 20th 2015
     
    Did you compare with Heat Genius? That was cheaper last time I checked.
    • CommentAuthorJonG
    • CommentTimeAug 21st 2015
     
    We have just started working with Evohome and Opentherm. 1 system is a simple cylinder, boiler, central programmer and 1 HR92 linked to an Intergas boiler via the Opentherm bridge, the other an Intergas combi linked to a central programmer via the bridge. With the base levels in place now though both can be expanded and upgraded as funds allow.

    We looked at the various smart systems on the market and felt EH was the best at the time but it does have its limitations and bugs! Have a trawl around the net and you will get a feel for it.

    There are bits of info too that don't feature in the manuals etc. that impact the systems.

    Opentherm if you are planning to use this is a bit of an unknown for the boiler manufacturers and Honeywell but is well used on the continent.

    Richard at Evohome shop is a very useful contact as and when you do decide to get started with it.
    • CommentAuthortopher
    • CommentTimeAug 21st 2015
     
    Hi Gravelld, yes I did compare. It is not as granular as Evohome which controls every radiator on it's own. Also the rad valves are poor in comparison with Evohome's.

    JonG, Interesting. I have spoken with Richard at Evohome Shop and will probably buy from him. He is not the cheapest, but his support is really good. So tell us about worst limitations and worst bugs please.

    Shall I tell of my experiences? Tell me please.

    One important point that took me a long time to discover is that Evohome needs a boiler bypass, even with a 3 position valve in a Honeywell Y configuration.
    • CommentAuthorgravelld
    • CommentTimeAug 21st 2015
     
    Heat Genius does control every rad on its own. It depends how you setup the system. The valves are Danfoss - they do make a noise when they adjust.
    • CommentAuthorJonG
    • CommentTimeAug 22nd 2015
     
    Which elements of the system are you planning to use topher and in what configuration and I will see if I can shed any light.
    • CommentAuthortopher
    • CommentTimeAug 22nd 2015
     
    JonG,

    I have 13 radiators, so will have to combine two, as the Evohome (EH) max is 12. I will put an EH controlled valve (HR92) on each. Two of the radiators are actually skirting board heaters - a long copper pipe with fins on it. Today they have no TRV, I plan to fit one on each.

    I am hoping the HR92s will control the temperature adequately, but I am prepared to buy a room thermostat if needed to better control the room comfort.

    I plan to fit the hot water controller as well. The heating comes from a 5 year old Valiant condensing boiler which has a just adequate output for a very cold day.

    The house has cavity insulation and double glazing.

    I got more advice on the boiler bypass yesterday which has to be 1.5 meters minimum in length, so as to dissipate a bit of heat if needed. I have to have one because the EH controller can shut all the valves, but keep the heating demand on in case a valve re-opens. Apparently the EH controller can keep the boiler on for 4 to 8 minutes with all valves closed; hence the need for the bypass. At my current level of ignorance, I think it would be better if the EH controller could be set to briefly open the hot water valve to use any excess heat from a hot boiler shutdown.
    • CommentAuthorJonG
    • CommentTimeAug 22nd 2015
     
    OK, no worries.

    First off depending on your motive there is a CBA to do because the savings may not justify the expense, especially if air tightness, insulation or both can be improved. If the EH is to give you more functionality and control, especially in your instance when it sounds as if toggling zones to limit the demand on the boiler is needed then fair enough.

    Zoning only works if you can fully segregate areas (think closed doors), otherwise you end up with homogenous heat transfer and heat moving from a hot area to a cooler one which then means that the higher target zone may never satisfy.

    Quite a few do leave some key areas like hallways/landings open circuit to keep a core of heat in the building and reduce the system cost and complexity, this also negates the issue with the bypass which is becomingly an increasingly thorny issue with modulating pumps (but that is probably a separate thread).

    It might be worth getting the wifi test kit to ensure that the signal is available from the furthest reaches of the property, any reflective insulation, steels, laminate foils etc may compromise the signal, test the heads when in situ too and be very wary if the signal strength is low.

