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Thread: HR92 not responding correctly

  1. #1
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    Default HR92 not responding correctly

    Hello all,

    I'm having some issues with one of my HR92s and I just wanted to make sure it's not me being thick.

    My study is an odd shape. One half of it has a mezzanine floor. So, standing on the ground floor, there is a ceiling above you at a normal-ish height. The other half has a spiral (well, helical!) staircase up to the mezzanine, and as such it's open to the floor above.

    Under the mezzanine, I have a small-ish radiator. At the end of the room where the staircase as, I have a larger (but not large!) radiator. There is no heating in the upstairs part. (In fact, there's no cavity wall insulation either, as you'll see from the following graphs, but that's not directly relevant). Because of the shape of the room and the uneven heat demand, I've set this zone to be a multi-room zone so that each radiator can respond according to its local demand. The larger radiator at the open end of the room will clearly need to work harder since a lot of its heat will be going straight upstairs.

    Here is a capture from my Domoticz monitoring showing the problem.

    DomoticzDevices.jpg

    You can see from the table that the smaller radiator (#604) is only calling for 14% heat, despite being 6C below the set point! The larger radiator (#530) seems to be doing its job just fine, but it's struggling to heat the room on its own as you can see from the following graph:

    DomoticzChart.jpg

    You can see from the graph that the square-wave is the set point. Currently, it's set to 18C. You can also see that the small radiator (I'm going to call the line yellow, but I'm colour blind!) just isn't heating at all. And you can see from yesterday (pink line, maybe) that the larger radiator did its best, but just couldn't manage with all its heat going straight up to the top floor.

    Some days, however, it works just fine, as you can see below. (It never quite reaches the set point, but I believe that's because of the shockingly poor insulation, which is being dealt with.)

    DomoticzChart2.jpg

    So, basically, sometimes the HR92 on the small radiator simply can't be bothered. And sometimes it's fine. It seems like the underlying problem is that it's only calling for 14% heat, when it should be calling for 100% heat. This suggests to me that it's the HR92 that's at fault, not the plumbing/radiator. If I remove the HR92 and manually open the valve, the radiator heats up quickly (assuming there's a call for heat somewhere else and the boiler is on, of course).

    Any suggestions?

  2. #2
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    Where are you getting the 14% heat demand figure from ? I don't see it in the table or graphs. Are you using an HGI80 ?

    What does the Valve position (option 10 in the HR92's menu) say under the conditions where you think it's at 14% ? The valve position and heat demand don't follow a one to one relationship (since the valve position includes learnt valve pin calibration) but they do move up and down together in unison.

    Have you tried rebooting the HR92 by removing the batteries and reinserting them ? Just a few days ago I had a situation where my bathroom HR92 didn't seem to be sending any heat demand - turning it up caused the valve to open as expected, and the new set point was even reflected on the controller screen, but the boiler relay failed to come on. I tried turning it right down then up again two or three times and still no response from the boiler relay. At the time no other radiators were calling for heat so I turned up the hallway radiator and the boiler relay came on immediately then went off again when I turned it down but the bathroom one refused to play ball.

    I removed and reinserted the batteries on the bathroom HR92 and it has worked fine since. I suspect its an obscure bug in the HR92's firmware - I've seen one or two reports of this kind of behaviour on the forum over the last year but it seems very uncommon and it's the first time I've witnessed it first hand.
    Last edited by DBMandrake; 19th January 2017 at 11:51 AM.

  3. #3
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    The 14% comes from the Domoticz table. Where is says "On: 28". It's on a scale of 0-200! So when things are flat-out they say "On: 200" - like the large rad does. Yes, I'm using an HGI80.

    After posting, I unclipped the head from the body and re-attached it, and it cycled the valve (which it seems to do every time I unclip, so I guess this is normal), and then immediately demanded 100% heat, and promply started heating up very quickly.

    I hadn't considered off-and-on-again! I'll give it a go next time I see the problem. For today (and maybe 3 or 4 days hence), it's fixed now.

  4. #4
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    I've checked the valve positions (not that the problem is occurring right now...) and the small rad is reporting 53% (and Domoticz is showing a demand of 106/200 = 53%), and the large rad is reporting 95% (and Domoticz is showing a demand of 190/200 = 95%). So, at the moment at least, the valve position and the demand seem to be tracking one another.

  5. #5
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    I actually meant a full battery out reboot - but its interesting that unlatching it and latching it again was sufficient - this triggers a pin travel learning cycle where it will re-learn the pin travel limits so that it can calibrate 0-100% pin travel.

    Is it possible it wasn't latched on securely ? An HR92 won't send a heat demand (or perhaps continue to send the last known heat demand ? Must test that...) when the latch is not closed, however it will also stop it from turning the motor, so shouldn't in theory stop sending heat demands yet still allow the motor to adjust the valve...

  6. #6
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    I doubt it wasn't latched properly. I'm aware of this as an issue, and the latching action is pretty positive. Plus, it seems to work for 3 or 4 days, then stop for a couple, then work again, then stop again.

    Just re-checked the valves vs Domoticz. The demand is dropping now as it nears the set point, but the Domoticz number and the valve position still match (adjusting for the scale).

  7. #7
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    Quote Originally Posted by dty View Post
    I've checked the valve positions (not that the problem is occurring right now...) and the small rad is reporting 53% (and Domoticz is showing a demand of 106/200 = 53%), and the large rad is reporting 95% (and Domoticz is showing a demand of 190/200 = 95%). So, at the moment at least, the valve position and the demand seem to be tracking one another.
    Ah - that is very interesting, because nobody with an HGI80 has ever confirmed the relationship between the reported valve position and the transmitted heat demand before. (I don't have one)

    That has some interesting implications, because not all valves calibrate to open at the same percentage! Usually it tries to calibrate so that a valve just starts opening at 40% indicated pin travel, but that would imply that it is already sending an almost 40% heat demand (which would run the boiler ?) before water is even flowing through the radiator, which seems unlikely.

    I've also noticed on some of my radiators that after a few days the calibration must shift because it starts reporting lower figures like about 20% as being the point where the valve just starts to flow. Hmm...

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    I've just checked a handful of other HR92s (I've got 12, and I've only covered the downstairs so far!!!), and they Domoticz number "matches" the valve position.

  9. #9
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    Quote Originally Posted by dty View Post
    I've just checked a handful of other HR92s (I've got 12, and I've only covered the downstairs so far!!!), and they Domoticz number "matches" the valve position.
    Thanks for confirming that - we've just reverse engineered one more fact about how the system works...

    Somebody with an HGI80 needs to capture a table of heat demand figures taken from a variety of conditions over time for analysis so we can work out what algorithm is used to combine all the individual heat demands from the HR92's to the final heat demand sent to the boiler relay - because now we know the HR92's are just sending raw valve pin travel figures as their "heat demand" (which will have a very non-linear relationship with actual water flow through the radiator, since there is a lot of dead band at each end of the pin travel where water flow doesn't change) the Evotouch must be applying some additional intelligence to these received heat demands when calculating the overall system heat demand to send to the boiler relay.

    For example if all radiators except one were completely closed, but one was near the set point with a "heat demand" of 20%, that is actually below the valve opening threshold on most TRV valve bodies (no water will flow) so you wouldn't want the boiler to fire up at a 20% duty cycle when no radiator will actually make use of that heat...
    Last edited by DBMandrake; 19th January 2017 at 12:38 PM.

  10. #10
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    Quote Originally Posted by DBMandrake View Post
    because nobody with an HGI80 has ever confirmed the relationship between the reported valve position and the transmitted heat demand before.
    Pretty sure I have. Unless I dreamt I did it!

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