Have been trying to follow this thread, but not sure I’ve really understood it all
My HeatGeek in-progress proposal has just changed, replacing the Vaillant uniSTOR 200L with a Newark HG200A. Still looking at a Vaillanot Arotherm+ 7kW.
It’s a 4 bed/2 bath house, so understand that it needs to be sized for a potential family.
But since I don’t use much hot water, probably averaging less than 30l/day over a month, how do I calculate whether the Newark HG200A is likely to use more, or less, energy than the Vaillant uniSTOR 200L?
My Heat Geek wasn’t keen on the Vaillant uniSTOR 200L, but I’ll need convincing that the extra cost is justified. Looking at change in combined costs for parts and labour, it’s about £450 more. That could go towards OEM heatpump monitoring kit…
Of the 30L of hot water you use, what temperature is said hot water?
If you are using 30L of 60°c hot water then you will use more hot water (by volume) when it is only heated to 45°c, it will obviously be much cheaper to heat to 45 than 60°c though.
One other thing to note is that MCS recommendeds that the hot water cylinder be sized based on the houses occupancy or size (whichever is greater) as there is nothing to say you won’t need to sell at some point and the system would need to be usable by a 6 person family who all use 50L each (allowing for some reheating obviously).
If you look up ‘Domestic HW cylinder selection guide’ you will see some of the sizing recommendations made by MCS and how to calculate what you may need.
I have estimated that the water comes out of the kitchen tap is at c 45 degrees (using a jam thermometer ), and this is perfect for filling the washing up bowl, and doing a pile of dishes.
Shower has hot water feed and mixer, which I adjust a couple of times a year with the seasons.
Washbasin in bathroom ok as it comes out of the hot tap because it starts off cold, and then mixes with hotter water.
Very occasional bath (3 or 4 times a year) needs some cold adding. Guess that would use up more than one person’s allowance, but not the whole cylinder.
Also curious about the variation in temperature of water coming out of the taps. Do you have to worry about constant fluctuations in water temperature? Particularly after a legionnaire cycle?
While I’m aware that a cylinder is, if not for life then, for a generation, it also doesn’t make sense for me to be using energy to keep masses of water hot, and the HG cylinder (as well as increased initial outlay) seems to have higher standing losses than the Vaillant cylinder, so higher standby running costs as well. I can’t be the only person facing this dilemma…
Don’t forget Mick, your heat pump capacity is small 5kw??, so you can only put 5kw into that cylinder on a cycle.
All smaller capacity heat pumps will be slower heating the hot water compared to a 12kw for example. When my 12kw goes into hot water, it will try and through 12kw into my coil.
The main heat up of out tank is done at night, my rate being 0.09 pence.
This is not accurate depending on the heatpump, most with solar diversion technology have a input for a pulse meter that would be linked to the mains tails.
This allows the heat pump to modulate based on available export at the time.
I have this setup with a Daikin EDLA08E2V3 and it is setup and working as expected so I know this is an option.
Not saying all have this or that people would usually read that far to configure this but it is possible.
And buffering hot water or rooms with excess heat using an ASHP will always be more efficient than using a immersion. Just be sure to set include diverted to yes so it will trigger the ASHP correctly.
), and this is perfect for filling the washing up bowl, and doing a pile of dishes.