Are complicated controls/thermostats/hydraulics needed for ASHPs at all?

[siletto]

Greetings BuildHub'ers! 😄

 

I am grateful to have you here, as in my County, ASHPs are only started to get installed in the recent years, so few experience is available.

Now, they are installed like there's no tomorrow, but the hydraulic and control 'finesse' is completely missing from most of the installers inventory. Basic 4 port normal buffer tank with huge coil surface area DHW tank. AA battery powered on-off thermostats, no statified tanks, no 3 port configurations, no external plate DHW heat exchanger like I've read in this site. The most ambitious installers make a H-type route changing circuit from manual ball valves(to have the colder water at the buffer tank bottom when cooling), and that is all, no more than the heat pump reference designs from 10 years ago.

 

I am also an AC and ASHP certified installer, licensed electrician and controls engineer by trade; our family home is under planning and construction now. All solutions should be considered with B2B installer pricing.

It is a ~155sq.m2 ground floor house, 4 bedrooms, with normal-to-good insulation for new homes EU regulations.("porotherm" clay brick 30cm walls and 20cm EPS foam sheet insulation on the walls, 35cm rockwool on the ceiling, warm edge, 3-pane glass windows).

The heat demand is 7.5kW @-15°C, which is the traditional design temperature here, although very rarely gets this cold.

I plan to install the 9kW LG R290 Monoblock heat pump next year for underfloor slab heating, DHW and fancoil heating and cooling. Cooled ceiling is not considered.

 

As a control engineer, i quickly got attached to the super-smart contollers and thermostats, like 0-10V thermostatic actuators, 0-10V fancoil speed controllers, etc. Then I came across the pricing lists....

 

The initial plan was Siemens RDG200 series  thermostats per room, with 0-10V or NC underfloor actuators, and 0-10V fancoil speed control. It is one of the most expensive thermostat available, excluding the KNX ones, but it is possible to run both systems with it, albeit the set of these thermostats costs almost half of another a2w heat pump. I want to control both the heating, and cooling circuits with one controller, if possible in a financially sensible way.

Many say here on the forums, that the heating does not need any zoning in this moderate sized home, because with good sizing and weather curves, the heating does not stop at all, so any thermostat is useless.

The cooling must be adjusted per room, as it is needed occasionally, during the peak weeks of July and August. 

Heat pump heating and DHW with split AC cooling would be the most effective solutions, but sticking 2-3-4-5 outdoor units onto the facade does not seem to be an elegant solution; then the ashp is not needed at all as a gas boiler is way cheaper for heating only.

 

My main question is, does a modern, well-built and commissioned heat pump system need high-priced control equipment to run with good comfort, or stick with a good weather compensation setting?

Do zoning have any advantages compared to thoughtful hydraulic setting in terms of UFH?

What other control options do you suggest to control fancoil cooling, to be as similar to a high wall split AC IR remote control?

 

Every opinion, experience or tip is welcomed here.

[JohnMo]

1 hour ago, siletto said:

main question is, does a modern, well-built and commissioned heat pump system need high-priced control equipment to run with good comfort, or stick with a good weather compensation setting

I have a thermostat, but could just as easily be a time switch as it does little or no temperature control. That's it a 3 way diverter to the cylinder or UFH, no buffer. Any cooling is done via UFH circuits. All done via WC. ASHP modulates it's output based on return temperature without any interference from me.

 

Are you sure you need 9kW with a 155m2 house?

[jack]

I have a home automation system and I haven't bothered using it to do anything other than act as a thermostat for our ASHP. It works fine in our highly insulated house with a single downstairs UFH zone.

 

The only thing I currently wish I could do (without having to hack into the ASHP's external temperature sensor to make it think the weather is colder) is to bump up the UFH supply temperature when energy is cheap. With an Octopus EV tariff, I can get 6 hours of cheap energy overnight. I use two hours of that for DHW heating. It'd be nice to bump up the UFH temperature during the other four hours so I can pump as much energy into the slab as possible.

 

I understand that's possible with more advanced controls, but for my Panasonic Aquarea unit, they were hundreds of quid more than the standard controller.

[Bramco]

10 minutes ago, jack said:

The only thing I currently wish I could do (without having to hack into the ASHP's external temperature sensor to make it think the weather is colder) is to bump up the UFH supply temperature when energy is cheap. With an Octopus EV tariff, I can get 6 hours of cheap energy overnight. I use two hours of that for DHW heating. It'd be nice to bump up the UFH temperature during the other four hours so I can pump as much energy into the slab as possible.

 

Why don't you use the cheap rate directly for DHW heating using a timer on the DHW immersion supply and let the ASHP run for the full 6 hours on the cheap rate. This is the way we do it. We're on Go, so the cheap rate is 9p. The night after sunny days, the DHW doesn't take much to get back to temperature.  We find the 4 hours of Go a night is enough to heat the house for the rest of the day unless it's below zero outside.

