Heat Pump Setup - Multiple Zones or Single Zone + TRVs?

ixoy

Have a relatively small bungalow build (~100 sqm) being set up with a heat pump system (insulation being completed first). Current gas boiler system is 2 heated zones (bedrooms / living area). Both setups will use radiators.

As we don't use certain rooms at the weekends (office) or during the day during the week(a gaming room, bedroom) I had thought more zones would make sense - why heat rooms not in use? why not have finer grained control ? - but the design is specced for 1 heated zone + use of TRVs. This seems to be a fairly standard setup for heat pumps in Ireland I think? The logic is that it's more efficient to just have one zone and use TRVs in a couple of rooms instead. The TRV would be responsible for ensuring the bedroom is not too warm, for example, rather than a specific thermostat attached to a zone. We're not over drawing power using a single loop (it seems) and I might be stuck in an older gas-boiler mindset.

Have others gone through this single zone approach + TRVs and found it fine (and efficient) over multiple zones? TRVs obviously have an impact too on efficiency but (from what I can gather) less than the draw required with multiple zones. Trying to get a balance between costs of running a heat pump and comfort and this is something I need to get sorted at the beginning.

TerraSolis

Heat Geek in the UK are basically the special forces of hydronic heat pump systems - they say don't zone, no TRVS. Tune your emitters properly.

Their YouTube channel is here:

https://www.youtube.com/watch?v=zpTVIeUh04E

graememk

What you are suggesting will work and the one zone + TRV as temperature limit not a target.

What you should be aiming for is the main open loop of your house (say kitchen, living room, hall) to be more than the minimum output of the heatpump so it runs low and slow and doesn't have to turn itself off.

ixoy

So Heat Geek seems to make the argument multiple zones (with different temperatures) is less efficient due to heat loss between "on" and "off" rooms/zones, so the heat pump has to over-compensate for the heat differential.

Assuming his maths is correct (I'm no way qualified to dispute it either way), there's also a question of comfort. A TRV in a bedroom at least allows for lower temperatures - I want to sleep and not be baked at the standard 21c.

So is a smart TRV any better/worse than a zone (as I can fit TRVs at a later stage rather than committing to zones from the outset).

JayBee66

This is what confuses me and is highlighted by the HeatPunk website app.

Turning down radiators makes radiators in other rooms work harder because they are trying to heat the unheated rooms too.

Is it better to have the whole house at the one temperature or can you have the living at 20C in the evening and the rest of the house at 18C without a drop in efficiency?

I should play around with different radiator sizes on the HeatPunk site but it would be nice to get it straight in my head so that I understand the end goal.

graememk

I am doing something like it, more of my own curiosity and tinkering with things.

I'm heating my living room to 21, hall & kitchen to 20. Rest of rooms at 18, generally don't look for heat unless really cold outside or not much other heat in the house. (Bungalow, hall has no direct exterior walls)

Bathroom rad is open, just balanced, take whatever heat they are given.

Flow temperature currently at 50c. All doors are generally open in the house.

Hall gets to temperature fairly quickly. Living room does be looking for some heat most of the evening.

Cop is currently sitting at 3.3-3.5 with the above flow. Heatpump compressor has slowed its output to match the heat demand.

The real balance is more heat spread out everywhere but at a higher efficiency (lower flow temperature) and possibly use more or focus the heat to have one warm room for the evening, higher flow temperature, lower efficiency, possibly less overall requirements.

I have played with pushing the hall higher and have seen the living room not calling for as much heat.

Only issue with the smart trvs is that they over estimate on how hot the room is when heating. The temperature probe is on the trv afterall.

When not heating it's pretty spot on.

ixoy

https://www.boards.ie/discussion/comment/121975917#Comment_121975917

So can you say what is your mixture here in terms of zones + trvs?

I'm getting the impression there's no "right" answer here, especially once people start tinkering to optimise.

graememk

https://www.boards.ie/discussion/comment/121977257#Comment_121977257

One "zone" all rads on smart TRVs. (Tado)

I have a large buffer tank (heat battery), but I can choose to bypass it.

