@jamespa 

The thermostat on the tank is seperate to the DHW temperature so I can set either to whatever value I want.  45C on the tank seems adequate for hot showers even for my wife’s lengthy showering demands - just about!  If I set the ASHP hot water loop to lower then it surely must take longer to heat the tank.  I will try however.

The main UFH pump shuts down when the DHW loop activated but the manifolds have their own pumps which draw warm water from the then inactive loop, thus it becomes cold soon.   I’ve tried lowering th room thermostats whilst the hot water is active but it’s an inaccurate science as independent thermostats and anyway it largely didn’t have much impact overall, perhaps 0.3C at most.

I think I’ve misled you.  The UFH loop isn’t at 55C, the ASHP reporting shows it is going out at 35C and returning at 30C.  The manifold mixer has been set to 55C to simply remove it from the equation as it otherwise was blending in the return water and lowering the inlet temp.

Yes I know boilers are very different to ASHP as does the plumber.  He is knowledgeable about ASHP but he does not know the grant settings inside out which is what I need. He normally commissions a ASHP in one go, so the grant engineer would at it up, but due to my phased implementation that cannot happen for 12-18 months.

no system diagram, I will try draw something out tomorrow morning and upload.

Simplistically its one main heating loop servicing two heatmeister manifolds each one controlling a sub loop for half the house with 8 valved loops each,

typically 1-2 loops per room.  At the moment only one manifold is active with 4 valves servicing the main living space 4 loops all controlled by a single thermostat in that room.  It’s a big room - 95 sqm. 3L p/min on each flooring loop is seeing water go out of the ASHP main loop at 39-40C and returning at 35C. Room is stable at 18.5 to 19C most days but there’s some gaps in insulation still to resolve next week.

turning off the volumisers today has definately reduced total power consumption.

the question remains how to enable them without them going AWOL again and also what if any changes to make to the ASHP default settings to improve efficiency overall.  The factory defaults must surely need considerable tweaking otherwise what’s the point in paying for “commissioning”.  

Basically I want to do the best interim commissioning job I can to bide me over for the next 12-18 months even if I have to do it all again after phase 2 and phase 3.

Posted by: @adam

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!  If I set the ASHP hot water loop to lower then it surely must take longer to heat the tank.  I will try however.

Sorry I misunderstood 55 to be the dhw temp not the flow temp for dhw.  That being the case I wouldn't change it.

It sounds like everything is basically set up to run open loop no thermostats etc.  Assuming you are running 24x7 and your room temperature is right, there isn't much more you can do.  Generally it's turn down the wc curve until it only just heats the house with everything open, but it sounds like it's as low as it can be without your house chilling.  Unless that is, something is switching the ashp on and off which you haven't mentioned or I didn't spot when you said it.

It may be the high oat end if the wc curve needs tweaking, what is that set at?

Re the volumisers, their main purpose is to increase the water volume in the system (hence the name).  The electric backup heater is very much a secondary function for a volumiser.  You hopefully never need it, so as long as its not switching on don't worry about it.  I indicated my take on the settings above.

It sounds like some if the factory defaults must have been changed already by the installer if its outputting water at 35.

My installer took less than an hour to alter the settings on my vaillant.  Most if the work is in the plumbing not the operating parameters.  The latter are very important but, apart from adjusting the wc curve to suit the house (which really needs days) they don't take long.

It's beginning to sound like your system is in fact pretty well adjusted but the volumiser has unsettled things.  It's important to understand that it's primary function is just a tank of water that doesn't need configuring, and the elements are there as emergency backup or for very very extreme weather so may never actually be needed.

@jamespa

Hi James

Yes we run the UFH 24x7 other than twice a day when the DHW kicks in and disables it for 2 hours or so at a time.

WC is set to on and default values which are:

Min outside temp -4C gives 45C max loop temp

Max outside temp 20C gives 30C min loop temp

hysteresis set to 8C

installer has not changed those, that’s Grant factory setting defaults according to the manual.  Enquiring on the controller confirmed all settings other than the ones I have changed myself were default.

My recent tests showing around 39-40C outbound make sense given it’s been generally between 0-5C outside at that time.

i was thinking of tweaking up the min external temp from -4C to 0C to add maybe 2-3C of loop temp on colder days but thats only going to make my electricity drain worse, albeit may get the room to my target comfy temp.

