Posted by: @adam

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Please can somebody help with how to enable the volumisers so they dont eat lots of power, AND / OR any other critical changes we should make either alone or in conjunction with the params in the volumiser manual.

Welcome to the forum and feel free to ask questions.

Can you tell us more about the 'volumisers' including ideally a system diagram and a photo.  What is normally called a volumiser cant be switched in and out, but Im guessing you are actually talking about an immersion heater within the volumiser (often called a backup heater').  If so, this is for use in extremis only, preferably never, as it will chew electricity at 3* the rate of a properly adjusted heat pump for any given output.

Some of your numbers dont quite stack up.  Do you know how 2*10kW was arrived at?  Thats one hell of a big demand if its real (which I doubt).  My guess is that you may need only 1 * 10kW.  What was the assessed heat loss of the house?  Also can you confirm the capacity of your battery (which is measured in kWh not kW)

In addition can you send some photos of the plumbing around the volumisers.

If you can give a bot more detail it may be possible to point you in the right direction.

@jamespa 

Hi James

thanks for your reply.

The volumisers are the offical Grant volumisers (yes they do have an immersion heater inside each).  Model is as per the recommended model (link to manual below with diagrams and pictures of the models.  Mine are identical to these, installed outside on the same plinths as the ASHP’s.

GRANTUK.COM "https://www.grantuk.com/media/5298/grant-external-volumiser-installer-uk-doc-0183-rev-1-1-march-2023.pdf"

Pics of the plumbing around them attached.

and yes, I understood they were for extreme use only such as assisting with defrost only.

Now to be fair it’s been very cold here and below the defrost param values here for a few days now, but they seem to kick in all the time.  That’s precisely my issue I am posting about - how do I set them up to stop this behaviour?

I don’t have the system design specs but the original ASHP spec with the SAP calcs was originally 27kw in total then downgraded to 20kw when additional clarity was given about the insulation and few other mistakes in the first SAP calcs.  The house is around 4500sqft open plan bungalow with a lot of glazing albeit high spec glazing.

The batteries are 16.2kwh - I simply missed the “h” off above.  2x 8.1kwh sigenstor batteries.

i would estimate over a 6 hour window the volumisers have been drawing around an additional 6kwh of power, so certainly not on all the time but equally quite an additional overhead for no apparent gain.

thanks

Am I correct in interpreting the photo as showing the volumisers outside and uninsulated.  If so that's dreadful, to the point that this needs to be fixed.  Why would you put a radiator outside?  They also appear to be obstructing the air intake.

Ok I have now read again and read the manual which, surprise surprise , doesn't specify the heat loss.  It doesn't even have decent insulation, just mineral wool 

This is madness, no way would I do this, but ultimately it's your choice.

Rant over, I will reread when I am at a full size screen and make some suggestions for what you could do to address the issues you raise.

@jamespa 

Hi James

The Grant Volumisers are fully insulated and sealed and do not need any additional insulation other than on the pipework.  They are installed on the same plinths in accordance with the manual and do not obstruct the air intakes.  AFAIK they are installed correctly.  I believe the issues I am having is with the lack of setup on the parameters, in that everyting is factory default and not in any way tuned for my "interim" phase1 living conditions.

See the manual (I posted the link to it in my prior response) on page 4.

Quote from manual:

"The Grant External 30 litre volumiser is an insulated rectangular
tank fitted with a single 3kW electric immersion heater and is
designed for use with the Grant Aerona³ air source heat pumps.
This is housed within a weatherproof external casing with a
removable cover at one end to access the electrical connections
and immersion heater.

It is designed to be located behind the Aerona³ heat pumps, on
the same anti-vibration mounts (Grant product code: HPIDFOOT/
KIT2) as the heat pump, using the mounting brackets provided
with the volumiser. See Figure 1-1."

I apologies for my reaction.   I was initially shocked that anyone would do this and then shocked that anyone makes it into a product.  I still am TBH and the fact that its fully insulated doesn't comfort a lot, compare the thickness of the insulation to the thickness of the insulation in your loft!

That said and in fairness

1. Grant make it fairly clear in the manual that its a product of last resort

2. The losses are mitigated somewhat by the fact it heats the air intake.

I do agree that your problems are not connected with this.  I would expect them to be set to 3 supplementary mode and in practice never to fire up.  If they do then something is wrong with the master/slave relationship.  in fact you should be able to disable them entirely and your house should be warm, other than possibly in very extreme weather.  Am I right to understand that this is NOT the case (your house is not warm?).  Please confirm so we can diagnose the reason why.

