Posted by: @downfield

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I am interested in getting more accuracy than the normal "estimated" figures given on the MELcloud app without going the full HA/Pi route, but not sure if this will help or possibly be overkill.

I'm assuming you mean the EMP3-M-1PH monitoring pack? I've found it online at anywhere between £1,000 to £1,750 and even OpenEnergyMonitor devices aren't that expensive (and they're RHI MMSP compliant too).

Do you need the RHI MMSP compliance or is it just the accuracy of that compliance that interests you?

Posted by: @majordennisbloodnok

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Do you need the RHI MMSP compliance or is it just the accuracy of that compliance that interests you?

I found it for just under £100 and the EMP2 package is listed at £96 on the Mitsubishi price list.  So some price gouging going on methinks.

I don't need it but am curious why the MELcloud app caveats their energy reports with "estimated" and just wonder whether the COP you calculate using their "estimates" of power in and heat out is anywhere near the truth.

I also recently found an app on the iOS app store called Ecodan e-Monitoring tool which seems to need a widget/dongle to be connected to the FTC board, viz:

but it doesn't say what the dongle is or how to get hold of one.  Another mystery.  But I suspect that it would allow you to see monitor the HP performance from the comfort of your iOS device via Bluetooth, rather than using the normal wired display.  Not sure though.

Posted by: @downfield

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I found it for just under £100 and the EMP2 package is listed at £96 on the Mitsubishi price list.  So some price gouging going on methinks.

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Ah, OK.

This document from Mitsi has a table comparing all the monitoring packs they offer and EMP2 differs from EMP3 in that EMP2 doesn't have a heat meter. If that's the case, you could probably achieve the same as EMP2 with a couple of CT clamps and associated monitor, but if you're happy with £100 then it's certainly an option.

Posted by: @downfield

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I don't need it but am curious why the MELcloud app caveats their energy reports with "estimated" and just wonder whether the COP you calculate using their "estimates" of power in and heat out is anywhere near the truth.

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The document I mentioned above also implies an answer to your second point. The inbuilt monitoring that comes with the control unit apparently calculates energy to the nearest kWh whilst EMP2 and above record and measure to 1 pulse per Wh, thereby avoiding rounding errors over time. If, apart from rounding, EMP1 is still accurate then a separate energy monitoring pack may well be overkill; that's your call. However, if I were you then I'd ask around friends and acquaintances to see if anyone is or knows of a tame sparky, and then ask said sparky if he or she could do a wee bit of comparative monitoring. If the known accurate monitoring marries up closely enough with what Melcloud says, I'd personally leave it at that and use what's been provided as standard. If not, it'd be interesting to see what the margin of error is.

@majordennisbloodnok That's helpful, thanks.

I had seen a similar EMP brochure but the link you sent had more information.  I saw the EMP3 with the heat meter for £97, which seems OK but then there is the cost of fitting.  (I have asked Mitsi for a technical/installation instructions but nothing so far).

I think the "estimated" terminology seems to be a warning not to rely on the numbers for RHI purposes, but otherwise the built-in monitoring seems good enough.

Do you know if the outside unit has a heat meter?  On OpenEnergyMonitor they all seem to be fitting heat meters to their systems so I thought maybe the "heat produced" was just an estimate rather than a measured quantity.

Having said that I don't really understand how a heat meter works anyway - it must be flow * temperature?

You're welcome, @downfield.

Posted by: @downfield

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Do you know if the outside unit has a heat meter?  On OpenEnergyMonitor they all seem to be fitting heat meters to their systems so I thought maybe the "heat produced" was just an estimate rather than a measured quantity.

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Sadly I don't know, but would be interested to know since I have a Mitsi myself. Nor, like you, do I know the detail of what a heat meter is actually measuring or the specifics of how it does it.

