No, I’m not actually fitting any pumps, I am just going to say I have and just add 100W to my heat output.
My COP will improve.
Obviously I am not actually going to do this!
Potentially yes, though as @Andre_K comments above we don’t know how much goes into the water vs. how much into the surrounding air. The pumps could be losing more heat from the circuit than they contribute into it. 
One can argue that the waste heat from all household appliances will warm the house - we could count them as part of the heating system, but we don’t (except when doing heat loss calcs).
Immersion heaters are usually quoted to be 100% efficient as they are directly inserted into the water cylinder and the energy from it cannot go anywhere else. I’m not sure how it would be possible to measure the heat from it otherwise.
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I disagree 
take this example, if we connect the return and flow on the side we would usually have a heat pump with an insulated pipe with no losses the heat meter will register 0 regardless of the pump power.
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What is certain is, it is uncertain!
Sorry, I mixed up immersion and backup heater. Immersion heater is of course almost 100% effective. I will measure flow+return after the backup heater to also include its heat contribution in the rare case it comes on.
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Wouldn’t this already be measured by the heat meter, as it will be inline on the primary circuit?
Not on my Vaillant, the built-in heat meter is internal to the outdoor unit and my own temperature sensors are on the same flow/return pipes directly after the pipes enter the house and thus only capture power of the outdoor unit minus the losses of 1m of well-insulated pipe. The backup heater is inside the indoor unit and also houses the three-way-valve. The only way to measure heat pump and backup heater heat directly is by having two heat meters (or at least temperature sensors) after the indoor unit, one on the DHW circuit and one on the CH circuit.
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I agree with your disagreement Trystan 
@Timbones The primary circulation pump adds a bit of heat to the water. The temperature sensor needs to be on the ‘emitter’ side of the primary circulation pump otherwise the heat meter is only recording the heat from the compressor, not also the heating effect of the primary circulation pump.
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Just wondering about the significance of all this, I did some calculations on my own circulation pump (Grudfos UPS 2 25-80), operating at a typical 28 litres/min.
Based on the vendor pump curve at my selected pump speed, the head is 6.0m.
At density 1022kg/m3 (I have 20% glycol), that’s a hydraulic power of 28W.
Assuming 0.6 hydraulic efficiency, that would require a shaft power of 47W, thus heat liberated is (47-28) = 19W.
Even if all 19W entered the circulating fluid (in reality a proportion would escape to the environment through the pump casing), with a Cp of 3830J/kg/K that would cause a temperature rise (suction to discharge) of 0.01degC. This is the precision of my heat meter (a Sontex 789, for which I only have precision data, not accuracy data).
If we are effectively operating in, or close to, the “noise” range, is this whole debate over measurement boundaries really meaningful, I wonder 
?
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It’s certainly a fair question Sarah.
Just to confirm my understanding of your terminology (my mechanical engineering degree was a long time ago!):
- The 28W of hydraulic power is what goes into the working fluid, by virtue of its pressure and velocity being increased
- And would be measured by a heat meter, assuming its flow & return probes ’span’ the circulation pump
- The 19W is the ‘waste heat’ which will heat up the pump casing, by virtue of the pump not being hydraulically perfect
- Like you say, some of this will go into the working fluid (especially at low flow temperature) and some will be lost to the ambient air
- The portion going into the working fluid would also be measured by a heat meter
Did I get that right?
For a single (primary) circulation pump, where the hydraulic power is being captured by the heat meter, I agree it’s fair to claim the (fraction of) ‘19W’ is negligible ’noise’, in relation to multiple kW coming from a compressor.
For multiple (secondary) circulation pumps, where the hydraulic power isn’t being measured, there comes a point when this is definitely beyond ‘negligible’. My rough calculation for my system shows well over 10% of the total electricity consumption is going into the secondary pumps (because the heat demand from my house is so low).