With regard to 

Posted by: @adam

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The ASHP seem to be rated at around 2.5kw input whereas the tanks are 3kw each, so bizzarely the tanks can draw more power than the actual ASHP's!

The volumisers use resistance electric to generate heat.  For each 1kWh you put in you will get 1kWh out.  The heat pump is exactly what it says on the tin, it pumps heat extracted from the outside air into the house, rather than generating heat.  Its rather good at this, for each 1kWh you put in you will typically get 3kWh out (this figure varies with outdoor air temperature and flow temperature, but its in the region 2-6 with 3-4 being the expected average).  For a description of key heat pump concepts can I suggest you read this introduction?

Please also post the setting values that are not the defaults.  Also is this the R290 pump or the R32 pump - if you dont know then please just post the model number.

Finally have you got any thermostats/TRVs in the house and if so what do you know about how these are connected?

Hopefully with this information it should be possible to start working out what is going on.

A few comments from me on what I've understood thus far on your installation of Grant ASHPs:

A:  There is another new topic here on a Grant 17kW ASHP.

I would expect there to be some cross-over of comments, so please click the orange Subscribe button at the top of that one.

B: I'm immediately concerned at the state of the seals on your external pipe insulation.
That looks extremely like silver Gaffer-tape to me.

It may well be a UV resistant variant, but it needs to use impact adhesive in order to adhere to Nitrile-rubber insulation.

Please note what I've posted on pipe insulation here,
and the photographs I annotated on the following page here.

C: Two 10kW ASHPs means that you should have a 3-phase domestic supply.
I would've expected your DNO to have stipulated so when they sent a Letter of Consent in response to your LCT (Low Carbon Technology) Application.

But I don't believe Grant have any 3-phase heat pumps in their portfolio.

What's the design strategy behind you selecting Grant as the preferred manufacturer?

Has the installer got them connected to different phases?

What phase(s) are the two  Volumisers connected to?

D: Please describe what you're trying to achieve by having storage batteries.
Avoid technicalities - just tell us what you want.

Irrespective of the 16kWh of storage, what's the make and model of the inverter(s) which charge and discharge them?

I found this specification for a Sig 8kWh battery online:

Does that sound like your units?

As they have only 9-cells using LiFePO4 technology, they will be working at around 29v DC.

That means they can be charged at a whopping 208Amps!
Ie 6000 watts / 29v

This is a very unusual configuration.
Such high currents require hefty copper cables, and they're not cheap!

The majority of home batteries using LiFePO4 cells are operating at a nominal 52v, using 16-cells.
So you're locking yourself into a strategy for which Sig would appear to be a sole supplier.

I'm going to leave you discussing the volumisers with @jamespa

@jamespa 

Hi James

thanks again for your continued replies.

They are the R32 models.  2x of HPID10R32 model.

The main living space is warm, we’ve got it up to 18.6C but there’s still some issues with small air gaps on window seals which will be resolved next week, plus the rest of the house it totally unheated at the moment so that’s sucking the effecient out of the setup.  I am confident that once these issues are resolved the room would ordinarily be able to achieve 20C no issues.

The room is warm with or without the volumisers enabled, seems to have made no adverse impact today turning them off again.  

I’d like to get them setup right given I have no doubt paid for them in the original quote, but at the time I was non the wiser either way.

The issue I have is how to setup the ASHP parameters generally and specifically anything related to enabling the volumisers without them eating a load of electricity.  Since I disabled them again this morning the power use has reduced.

even though the room is warm I want to ensure it’s running efficiently, no one wants to throw money away on a “default setup” running inefficently but equally having paid for them installing I want to see them being used correctly.

For the avoidance of doubt, I have no loft at all, the house has an almost flat roof, 2.5deg pitch. It’s a warm roof with very little gap between ceiling plasterboard and the warm roof sandwich which has 150mm of kingspan.  Our basement is our loft as such. 

We have heatmeiser neo wireless thermostats in each room, connected to heatmeiser manifold control centres. 

the rather simple analogue thermometer on the manifold says that the inlet temperate is 32C at its peak, dropping to 25C at its lowest.  I must have checked them 100 times in the last week.  The ASHP control centres report the loop temp as 39-40C and the return temp as 34-35C on a day when the outside temp was around 5C so reasonably as expected with weather compensation on.   I suspect the cheapo thermometer on the manifolds is understating the actual temp.   The floor feels warm to the touch, but not hot, likely it is mid 30’s I would say.

