Sorry, I used the wrong word. I meant flow-sensor, not switch. The flow rate is on ‘running information’ code 540… you would expect it to be readable on the melcloud facility
@Timbones is your primary pump pulling water through the system rather than pushing? Is that normal and are there any advantages to having it on the return rather than flow?
I’ve just tried changing the angle of the Sika flow meter to see if that makes any difference. It didn’t.
Flow rates only ever seems to be about 12 l/m on low pump settings, 13 l/m in mid setting and 14 l/s on high.
The meter is straight after the pump so I’m wondering if that’s the issue.
Depends which way you look at it - it’s pushing water out to the heat pump. I guess this is “normal” as that’s how the pre-plumbed cylinder comes (with LLH). I don’t know if it matters which side the pump is.
It could be that the meter is affected by turbulence from the pump, but I don’t know.
Well after a bit more prodding and poking something I have done has improved things.
Not sure for certain but I removed the cable from the flow meter, causing the FTC to error, then plugged it back in and reset at the main controller.
Now it is giving the correct value, maybe done 1-2 l/m on what the OSM flow rate is.
I’ll keep an eye on it but leave it for a bit. There is some cold weather coming up so if my bad DHW cycles are going to happen again it is likely then. I can then get Mitsubishi to take a look again.
P.S. Annoyingly the Mitsubishi person looking at my data yesterday on MelCloud means my pymelcloud script can’t connect as it is being throttled.
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So now I have sorted my FTC6 connected flow meter Mitsubishi support can see the correct values.
Their suggestion to fix the problem was to up the flow rate to 24 L/min.
Not sure why it would need to be right at the highest supported flow rate but thought I better give it a go to prove it wasn’t that.
Unsurprisingly the same pattern of flow temp collapsing to the same as return temp and eventually resorting to immersion is happening.
So I have asked them to explain what else could be wrong.
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Since our Ecodan 8.5kW (Emoncms - app view) was installed in the summer we have been running without a hall radiator.
The old panel (no fins) radiator was obviously not going to be up to the job so I removed it and we bought a 600x1200 vertical type 22 radiator that then sat on its side waiting to be plumbed in.
So this has meant we’ve been running with reduced emitter output but to make matters worse our FTC6 main controller is in the hall meaning it would be running things hotter and seeing the effects of heating up later as this would have to spread from the other ground floor rooms.
As of 22nd/23rd of Feb I finally got the rad installed. Although I then had to replumb it after realising the installer had put the wrong coloured handles on the shut offs I connected to so the flow and return were the wrong way around (now fixed). I’ve also been messing around with balancing and replumbing our kitchen plinth heaters since then.
It looks like there has been some effect on the running of the system although it is a bit hard to tell as installing the radiator coincided with a significant drop in outdoor temperature.
However I’m a bit disappointed the improvement in our system hasn’t been more significant.
I’m at a bit of a loss as to what is now holding it back.
- Is the heat pump too large, it seems to start cycling as soon as its trying to hit a flow temperature of 40C or less?
- Is the hallway still too cold (need to insulate under the suspended floor) so the controller keeps the flow high?
- Although I’m sure our emitters are still to small (especially those that are in play at any given time due to the bedroom TRVs closing down, all other rads are fully open)?
- Do I need to balance better (maybe controlling the system pump to try to keep a ΔT of 5K or getting better lockshield valves especially on the towel rads)?
- Could some of the settings be improved, especially the Auto Adapt ones?
- Do I need to leave Auto Adapt longer to get to know the changed system (I’m not sure over how long it adapts for or if it is more reactive to the current conditions)?
- Something else?
I’m never expecting my SCOP to be amazing as it is a heat pump added into an existing system but at the same time I would have thought it would stand a fairly good chance of being higher than it currently is as the fundamentals of the system don’t seem to be too bad.
Wousers here’s a good one Emoncms - app view!
Looks like they must have at least double the (in play) emitters that we do.
They have a very high flow rate but again I assume that’s because the emitters are dumping a huge amount of heat.
Very likely, yes. Or more specifically, the heat pump is too large for the emitters you have. Ensuring you have as many radiators open as possible will help. I’m not sure balancing will necessarily improve things, unless there are a couple rads short-circuiting hot water to the return. Restricting lock shield valves too much could have a negative effect.
