Octopus Heat Pumps

Reed_Richards

matt_drummer said:

I don't see any way that a third party controller could integrate with the heat pump controls sufficiently to control anything more than on or off.

I'm sure that is true for heat pumps in their current state of development.  But gas boilers can do much more sophisticated things with a third party controller because a number of boiler manufacturers got together and agreed a standardised form of control, which is branded Opentherm.  I don't see why you could not make an Opentherm compatible heat pump; I think there might even be one but if so it's the only one.  

FreeBear

matt_drummer said:

Spies said:

So can you not have weather comp and modulation at the same time? 

You can with a Madoka.

You can set a weather dependent curve for the heat pump set in the MMI.

I haven't tried it, obviously, but I am pretty certain that you can only have modulation (load compensation) using the Madoka controller with a Daikin heat pump.

I don't see any way that a third party controller could integrate with the heat pump controls sufficiently to control anything more than on or off.

There are a handful of manufacturers out there claiming to offer products to control a number of different heat pumps. Most of them are darned expensive and aimed at commercial installations. However, after doing a bit of digging this afternoon, I've come across a couple of open source projects that can control some Daikin heat pumps and possibly Hitachi & Mitsubishi models (all three appear to use an interface/protocol specified by the Japanese government, probably with their own tweaks).

Vaillant use eBus on at least one of their ASHPs, and although it is a proprietary interface, there are third party controls that can talk the language. Perhaps not everything needed for absolute control.. Then there is KNX, touted as a complete system for home & commercial building management system. Various modules exist to connect Japanese & European heat pumps to a KNX system at a price.

Quite frankly, the heat pump market is a mess when it comes to open and fully functional control. OpenTherm has a group of functions dedicated to heat pump control, and it is a shame that few (if any) use it. Until it is widely adopted, us mere mortals are stuck with either paying through the nose for manufacturer specific controls, or taking a chance that a low cost open source interface supports all the functions we need.

Bendo

Reed_Richards said:

matt_drummer said:

I don't see any way that a third party controller could integrate with the heat pump controls sufficiently to control anything more than on or off.

I'm sure that is true for heat pumps in their current state of development.  But gas boilers can do much more sophisticated things with a third party controller because a number of boiler manufacturers got together and agreed a standardised form of control, which is branded Opentherm.  I don't see why you could not make an Opentherm compatible heat pump; I think there might even be one but if so it's the only one.  

Even for gas boilers Hive is, frankly rubbish as it doesn't do Opentherm.

Using it for a heat pump that is going to require a lot more than on/off control for any reasonable level of efficiency is absolutely madness.

oliver1951

matt_drummer said:

Spies said:

What's the overshoot value set to under Space heating on the MMI?

Overshoot is normally adjustable between 1c and 4c, but may not be depending on the heat pump, the heating mode chosen and the firmware installed on the heat pump.

My 8kW required a firmware update to make the adjustment possible in radiator mode, it was locked at 1c before the update.

Overshoot sets the amount the heat pump can exceed the requested flow temperature, either a fixed flow temperature or that determined by the weather dependent curve.

There is also modulation which is only adjustable once activated and only in use if using the Madoka to control room temperature. It is adjustable between 1c and 10c and is what is known as load compensation.

Neither of these setting will change what is going on with @oliver1951

What you are seeing is the hysteresis on the room temperature control. It is 2c and not adjustable.

If the room temperature is set at 20c then the heat pump will turn off at 20.5c and come back on at 18.5c.

I don't like it and it is one reason I don't use it.

You can make it take longer to get to the required room temperature by reducing heat output but once the required temperature +0.5c) has been reached the house has to cool by 2c before the heat pump will come on again.

It's uncomfortable for me and I wanted a constant heat.

I also found it inefficient in terms of COP.

The heat pump runs less but when it is running it uses more electricity at a lower COP.

So, if you want 20c, set it to 21c, it will heat to 21.5c and come on again at 19.5c

With regard to user profile, you can adjust very little as an advanced user (code 1234). You need to go into installer settings (code 5678) to make any real changes.

Thanks to all of you for the responses. So I did get into the MMI using the installer code. I was surprised by what I found, but I may need your help for interpretation. Increase around 0c, increase 2c, span 4c. Overshoot is 4c. Pump operation mode is request.pump limitation 80% pump speed during sampling. Pump outside range - restricted.

if I had seen these earlier I definitely would not be expecting the heat pump to be operating as it is. However I am unclear how these setting are working given that I have the hive, maybe the hive just ignores them. Or maybe they don’t mean, what I am guessing they mean.

Spies

How are octopus going about installing wider radiators? Are they just extending pipes above floor level or are they cutting/lifting boards to extend it under the floor? 

mickyduck55

Spies said:

How are octopus going about installing wider radiators? Are they just extending pipes above floor level or are they cutting/lifting boards to extend it under the floor? 

My install they just extended the pipes above floor level.  At some point I will sort the ones in my living room properly as these do irritate me a little.

Spies

That's what I thought they might end up doing as it seems the easier/least disruptive way of doing it

oliver1951

Hi, I have a couple of further questions. When you talk about modulation, is that different to using varying amounts of power. I have been monitoring the usage very closely ( using my smart meter) and can see that the pump is using slightly varying amounts of power. It’s starts at 1kw for three quarters of an hour and then drops to .8kw until it reaches temperature. Not particularly subtle, but a small change. 

Second question, I note that it takes around an hour to achieve around a 0.45 degree C rise in temperature. Is that about what you’d expect. I am running from around 16c to 18.5 c. While I am trying to see how it performs. I have to set it back then otherwise it keeps cutting in for two minute cycles as I think I mentioned previously. 

Thanks

Reed_Richards

oliver1951 said:

Thanks to all of you for the responses. So I did get into the MMI using the installer code. I was surprised by what I found, but I may need your help for interpretation. Increase around 0c, increase 2c, span 4c. Overshoot is 4c. Pump operation mode is request.pump limitation 80% pump speed during sampling. Pump outside range - restricted.

if I had seen these earlier I definitely would not be expecting the heat pump to be operating as it is. However I am unclear how these setting are working given that I have the hive, maybe the hive just ignores them. Or maybe they don’t mean, what I am guessing they mean.

oliver1951 said:

Second question, I note that it takes around an hour to achieve around a 0.45 degree C rise in temperature. Is that about what you’d expect. I am running from around 16c to 18.5 c. While I am trying to see how it performs. I have to set it back then otherwise it keeps cutting in for two minute cycles as I think I mentioned previously. Thanks.

Your Hive controller will turn your heat pump on when it thinks the room where it is located needs heating and off when it thinks the room is warm enough.  It has no idea how your heat pump control settings are operating so in that sense it "ignores them".  Hive seems to have been designed for gas boilers and although it is claimed to work with other types there doesn't appear to be any means of setting the boiler type, in which case the claim is specious.

No boiler or heat pump should ever operate in 2 minute cycles (except possibly an electric boiler could cope).  But you may find it difficult or impossible to tell if these cycles are caused by the heat pump or the Hive controller. 

oliver1951

I have a partial answer from BG. I have the hive fitted rather than the madoka, because the madoka is a zero volt system and as I have a mixergy cylinder ( because of low water pressure) the madoka will not work with it. That’s me paraphrasing, but not very well. Bottom line you apparently can’t fit a madoka when there is a mixergy cylinder.