I don’t believe the master/slave setup is working correctly if I am honest but then everything is on factory defaults so I’m not surprised.  That’s also one of the key things I am trying to resolve, probably more so than the volumiser setup.  The plumber said, “you are only trying to heat a quarter of the house at the moment so the slave isn’t needed and the system software will only fire it up when there’s demand on the loop to warrant it.  I can’t prove or disprove that of course until the house is complete but by then the grant engineer will have fully configured them.  For now I have to get it working effeciently on half the house.  A master alone should be able to do that just fine.

The only para a I have tinker with other than the ones in the volumiser manual are as follows:

31-11 Hot water comfort, changed to 55C from 50C

43-01 internal temperature for frost protection, changed from 14C to 7.5C

43-11 external temperature for frost protection, changed from 4C to 3C

that is it.  Everything else is factory default.  I have checked every single setting to be sure they are all still on default and they are.

@transparent 

Hi Transparent

Thank you for your reply.  My responses as below.

A) I will read that thread and your relies there, thank you.  Hopefully something relevant to my situation will come out and help me with my setup.

B) I think you have made a very valid observation and I will raise with my plumber / installer next week.  Although it is very helpful and will improve my setup and long term use I don’t think it’s at the heart of the issues I am posting about.

C) No the Grant ASHP are single phase.  We have an old 100A circuit and our G99 has approved the use of a 10kw inverter on a single phase.  A single phase can in theory go up to 24kw, I’ve never seen it top 18kw even in the most extreme loading.  The inverter cannot top 9kw with just two batteries as the max at 4.5kw charge / discharge each.

both my architect and ASHP supplier quotes stilputalted Grant as their preferred brand without consulting each other. Accordingly I accepted the brand as a fairly decent choose. I am where I am now and changing isn’t really an option 6 months in.

D) yes those are my batteries.  I have a single phase 10kw sigenstor inverter with just two 8.1kwh batteries.  I can add up to 6 batteries per inverter so a whopping 48.6kwh but each battery has a max charge rate of 4.5kw and the inverter 10kw, so 2-3 batteries is the sweet spot to fully recharge charge in the 3 hour cheap sessions on octopus cosy.

yes my batteries regularly charge at 8.8kw most sessions from near flat to full.   The total drain is around 11-12kw without the volumisers on, but I’ve seen as much as 18kw peak with the dryer and washing machine on as well as charging. 100A gives 24kw max and I keep an eye on it so as not to get too close to that and pop the main house fuse! So far plenty of headroom.

The batteries serve two purposes.  In winter they allow us to hop from cheap supply zone to zone on Octopus Cosy without ever needing to pay for regular priced electricity. Hence its key the power drain doesn’t exceed their capacity over 6 hours which is the longest peak priced window on the cosy tariff.

in summer they allow us to store up power generated in the extended sun and sell it overnight.  We are limited to 6.4kw export so with our 10kw array we might generate as much at 8.5kw per hour peak and this storing up the excess 2.1 kw gives us 8 hours of excess to store before selling it when the sun goes down.  Here in yorkshire the sun never shines that long anyway so the winter setup is the priority really, but it was designed to be a win win setup.  We might need a 3rd battery but I planned to give it 12-18 months to fully understand the peaks and troughs before making that final investment.   Again this isn’t really relevant to the volumisers eating electricity through lack of setting up correctly really, although I’m happy to share the system design strategy.

it was all well thought through I thought, but I never anticipated issues with the interim “default setup” we are living though, it’s going to be 9-18 months before the whole house is finished and the ASHP professionally commissioned:  

Thanks.  I know a fair bit about heat pumps but not grant specifically, and I certainly dont know about their master slave setup.  However i suspect the plumber may well be right that the second pump will only fire up when there is high demand, which may  rarely occur.

The only purpose of the element in the volumiser is to kick in if the demand can't be met by the heat pump.  That may never occur, ever, and you don't want it to because it's expensive to run.  If it runs at all when set to supplementary mode I would set it to disable and have the grant engineer set it up correctly.  I can't stress enough that you don't want these elements on unless there is no other way to heat the house.

Heatmiser (or any other) thermostats are bad news,  You ideally want all zones open and the heat pump running on weather compensation, with the weather compensation curve as low as possible consistent with heating your house.  That's the most efficient.  However with only half a house, trying to get this right is unlikely to be productive so i wouldnt necessarily make changes yet unless you want to do hhe job twice.  I would also recommend setting your dhw back to 50 unless there is a really good reason to run it at 55.  It's quite a bit more efficient and you don't (I presume)  really need water at 50.  48 is often recommended in fact.

Given that you are warm enough I would personally make changes to the volumiser set up and dhw temperture only at this stage, then optimise the wc once you have a complete house.  In the meantime I would read up a bit about how to operate heat pumps efficiently (the abc on this site is a good starting point) (forgive me if you already know thus stuff) and if there is something that doesn't seem to make sense ask.  Then you will be prepared when the grant engineer comes to commission and you can ask him the right questions/make sure he does the right thing!