    The battery life in the central controller is pants, so it does need to be on the stand or wall mount, either plugged in or wired in respectively. It can take up to 4 mins for signals to be sent and received between the various items and if the power is dropped it can be sometimes up to an hour to re-establish contact although 15 mins is more usual. This can engender panic, rage, frantic re-binding and general social unrest if you don’t know. If you manually override the signal re-establishes sooner.

    Failures do happen straight out of the box, Richard at Evohome will pre-bind and test for the trade, not sure if he offers this to private clients though. There are some rumblings in the trade about the quality of back-up from Honeywell generally.

    If you are using the hot water kit the sensor benefits from plenty of thermal paste or a dedicated small diameter sensor pocket and in either case some insulation to plug the orifice once it is in.

    The Vaillant I believe, won’t allow you to use either Opentherm or weather compensation with the system which is a shame because it negates some of the efficiency that either of these engender.

    The BDR91’s and cylinder sensor transceiver are best located 300mm away from each other and metal lumps like boilers and cylinders if possible.

    It is a good system but it’s not a magic bullet and has to be installed and commissioned carefully.
    • CommentAuthortopher
    • CommentTimeAug 22nd 2015
     
    JonG,

    Brilliant comprehensive reply. Many thanks. I will do a cost benefit analysis, but my decision to buy is in part because I am a gadget freak and love the latest technology. Also SWMBO has given permission!

    My idea is to have every single rad controlled because if I leave some rads without HR92 then they will come on every time any HR92 calls for heat, so the landing rad will get hot at say 8 pm when the lounge HR92 is calling for heat.

    My pump is not modulating, just old fashioned on and off.

    I have done the Honeywell installers training (and passed).

    One thing I am not clear on is balancing the radiators. I can adjust the gate valve to get the 12 degrees temperature drop, but I believe I have to start with the first rad and move on to the 2nd, then 3rd etc. I think I will have trouble in finding out the order. Any tips?

    This is a very valuable tip. . .This can engender panic, rage, frantic re-binding and general social unrest if you don’t know. If you manually override, the signal re-establishes sooner.

    Thanks again.
    • CommentAuthorJonG
    • CommentTimeAug 22nd 2015
     
    No problem topher hope it goes well.

    In terms of balancing it is indeed a dark art, usually conventional wisdom was get the furthest rad away sorted then work your way back. Don't underestimate how much you can close the lockshields, the closer you get to the boiler the more you will have to throttle and you may have the valve barely a quarter or half turn open.

    To get started open everything full whack and see which rads get hot first and last and this will give you a feel for the hydraulic layout.

    However in a system like EH or even just with TRV's generally the flow and pressure changes so regularly that accuracy is very difficult to achieve. Also dont even think about doing it until there is a decent cold weather demand in the house, because obviously the delta closes as the rooms reach temp.

    I am also unclear why HW recommend 12 degrees, a condensing boiler is looking for 20 degrees and it is better to adjust the delta by throttling the pump speed because this reduces energy consumption.

    It really will be trial and error and unlikely to be a one off experience!

    In terms of the gadget freak thing, I think HW could have included more visible data about what the system and individual components are doing at any one time even if it was hidden in the installer menus, the actual interrogative level is disappointing from that perspective.
    • CommentAuthorringi
    • CommentTimeAug 22nd 2015
     
    Posted By: JonGalso unclear why HW recommend 12 degrees, a condensing boiler is looking for 20 degrees and it is better to adjust the delta by throttling the pump speed because this reduces energy consumption.


    A dT of 20 degree will only give enough heat if the radiators are large enough, often they are not.

    As EV using TPS type control system (if not using OpenTherm) the boiler will hardly ever get up to the flow temp it is set for, so will condense well most of the time.
    • CommentAuthorringi
    • CommentTimeAug 22nd 2015
     
    Posted By: topherI got more advice on the boiler bypass yesterday which has to be 1.5 meters minimum in length, so as to dissipate a bit of heat if needed. I have to have one because the EH controller can shut all the valves, but keep the heating demand on in case a valve re-opens.


