Im just going to jump in here and defend the Samsungs control system. Whilst it is basic and may lack some of the more sophisticated options like a different WC curve for setbacks, I have to say I much prefer it to Vaillant which seems to me to be over complicated and unintuitive. Why they felt the need to invent different preset curves when you can just set min and max flow temperatures is beyond me. My brother in law who has a Vaillant cant get his head around it and leaves well alone.

Posted by: @bontwoody

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Im just going to jump in here and defend the Samsungs control system. Whilst it is basic and may lack some of the more sophisticated options like a different WC curve for setbacks, I have to say I much prefer it to Vaillant which seems to me to be over complicated and unintuitive. Why they felt the need to invent different preset curves when you can just set min and max flow temperatures is beyond me. My brother in law who has a Vaillant cant get his head around it and leaves well alone.

Obviously its a matter of opinion which is easier, however the strength, as I see it, of the Vaillant is that once you have chosen a curve you can dial a 'room temperature' up or down and under the hood it changes the curve.  Likewise you can timetable a setback to room temperature or increase in room temperature and again under the hood it changes the curve.  Several other Samsung owners have said thats not possible with the Samsung unless you invoke the room temperature sensor, which doesnt in fact change the WC curve it switches the heat pump on and off (ie its less efficient).  The upshot of this is that you can operate the Vaillant fully on weather compensation and have programmable increases or decreases in flow temperature eg for night time setback or to take advantage of ToU tarrifs.

I think Vailant's concept (actually I dont know its theirs - several other manufacturers use it) is that the installer sets the curve and then all the homeowner has to do is dial in a temperature profile, something which every homeowner is used to.  I don't know of any home owner who is used to setting 4 points on a WC graph, other than someone with a heat pump, which is very few people.  Obviously whether this is easier or not than the 4 point approach when you first set the WC curve is a matter of opinion but, unless you tell me otherwise, the extra capability is real.

Its probably worth adding that I didn't really understand it (or see the point) until I got one, then the penny dropped as to why they had gone this route and what advantages it had.  Even my wife can tweak the house temperature (by the 0.5-1C that one wants from time to time) even though we are operating on pure weather compensation.  I dont think that would be realistic with a 4 point system, she is bright but not particularly techy!

@jamespa You are right James that the Vaillant is a more sophisticated beast, but it does come at a significantly higher price point. I would indeed like to have the facility to alter the WC curve on the fly!

Perhaps the 4 point system appeals to me because I view it from a science background, though I think that if UK householders had gotten into using WC with gas boilers a lot more would be familiar with it 🙂

As has been pointed out previously though, system design is much more important than the make of heat pump. My brother in laws Vaillant struggles to get a SCOP of 3.2 whereas mine is 4.3 with a much higher indoor temperature.

To be fair I think either would be a good choice for the original poster.

Posted by: @bontwoody

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@jamespa You are right James that the Vaillant is a more sophisticated beast, but it does come at a significantly higher price point. I would indeed like to have the facility to alter the WC curve on the fly!

... Certainly with the quotes that OP has so far shared.  Unless they can get a better quote for the Vaillant, then Samsung plus homely (to give a friendly UI to altering WC on the fly) looks like a good bet!

Posted by: @bontwoody

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I think that if UK householders had gotten into using WC with gas boilers a lot more would be familiar with it 🙂

Maybe, although another angle says that many of the European manufacturers have adopted the same scheme as Vaillant, and Im guessing thats because they sell boilers in countries where WC has been mandatory for a long while and thus have, over the past 20 years, found a way to present it that (they think) is more user friendly.  So if we had gotton used to WC with boilers, its quite likely it would be the Vaillant style interface.  

@eliuccio  Hi. Firstly, I am not associated with any commercial “Heat Geek” of the same name. I am a private individual with a Samsung Gen 4 for the past 10 years. My prognosis will be different to what most others will advocate but you can choose for yourself after talking to your installer. Your situation is a no brainer. Look no further than the Samsung R290. The quote does not specify the model (it must) but I assume it is AE050CXYBEK. The Samsung has the latest natural R290 refrigerant, if you are environmentally conscious. Others have R32 which is being phased out in 2026. Secondly, the Samsung has a built-in variable flow PWM pump which adjusts the heat flow according to demand. This means that you can put a thermostat to CONTROL the lounge and kitchen as the master zone and have TRV’s on 2 bedroom radiators. Leave bathroom radiator open. The Samsung will turn the flow down when the TRV’s turn off. The master zone heat loss is close to the minimum output of the Samsung. Steer clear of the Vaillant. It is a constant flow device.