All that said if you do want to make a start on optimising the weather compensation and ensuring those heatmisers aren't costing you money, just say and I or someone else will provide some pointers to the sequence of changes to get it running as near as possible at the lowest flow temp (= highest efficiency).

@jamespa 

Hi James

thank you again! 🙂

the DHW was set to 55C to try heat the hot water quickly in the 3hr window when the electicity is cheap, it seems to take about 2-2.5hours with the tank thermostat set to 45C which is hot enough for us.  I wanted the hot water heated up quickly then back to heating the UFH. A bigger differential between hot water loop temp and cylinder thermostat max means a faster warm up time, means we go back to heating the floor again sooner!

i have the hetmiester thermostats set to 22C so at the moment they never turn off anyway as other when the sun shines into the room it never gets that warm. So far that’s only happened a couple of times so largely the UFH is on full time other than when the hot water is on.  

With the default hot water prioty however than means the heating loop goes cold after about 30-45mins after the hot water loop closes it off, thus the manifolds then effectively drag heat out of the screed in reverse so heating up the hot water quickly on cheap mains electricity and not battery draw seemed to make sense.  I’ve tried lowering the temps on the thermostats whilst the hot water is active to reduce the negative draw from the floor but it has very little impact in reality.  We’ve ended up with t the 4 loops in the living space set to 3L p/min to achieve a stable 18.5C with the manifold mixer set to max (55C).  The loop temp acts as our limiting factor.  I have not yet tinkered with the weather compensation settings but my gut feel it to try raise them loop temp by around 5C in and out.

i will try setting the hot water back to 50C again and see what happens for a couple of days.  But the hot water is only heated during cheap electricity period so this really has little if no impact on the battery life.  

My theory is the sooner the floor is heated again, the less it will draw later to heat the floor whilst on battery.  

My wife can use almost an entire 250l tank of hot water though in a single shower it seems, so we end up heating the whole tank fully twice a day to keep her happy so a fully heated tank is essential to a happy life!

I agree it’s a bit of a thankless task setting everything up for half a house but I am enthusiastic to learn and quite capable and confident of trying settings. i am more than happy to do it all twice if necessary. 18 months is also a long time to run a system not setup right and winters are cold, we have at least one more before the house is finished.

I discuss every change first with the plumber who is friendly, helpful and supportive but lacks Grant ASHP parameter specific knowledge, but knows generally what’s what with boilers so we make informed decisions each time. I doubt he has many customers as keen as I am to fiddle with settings.

Posted by: @adam

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the DHW was set to 55C to try heat the hot water quickly in the 3hr window when the electicity is cheap, it seems to take about 2-2.5hours with the tank thermostat set to 45C which is hot enough for us.  I wanted the hot water heated up quickly then back to heating the UFH. A bigger differential between hot water loop temp and cylinder thermostat max means a faster warm up time, means we go back to heating the floor again sooner!

Is there a setting allowing you to increase the differential between flow temperature and target dhw temperature.   Then it would heat up quickly to a lower temperature. 

Posted by: @adam

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, thus the manifolds then effectively drag heat out of the screed in reverse

Do you have a separate circulation pump for the ufh.  If so it should shut off while heating dhw so this doesn't happen!

Posted by: @adam

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manifold mixer set to max (55C).  The loop temp acts as our limiting factor.  I have not yet tinkered with the weather compensation settings but my gut feel it to try raise them loop temp by around 5C in and out.

That's really high for ufh and pretty high even for radiators.  Ufh is usually designed to work at 35 or below, which is one reason it is good for an ashp.  The lower the flow temperature of the water leaving the ashp the less it costs, and it's about 3% per degree so every degree matters!  Are you somehow mixing down high temperature water from the ashp to a lower temperature for the ufh.  If so we definitely need to tweak some parameters. 

Posted by: @adam

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, but knows generally what’s what with boilers

Sorry to say this but that may not help.  Ashps are run in a completely different way to the way we run boilers (to be precise tge way we run bpilers in the UK, some more enlightened countries run boikers differently, more like ashps, which even for a boiler saves 10%)

Posted by: @adam

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i have the hetmiester thermostats set to 22C so at the moment they never turn off anyway as other when the sun shines into the room it never gets that warm. So far that’s only happened a couple of times so largely the UFH is on full time other than when the hot water is on.  

If this is the case and you are running at 55c somethings is wrong.  Can you please clarify what the water temperatures are at the various points?  Do you by any chance have a system diagram, if not could you please post a sketch?