Possibly reducing WC hysteresis to 5C might help stability but again it’s going to make CoP drop with more startups and thus raise electricity drain.

still wondering as to how to enable the volumisers in a productive way so they do what they are supposed to do and not just drain power every single time the ASHP kicks in.  

1. I am wondering if param 46-00 set to “2” emergency mode maybe what I want rather than “3” supplementary mode which clearly did not work as expected ?? 

Hi James

Yes we run the UFH 24x7 other than twice a day when the DHW kicks in and disables it for 2 hours or so at a time.

WC is set to on and default values which are:

Min outside temp -4C gives 45C max loop temp

Max outside temp 20C gives 30C min loop temp

hysteresis set to 8C

installer has not changed those, that’s Grant factory setting defaults according to the manual.  Enquiring on the controller confirmed all settings other than the ones I have changed myself were default.

My recent tests showing around 39-40C outbound make sense given it’s been generally between 0-5C outside at that time.

i was thinking of tweaking up the min external temp from -4C to 0C to add maybe 2-3C of loop temp on colder days but thats only going to make my electricity drain worse, albeit may get the room to my target comfy temp.

Possibly reducing WC hysteresis to 5C might help stability but again it’s going to make CoP drop with more startups and thus raise electricity drain.

still wondering as to how to enable the volumisers in a productive way so they do what they are supposed to do and not just drain power every single time the ASHP kicks in.  

I am wondering if param 46-00 set to “2” emergency mode maybe what I want rather than “3” supplementary mode which clearly did not work as expected ??  

Anyone know exactly how 46-00 works?  there’s nothing useful in either manual which came with the system.

The main ASHP flow pumps come configured via DIP switches and are set to maximum flow on each. Both my flow valves are fully open and the flow gauges don’t show anything so my assumption is they are maxed out and therefore not visible.

How do I work out what the required flow rate is for the main loop and given I have two ASHP do I half each flow valve or set them both to the same required value?

Anyone know if param 42-00 (main water pump configuration) should be set to 0 (default “always on” setting) or 2 (on/off based on detect cycles)?

Posted by: @adam

↑

still wondering as to how to enable the volumisers in a productive way so they do what they are supposed to do and not just drain power every single time the ASHP kicks in.  

Honestly, my first call would be to disable them.  As I say above the main point of the volumisers is simply to add water volume (ie its a tank).  They are doing this already.  The element is a secondary function for use only in extreme conditions and may never be used.

Alternatively, so that the backup heaters could (but probably wont) do something set them to 'Backup heater' then try 3 - supplementary mode.  If it still fires up (which it shouldn't) drop back to 2- emergency mode.  If it still fires up (which it shouldn't) drop back to 0 - disable.  There is a bit of an explanation on pages 111-119 of the original Chofu manual which is better than the explanation in the Grant manual (not uncommon)

Posted by: @adam

↑

Anyone know if param 42-00 (main water pump configuration) should be set to 0 (default “always on” setting) or 2 (on/off based on detect cycles)?

2 is better if it works as it switches off the pump when not needed.  What 'detect cycles' mean is that the pump is switched off, but it switches back on again from time to time so it can sense whats happening in the house.

45C loop temp is high for UFH, 35 is more common.  Hopefully you will be able to reduce this when you finish the house.  WC hysterisis of 8 is high, but as you say is linked to frequency of cycles.  Are you getting rapid cycling (say more than once every 20 mins).  

Regarding setting pump speed we need a system diagram to advise.  The min required flow rate will be in the manual and each pump needs to see that.  This isnt a Grant specific question, but without a system diagram its difficult to say how to set it.  Of course you could just turn it down a step at a time until the heat pump complains!

I am concerned that you drain the UFH loop of heat during DHW cycles, this is wrong.  Again a system diagram may clarify and again not grant specific.

Hope that helps, if anyone is a Grant specialist they may be able to advise further.

Hi James

thanks for the tip about the Chofu manual, I’m reading that now and will post again soon as it’s much more informative about the volumisers! 

for now here’s my effort at drawing out my system diagram.  Hopefully it’s understandable.

<deleted>

I will post again in a short while regarding the settings you suggest.

cheers

Thanks, thats helpful.  There seems to be a circular path around the upper volumiser, is this correct (it could be, perhaps the upper heat pump is the slave and when its not working the circuit causes it to be bypassed).