    Most boilers need a bypass, as the pump is kept running after the boiler shuts down for a few minutes, otherwise the heat exchange overheats. (The boiler is still filled with hot gases even after the flame goes out.)
    • CommentAuthortopher
    • CommentTimeAug 23rd 2015
     
    Hi JonG and Ringi,

    As you can tell, I am a beginner on the radiator balancing thing. I watched a few videos and have the general idea. I got the figure of 12 degrees temperature drop across a rad from a video (sorry I can't find it now).

    Watching a few videos, the easy way seems to be having the rads closest to the boiler lock shield valves cracked well down, the gradually opening up as you get to the last rads on the circuit. I can do that. I have bought an inexpensive infrared thermometer and can measure input and exit temperatures. So I might be able to tweak to a specific rad temperature drop too. Any idea of what this value should be?

    But I note what JonG said. . . .a condensing boiler is looking for 20 degrees and it is better to adjust the delta by throttling the pump speed because this reduces energy consumption.. . . . .

    So after balancing the rads, I need to get 20 degrees across the boiler. My pump has 3 switched speeds, but If I am a long way from 20, I suppose I could crack open or crack down all the lock shields to modify the flow. Is this practical? Or I could partly close the isolating valves fitted on each side of the pump.

    May be this is a storm in a teacup because with EH the load on the boiler will be going up and down like a yo-yo as the HR92s will be opening and closing all the time, and the hot water will change the system yet again as it has very little flow restriction.

    May be give it my best shot and forget it.

    P.S. What is "TPS type control system"? Google is unhelpful.
    • CommentAuthorJonG
    • CommentTimeAug 23rd 2015
     
    We usually find that rads are oversized mainly due to in-acurracy originally and a desire to avoid a cold client. Plus often the heat loss has dropped due to CWI or loft insulation upgrades.

    Ringi why would the boiler not hit flow temp? Depending on load, cyclical rate, system design, rad size etc it may have to reach set point to achieve the design room air temp.

    Once close to set point the HR92's will open and close according to the TPI algorithm to avoid under/over shoot but this shouldn't affect the set point FT unless the boiler is cycling on the limit stat, which would indicate a flow related issue and even then the HX would have hit set point.

    Surely this is why OT and WC make sense because the FT is flexed depending on load or external temp?

    The infrared's are OK but I would only rely on it for a reference delta and use masking tape or similar on copper/rads to avoid it bouncing.

    If the lowest pump speed is not low enough (and you still have to consider system response times in all of this), it may be better to introduce a flow setting valve to throttle the flow speed if you can fit one, Taconova do a comprehensive range.

    However as you say the changes in velocity in the system may frustrate your efforts, it may be that as the popularity of systems like these increase we see a higher incidence of low loss header usage, which hydraulic decouple the boiler from the system and allow it to work at a constant delta irrespective of what the downstream system is doing.
    • CommentAuthorringi
    • CommentTimeAug 23rd 2015
     
    Sorry it is TPI (Time Proportional & Integral)

    http://www.draytoncontrols.co.uk/installerzone/trainingcentre/howtoarticles/jargonbusted/ gives an overview

    "Traditionally, room thermostats have used an on/off algorithm. Put simply, this means that when a room’s temperature is below the thermostat’s setting, the heating is on, and when it is above the necessary temperature, the heating is off. This effectively means that the actual room temperature is constantly fluctuating around the target temperature and consequently, wasting energy.

    However, more advanced room thermostats use Time Proportional Integral (TPI) control to ensure more accurate temperature control and the resulting energy savings.