 

We actually have our ASHP set to heating only, so rely on the PV and 9p Go rate for all hot water.

 

Another thing we've done recently is to put a timer on the immersions in the UFH tank. That way on really cold nights when the ASHP is defrosting several times in the 4 hour Go period, the UFH is boosted by the immersion in the UFH tank.

 

Simon

[joe90]

I know it’s been said here before but a previous member designed and installed his own smart weather compensation heat controls but took them out and replaced with a single thermostat and found it just as good, main reason was if he passed away his wife and any future owner would not know how to repair or replace it and tech goes out of date quickly. I too found my a single room stat in the hallway a simple solution, far better than the over complicated controller I bought (and failed to fully understand).

[JohnMo]

19 minutes ago, jack said:

I have a home automation system and I haven't bothered using it to do anything other than act as a thermostat for our ASHP. It works fine in our highly insulated house with a single downstairs UFH zone.

 

The only thing I currently wish I could do (without having to hack into the ASHP's external temperature sensor to make it think the weather is colder) is to bump up the UFH supply temperature when energy is cheap. With an Octopus EV tariff, I can get 6 hours of cheap energy overnight. I use two hours of that for DHW heating. It'd be nice to bump up the UFH temperature during the other four hours so I can pump as much energy into the slab as possible.

 

I understand that's possible with more advanced controls, but for my Panasonic Aquarea unit, they were hundreds of quid more than the standard controller.

Heat pumps even quite basic ones, normally have a dual set point option, that is selected via an open/closed zero volt switch. Dual, or double set point have seen in lots of manuals. Normally need an external switch or relay to operate. If you have a simple time switch or smart relay - done.

 

8 minutes ago, Bramco said:

 

Why don't you use the cheap rate directly for DHW heating using a timer on the DHW immersion supply and let the ASHP run for the full 6 hours on the cheap rate. This is the way we do it. We're on Go, so the cheap rate is 9p. The night after sunny days, the DHW doesn't take much to get back to temperature.  We find the 4 hours of Go a night is enough to heat the house for the rest of the day unless it's below zero outside.

 

We actually have our ASHP set to heating only, so rely on the PV and 9p Go rate for all hot water.

 

Another thing we've done recently is to put a timer on the immersions in the UFH tank. That way on really cold nights when the ASHP is defrosting several times in the 4 hour Go period, the UFH is boosted by the immersion in the UFH tank.

 

Simon

Like this one also.

[Gary68]

Agree with what has been said before, I have 4 zoned thermostatically controlled UFH downstairs, bypassed all the thermostats but the one in the hall so now works as a one big single zone.

[jack]

4 minutes ago, JohnMo said:

Heat pumps even quite basic ones, normally have a dual set point option, that is selected via an open/closed zero volt switch. Dual, or double set point have seen in lots of manuals. Normally need an external switch or relay to operate. If you have a simple time switch or smart relay - done.

 

I wish it were so, but here're all the inputs and outputs for my unit:

 

 

There is an offset function that moves the weather compensation curve up or down by up to 5 degrees, but that's something you set manually via the controller.

[jack]

25 minutes ago, Bramco said:

Why don't you use the cheap rate directly for DHW heating using a timer on the DHW immersion supply and let the ASHP run for the full 6 hours on the cheap rate. This is the way we do it. We're on Go, so the cheap rate is 9p. The night after sunny days, the DHW doesn't take much to get back to temperature.  We find the 4 hours of Go a night is enough to heat the house for the rest of the day unless it's below zero outside.

 

We actually have our ASHP set to heating only, so rely on the PV and 9p Go rate for all hot water.

 

I'm not against this approach. For a while I did have things set up to use the immersion to boost DHW for the last hour when we were on Go.

 

Unfortunately, my Octopus Go contract ended a few months ago and I'm not able to sign up to the other cheap overnight tariff until I get a compatible car or charger (I didn't want to tie myself into the latest Go tariff, as the numbers are nowhere near as good as the other cheap overnight tariff).

 

I'm due to replace my car soon and will be installing a charger at the same time, so I'll be able to get onto the new tariff. I'll need to do the sums to see what works out best once that happens. I was hoping that four hours at a decent temperature would cover most if not all of our heating needs, but if it doesn't, adding in the immersion to help the DHW heating may be the way forward.

[JohnMo]

1 hour ago, Bramco said:

 

Why don't you use the cheap rate directly for DHW heating using a timer on the DHW immersion supply and let the ASHP run for the full 6 hours on the cheap rate. This is the way we do it. We're on Go, so the cheap rate is 9p. The night after sunny days, the DHW doesn't take much to get back to temperature.  We find the 4 hours of Go a night is enough to heat the house for the rest of the day unless it's below zero outside.