I dont see any external pumps so dont understand how heat is extracted from the UFH when DHW is selected.  Are you able to clarify.  Im presuming the two motorised valves are wired either-or but never both.

Main heat loop seems to be a shunt/short circuit for the UFH loops.  Is this correct?

Im still typing up a very long reply having read the chofu manual which is extreemly helpful on the volumisers!    I will post on that soon.

Posted by: @jamespa

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Thanks, thats helpful.  There seems to be a circular path around the upper volumiser, is this correct (it could be, perhaps the upper heat pump is the slave and when its not working the circuit causes it to be bypassed).

I dont see any external pumps so dont understand how heat is extracted from the UFH when DHW is selected.  Are you able to clarify.  Im presuming the two motorised valves are wired either-or but never both.

Main heat loop seems to be a shunt/short circuit for the UFH loops.  Is this correct?

In response to this post..

The loop is a mistake in my drawing, my apologies.  Corrected diagram below, please disregard prior drawing.

There are no external main loop pumps that is correct.  Each ASHP has a pump which is by default set to maximum and the output is covered in the grant manual.  I do not know what mine should be so I have not changed anything here from the default max. Its changed via DIP switches on the ASHP themselves.

Each manifold has a smaller pump that if ANY of the loops are activated by the room thermostats then the wiring centre enables the manifold pump to draw water from the main HEAT loop and it in turn triggers the HEAT supply to the Grant wiring centre which activates HEAT on the ASHP's and thus activates their pumps and opens the HEAT valve.

So the reason the a manifold can drain the HEAT loop during DHW cycles is because the DHW demand closes the main HEAT valve and thus the HEAT loop becomes trapped.  After around 20-30mins the manifold has slurped all the heat out of the stationary HEAT loop by still pumping around the UFH loops.   I have tried disabling the manifold pumps by allowing a 2 hour window during the DHW cycles which I think works but in 2hours the water in the HEAT loop looses a lot of warmth anyway so it didnt seem to make much difference really.   I did this by simply setting the room temps on the thermostats to like 9C during the DHW cycles which then tells the manifolds to close off and their pump disables.   Bit of a crude cheat, but it was the only way I could think to do it.

The only other option is to allow the HEAT loop to remain active whilst the DHW is on.  My worry there was that it would take ages to heat up the hot water as the ASHP would have to heat up the whole HEAT loop to 55C as well as the much smaller DHW loop, albeit the thermostatic valves on the manifolds could still limit how much water they allow into the UFH loops if I set them to 35C say.

Not sure which of these two options would work out best but Ive been focussed on the other issues before having the time "in days to test" such a setup yet.  Its on my "to do" list...

Ok that's clearer.

It's a pity about the manifold pumps, they effectively stop the ashp having the control it needs to make sure everything works properly.  I wonder if they are actually needed (did your plumber do the calculations?)

I definitely wouldn't enable dhw and space heating simultaneously, you are likely to lose too much heat to the ufh. 

Posted by: @jamespa

↑

Honestly, my first call would be to disable them.  As I say above the main point of the volumisers is simply to add water volume (ie its a tank).  They are doing this already

.  The element is a secondary function for use only in extreme conditions and may never be used.

Alternatively, so that the backup heaters could (but probably wont) do something set them to 'Backup heater' then try 3 - supplementary mode.  If it still fires up (which it shouldn't) drop back to 2- emergency mode.  If it still fires up (which it shouldn't) drop back to 0 - disable.  There is a bit of an explanation on pages 111-119 of the original Chofu manual which is better than the explanation in the Grant manual (not uncommon)

 

I had them set to "3" supplementary mode when they were using loads of electricity...

The Chofu manual is indeed much more helpful, thank you, I had no idea they were the same thing...

Ok, having read manual I think I have a lot more idea of whats going on!   Looks like param 6-10 is part of the reason to blame for their recent constant activation!

46-10 is conditions to be available DHW backup heaters "0" default is always enabled and "1" is depends on outdoor temperature.

46-13 is linked to the setting "1" above and is "the outdoor air temp to enable backup heater in supplementary mode" and default is 5C.

So I am thinking I need to set param 46-10 to "1" and set 46-13 to say -5C and try again?   That way they will only kick in to help when its VERY cold outside and I probably need them anyway!

Also param 46-20 seems key, which is not mentioned at all in any Grant manual!   Page 118 in the chofu manual.   

Looks like I need to set 46-20 to "2" which is "enabled during defrost". 