    TPI offers a more complex algorithm, which uses past information to estimate the correct steady state ratio of each room within six, ten-minute cycles per hour. During each one of these ten-minute periods, the algorithm has set a period of time with the heating on that is calculated to maintain thermal equilibrium. The ‘I’ (integral) part of the TPI control makes small, long-term adjustments to the process, varying the length of the heating times to keep the room temperature even more precisely on set-point. "

    So rather then the boiler working very hard to get the house hot, then being turned off for 30 minutes, then having to work very hard again, the boiler is turned on for a few minutes every 10 minutes. Therefore for most of the year, the water in the system is warm rather then hot.
    • CommentAuthorJonG
    • CommentTimeAug 23rd 2015
     
    Hi ringi I still dont think it will affect FT though, we have used CM927's and DT92E's for years with boilers and heat pumps and with heat pumps the FT is critical, it does as the quote says above control fluctuating room temperature but if the heat source isn't hitting set point the design of the system is compromised because the MWT in the heat emitter could be too low.
    • CommentAuthorringi
    • CommentTimeAug 23rd 2015
     
    The boiler does hit "set point" when it is very cold outside, most of the year it does not need that much heat.

    Hence the set point can be higher, yet you still get condensing most of the time.
    • CommentAuthortopher
    • CommentTimeAug 24th 2015
     
    Thanks for my continuing education, all the comments are very useful.

    Could I ask a favour please? I am somewhat in the dark with all the abbreviations. The words that go with the following would be great. Some I might guess like CWI = cold water inlet. But that could be wrong.

    FT, MWT, OT, WC, HX, CWI,
    • CommentAuthorEd Davies
    • CommentTimeAug 24th 2015
     
    CWI = cavity wall insulation

    Most of the others are specific boiler parameters, I think.
    • CommentAuthorJonG
    • CommentTimeAug 24th 2015
     
    FT=Flow temp
    MWT=Mean water temp (the average temp in the rad taking into account the FT/RT and the delta)
    OT=Opentherm a control protocol that modulates the boiler gas valve increasing and decreasing the FT according to load
    WC=Weather compensation a control protocol that modulates the boiler gas valve increasing and decreasing the FT according to external temp via a sensor
    HX=Heat exchanger
    • CommentAuthortopher
    • CommentTimeAug 25th 2015
     
    Thanks for the abbreviation info. Clearly I got CWI wrong!

    I have a cunning plan. I would be delighted to read your comments.

    When I install the EH, I have to have a boiler bypass. The installation of this is planned. My understanding is that the EH system can have all the HR92s closed, but still be calling for heat from the boiler. This call for heat can remain on for 4 to 8 minutes. The bypass is to allow a path from boiler flow to boiler return, so that the boiler heat exchanger is not damaged by excessive heat. Valiant, the boiler manufacturer, say the bypass has to be at least 1.5 meters away. This I am told, is to make sure that the pipe work is at least 1.5 metes long and thus able to dissipate a little heat.

    This is the cunning plan - boiler bypass flow starts at the pump output and before the three way motorised valve as per normal. The pump is directly connected to boiler flow. The return side of the bypass is connected to the domestic hot flow side, after the three way valve - the excess heat is directed through the heat exchanger in the HW cylinder. The merit of this is that the excess heat goes to the hot water cylinder, where it may take the temperature a little beyond the set point, but it is not waisted as in the standard bypass pipe routing.

    When the cylinder 'stat is calling for heat, the bypass valve won't operate, because the flow resistance through the HW cylinder is much lower than the by pass setting. When the rooms are calling for heat and the HW is not calling for heat the motorised valve is closed for HW, so nothing happens on the bypass.

    Sorry this is a bit tedious. If you can't understand, I could try a sketch next time.
    • CommentAuthorJonG
    • CommentTimeAug 25th 2015
     
    Hi Topher any chance of a drawing showing what you are thinking.

    Also is the pump on your boiler internal or external, I am also guessing it already has an ABV that will need to be shut to allow the new bypass to work.

    Whatever you do aim to keep it simple, would be my advice.

