Octopus Heat Pumps

Reed_Richards

QrizB said:

Reed_Richards said:

barker77 said:

Spies said:

They put dumb TRVs on the radiators

Hmm thats a bit annoying ! 

I think Building Regulations oblige them to fit TRVs.  You might be able to pay extra to have smart TRVs but it's debateable whether these are a good idea with a heat pump.  

If memory serves, at least one forum regular has said their heat pump works best with them all set to MAX, with the temperature control mostly via lockshield valve adjustment and weather compensation.

That's what I call "hard core" weather compensation, you don't use a room (or other internal) thermostat.  I think it works best when you want your house to be exactly the same temperature 24/7.  But anything that disrupts the normal temperature of the house, such as solar gain on a sunny day, a party with a lot of people in the house, wind chill on a windy day, opening a window etc will not be controlled.  So, for example, if solar gain makes your house hotter than usual, "hard core" weather compensation won't know about this and will continue to pump the same amount of heat into your house.  If you have a room thermostat you can set it a few degrees higher than you want your room temperature to be to act as a backstop in case of sunshine but if something happens to chill the house it can take a long time for the internal temperature to recover.

A few heat pumps allow you to set two weather compensation curves and switch between them so you can at least have a night-time set-back.  My heat pump can only adjust the weather compensation curve by means of a manual setting.  I really want a night-time set-back and I also like my house to be a degree or so warmer in the evening than in the morning, so I have to use a room thermostat to achieve this.  Thus "hard core" weather compensation does not work for me and my weather compensation curve sets the target temperature a little bit higher than the "hard core" value would be so I have room for manoeuvre.  This means I have the control I want but I'm probably sacrificing a little bit of efficiency; which is what "works best" for me.    

matelodave

My 15 year old Daikin has the facility to adjust the weather compensation slope up or down up to five times a day  around the basic setting. Which means I can set it back overnight by say 4 degrees and then up a bit above nominal by say 2 degrees to reheat the place in the early morning and then back to nominal during the day with a slight uplift in the evening if we want it. The slope doesn't alter it just shifts up and down. by up +/- 5 degrees in one degree steps.

We did have zone controls on our underfloor heating, each room was separately controlled by its own thermostat but all that did was to cause the heatpump to short cycle as each room shut itself down and the system needed a bypass valve to avoid the whole system shutting down and cutting off the flow.

Since taking off all the actuators and adjusting the loop flow rates to get a deltaT of 5 degrees between flow and return and, as @Reed_Richards suggests, setting the lounge stat to work as an overheat override the whole place is so much more comfortable. It takes a bit of tweaking to set the flow rates (the loop flow valves are like TRVs but use an electric actuator rather than a wax sensor) - flow rates are set by adjusting the flow adjusters, just like you would with a lockshield valve. Its much easier to do with a radiator as its more responsive than an underfloor heating loop connected to a manifold.

The system runs at a lower temps of around 30 degrees (often less) than it did before (around 35 degree). If we do get excess solar gain then its just about self regulating anyway. If the room is warm, then as less heat gets extracted from the flow, the flow temp drops or the heatpump stops because the return water temp is too high - it doesn't keep pumping water at the same temperature all the time. Short cycling is now a thing of the past and although we do get some frost on the unit, it doesn't freeze like it used to and it dissipates almost instantly (although it hasn't been as cold this winter as some previous)

The unit idles for most of the time as its not stopping and starting like it used to, and the only time it really goes full out is when its really cold or heating the hot water.

this is quite interesting - https://www.youtube.com/watch?v=0oszaqP0TI4

Reed_Richards

matelodave said:

My 15 year old Daikin has the facility to adjust the weather compensation slope up or down up to five times a day  around the basic setting. Which means I can set it back overnight by say 4 degrees and then up a bit above nominal by say 2 degrees to reheat the place in the early morning and then back to nominal during the day with a slight uplift in the evening if we want it. The slope doesn't alter it just shifts up and down. by up +/- 5 degrees in one degree steps.