Also I think I likely have to set 51-46 "DHW electric heater of backup heater to "1" backup heater again.  This is the main setting that seemed to basically turn them on or off before!

I think this combo will then give the behaviour we are both expecting i.e. they only kick in when its very very cold outside or to aid with defrost cycles.

However I think this will only solve the DHW use of the volumisers / immersions, not the heat loop, which seems to be a little more convoluted according to pages 120-125

So to do the HEAT loop (EHS) I am thinking I need to set

47-00 is EHS type of function to "2" supplementary mode

47-01 is conditions to be available EHS backup heaters to "1" depends on outdoor temperature.

47-02 is Outdoor air temperature to enable EHS and disable compressor and by default is -5C, which seems fine to me - odd that the default differs to the DHW equivalent?

51-41 is EHS (External heat source for space heating) mode, set to "1" enabled.  This appears to be the equivalent of 51-46 for DHW I think?  not entirely sure as its worded slightly differently but seems to mean the same thing to me anyway.

What I am not sure about is if I need to do anything for EHS settings or just tinker the DHW settings for now and see what happens with the volumiser immersions.

Posted by: @jamespa

↑

Posted by: @adam

↑

Anyone know if param 42-00 (main water pump configuration) should be set to 0 (default “always on” setting) or 2 (on/off based on detect cycles)?

2 is better if it works as it switches off the pump when not needed.  What 'detect cycles' mean is that the pump is switched off, but it switches back on again from time to time so it can sense whats happening in the house.

45C loop temp is high for UFH, 35 is more common.  Hopefully you will be able to reduce this when you finish the house.  WC hysterisis of 8 is high, but as you say is linked to frequency of cycles.  Are you getting rapid cycling (say more than once every 20 mins).  

I will try 42-00 then.  To be fair if both DHW and HEAT are off then the ASHP seem to shutdown after a few mins and do not pump so I suspect its acting like "2" anyway even though its set to "0", which I dont really understand but it is....  Maybe its something to do with the fact I do not have external pumps in my setup.

My loop temp seems to be hovering around 39-40C on a day like today when the external temp is around 0C, but the room isnt as warm as we would like.  Given the loop pumps are running near maximum at 3L p/min I think the only way to get more warmth into the floor is to raise the loop temp isnt it?  It would only get to 45C at -4C outside temp based on my proposed change, which maybe necessary until the house is finished. I suspect we loose a lot to through internal walls to the next door rooms which are unheated and very cold, around 7-9C at most at the moment.

Finally one last point.  It was cold here last night, around -1C. Turning the volumisers off has definately reduced electricity but the room temp this morning was 17.5C which is a whole 1C down on where its been since I enabled them, so whilstt they were slurping a whole load of power it was increasing the temp somehow.  Oddly the HEAT loop temp this morning seemed to be broadly the same 39C out and 33C return so I am a little confused as to why, but it could simply be a coincidence that I turned them off on a day when it got even colder outside.  Only time will tell, and whileever I tinker other settings daily its hard to keep track of whats impacting what of course!

Thanks again, and looking forward to your comments and help on all / any of the above.

Cheers

Good morning @amiddlemass 

I realise that @jamespa and I  are discussing different subjects with you simultaneously.
Let us know if this is getting too confusing.

I'm going to leave the storage battery issue to one side temporarily, and address only the electricity supply to the bungalow.

Please give your architect, electrician and heat-pump installer the URLs of this topic.

It's unlikely that you have the Consents which you think you've received from SP Energy Networks.

There are two entirely separate assessments which the DNO has done:

• G99 application for solar panels, inverter and storage batteries
• LCT application for heat pumps

An LCT (low carbon technology) application is also required for any proposed EV charger, although we don't know if you ever intend installing one.

Both assessments are made with reference to the local substation transformer, the supply cables to you, and those to your neighbours.

The calculations are dictated by the laws of physics, based on the information which you (or your architect/electrician) have provided.
They cannot be 'adjusted' to make allowances for something which wasn't known at the time.

Physics doesn't work like that.

Three things aren't clear to me at this stage:

1: Was an LCT application made for the ASHP system, or was this omitted on the grounds that you intended running them from storage batteries?

We need to recognise that the heating system will be operating directly from the grid (bypass mode) when the batteries are being recharged.
Both demands can operate simultaneously.

2: Did any such LCT application make clear that there were to be two 10kW heat pumps?

