@derek-m that is precisely what the evohome system does. every room is a zone. we don't have all zones on at the same time - only the ones that needs heat, which is usually less than half of them.And the system spends plenty of time off, so I know the average heat demand is way lower. (I also monitor it at the meter).

however, worst case MCS scenario, if I've bought a 14kw heat pump, I do want to be able to get 14kw out of it if the house needs it!

also re the brands and DT settings - I'll try and RTFM for the major ones to see if its mentioned

Posted by: @editor

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I believe that @grahamh has just had one installed at his home. Sounds like a very interesting unit.

@grahamh how is the new Samsung unit? Are we likely to see a review of it any time soon? How does it compare with the other heat pumps of this generation for efficiency, noise, etc, in the field?

@olly there is a technical issue with it not being on the mcs yet, i think its supposed to be on in December, after that reviews will pour in. But from my experiences so far its peerless. Stupidly quiet and hot as hell. everything else is so last year.

@grahamh, and I assume the running costs are reasonable/competitive?

Hi @grahamh Just a bump on this topic, as we are looking at the Samsung GEN6 v the new Samsung HT. Space/Noise are no issue for us, nor is the high temps as we are a new build with over the odds insulation.

The HT is £2k extra, so I am trying to understand what differences there are vs paying for the newer unit which only upgrades feature we don't use. Unless it is materially more efficient, ill stick with the GEN6!

@andehh the Samsung EHS Mono HT has a more complicated refrigeration system with intercoolers to stop the refrigeration circuit cooking itself for high temperature hot water delivery. Why Samsung used R32 refrigerant on a new product is a mystery, probably as the domestic a/c and heat pump industry has centred around that. R32 is subject to environmental greenhouse gas EU draw down on refrigerant quantity placed on the market, legislation the UK also signed up to post Brexit. Manufacturers will need to transition to using [probably] R290 propane, but Samsung et al make products for a world market and all are rather slow to react.

Consider the CoP of the units 4.42 (?) for the GEN6 vs 5.11 for the EHS HT model. EHT has, on paper, 15% lower running costs. Work that out over the life of your ASHP unit, based on the kWh your MCS or similar calculation predicts you will consume annually for CH and HW, you may find the payback on the extra £2k is reasonably quick, thereafter you're saving cash. Bear in mind also energy costs are only going to rise for the next 2-3 years.

Gen6 is small enough to slip in under PD, the new HT mono or HTQ, whatever they call it is larger than 0.6m2 so needs planning.

Thanks very much both!

The sizing and planning are fine for us, we have permission for one to be installed and plenty of space for where it will go. 

It's more the actual benefits of the HT V GEN6. The engineer in me knows as products get designed to meet singular extreme capabilities other areas can be compromised in the pursuit... I just don't want to fall into a trap with this unit.

the HT also isn't in the MCS database, so can only rely on Samsung stated Cop....can these usually be trusted? Thank you! 

Posted by: @andehh

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the HT also isn't in the MCS database, so can only rely on Samsung stated Cop....can these usually be trusted?

If you search for "EHS LNHT" in the MCS Product Directory it is present but is a bit harder to find. There are combinations for (heating, heating and cooling) x (MIM-E03EN, MIM-E03CN, Samsung Climatehub tank).

Posted by: @iancalderbank

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whereas a wider DT of just 7 drops the flow rate needed to 28.4 l/min and it becomes feasible in 28mm copper, and the nuance that I'm considering to split it into 4x 28mm plastic  (2 per direction, half the flow rate per leg) to go through the "wiggly under roof valley shortcut" currently used by the boiler primary (which is in 2x 28mm plastic), becomes feasible as well, and all of a sudden it becomes quite do-able..

@iancalderbank. In a recent post @heacol stated that the ideal DT is 8 degrees C, so it may be worth asking him if the Panasonic heat pumps that he fits are set to this DT and whether the flow rates are reduced as a result.

@iancalderbank  I am not sure if the new Samsung will allow the setting of the Delta T (gather you can install a PWM pump on it), I install the Panasonic unit which has the facility to set it to what you want. Heat pumps work best with a delta T of between 5 and 8, but up to 10 only has little effect on performance. However, if you do not allow the heat pump to control the system and house temperature, you may as well install a Gen 1 Samsung unit as you will get a similar SCOP. 

Heat pump performance is influenced more on how you control the flow and return temperatures more than how the refrigerant circuit is configured, most use similar gasses, compressors, expansion valves and heat exchangers, therefore have similar performance.

I have done sone very interesting research on system configuration and performance, it really is surprising how system configuration and operation affects performance. Mars has alluded to it a while ago, and I will be publishing it here shortly.

The jury is out on the New Samsung unit, until I have seen some actual performance figures, in our climate and understand the control strategy, I will not comment on it regardless of what anyone says.

The Cool Energy Invertech range will modulate the pump to match a target delta-T

I need to check the manual to see if that’s adjustable.

Daikin altherma also supports a choice of target delta-T settings, one for rads, one for  FCUs, one for ufh.

Samsung gen5 has always supported a pwm primary pump, it’s just that the only instructions that mentioned using one were those from midsummer wholesale. And as the Samsung needs an external pump, and most plumbers are idiots, asking them to wire up another cable to a pump is too much complexity. As a result, most Samsung installs are with a fixed speed primary pump.