 

We actually have our ASHP set to heating only, so rely on the PV and 9p Go rate for all hot water.

 

Another thing we've done recently is to put a timer on the immersions in the UFH tank. That way on really cold nights when the ASHP is defrosting several times in the 4 hour Go period, the UFH is boosted by the immersion in the UFH tank.

 

Simon

So have just adjusted stuff, upped WC curve up a couple of degrees and set thermostat to 20.5, so it controls the temperature, have set it at 20.5 from 0:40 to 20:00hrs.  Our PV diverter has a built in boost timer, so have set immersion on timer overnight during E7 hours for four hours.  Tonight's temps very similar to last 24hrs, i.e. sub zero, so can compare usage day on day tomorrow evening.

[joth]

1 hour ago, jack said:

I have a home automation system and I haven't bothered using it to do anything other than act as a thermostat for our ASHP. It works fine in our highly insulated house with a single downstairs UFH zone.

 

The only thing I currently wish I could do (without having to hack into the ASHP's external temperature sensor to make it think the weather is colder) is to bump up the UFH supply temperature when energy is cheap. With an Octopus EV tariff, I can get 6 hours of cheap energy overnight. I use two hours of that for DHW heating. It'd be nice to bump up the UFH temperature during the other four hours so I can pump as much energy into the slab as possible.

 

I understand that's possible with more advanced controls, but for my Panasonic Aquarea unit, they were hundreds of quid more than the standard controller.

Are you using input 12 (HEAT) to send a call-for-heat signal from Loxone to the heatpump? So the setpoint is managed in loxone, in which case it's easy to change the setpoint based on a schedule. (Or, use the Excess Heating input on a Climate Controller loxone block, which is what I do but actually a lot more complicated way to do the same thing)

What am I missing?

 

 

[JohnMo]

14 minutes ago, joth said:

What am I missing?

He is wanting the heat pump to output a higher temperature that it's currently programmed to do. So instead of flow say 30 degs, increasing to 32 during cheap rate. Lexone will manage house temp, not flow temperature.

[jack]

Just now, JohnMo said:

He is wanting the heat pump to output a higher temperature that it's currently programmed to do. So instead of flow say 30 degs, increasing to 32 during cheap rate. Lexone will manage house temp, not flow temperature.

 

 

Correct. Loxone calls for heat, and there's some (programmed) flexibility about how that happens, but flow temperature (including weather compensation) is set by the ASHP controller.

 

Ideally I'd have Loxone control the flow temperature too, based on various current and predicted temperatures and the availabilty of cheap power (overnight) or free power (occasional excess PV during winter), but that isn't possible with my current setup.

 

Depending on the rate at which my slab can absorb energy, the solution may be to just increase the flow temperature across the weather compensation curve. That might be enough to get me over the line. The problem I have is modelling all of this. I may just need to try it out when it gets colder.

 

23 minutes ago, joth said:

Or, use the Excess Heating input on a Climate Controller loxone block

 

I've thought about using this in the past, mainly for when there's excess PV but the house is already up to temperature. The main issue is the very long time constant of my slab. I'm sure there's a way to program in some guardrails to make it work though.

[siletto]

3 hours ago, JohnMo said:

I have a thermostat, but could just as easily be a time switch as it does little or no temperature control. That's it a 3 way diverter to the cylinder or UFH, no buffer. Any cooling is done via UFH circuits. All done via WC. ASHP modulates it's output based on return temperature without any interference from me.

 

Are you sure you need 9kW with a 155m2 house?

No, I am not sure, but the EN 12831 standard calculation gets this result. At - 5°C, which is closer to the UK design temp., the heat loss is only 5.4kW. 

 

Ok, so zoning heating does little to comfort, or energy saving, but what about the cooling? 

 

How's you UFH cooling is set up? 

Does it have dew point sensors, or just works with non-condensing flow temp? 

The "traditional" plumbers and heating technicians consider it an evil's thing, but I've read many times, that it can be utilized well. 

 

Other than that, i don't think cooling the whole house's slab is too efficient, when you need just half an hour of cool breeze in the living room, isn't it? 

 

[JohnMo]

1 minute ago, siletto said:

How's you UFH cooling is set up?

Flick a switch changes ASHP from heating to cooling. Just set to run at 11.5 degs, (no condensation seems to form at that temp) run at times likely to have a decent amount of solar.  Need to automate it for next year. Have home assistant and solar forecast already built in. So thinking, June to Aug, if solar forecasts X kWh forecast the smart relay switches on heat pump from say 10am to 5pm. It's not fantastically effective, but does knock the excess heat off - solar gain only reason we get hot inside.

