Posted by: @trebor12345

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It's not a sustainable way to run the heating.  

Does it tell us anything else?

I am looking at setting up the WC.

I dont think it tells us anything else other than the time it takes constant for getting the slab to equilibrium at the specific flow temperature (which is useful!)

Posted by: @trebor12345

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I have always expressed the view that the HP is oversized, as you have found the Night/ECO setting, I turned it down to 50%.  This is the result.

Turning it to 50% is unlikely to help much.  It wont change the minimum output.  It will clamp maximum output which might slightly moderate what it does after an off period, and thus help a little bit, but this is not on its own the solution to getting stability.  For stability you need to match energy supplied to the slab with energy lost by the house.  Weather compensation is the facility provided by the controller in order to do this.

@jamespa 

Looking at setting up the weather compensation.

I know from the building that 32C is fine for temperatures below 0C and 5C.  But don’t know much about the lower end.

From my temperature probes attached to the pipes:

Flow is typically 32C

Return is typically 27C

I know from last year, it didn’t like anything below 29C in milder conditions, kept short cycling.

Not sure how this 4C Thermo Off rule is going to like this.  So if we set a flow of 30C then Twi into the exchanger will be 25C (delta 5C) heating will not come back on till Twi 21C.  The floor is typically between 23 and 24C.  Hope you see my logic?

Your thoughts please on what I should set.

@jamespa 

Looking at setting up the weather compensation.

I know from the building that 32C is fine for temperatures below 0C and 5C.  But don’t know much about the lower end.

From my temperature probes attached to the pipes:

Flow is typically 32C

Return is typically 27C

I know from last year, it didn’t like anything below 29C in milder conditions, kept short cycling.

Not sure how this 4C Thermo Off rule is going to like this.  So if we set a flow of 30C then Twi into the exchanger will be 25C (delta 5C) heating will not come back on till Twi 21C.  The floor is typically between 23 and 24C.  Hope you see my logic?

Your thoughts please on what I should set.

Its impossible to be precise but based on the above I suggest something like

35 @ -5

23 @ whatever outdoor temperature you dont need any heating, 

I really wouldnt worry about cycling at this stage.  Once its more or less right we can consider options (of which there are several)

The 4C thermal off rule is very likely going to interfere when its warm outside, less so when its cold outside.  I am not sure how to deal with this TBH. The whole thermo off thing isnt well explained  Here is what it says in the controller manual

And here is the corresponding bit in the IDU manual.

Thats  about as clear as mud.  What can you add to this from what hitachi told you?  I think it may be necessary to revert to 'standard conditions' and then control the cycling using the facilities on the controller to specify min on and min off times!  Alternatively it may be that the FT at any temp will have to be higher than it ideally would be, and compensated for by setting the system to run part time.  I wouldn't change this yet however, although I might take a picture of DSW5.  Can you anyway post what the settings are currently on the screen above and also the two screens at the end of the post?

@jamespa I have good news.  I now have the instructions for:

1. Thermo Off.  This can be changed to 2C or OFF.  I think I will go with the 2C option.  From my charts that will give me a 30 minute off time, which I think is much better.  This is a DIL switch setting on the indoor control panel.  I will have to have to have a engineer call to make the change.
2. Defrost Cycle.  I want to change my defrost cycle from Default to Cold/High Humidity.  This should prevent the build up of ice and the rattling of the HP in iced up conditions.  Once again, an engineer visit to make the change.

I do at the moment workable solution, though not sustainable.  Still having to manage the heating because of power cuts as well.

Posted by: @trebor12345

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@jamespa I have good news.  I now have the instructions for:

1. Thermo Off.  This can be changed to 2C or OFF.  I think I will go with the 2C option.  From my charts that will give me a 30 minute off time, which I think is much better.  This is a DIL switch setting on the indoor control panel.  I will have to have to have a engineer call to make the change.
2. Defrost Cycle.  I want to change my defrost cycle from Default to Cold/High Humidity.  This should prevent the build up of ice and the rattling of the HP in iced up conditions.  Once again, an engineer visit to make the change.