There is an optimal flow temperature for your system where your heat pump will settle into a steady state, when the radiators can emit the heat that the heat pump is producing. The more (bigger) radiators you have, the lower that flow temperature will be, and better performance.
These are the settings that can influence Auto Adapt:
Dropping the Lower limit and/or increasing the Interval can increase the time between cycles, allowing the system to cool down some more and potentially perform better. Probably not enough to make a big difference, TBQHWY.
My own 11.2 kW system (link in bio) also has a minimum flow temperature of about 40°C.
I decided to try Weather Comp this afternoon and I’m trying to get my head around what is going on.
Can someone explain why the dT starts low at the start of each cycle but then suddenly starts to go up.
Then why does the heat pump look to make things work with an extra blast at the end of the cycle?
Just a quick reply without looking in any depth… I guess you have a fixed-speed circ pump. (not one that adapts to dt), so the dt will vary with heat-ouput power. Its normal, and not a problem. The rev-up is annoying isnt it? why speed up so much, then stop, then re-start so quickly after. What model is this? I think Mitsi realise they set the algorythm with too much ‘panic’ for adequate heat, with not enough concern for running costs. This should be able to run in a steady state.
It’s a PUZ-WM85VAA
I have been experimenting with controlling the pump to try and achieve a constant dT but very early in the tuning of the PID controller. That’s why I was experimenting with Weather Comp again.
You’d think the ramp up at the end of the cycle could be beneficial in increasing the gap between cycles a bit but doesn’t appear to do that.
It’s a pitty there doesn’t appear to be software updates to refine the algorithm.
I still don’t really get why the heat output is low to start with then suddenly jumps, it doesn’t look like the return is going up just that the flow temperature starts ramping up. Seems to happen before the HP decides to up the input power.
I keep coming back to a thought about how the flow and return temperature sensors connected to the FTC would effect performance / behaviour of the system (in my general clutching at straws to try and explain the difference in performance of different Ecodans).
ASAIK the thing the controller is controlling is the flow temperature from the outdoor unit, and also maybe the dT between that and the return? If so the temperature sensor placement and how they are installed could be very significant.
So I’m wondering if in systems like mine, @Timbones’s and others, where the outdoor unit is quite a distance from these sensors whether the lag in temperature measured on the flow when the compressor modulates and the potential heat loss between the return and flow sensors could have an impact on how the algorithm used by the controller acts and reacts to changes.
If there is significant heat loss from the pipes between the sensors the unit will also potentially be measuring a different dT to that at the outdoor unit.
I might be wasting my time thinking about this as the controller might account for variation in the position of these sensors in the system and might react to these readings slow enough that it isn’t an issue.
My sensors are probably around 8m of pipe away from the outdoor unit. I believe @Timbones yours is about 10m away.
I think the distance isnt a problem. Surely Mitsi have thought of this, and they dont specify a distance restricion. I recall seeing one at a great distance, and no obvious control diffrence.
My old 2009 ecodan (fitted on a friends house) seems steady as a rock, and i do feel that in trying to ‘improve’ things, in certain conditions, there seems to be problems. I will be meeting Mitsi in a couple of weeks, and yours is actually a good example for me to discuss with them.
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Oh excellent, good to hear they are engaging.
Let me know if you need any information about my system or if it would be useful for me to try any settings to get data to show them.
My DHW woes (where heat output collapses but while the compressor still draws power before having to resort to immersion) have come back again now that it has gotten a bit colder at night again. I have it in Eco hot water mode that I don’t think helps. I did raise a ticket with them about it and after we ruled out flow rate haven’t heard back again.
From the ‘Mitsubishi Ecodan Help & Advice (UK & Ireland)’ Facebook group:
I’ve always had the black SD card icon with white letters, indicating abnormal behaviour, rather than the white one with black letters indicating normal behaviour.
I replaced my SD card on Wednesday and the icon has gone white. Will see if AA gets better at adapting using a longer history.
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The SD card icon is on the very top row of the main FTC screen: (number 15)
If it’s not there, then perhaps there’s no SD card fitted. The manual suggests that it is usually supplied with the heat pump.
(snippets from manual for FTC6 Installation Manual - best read the whole thing before messing)
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Thanks @Timbones - there is no symbol on my controller. Looks like i need to empty my airing cupboard and open the panel again!
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