Hi Tim.
What is the point of that?
We have installs in well insulated houses that may not run for months.
Then it does not give a true representation of how a heat pump is performing when needed.
Hope that makes sense!
Hi Matt,
I use it when My battery is full and have excess solar.
Tank is up to 58oc with heat pump (this affects my reported COP and SCOP!).
Then immersion in Buffer gets turned on and is controled by battery status, on at 100% off at 95%.
Issue of using the heat pump is if you are not home to monitor it it maybe on when no sun available.
Has anyone got an immersion heater as a separate feed I can test immersion heater app support with? Ideally on emoncms.org 
This is live on emoncms.org, see app configuration:
Latest version of the app’s module is v3.0.0 and requires a database update.
Thanks Trystan. I’ve just added one to mine (Derby NIBE F1145 GSHP):
https://emoncms.org/app/view?name=MyHeatpump&readkey=6d0aa54296732b559a2afc0256180f21&mode=daily&start=1724803200&end=1727481600
I only just created the Feed and briefly ‘forced’ the immersion On for a quick test, but it’s showing up OK. Tomorrow it should start registering solar PV diversion.
For clarity, this is intended to be the immersion heater installed in a DHW cylinder, right?
(Not the separate ‘auxiliary’ or ‘booster’ heater within the heat pump.)
Thanks @dMb
Yes DHW immersion only.
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Was just having a look at your standby, ~ 56W, or 500 kWh for all time in your dashboard. If that was treated as heat gained given that it’s in the heated envelope that would increase your SPF from 3.50 to 3.73 (I think you did cover this above?)
It is an interesting question all of this, how to report the physical reality as accurately as possible, rather than using SEPEMO assumptions… I imagine my 11W of standby is probably 4W in the inside unit, If I added this to the heat side of the equation my SPF over 4 years would increase from 4.07 to 4.09, so fairly inconsequential and likely a smaller error than the metering.
But in your case it is more important as missing 500 kWh of useful heat gain and 0.2 SPF is more substantial.
Your COP when running for all time is also pretty great at 4.44! and between 4.0 and 4.4 on the coldest day! The benefit of high performance on the coldest day from a grid perspective is something that is easy to overlook.
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PS good posts @John @dMb , all very well said. I will have to think a bit more about how far we go in terms of providing options for dis-aggregating.
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My Primary circulation pump is running a lot of the time too, during the heating season, which helps move the water through the volumiser tank; I normally reckon on 45W for the controller and another 15W for the primary pump. But yes, everything is inside the heated envelope so all the energy ends up in the house. I’d done a quick calculation of the impact on SPF from my Secondary circulation pumps and come up with an increase of about 0.2, so 3.50 → 3.73 sounds about right. Adding in the resistive heat from the controller and the Secondary pumps (but not the Primary pump, which is already heat-metered) should get me more like 3.9.
Currently (with no space heating demand and DHW done via excess solar pv diversion) my system is showing a COP of 0, which does seem a bit unfair; it should really be 1.0.
Yep; it does very well when it’s shifting lots of heat - it just doesn’t need to do that very often, and the relatively high standby drags it down overall. Ground Source still has advantages - especially overnight and especially early in the winter, when the ground is still relatively warm. I know it’s often not suitable for retrofit but for a new-build (like mine) it can be a very good choice. No defrosting!
I have the PV surplus from a Mk2 router connected onto the same immersion element wired together with the heat pump’s feed into the same connector.
The heat pump’s feed to the immersion is included in my only MID meter. The Mk2 router’s output to the immersion is on a c.t. which is only sampled intermittently to emoncms.org every few seconds. I guess this sampling rate is not at all accurate enough for what we have in mind here.
My Mk2 has several outputs so I can’t see that putting a MID meter in the Mk2 input cable would capture just the feed to the immersion, and putting the MID meter on the relevant MK2 output would make comms power in the MID intermittent too, which probably wouldn’t be useful either.
What metering do you suggest I install?
While interesting to see I think Im of the view that we should not be including PV diversion as part of SEPEMO boundary calculation for cross trial comparison. Is there a way to only include immersion heater use triggered specifically to make up for an otherwise deficiency in the heat pump capability as @Timbones puts it? E.g only immersion heater use triggered by the heat pump or other controller for legionella protection?
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Good question, probably a MID meter on the input to the Mk2 or a second meter on the input to the heat pump only (probably better), that would at least give you the option to isolate the heat pump and report a H2 boundary. If most of the immersion is PV divert, Im of the view that this should not be included as I feel it’s a different system.
Thinking about it, a boilers fuel input and efficiency is not included as part of hybrid heat pump performance measurement, perhaps PV divert is similar, it’s more a hybrid heat technology rather than strictly a requirement to address a deficiency in the heat pump …
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I think that’s a good way to look at it, yes.
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In my case that would be the ‘auxiliary’ resistive heater which is part of the heat pump itself; my NIBE system has no mechanism to fire up the DHW cylinder’s immersion element, but it will use its own resistive heating element if it thinks the compressor isn’t able to deliver the heat required (either for DHW or for space heating). I get data on the use of the ‘auxiliary’ heater from the NIBE API and could subtract that from the electricity meter reading and report it separately - but in my case it would almost always report zero since I’ve made configuration changes to try to ensure that heater never kicks in.
I’m happy with that - which was the main reason behind my slightly cryptic question about ‘which immersion’ the other day. My new favourite SEPEMO diagram, as posted to this other thread and linked below, shows two immersion elements - one in the ‘heat pump’ and one in the ‘hot water tank’ - and there’s no metering shown for the ‘hot water tank’ one (although it is inside the H4 boundary line) which supports your view that it’s a separate “system”.
In that case I’ll disconnect the ‘immersion’ feed from my MyHeatPump app (but leave the feed in place so I have the data available if required).
I’ve just added my immersion feed.
It’s only used for PV diversion when there isn’t enough PV for the heat pump to run.
Am I right to have added it or have we decided it’s only for when the heat pump can’t complete a DHW run itself?
Thanks @ajdunlop I think so.
I’ve added clarifying questions to the form:
1. Does the system have a back up heater installed and in use (this is an inline electric element that can top up the heat pump output mostly for space heating):
If this is ticked, an option becomes visible in the metering section to ask if it is metered.
2. There is a specific question in the hot water legionella section to ask if the cycle uses an immersion heater, this then if ticked enables the metering option to indicate if metered.
3. In metering section, if an immersion heater and backup heater is present the options to indicate if these are metered appear:
There’s also an option to indicate if secondary pumps are metered if you have hydraulic separation selected earlier in the form.
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There’s a bit of work needed to check each system to make sure these form entry values are consistent with the monitored data. The way the form options were previously presented did not help. Any help going through systems to check for consistency would be much appreciated.
Apologies for jumping in on this. Could this be pre-fixed with ‘dhw’ to avoid any confusion with a boost heater?
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