My monitoring, (room temperature is buffer tank)

https://emoncms.org/app/view?name=EcoAir&readkey=82a75750e2f56ccdc7e96768b9776268

ixoy

https://www.boards.ie/discussion/comment/121977310#Comment_121977310

Thanks. So somewhat what I was thinking. Tado seems to allow you to simulate zones too. Were you able to fit them yourself or did you need a plumber?

And what purpose does the buffer tank serve? Never saw it offered.

graememk

https://www.boards.ie/discussion/comment/121977404#Comment_121977404

Yeah myself, not a plumber but fairly handy.

Buffer tank is currently a heat battery(it's a 500L tank!), heat it on night. I had that for a year and a half before the HP as sorta an electric boiler, that I heated via immersions on night rate (was cheaper than oil per kWh!)

Tado yes can simulate zones but doesn't really work with heatpumps. I've made it work through extra automations etc.

If I was in your position I wouldn't bother the buffer, simple always open zone on a thermostat, trvs to limit the bedrooms to whatever you want.

I am working on making mine simpler but that still is a work in progress (I also have to change my logging to show DHW heating)

JayBee66

https://www.boards.ie/discussion/comment/121977639#Comment_121977639

A few questions…

Are your radiators fed by the 500 ltr buffer tank?

What is the temperature of the water flowing to the radiators?

Does the buffer tank handle hot water for the kitchen and bathroom too?

If so then does the heat pump provide 60C+ water or is there an immersion heater topping it up?

Thanks.

graememk

Are your radiators fed by the 500 ltr buffer tank?

Yes, it's directly plumbed into the heating water, it is the heating water.

What is the temperature of the water flowing to the radiators?

Depends on how hot the water is 😂, but about 50c. When running directly that's what it is set to on the heatpump. When heating DHW It could go as high as 80 I think but I tell it, it can go to 60, never pushed it that high though.

Heatpump is currently handling the DHW directly, the buffer can heat the DHW tank but unless it's at 60 odd it's not great. DHW is a separate tank in the house, buffer is in the garage.

Before heatpump and heating with immersions. I had a thermostatic mixing valve on the output so the 70+ water got mixed down to 45-50c.

Haven't used any oil since march 22 when I ran out, although did use a lot of solid fuel which has drastically reduced (practically nothing since Feb).

I did swap out a 1600mm double rad in the living room with a 1800, as it was also blocked up a bit.

Heatpump can hit a COP of 3 with a water temp of 55, air 7c

Increase the air or decrease the flow cop rises.

Will never beat a R32 at low flow temperatures but sure can at high temperatures.

It will never be cheaper than turf. And now well into spring I'm generating more and more solar.

JayBee66

https://www.boards.ie/discussion/comment/121981004#Comment_121981004

Thanks for that.

If you increased the size of your radiators (at great cost) would that lower the flow temperature and increase the efficiency?

graememk

By increasing the radiators (or pumping the walls) I'd reduce the heat loss and would be able to lower the radiator temperature.

Measuring the room temperature of my living room via the wall thermostat from tado and an IKEA air sensor and when idle watching TV at 21 it's a bit chilly, but at 22 it's nicer.

Other option is push the hall to the same as the living Room.

One of the rads in the hall is only a single panel, wouldn't be too hard to double that one up.

Next step is to maybe run some weather compensation.

ixoy

Thanks for all so far.

I suppose the big question is how bad are your bills? This is the main thing I fear despite the insulation measures.

graememk

Bills for me isn't a good comparison.

But heatpump is sitting at 2880kWh since I started logging in December. That's all either been on night rate, solar or battery power.

My night rate is 14.75c, (oh to the days of 5-8c night rate)

Battery is about 20% more " expensive " than pure night rate.

My night use for Dec Jan was something like 4500 but there's an EV in that, and also a farmyard (not dairy but we crush our own barley)