Install of a largish MyEnergi Libbi battery

[nowty]

The radiators are specially designed to work with heat pumps, hot and cold flow, and have a heat exchanger and hybrid fan within the radiator casing.
They also have less water content which helps the flow around the heating system.

Can you link to spec /website.

Ahh fan assisted ones, yes they do work.

https://www.kensaheatpumps.com/wp-conte ... ors-V2.pdf

If Kensa say they work, I believe them.

But I would not have them, not enough thermal mass for me.

[Krill]

Yeah, please do not think that I'm saying the radiators (should) have a smaller surface area. I'm absolutely not saying that, I was just describing the linkage between the heat pump itself and the radiator. There is nothing stopping a radiator having a large surface area but a small capacity for water storage.

After all, if there is three times the water in the radiator system in a conventional system versus what Yuff has had installed, then it takes three times as much energy to heat that water to whatever temperature is desired (doesn't matter what the differential itself is, the volume of water is the only variable). That's just basic physics and I don't see how that point is itself arguable.

Lower inertia in terms of heating up the heat transfer agent ie the water because there is less of it. The ASHP needs to use less energy to heat up the entirety of the water in the system, to X degrees c to create the temperature differential that then heats each room. The downside is that when the AHSP switches off, there is far less energy in the system so it stops warming the radiators/floor quicker than the system with greater water content.

So faster to heat, uses less energy, but quicker to cool.

The principle makes sense to me, but its not energy saving at all, in fact probably the opposite as cycling often isn't good. Also normally you would not cycle an ASHP so isn't really logical/applicable for the use.

I have no idea what sort of energy savings Kensa quote, and frankly I don't understand all of the physics, but I think one element of it is that when the heat pump turns off there is less energy invested into the system that is "wasted", but then that is more of a user issue ie at what point should the radiator be turned off. ie I agree that I would not expect there to be an energy saving. I suppose a more important point is that we don't have radiators taking up all the wall space and hence it is easy to retrofit?

[Yuff]

The radiators are specially designed to work with heat pumps, hot and cold flow, and have a heat exchanger and hybrid fan within the radiator casing.
They also have less water content which helps the flow around the heating system.

Can you link to spec /website.

https://jaga.co.uk/wall-mounted/strada

[Swwils]

You'd still need the same flow to the radiator. It just emits more since it has fans thus will be smaller than an equivalent regular rad.

The rad system volume is kinda meaningless when you are pumping 5L a second.

[Ken]

This is all about balance of HP output, distribution capacity, heating requirement. The one that is least up to the job is the limiting factor. As eg huge HP, huge heat demand but piddling emitters then the problem of emitters needs to be addressed by upping water temp, upping emitting capacity by larger rads, fan rads,underfloor etc.

The problem with most HP systems is they are not in balance and this is often but by no means always due to the emitters capacity due to the installer trying to show a lower price or the customer wanting the cheapest and the boss not wanting to see bigger rads and the upheaval.

Fan assisted rads have there place by reducing the size and hence wall space etc. Water capacity is largely irrelevant it is the emitting capacity of the rad. Initially the HP is flat out and initially is the limiting factor and after a while the limiting factor will become the emitters.

but for me this is irrelevant as a HP system should be kept on more or less 24/7 at the lowest water temp poss and if not 24/7 turn the flow temp down so it is.

On start up the HP is at its max given output and that is the max amount of energy that can be delivered around the house, depending on the actual output of the emitters and the heating requirement as to how qickly they will reach stable steady state conditions and not the quantity of water. You cannot change the output of the HP and emitters by changing the volume of water in the system.

[Yuff]

Our radiators needed to be changed for either larger ones or the Jaga type ones - which we went for. The cooling function was quite an incentive to go with Jaga along with keeping the rads the same size.
The radiators we had, which have now been removed, did not work very well as they were designed to work with a gas boiler and also the number of extensions to our house did not help.
Less water in the system will hopefully make it more efficient.

[Tinbum]

Less water in the system will hopefully make it more efficient.

I'm sure it wont. Most ASHP systems use buffer tanks- which tells you a lot.

[Swwils]

A decent system will have no buffer at all.

[nowty]

Better to design your system without a buffer tank (like mine), as a buffer tank is a permanent step change of inefficiency because the buffer tank, and therefore the flow temp will be higher than the radiator temp.
https://www.kensaheatpumps.com/wp-conte ... els-V1.pdf

System Efficiency
If not designed correctly buffer vessels can be a cause of inefficiency, due to extra water pumps, heat losses and the possible requirement for running the heat pump at a higher outlet temperature.

[Tinbum]

If not designed correctly buffer vessels can be a cause of inefficiency, due to extra water pumps, heat losses and the possible requirement for running the heat pump at a higher outlet temperature. [/i]

I'm certainly having a buffer tank in my system. I want to be able to run my ASHP at the most efficient times.