HeatpumpMonitor: Immersion heater vs. System Boundaries

Hardware Heatpump
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:joy: that’s a bit harsh @matt-drummer!

  • Secondary pumps are common, auxiliary power for things like fan assisted radiators is another possible use of electric where heat is not accounted for by the heat meter.

  • Separating out booster heaters and immersions allow us to give results to different boundaries. It would enable toggling between H2 and H4 boundaries. Different figures for these two boundaries are often given in field trials.

Im currently working my way through adding support for cooling. Once I get that done I will add one immersion heater feed option and see what is involved with that before adding further options. I will report back with how I get on either way.

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Yes, I know, @TrystanLea

I did apologise in advance, maybe no excuse though for being rude!

But it was, and is, meant in good faith.

I was surprised to see how old it was and the technology is even older.

There comes a point when it’s not worth fussing over, the performance isn’t great and if all the other stuff is added in it will show as worse.

heatpumpmonitor.org is already loaded with data and quite complicated.

I think there is a danger of making it incomprehensible for many people and that is not a good thing.

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Fan assisted radiators @TrystanLea

If the water flows through the heat meter surely the heat is accounted for, just not the electricity consumed?

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At the risk of sounding super-defensive…

I don’t know why you think 8 years is “old” for a heat pump installation - I’m fully expecting mine to last for 20+ years and I won’t be replacing it until it breaks.

My system delivers a CoP around 4.5 when average daily temperatures are below freezing and it’s working hard, and it’s easily the best-performing system on the whole of HeatpumpMonitor on a per-square-metre basis. But in your opinion that “isn’t great”…

Sure, it spends a lot of time in ‘standby’ (because it’s not always below freezing all day) which reduces the overall performance stats, but modelling the performance more accurately makes for a more reliable comparison with other systems.

Trystan has already declared he plans to add support for the extra feeds (and there’s no question he’s the one who gets to decide what features are appropriate) - I’m simply volunteering to help him test those if and when he finds the time.

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I never intended to offend you although I’m sure that I have, so I apologise again. But I needed to be blunt to get to my point .

I mentioned the age because you did in another post making it sound like it was old and outdated technology, you said `it doesn’t even have a variable speed inverter drive for the compressor’

I took your lead. I don’t think it’s ready for the scrap heap but it’s not a brand new installation that is being set up. It’s already there and nobody can buy that heat pump anymore?

You said it had an SPF of 3.7 and that doesn’t include a lot of hot water heating and you are going to make it lower when you add in the secondary circulation pumps.

That doesn’t sound great compared to other monitored systems.

I don’t know what you mean by per square meter basis? I can’t see your data as I have no idea which one it is.

I am sure that Trystan and the rest of OEM do decide what happens but they do ask for input at times.

You helping him test stuff is great, but I don’t think the extra feeds were planned, you asked him to do it in post 18 even though you thought you would be the only person using it. A change, just to suit you at the moment.

What I don’t like is adding in extra heat on top of that measured by a heat meter, I don’t think it is correct, just measure the heat through the heat meter and measure the electricity consumed by the heating system.

Adding in heat not accurately measured isn’t right. Where will it stop, are we going to start including ovens, microwaves, hairdryers, kettles etc, to the heating system?

Solar diversion and adding in extra heat is all going to make it more complicated and comparison less reliable in my opinion, and all it will do is change an SPF of 3.7 by very little.

As you were already mocking the age and lack of modern features of your heat pump yourself I think it is safe to assume that you can no longer buy this system?

If that is the case, the data, whilst interesting, is not useful in influencing anybody’s buying decision so does it matter if it doesn’t quite include every piece of electricity consumed?

That is really what I am asking, extra data, columns, etc, all to accommodate one heating system that is unlikely to be replicated?

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I thought a little more about what I am trying to get across on this and some other topics.

Systems on heatpumpmonitor.org are marked as MID on the basis that all of the data comes from MID certified measuring devices.

The `H’ status denotes what elements of the heating system are monitored.

All good.

But if MID systems now start adding in data from non MID sources I don’t see how they can continue to be noted as MID systems.

Adding data from unverified and potentially inaccurate data sources makes comparison less reliable. It opens a whole can of worms about what people can and can’t include in their data and still retain MID status.

So I think anybody can include and report whatever they feel appropriate but MID status can only be granted to systems that truly are 100% MID.

I’m sorry that it took me a while to get to this and the way I have to go about it, but it’s what it took for me to explain my problem with modifying what is supposed to be certified data.

I hope it makes sense and it is, of course, just my opinion.

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Btw I don’t think this is a valid approach, at least for Daikins. Immersion will come on to heat 50+ or 55+ depending on model, but can also come on in parallel with compressor if DHW is taking a long time, or if boost selected.

I have legionella cycle is disabled, but will run cylinder to 60C during negative pricing with immersion. Should it be disabled or set to dynamic?

Backup heater may frequently come on with defrosts, or various other reasons, but not sure if included in above logic. Backup heater can also be on in parallel with compressor.

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Comparison between systems in heatpumpmonitor.org can only be taken so far.

Supposing there are two identical installations in two identical properties, we can still expect their SPFs to differ.
Property #1 has folk who feel the cold and like the thermostat set high. They also take 3 deep baths each per day.
Their SPF will likely be lower than the folk next door who prefer a lower thermostat temperature and take a short shower once a week, whether they need it or not!

We don’t have fields for occupancy and lifestyle in the app, and I’m not suggesting that we should!

If folk want to supplement the DHW heating with surplus PV via a diverter then I think that’s fine and I don’t think it skews the SPF any differently than them adopting a lower consumption of hot water.