The HP should be directly connected to the radiator circuit. Its pump head should be plenty sufficient for this unless you have very thin pipes. Because of the variable flow control, you can run the static Samsung WC curve adjusted for radiator non-linearity. The quote includes a buffer tank and second pump. You do NOT need this. The 25l buffer tank should be connected as a 2-port volumizer instead and the second pump ditched. You should rather spend money on getting new radiators as big as possible if you have the space. The difference between 50C water temperature and 40C water temperature is 20% on running cost. A 150l water tank is rather small unless you are happy with this. Note also that the Samsung has 4 level silence mode with lowest level of 35dB (very quiet). As the HP is larger than you need, using silence mode also derates the power output of the heat pump so is also a way of turning down the power output to 65% minimum without (I presume/hope) compromising efficiency. Ask your installer (if he knows). It will also keep your neighbours happy.

Just keep it simple. You don’t need something to fiddle with. I hope that this gives some food for thought.

@eliuccio

Unfortunately, whilst I agree with a lot of what is said above, I dont agree with all of it.  For clarity:

Firstly

Posted by: @heatgeek

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Look no further than the Samsung R290. The quote does not specify the model (it must) but I assume it is AE050CXYBEK.

Whilst I agree that this model may well be a good choice, best check whats being offered carefully.  The R32 Samsungs are still very much around, very much cheaper and definitely still being fitted just from the posts here.  I wouldn't assume that's what you will be getting unless it expressly says so!

I should add that Im not sure there is anything wrong with the R32 models, but they look very different and @eliuccio seems to have a view on them, which I cannot comment on

Posted by: @heatgeek

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This means that you can put a thermostat to CONTROL the lounge and kitchen as the master zone and have TRV’s on 2 bedroom radiators. Leave bathroom radiator open. The Samsung will turn the flow down when the TRV’s turn off. The master zone heat loss is close to the minimum output of the Samsung. 

Whichever you get please DONT do this unless you want to spend more running the system than you need to.  Instead (unless you get Homely) turn the thermostats and TRVs up to maximum and adjust the WC curve until the house is just warm enough.  Having done this you can then use thermostat/TRVs as temperature limiters but not as temperature controllers (unless you want to pay more than you need to). 

Posted by: @heatgeek

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Steer clear of the Vaillant. It is a constant flow device.

There is only limited evidence to support the comment and absolutely no evidence to support the suggestion that its detrimental.  Of the top 25 air source heat pumps on heatpumpmonitor.org, 18 are Vaillant and 1 is Samsung, so whatever design choices Vaillant have made, they appear not to be negatively impacting performance!

Posted by: @heatgeek

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The HP should be directly connected to the radiator circuit. Its pump head should be plenty sufficient for this unless you have very thin pipes.

Completely agree

Posted by: @heatgeek

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The quote includes a buffer tank and second pump. You do NOT need this. The 25l buffer tank should be connected as a 2-port volumizer instead and the second pump ditched. You should rather spend money on getting new radiators as big as possible if you have the space. The difference between 50C water temperature and 40C water temperature is 20% on running cost.

Completely agree and I would go even further than dont need, you dont want a buffer tank because it is detrimental to the operation of the system  2 port volumiser and no second pump

Posted by: @heatgeek

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Just keep it simple. You don’t need something to fiddle with. I hope that this gives some food for thought.

Completely agree, hence my suggestion to consider (its not essential) a Homely in addition to the Samsung (and instead of any other external controls) which others here have reported makes it particularly simple to operate efficiently and in a user friendly way, or the Vaillant because its natively simple to operate (but only if you can get it at a sensible price). 

For clarity I am not connected to Homely and don't have one.  I am not connected to Vaillant but do have one.  I don't have a Samsung

Thanks everyone!

So far I only received a response from Sustain and Smart Heating. The latter should be sending an updated quote for a 45C system.

Sustain came back to me with the following:

"I'm not familiar with the modulation range of the Samsung unit. Can you advise?

Larger radiators will enable lower flow temperature and higher efficiency with any heat pump. We design to 45/40 by default, but can design to a lower Flow/Return temperature upon request."

I reckon it may be possible to ask them for a Samsung+Homely system but I am not so sure of how big I could make my radiators. Perhaps I can ask them to advise based on their survey data?

Cheers!

E

@eliuccio some people fan assisted radiators to good effect to get extra output. They are expensive but there are diy options which aren’t.