    If you can post a drawing we can have a look at it for you.
    • CommentAuthorringi
    • CommentTimeAug 25th 2015
     
    The water that is being pumped round the CH at the time the bypass operates is very likely to be closer then what is in our hot water tank.

    When the pump stops operating, it WILL be coiler, as the flame is turned off before the pump.

    Bust just to put the bypass pipe in your airing cupboard.
    • CommentAuthortopher
    • CommentTimeAug 26th 2015
     
    Hope you can understand sketch, had to use 200 bpi to get it accepted . . .
      Scan.jpeg
    • CommentAuthorJonG
    • CommentTimeAug 26th 2015
     
    Hi topher it could work like that, but couple of things to bear in mind.

    If there is a differential between the flow temp and the cylinder temp one will strip the other and could possibly increase the heat in the exchanger in an extreme example whilst also depleting the cylinder contents.

    If you did end up changing the pump you would have to purchase a modulating version, with an ABV this might mean you have to use the fixed speed option to ensure that the bypass still opens as the pump ramps down due to resistance in the system, or risk a short circuit loop because the ABV is set so low.

    Another possibility could be to leave a towel warmer or 2 open circuit to accept the flow where it would actually be more useful.

    Is the 3 way valve a diverter or mid-position because this may influence your design depending on what state it is in when the bypass is needed. If it is a diverter the path to the hot water would be open when the heating port is closed.

    You will have to check if a bypass already exists in the boiler and throttle it if it does.
    • CommentAuthortopher
    • CommentTimeAug 26th 2015
     
    I think this is the point I missed. You said . . . . If there is a differential between the flow temp and the cylinder temp one will strip the other and could possibly increase the heat in the exchanger in an extreme example whilst also depleting the cylinder contents. . . .

    If the boiler had just heated the HW and the last HR92on the radiator circuits closes, then your point above applies. I could hasted the death of my boiler due to overheat.

    So I will go back to the normal connection.

    A better solution would be to alter the firmware to keep just one HR92 open white the 4 to 8 minute EH shutdown occurs. Anyone know how to do this?

    You said. . . . Another possibility could be to leave a towel warmer or 2 open circuit to accept the flow where it would actually be more useful. . . . . . How do I leave a towel warmer open? I guess I leave the normal TRV in place, but this means the towel rail heats up when any HR92 call s for heat - a bit of a waste?

    Thanks,.......Topher.
    .
    • CommentAuthorringi
    • CommentTimeAug 26th 2015
     
    Posted By: topherA better solution would be to alter the firmware to keep just one HR92 open white the 4 to 8 minute EH shutdown occurs. Anyone know how to do this?


    This is not enough, as most boiler have a pump override so the pump runs for a short time after the "call for heat" has ended. It is also not save to assume that the HR92 will open when told to so do, as the boiler can be written off if heat can not be removed from it.
    • CommentAuthortopher
    • CommentTimeAug 27th 2015
     
    Hi, Thanks the contributions. My understanding is much better now.
    • CommentAuthortopher
    • CommentTimeSep 5th 2015
     
    I tried to calculate a realistic return on investment for my proposed Evohome installation.

    1. For the installation cost, which I plan to do, I took the cost of all the Honeywell products, plus the cost of a plumber installing a boiler bypass.

    2. I got the amounts I had paid for gas last year and the year before, and averaged them

    3. I have assumed that the cost of gas rises at 5% per year - trying to be conservative.

    4. For the annual savings in gas I used 30%. The University study said the average house with average family would save 40%. I am trying to be conservative.

    If I have done my sums correctly,at the end of year 7 the savings move to a profit of £69. So not brilliant, but the increased comfort should be considered too.

    I am still planning to go ahead
    • CommentAuthorJonG
    • CommentTimeSep 5th 2015
     
    Hi topher which study are you basing the 40%/30% on?

    If it was the Salford (?) one the 40% was a house going from a boiler stat to time and temperature and trvs, so would depend on what you have already?
   
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