One thing I would say, though, is that you mentioned not wanting to go down the full home automation route and if keeping an eye on your heat pump is the only thing you want to do then I'd agree. Particularly with Mitsi, linking directly with your heat pump to get stats out will involve purchasing an add-on modbus module since they're not provided as standard. Even if you do decide to do some form of home automation then it's highly likely that linking in with the Melcloud API will suit your purpose just as well since the heat pump, now set up, doesn't really need much "controllng" as such and you're only wanting to read data - at least that's the conclusion I've come to so far with mine. Other devices - battery, inverter, car charger, TOU tariff etc. benefit from far more active management and so are prime contenders for true integrated automation, but the pump in isolation not so much.

Posted by: @downfield

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Having said that I don't really understand how a heat meter works anyway - it must be flow * temperature?

I recall some basic maths

kwh= LPS X DT X SHC

Where the SHC is specific heat carrying capacity (SHC of water is usually quoted as 4.2 whereas glycol is a bit poorer at heat transfer. LPS is ltrs per second (LPM x60 oops divided by 60). I tend to just rely on the MELCloud graphs to gat an approximation but I know it’s not exact.

some graphs are more reliant than others.
I’d be interested in what you come up with as a useable piece of kit.

once upon a time I worked out our HP output at our flow rate of 16 lpm so I could see the output at various DTs. 

just in case I’d ever need it….😂

Posted by: @majordennisbloodnok

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You're welcome, @downfield.

Posted by: @downfield

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Do you know if the outside unit has a heat meter?  On OpenEnergyMonitor they all seem to be fitting heat meters to their systems so I thought maybe the "heat produced" was just an estimate rather than a measured quantity.

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Sadly I don't know, but would be interested to know since I have a Mitsi myself. Nor, like you, do I know the detail of what a heat meter is actually measuring or the specifics of how it does it.

Mitsubishi's use a Sika flow meter and two thermistors (attached to the outside of the flow and return pipes) in the "plant room". From those the flow rate and dT can be determined (SUNandAir's post describes why these are important). In comparison to OpenEnergyMonitor kit, the flow meter is also a class 2 device but the thermistors attached externally are far less accurate (OEM uses digital temp probes in the water), so OEM kit will be able to more accurately calculate the heat/power produced. In addition, the OEM kit uses a class 1 electricity meter to measure electrical input - I don't know what Mitsubishi use for their COP "estimates". 

Having a Mitsubishi with both Mitsubishi's and OpenEnergyMonitor monitoring, Mitsubishi/MELCloud gives a rough idea of what is happening but OEM is more accurate and gives far more detail. 

Hi @Robs - would the OpenEnergyMonitor be able to compute a COP on a cascade system? I am currently using a combination of a solar app (Sunsynk) and smart meter readings to try and estimate usage (also comparing to previous years). 

but as Jan and feb have been unusually cold this year I am finding the electric usage very high - (I suspect that had we still been on LPG that usage too would have been very high) but I don’t yet know the efficiency I am getting out of the system. I am running pure weather compensation trying to keep downstairs at 19 or 20 degrees and upstairs a couple of degrees cooler. (All TRVs open, and all room stats set above these temperatures) 

i am acutely aware that I am unable at present (should ofgem ask - which is their right under the terms of the BUS grant) to measure my energy usage because the MELCloud cannot compute energy usage for cascade systems. Can anyone help here please? Does anyone else have this issue? 

Posted by: @carpenterstation

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Hi @Robs - would the OpenEnergyMonitor be able to compute a COP on a cascade system? 

That's really a question for the OpenEnergyMonitor folk (hello@openenergymonitor.zendesk.com) but if you just wanted to monitor the combined input/output then it seems likely. If you could fit the flow meter and temperature probes in pipework where the water to/from your two heat pumps is combined then it would look like just one heat pump to the sensors. How are your heat pumps wired up? Two single phase circuits or a single three phase? The OEM kit can monitor multiple electricity meters, at 45 amp per single phase and 100 amp three phase. 

@robs I have no idea how the supply is wired but it is off one of the consumer units that is attached to one of the phases - so I guess 2 single phase circuits. 

should the functionality to measure my usage have been provided by the installer as a condition of the MCS accreditation? Or do I now have to pay more for it?