Passivhaus Under Floor Heating & Water Supply

[JohnMo]

Worry when a plumber doesn't know a standard plumping term - UVC is an unvented cylinder.

 

The black unit will be a low loss header. There because you have lots of zones, adds inefficiency to the system generally as it elevated running temperature. It shouldn't be allowed to heat water directly via an immersion as will start to cost lots to run.

 

Good he found some things to fix.

We run our UVC at 50 degs. It ends up charging once or twice a day.

 

Your WC curve looks high for a passive house with UFH, but that maybe due to the low loss header and mixing that occurs within it. So possibly loosing around 0.5 in CoP because of it.

 

 

[Carpe Diem]

Yes, TLA's are the devils work.
I have attached a pic of the black unit.

 

Not good that it adds inefficient.  Any suggestion on how to change this or how they could/should have done?
He definitely said that it does not take the heated water from the HW cylinder so it must have an emersion heater in it.

They are going to look at introducing a small cylinder just for the UFH but he said to wait and give it a few weeks or months first and see how we get on.
By which point... winter will be over of course so no heating likely.

Ref the CoP and curve; he said to start it off as recommended and if the house is warm..... reduce the curve every few days.
Generally, I tend to find the house is too warm in the bedrooms in the bedrooms of an evening.

 

[JohnMo]

That is a low loss header.  You basically need it or a buffer (same thing but bigger volume) because you have zoned your house in to small volumes. One or two zones only, you could delete it all together.

 

No heating element so all the heat is coming from the heat pump, which is good.

[Carpe Diem]

But that then means that if, for example, one room is calling for a tiny amount of heat (2% valve open) that the heat pump runs.
What I am seeing from the Loxone app is that the heat is called for frequently in small amounts to maintain the temperature of the slab, which I presume helps with efficiency.  But, is this not bad when it keeps calling the heat and short cycling it?

[JohnMo]

13 minutes ago, Carpe Diem said:

But that then means that if, for example, one room is calling for a tiny amount of heat (2% valve open) that the heat pump runs.

Heat pump possibly just short cycles produces next to no heat and consumes a bucket of energy.

 

Example my house is not passive (not a million miles off, but leaks heat faster), its 8 degs outside, misty and raining, so no solar gain, my heating has been off for 7 hours and is unlikely to kick on, until after midnight. House temperature has not changed more than 0.1 degs so far.  

 

Your house floor just needs to charged once per day and then switched off (act as a storage heater) or a proper WC curve and run all day on a fully open system.  But I find running flat out for a number of hours is way more economical than running all day or lots of stop starts.

 

Been there had thermostats everywhere, and I started to actually monitor what was going on, after my first winter bill being twice what I expected.  Stripped more and more equipment out and monitored energy usage.  The simpler I got the more efficient I got. If a room is a bit cooler than I like I open the room door and its same temp as everywhere else 30 mins later. Went from 7 thermostats to 1.