Plus it would be good to understand the full picture, so we’re all clear what we’re assuming to be ‘negligible’.
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I think you also need to add in - or maybe not, depending on the design of the pump - any heat from the copper and iron losses in the pump motor. I guess most of these would be lost to ambient if the pump body is a reasonable heat insulator, but a metal body may well conduct some to the circulating fluid.
Yep, I think so too. Sarah was very specific in referring to the hydraulic efficiency (and shaft power) whereas you rightly point out there’s a motor efficiency element as well.
Err, my chem eng degree was even longer ago (1973) 
- The heat meter is just doing (m.Cp.dT), so if it’s on LWT and RWT (e.g. effectively at the Outdoor Unit) it won’t include any circulating pump’s heat input. But if it does ‘span’ the pump (e.g. LWT and pump suction if the pump is on the return line; LWT and pump discharge if on the flow line) it will.
- A secondary circuit/pump will only get included if you wire it between LWT and secondary pump inlet (if in the emitter return line; outlet if in the flow line).
I estimate my external heat losses (conduction/convection from piping/buffer tank etc.) to be about 170W, which is considerably larger than my calculated ~30W heat from primary (19W) plus secondary (11W) pump heat input. Hence my skepticism about boundary arguments.
Responding to @Robert.Wall yes you are absolutely right (as usual…) - motor efficiency (I normally assume 0.7 for little pumps like we use) applies to shaft power, so in my example above (47W shaft power) the driver power would be 47/0.7 = 67W. I think it fair to assume that virtually none of the motor losses (20W in this case) enters the circulating fluid, but I’m happy to be challenged on this…
Sarah
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1988 for me - but I’ve spent all the time since then designing enterprise IT systems, so definitely ‘rusty’ on the engineering theory 
I was thinking earlier that if a circulation pump was outside the insulated envelope (such as in a garage or loft space) then it’s much more important to understand how much energy is going where (down the pipe or into the ambient air) - whereas if a pump is inside the insulated envelope it’s much more straightforward, because absolutely all the circulation pump input power ends up as heat within the house, one way or another.
With my ground source installation, the compressor and all the pumps are inside - it’s just the brine loop that goes out into the garden. While looking for the original SEPEMO ‘System Boundary’ papers earlier I realised that a lot of the SEPEMO research was done in Sweden, in 2011, where ground source would have been the dominant technology. Perhaps they didn’t give much consideration to installations with a lot more of the components out in the cold, with the sort of external heat losses you describe, when defining the H1 - H4 System Boundaries.
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A very interesting discussion. Apologies for the following lengthy post, which attempts to summarise my understanding and reasoning.
Question: What’s the purpose of hpm.org, as distinct from the other monitoring offerings (emonCMS local/cloud)? Is it to provide a direct comparison to earlier HP efficiency surveys? Or something else? Could it do a number of different things, via different views/included numbers??
Inter-survey comparison surely requires matching the data collection principles of the various surveys. To do that across multiple surveys requires data collection at a sufficient level of differentiation to enable different calculation bases, now and in the future. This would also allow others to apply their own aggregations/groupings to suit their current purpose for collecting/comparing the data.
Do we just provide a means of indicating the aggregation/source of the presented data by component, at whatever level of differentiation is required to address this, or is available to the provider? If my immersion input/output were separately recorded, it could be in or out, and counted as Total, or DHW or maybe even Disinfection. Alternatively, my data as it is currently constructed could be excluded from hpm.org, but accessible for assistance on emoncms.org.
As an illustration, I use emonCMS locally to enable tuning of the overall Heating/DHW system. I send the numbers to emoncms.org to permit input from more knowledgable folk to assist with this. My data is not MID, but I would argue the overall performance characteristics are not masked by this, especially as my interest is in changes and their effect. I added it to hpm.org because it seemed like a contributive act and potentially permitted me to compare to others.