That's a really useful feature that I don't think is available on many heat pumps.  Do contemporary Daikins still allow you to do this?

matelodave

Reed_Richards said:

matelodave said:

My 15 year old Daikin has the facility to adjust the weather compensation slope up or down up to five times a day  around the basic setting. Which means I can set it back overnight by say 4 degrees and then up a bit above nominal by say 2 degrees to reheat the place in the early morning and then back to nominal during the day with a slight uplift in the evening if we want it. The slope doesn't alter it just shifts up and down. by up +/- 5 degrees in one degree steps.

That's a really useful feature that I don't think is available on many heat pumps.  Do contemporary Daikins still allow you to do this?

Dunno about the later stuff which I'm sure is easier to drive and probably more informative.

My controller is decidedly clunky, no clever multicolour animated screens, just all numbered codes, so you need the handbook handy when tweaking it.
Like most the engineering settings, including weather compensation settings and timer programming are hidden unless unlocked. The function timer is a bit of a pain especially if you want something different on different days. 

There is no remote or wifi facility either. The only readings are hot water temp, flow temp and outside temp

Alnat1

Octopus fitted our Daikin heat pump in Jan. We use the Madoka thermostat they fitted to heat to 20C with a setback to 18C overnight. You can set several more time periods and temperatures.

All our radiators have the TRVs on full and the lock shields have been adjusted to balance temperatures. We've tweaked them so upstairs is a bit cooler 16/18 rather than the 18/20 downstairs

FreeBear

QrizB said:

Reed_Richards said:

barker77 said:

Spies said:

They put dumb TRVs on the radiators

Hmm thats a bit annoying ! 

I think Building Regulations oblige them to fit TRVs.  You might be able to pay extra to have smart TRVs but it's debateable whether these are a good idea with a heat pump.  

If memory serves, at least one forum regular has said their heat pump works best with them all set to MAX, with the temperature control mostly via lockshield valve adjustment and weather compensation.

Got manual TRVs on most of my radiators. When the (gas) boiler modulates down to minimum output (3.2kW), there is a chance that if a TRV operates and takes out one of the bigger radiators, the boiler will start to short cycle.

Although inverter driven heat pumps don't have the same modulation range, being smaller capacity to start with, minimum heat output could be as low a 1kW. So TRVs could prove useful as long as minimum circulation volume is maintained.

john-306

Alnat1 said:

Octopus fitted our Daikin heat pump in Jan. We use the Madoka thermostat they fitted to heat to 20C with a setback to 18C overnight. You can set several more time periods and temperatures.

All our radiators have the TRVs on full and the lock shields have been adjusted to balance temperatures. We've tweaked them so upstairs is a bit cooler 16/18 rather than the 18/20 downstairs

The reason we went off Madoka and onto pure weather compensation was that setting Madoka to 20deg, it would run up to 21.5deg, turn off, then not come back on again untill 19.5deg.
The span on those temperature's was just too big to be comfortable.
Setting pure weather compensation allows an almost constant house temperature.

Alnat1

john-306 said:

Alnat1 said:

Octopus fitted our Daikin heat pump in Jan. We use the Madoka thermostat they fitted to heat to 20C with a setback to 18C overnight. You can set several more time periods and temperatures.

All our radiators have the TRVs on full and the lock shields have been adjusted to balance temperatures. We've tweaked them so upstairs is a bit cooler 16/18 rather than the 18/20 downstairs

The reason we went off Madoka and onto pure weather compensation was that setting Madoka to 20deg, it would run up to 21.5deg, turn off, then not come back on again untill 19.5deg.
The span on those temperature's was just too big to be comfortable.
Setting pure weather compensation allows an almost constant house temperature.

It did that at first but I fiddled with the heat curve and lowered it until the thermostat never went much over 20C. It gets to around 20.2 and tootles along at low power. This still allows us to have the overnight setback and set it very easily with the Madoka.

We might try full weather compensation next winter but it seems more complicated to achieve the lower overnight temperatures that way.

koru

With my new Vaillant, there are two levels of weather compensation. One, known as Inactive, only cares about the outdoor temp and the target indoor temp. The other, known as Active, adds an element of room influence, so it doesn't overshoot excessively. 

With both, the weather comp curve adjusts depending on the target indoor temp, so if you set a night time setback, it reduces the curve accordingly.

Spies

Daikin does basically the same