i am electrical engineer , wanting to understand heat pump schematic and how system perform.
i am in the process off having my heat pump installed. i had 3 heat pump engineers turning up with all different design.
the house is fully insulated . 165m2 heating space and 7kw heat lost. 300l new cylinder (not 3m coil). ground floor UFH, 1st floor radiator circuit, 2nd floor radiator circuit (loft)
from my reseach and what i understand. i want to install 7kw vaillant heat pump, open loop and no buffer/volumiser.
engineer1 said. install bufffer. and new tank
engineer 2. install bufffer. and new tank + zone radiator circuits
engineer 3. suggest open loop system with no buffer and use existing cylinder with plate heat exchanger .
from my research and what i understand . i want to avoid buffer and have open loop installation with balancing valve to control flow. i am not sure if i should plate heat exchange on existing cylinder as it 10 people and 3 bath. and if i use volumizer as their is plenty of volume being 3 circuit.
i have boiler room outside and all the pipework run separate . the pump can be installed on same wall.
what would be the good and high efficiency set up?
I already replied to the same question on buildhub so I wont repeat my fairly detailed comment here!
In summary Engineer 3 is the closest and may even be spot on of you are prepared to be flexible in your thinking; engineers 1 and 2 are just wrong for suggesting a buffer and shouldn’t be trusted. You need to do a bit more due diligence on your DHW consumption, DHW tank and heat pump sizing before coming to a final conclusion. The Vaillant output numbers appear to exclude defrost so you should probably derate them a bit around zero C, which may matter depending on your design temperature.
7kw was sugested by all 3 engineer. from understanding vaillant 7kw can output 9-10kw energy output at -2. i am not expert at heating but i would like believe heat geek are and they have sugested 7kw aswel.
As per above it seems from some measurements reported on this forum that the Vaillant figures don’t account for defrost, although Im not aware of official confirmation. In the UK in particular this can be significant since, unlike much of continental Europe, we are both damp and design for a temp close to zero. If the climate is drier or colder defrost isn’t really a consideration because it happens well above design temp and us the load is less. My suspicion (for which I have no evidence other than its reasonably logical) is that the better designers must know this, but also know that house heat loss surveys, certainly if they use the default ACH value, tend to overestimate so mentally trade the two off.
The 7kW Vaillant may still be suitable as I suspect, based on what you have told us, that your house is < 7kW. For comparison my 200 sqm 1930s house solid wall is a measured 6.5-7kW - about 80% of the walls are internally insulated the rest solid), good quality double glazing, 300mm loft insulation but no floor insulation. Your dhw consumption is crucial here as your requirement is unusual, so please do work that out! Also do you have any independent measure of heat loss eg gas consumption?
After doing these calculations you may decide that you either need or prefer to go up a notch. Obvious choices in the same ‘league’ are the 10kW Vaillant (double fan), the 8kW Mitsubishi (single fan, R290 has twin compressor so a larger than normal modulation depth or the 11.2 Mitsi (single fan, single compressor). There are many others of course these are only examples.
Alternatively you may decide anyway that, if you have to use the immersion on a few cold days, thats not a great penalty and the benefit that it will definitely be working at more or less its optimum running point most of the time outweighs this relatively inconvenience.