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The backup heater should be already included in the electrical consumption and heat meter measurements, so that fits fine with “Includes booster & immersion heater” as well as the H4 boundary.

If the immersion can come on during “normal operation” then I would argue that it ought to be measured and included in the statistics. There’s an assumption that systems with “legionella disabled” won’t ever be using the immersion, so it doesn’t matter if it’s not included in the energy records. Hence why they can be considered to be in H4.

I would agree with this, yes. Same for maximising use of negative pricing.

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MID is purely concerned with the accuracy of individual energy meters.

Every installation is going to have at least two meters, sometimes more. MID says absolutely nothing about how the data from multiple MID-certified meters should be combined.

If an installation needs multiple heat meters and / or multiple electricity meters in order to capture all the heat output and electricity input (for a given System Boundary), then as long as they’re all MID-certified the “MID Metering” box should be ticked.

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I agree and I think that is what I said?

Everything has to be MID to tick the MID box.

The heat from secondary circulation pumps does not come from a MID heat meter, it would just be including all the electricity as heat and that may not be true.

We don’t all agree that some of the heat from the secondary pumps isn’t already included via the heat meter(s)

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If the electricity into the secondary circulation pumps is measured by a MID-certified electricity meter, all the meters in play are MID-certified, so it is correct to tick the “MID Metering” box. MID says nothing about how many meters are required or how they should be combined.

Trystan and Tim have carefully explained that the heat meter is only capable of reporting the heat added by the heat pump (and potentially its primary circulation pump, if that is included based on the temperature sensor placement):

  • The heat meter purely looks at the incoming (return) temperature and the outgoing (flow) temperature and the flow rate, and reports the heat added to the flow versus the return

  • There is no possible mechanism by which the heat meter reading can be influenced by what is happening on the emitter circuits

  • If there is further energy being added elsewhere in the system that should be included (in H4), in the most representative fashion

Anyway, Trystan is planning to add a new data feed for the secondary pump electricity consumption and, when / if he does, I will populate that with the data from my MID-certified meter. The software will decide how that feed gets handled, consistently across all systems using it.

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Not in the low loss header?

I have no problem with what you are saying or doing, I’m not 100% convinced it is correct but I don’t need to be as it really isn’t any of my business. I am just contributing to a discussion.

When I look at systems I started with a level of confidence that they were all the same, electricity input comes from electricity meters and heat comes from heat meters, that’s it, all the same and consistent.

I can’t fiddle with it and it’s safe and reliable data.

The minute systems can be modified and add heat from something other than a heat meter reduces confidence.

I am not saying that anybody is, or even will cheat, but now it’s possible.

I don’t think you are cheating or ever would, just to be absolutely clear.

I am an accountant/auditor and I like solid, safe and secure systems that can’t be cheated.

It’s just my nature, I felt comfortable with MID systems being a reliable source of data.

I don’t think it will be now.

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I get where you are coming from. The heat meter measures heat energy in the flowing water. We actually don’t know which percentage of electricity in any pump gets into the water. Some of it enters the water and is usable in any emitter, some goes into the air around the pump and, depending on where the pump is sitting, is usable or not (for me it would be in the unheated basement - totally useless). Same with immersion heaters, just adding the electricity to the heat feels like cheating. I will actually fit temperature sensors after my immersion heater to properly capture this effect

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This is perhaps the problem.

Each system will be different, it may be an appropriate way of dealing with it in some cases and in others not so.

The data is no longer consistent and is devalued in my opinion.

And then it’s open to abuse, another issue.

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The heating circuit is symmetrical, so you can look at it the other way: the heat meter measures the energy being emitted from the heating circuit. Any heat that is not emitted is returned to the heat pump, and not “seen” in the dT (flow temp increases instead). Opening more radiators would increase the dT, requiring the heat pump to increase power to maintain flow temperature.

So in actual fact, the heat meter measures the usable energy within the whole system, and it doesn’t matter which side of the thermal sensors the pump is placed.

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@Timbones

I think the heat meter picks up the energy transferred to water by the secondary pumps, or anything else.

Is that what you are saying?

I think it is.

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I am a Chartered Engineer and perhaps sadly, engineering, physical properties and the natural world just don’t work that way. You’re saying a MID meter is absolutely accurate? Sorry, but that’s rubbish. It’s accurate to within a specified tolerance and when certain conditions are met, that’s all. The world of engineering isn’t like currency where everything comes in discrete countable chunks.

I would contend that it’s not cheating to add a portion of the losses of the pumps, because it does contribute to the heat used and enjoyed by the occupants. It doesn’t contribute to the efficiency of the heat pump. And that distinction - already pointed out earlier. mustn’t be lost sight of.

As a former officer in my professional body, I’ve had the unpleasant task of helping to root out the rare individuals who didn’t have a sufficient degree of integrity and cheated and so weren’t worthy of the profession. I’d hope that the cheats in this community are as rare.

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I know that none of it is 100% accurate.

But we buy them and fit them in good faith and most of us aren’t qualified or knowledgeable enough to mess with them.

And we shouldn’t.

Do we know for sure that the `portion of the losses’ of the pumps isn’t already being measured?

What portion of the losses should be included?

What is stopping me `adding’ a couple of pumps to my system and boosting my heat output?

My `additional’ pumps are fed from my existing electrical supply so I don’t need a new feed for that.

I’ll just add 100W to my heat output.

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But you’ll then lower the efficiency of the whole system because part of that added electrical input will be “unusable” heat that is wasted. You’ve “cheated” yourself.