I do at the moment workable solution, though not sustainable.  Still having to manage the heating because of power cuts as well.

That all sounds good.  Basically two switches to flip.  Will the engineer visit for free?  Its going to take all of 10mins including taking off and replacing the casing.  Perhaps you can make a list of questions to ask him!

@jamespa No its a chargeable visit.  So be at least £200.

@trebor12345 Yikes! £100 per switch flick!!!! 😳 Toodles.

Posted by: @trebor12345

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@jamespa No its a chargeable visit.  So be at least £200.

Wow thats a lot, I think Id be flipping the dips myself! 

I hope it all works out in the end.  It should but as previously stated I cant guarantee.  That said I cant see you have a realistic alternative.

When the engineer is present you might quiz him about whether Hitachi insist on a buffer tank.  It just complicates all sorts of things and you already have an enormous buffer, namely your slab.  Without it you could use the system for light cooling in summer as well!

You could also ask him if its easy to change things so that the secondary pump comes on only when the primary does.  This probably requires a wiring change depending on how its currently wired.  For £200 he can afford to give you a tutorial! 

Posted by: @jamespa

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Posted by: @trebor12345

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@jamespa No its a chargeable visit.  So be at least £200.

Wow thats a lot, I think Id be flipping the dips myself! 

I hope it all works out in the end.  It should but as previously stated I cant guarantee.  That said I cant see you have a realistic alternative.

When the engineer is present you might quiz him about whether Hitachi insist on a buffer tank.  It just complicates all sorts of things and you already have an enormous buffer, namely your slab.  Without it you could use the system for light cooling in summer as well!

You could also ask him if its easy to change things so that the secondary pump comes on only when the primary does.  This probably requires a wiring change depending on how its currently wired.  For £200 he can afford to give you a tutorial! 

 

I could do the change, I do have an electronics background.  But due to health reasons, I am just not confident in doing such things.

He does have to travel an hour to get here.

Posted by: @trebor12345

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Posted by: @jamespa

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Posted by: @trebor12345

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@jamespa No its a chargeable visit.  So be at least £200.

Wow thats a lot, I think Id be flipping the dips myself! 

I hope it all works out in the end.  It should but as previously stated I cant guarantee.  That said I cant see you have a realistic alternative.

When the engineer is present you might quiz him about whether Hitachi insist on a buffer tank.  It just complicates all sorts of things and you already have an enormous buffer, namely your slab.  Without it you could use the system for light cooling in summer as well!

You could also ask him if its easy to change things so that the secondary pump comes on only when the primary does.  This probably requires a wiring change depending on how its currently wired.  For £200 he can afford to give you a tutorial! 

 

I could do the change, I do have an electronics background.  But due to health reasons, I am just not confident in doing such things.

He does have to travel an hour to get here.

Fair enough.  I recommend quizzing him to get your money's worth!

It’s a long time since I’ve looked at the manual but I thought I remember Thermo off just controlling any secondary circulation pumps?

I’ve spent hundreds of hours in those Hitachi config menus - happy to help if I can

May not be relevant but my Hitachi system was a ‘package’ supplied by Freedom Heat Pumps. This included a buffer, several mixing valves and Heatmiser room stats.

My system would suffer two daily faults - outside unit high pressure and inside unit low flow (11kW Yutaki split)

These are things I had fixed/replaced:

Refrigerant incorrect for length of pipe run - re ‘gassed’ by air con engineer 

Primary pipe work undersized - new larger diameter pipework installed 

Buffer tank repurposed as a volumiser to help with defrost cycles

Mixing valves  and Heatmiser actuators removed to create an ‘open-loop’ system

UFH manifolds balanced to better balance room to room temperature differences

I then spent days/weeks/months learning and experimenting with the controller settings to get a stable indoor temperature year round

My system could be further improved by relocating the controller to the middle of the house and combining the room stat feature with the weather comp

The issue I have is Hitachi customer service/tech support doesn’t exist in the UK so if my Hitachi fails (as it just has) there is nowhere to go for help 

it’s a shame as the kit itself and the features available in the controller seem very good.