The DNO process the application by first checking a database held by the Electrical Networks Association (ENA) which has data for all appliances for which grid-connection is approved.

The next stage uses a software modelling tool, into which is fed the supply characteristics for your area.
It's possible that the software only recognised the requirement for one 10kW heat pump.

3: G99 applies where there is more than one appliance which can export to the grid.

If there is an inverter which handles connections for both your solar panels and batteries, then that's only one appliance.
A single inverter would already have G98-certification for grid-tied operation.

So why was a G99 application made?

When making such applications, the form requires the electrician to provide a figure for total household demand.

This involves adding together all electrical devices in the home.

There are a few minor caveats.
For example I have 20+ power tools in my workshops.
But it could never be the case that I use them all at the same time!

If total household demand comes to 60A (14.4kW) or more, then you require a 3-phase supply.

You can't just look at your 100A Service Cut-Out and believe you're 'good for 24kW'.

That Service Fuse belongs to the DNO, not the home-owner.
It's there to offer a 'sanity check' which protects the local grid from damage.

I'm going to switch to using graphics to explain this point:

When houses have single-phase supplies, their varying demands cause phase imbalance at the substation transformer.
The imbalance generates heat, which is 'energy going to waste'.

Domestic supplies in Britain currently waste more than 10% of the electricity which arrives at the local substations.

That's unsustainable.

The fewer the number of houses that are supplied by a local substation, the more pronounced is the imbalance caused by an individual house.

Here's the effect of one property running an EV charger between 00:30 and 04:30 using the cheap-rate Octopus Go tariff:

Pay particular attention to the amount of current now flowing through the Neutral Wire.

When phases are balanced, there is zero current in the Neutral conductor.
For that reason a high proportion of Feeds from local substations use a smaller conductor for the Neutral.

Left unchecked, that Neutral current results in cable damage due to thermal stresses.

Here's a substation transformer collapsing under those circumstances,
despite engineers on site attempting to restart the supplies several times:

Only a handful of the 230,000 ground-mounted substations, and none of the 320,000 pole-mounted transformers have any monitoring.

The graphs here have been plotted by me having access to just a few monitored sites.
Your electrician is unlikely to have ever seen such data before, and will probably be quite interested!

We can see the same effect from a different viewpoint by looking at the current drawn by three houses, connected to different phases of a substation transformer:

I've drawn the demand from each house as if it's a spring being pulled away from the centre vertical line.

That centre line represents the Neutral.
It's straight because the load imposed by the three houses is balanced.

Now let's add four more houses, further away from the transformer at the foot of the diagram:

House 5b has solar panels on the roof.
So, although it's on the same phase as 5a, the overall current drawn from that phase is actually reduced.

However, House 6 is drawing greater current for an EV charger.
That pulls the Neutral away from the centre vertical position.

We are not being allocated electricity on an individual basis.

Our homes are part of a local grid system.
The Demand we make on the local substation transformer affects our neighbours,
and the overall integrity of their electricity supply.

Posted by: @jamespa

↑

Ok that's clearer.

It's a pity about the manifold pumps, they effectively stop the ashp having the control it needs to make sure everything works properly.  I wonder if they are actually needed (did your plumber do the calculations?)

I definitely wouldn't enable dhw and space heating simultaneously, you are likely to lose too much heat to the ufh. 

Plumber did ASHP and calcs and spoke with builder regarding UFH design who did the UFH loops and manifolds and thermostats.  It was the builder insisting that room thermostats were a good idea that resulted in the plumber changing the design in conjunction with the ASHP design sub-contractor of the ASHP's and adding a volumiser tank to each.  At the time I didnt really understand why but accepted the change as needed.

Ok I will give that a go then.  I think this is such a fundamental change however that I need to do this in isolation of any of the above reinstatement of the volumisers.  If I impact the amount and hotness of the Hot water then my wife complains very quickly that she has had a cold shower.  Making the change to run the two loops together could deffo slow down the hot water production I feel albeit would have the benefit of turbo charging the HEAT loop during the cheap electricity period meaning it would likely turn off after the DHW timer turns off for an hour or so running of the residual 55C heat in the loop for the hot water.

Ive got mixed feelings about how that will pan out, but its deffo worth a try, as you say loosing the HEAT loop for two periods of 2.5hrs a day whilst the DHW kicks in seems to put the UFH on a back footing always.