@eliuccio  Hello again. It is not a surprise that some installers do not know that heat pumps modulate. Some control temperature only whilst a few control temperature and water flow together (the proper way). Samsung is a good, reliable brand but they are awful at explaining how their units operate. One has to interpolate things often. According to their specification and circuit diagrams, the Samsung R290 Monobloc now has a PWM pump integrated. PWM pumps normally modulate water flow rate under control of the HP. Older models did not have a pump inside. Ask your installer why there is a PWM pump inside and what is it for? If for control of water flow, what is the modulation range? If he doesn’t know, he must get it from Samsung. It is fundamental.

Radiators are a crucial element for long-term running cost. Get as big as your budget and space will allow. As @bontwoody points out, there are even fan-assisted solutions to boost output. As for open loop, WC, etc, I did warn you that there would be disagreement. It is an issue that has to be resolved separately. In a compact house like yours, there will be other sources of heat variation, e.g. friends coming around, cooking in the kitchen, solar gain, sudden change in outside weather, showering, etc. This needs effective control. If it is confirmed that the Samsung does indeed modulate water flow (effectively turning power/flow up and down according to demand), this should do it. Relying on “over-heating” cut-off and fiddling with curves constantly doesn’t crack it, in my opinion. It’s your choice, however. If your installer is any good, he should be advising you of the options.

Posted by: @eliuccio

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So far I only received a response from Sustain and Smart Heating. The latter should be sending an updated quote for a 45C system.

 

Excellent

Posted by: @eliuccio

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Sustain came back to me with the following:

"I'm not familiar with the modulation range of the Samsung unit. Can you advise?

Well they should be, its in the data sheets (or at least it should be in the data sheets).  Can I ask what prompted them to say this?  Did you ask the specific question?

Posted by: @eliuccio

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I reckon it may be possible to ask them for a Samsung+Homely system but I am not so sure of how big I could make my radiators. Perhaps I can ask them to advise based on their survey data?

Homely/not Homely and size of radiators/flow temperature are two completely separate questions.  If Smart heating come back with a 45C design it will specify the radiator sizes for that FT and they are independent both of Homely and the brand of heat pump. 

The choice to fit Homely or not is purely one of convenience/flexibility of control as the Samsung controls are not quite as easy to operate efficiently/as flexible as some other models (but many people are happy with them nevertheless).  

Posted by: @heatgeek

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If it is confirmed that the Samsung does indeed modulate water flow (effectively turning power/flow up and down according to demand), this should do it.

This is, Im sorry to say, a red herring based on a misunderstanding, as is some of the rest of the paragraph in which it is to be found.

Every heat pump commonly available can be operated on pure weather compensation or with a room temperature sensor/thermostat switching it on and off.  Most include such a sensor in their control unit!   Every heat pump commonly available adjusts its heat output to match the demand from the house, unless the demand is too high (ie its undersized) or too low (this used not to be the case prior to inverter driven compressors, but they are now universal).  In the case that the house demand is too low case every heat pump will match the demand on average by cycling on and off.  UIn summary bothy control strategies discussed can be used effectively with any heat pump.

As to which control strategy is better, it depends on the house construction, the activities within and things like how strong solar gain/wind factor is. 

Many find pure WC works well, in the sense that it maintains a very steady temperature over a very wide range of conditions without any fiddling at all.  Contrary to popular belief in the UK its not 'new' technology or specific to heat pumps, its been around for decades and has been mandatory for boilers in some European countries for some while.  If it does work well then its going to be the cheapest way to operate unless you have a ToU tarrif, in which case you may want to adapt a bit. 

If pure WC doesn't work well for some reason then an element of room influence may help, but equally it may not.  The problem with control based on room influence is that the house has a time lag in its response, the heat pump only finds out about it after the fact, and may thus not be able to correct.  Different houses behave differently, and so it may or may not work or may work to a different extent, depending again on the factors above.  Some of the more sophisticated controllers learn about the house response and adapt, and homely can even take into account weather predictions (but this requires a subscription).  However even they cant predict when you cook!

@jamespa I asked Sustain if the Samsung was be able to accommodate the heat flow adjustment according to demand.

I understand better now that the radiators size is quite a crucial variable but I feel I will have to be advised on that based on survey data/assessment.

@heatgeek Sustain just replied that they are "not in a position to advise on the internal working of the Samsung heat pump as this is not one of our core brands. To upgrade form the Baxi, I would propose a Vaillant heat pump as this is a more advanced unit with better controls".

So I guess I am left with Vaillant unless 21degrees will come back with their updated quote.

Cheers!