My Daikin is flagged as H4, because I checked all those boxes, their being the case. My electricity monitoring tracks ALL the energy going into the heat pump system, which includes the Booster Heater (immersion/BSH) and the Backup Heater (BUH), undifferentiated. Since the circulation pump is in the body of the HP, that is the genuine total of all energy used by the system. I could buy/configure multiple energy monitors, but I didn’t see any benefit to that when I set it up.
However, during the legionella cycle, the HP fires up the immersion (BSH), consuming energy but not registering any generated heat energy. I use the HP-provided ModBus indicator for BSH On to add 3kW to the generated heat data in the processing flow for this period, both locally and in emoncms.org. Sadly, the DHW flag is off in this period, so the immersion power is registered as Heating. Except when it isn’t, in the winter, when I’ll get effectively both DHW and Heating inputs/outputs. I don’t know what to do about this - maybe drop the BSH input/output altogether, which would require some thought…
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The data on HPM would deliver maximum value to the widest range of users if we had separate data feeds for each of the “relevant” parameters, which could be used in different combinations to report against various System Boundaries (i.e. H4 versus H3 / H2 / H1), depending on what a particular researcher is most interested in.
The catch is, there are quite a lot of potentially-relevant parameters - and some of them are difficult to measure individually. I recently posted a diagram on this other thread, created by the SEPEMO research team (who are generally considered the authority when it comes to System Boundaries). That diagram shows:
- Mandatory Sensors:
- 2 heat meters
- 5 electricity meters
- 7 temperature sensors
- Optional Sensors:
- 4 more heat meters
- 4 more temperature sensors
You’d have to be really interested in monitoring to invest in 6 heat meters (plus each one restricts the flow slightly so reduces efficiency) and inserting MID-certified electricity meters for pumps and auxiliary heaters which are factory-integrated would invalidate the manufacturer warranty.
So we have to be pragmatic about what level of granularity is achievable and live with the fact that some of the parameters are going to be aggregated together at the point of measurement. In some cases (as with your Booster Heater example) it’s possible to use other information sources to dis-aggregate the readings, which I think is helpful; I’d have done the same if my booster heater was ever used (and might still do it, just in case it kicks in).
Then there’s the fact that system configurations vary between manufacturers and installations:
- Sometimes everything’s integrated into a single heat pump unit
- But some manufacturers will provide information which helps to dis-aggregate some readings
- Sometimes there’s an Outdoor unit and a separate Indoor unit, containing pump(s) and heater(s)
- In principle, these could have separate electricity metering without impacting any warranty
- Sometimes there’s underfloor heating, usually with a separate pump and thermostat
- Often that pump is remote from the heat pump and might be on a different electrical circuit
- Sometimes some of the components are installed in unheated loft or garage spaces
- This influences whether the heat ‘losses’ are retained as heat in the house or lost to the outside
The question then is what does that mean for the data feeds used by the MyHeatpump App which underpins HPM. It’s important not to exclude the installations which use the basic monitoring package of a single heat meter and a single electricity meter (as long as it’s clear which readings those meters are aggregating) but it would be good to also cater for more advanced monitoring installations which are able to separate out (some of) the parameters - a bit like we do for CH and DHW currently. It’s covering all the variations which complicates the coding though.
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Thanks @dMb! That’s what I was trying to say, but less obviously. A bit of analysis required… (also ex-IT enterprise architect!). And I’m definitely not up for 6 heat meters. Separating out the AC feeds is a pain too, I’d have to stick them in the HP case on the individual link wires, as the external cables are L/N/E obvs.
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Have you got a servicing sheet with the Ohms recorded and a live voltage reading? Would maybe give slightly more realistic power usage for the BSH? I know I often use the backup and booster due to price signals and my voltage can plummet down to around 210V at times when the house is pulling 20kW or so 
Hot or cold? Remember the element resistance does have a small dependence on temperature.
Hi Tim, Thats what is happening with my system, and looking for a solution.