 

It's all run on excess PV, so cost is basically zero. But get your point on a fan coil. Our outside temp rarely goes above 25 degs, so EER is circa 6 while cooling. 

 

[Beelbeebub]

3 hours ago, joe90 said:

I know it’s been said here before but a previous member designed and installed his own smart weather compensation heat controls but took them out and replaced with a single thermostat and found it just as good, main reason was if he passed away his wife and any future owner would not know how to repair or replace it and tech goes out of date quickly. I too found my a single room stat in the hallway a simple solution, far better than the over complicated controller I bought (and failed to fully understand).

This is an oft overlooked point.

 

As the designer and builder of an overly complicated homebrew tank thermostat I worry about this. 😁

 

My approach was to build the system for extreme simplicity. It basically runs on an Arduino with no internet dependence and all components off the shelf and modular.  I also did a fair bit of documentation.  It actually runs really well, 8 years of solid service through power cuts and all weather. One important function it does is control the overheat protection - in winter it activates the UFH and in summer (or if the UFH dumpmis insufficient) it will dump DHW down the drain.

 

I'm  currently faffing around upgrading it to put in weather compensation whilst preserving the UFH dump function.  The existing on/off thermostat does seem to be doing a pretty good job though, so I wonder if there will be any noticeable improvement.  

 

Still it's a nice intellectual exercise.

[joe90]

31 minutes ago, Beelbeebub said:

My approach was to build the system for extreme simplicity.

Yes, kiss

32 minutes ago, Beelbeebub said:

Still it's a nice intellectual exercise.

Oh yes I get that, I love inventing things..

[sharpener]

3 hours ago, jack said:

The problem I have is modelling all of this. I may just need to try it out when it gets colder.

 

Old joke. Two engineers in France:

 

"It works just fine in practice"

 

"Yes but will it work in theory?"

 

 

 

Edited November 16, 2023 by sharpener

[siletto]

3 hours ago, JohnMo said:

Flick a switch changes ASHP from heating to cooling. Just set to run at 11.5 degs, (no condensation seems to form at that temp) run at times likely to have a decent amount of solar.  Need to automate it for next year. Have home assistant and solar forecast already built in. So thinking, June to Aug, if solar forecasts X kWh forecast the smart relay switches on heat pump from say 10am to 5pm. It's not fantastically effective, but does knock the excess heat off - solar gain only reason we get hot inside.

 

It's all run on excess PV, so cost is basically zero. But get your point on a fan coil. Our outside temp rarely goes above 25 degs, so EER is circa 6 while cooling. 

 

On the hottest days, we get 37-40°C peaks, and it gets worse as the warming goes on. On a hot day, I expect condensation under 16-17°C floor temps, so UFH cooling in itself is surely not enough. 

 

There are stylish, slim fancoils available, but you either oversize it(price), or run at max with 35dB of noise, and no IR remote as far as I've seen thermostat options. 

 

[jack]

9 hours ago, siletto said:

On the hottest days, we get 37-40°C peaks, and it gets worse as the warming goes on. On a hot day, I expect condensation under 16-17°C floor temps, so UFH cooling in itself is surely not enough. 

 

I run our downstairs underfloor cooling at 15 degrees flow temp, only during the day when the sun is out and the pv is generating power. This keeps the floor at about 19 degrees, which makes for a very comfortable room temperature, even in a run of high 20s days as we occasionally experience. Admittedly we have concrete floors, which do tend to be good at sucking the heat out of the room (and your feet - heavenly when it's really hot outside).

 

I have no idea how well it would work in the sorts of temperatures you're talking about. I suspect air conditioning would be more effective, especially upstairs where it tends to get a lot warmer.

[SteamyTea]

9 hours ago, siletto said:

On the hottest days, we get 37-40°C peaks, and it gets worse as the warming goes on.

That is quite interesting as when I was studying climate change 15 years or so ago, Hungary was a case study for future weather extremes.

Under any of the climate models, your part of Europe was going to get a lot hotter in the summer.

As you are still at the design stage, are their things you can do to mitigate higher temperatures i.e. window shading, tree planting, body of water as a heat dump, PV on a roof and side walls (it can suck up 20% of the incidental solar energy).

I lived on a 'tropical island' that often had sustained 35°C+ temperatures, luckily it was permanently windy, but large land masses do not have that affect.  You may find Air to Air heating and cooling is better than slab heating/cooling.

Edited November 17, 2023 by SteamyTea

[joth]

16 hours ago, jack said:

 

 

Correct. Loxone calls for heat, and there's some (programmed) flexibility about how that happens, but flow temperature (including weather compensation) is set by the ASHP controller.

 

Ideally I'd have Loxone control the flow temperature too, based on various current and predicted temperatures and the availabilty of cheap power (overnight) or free power (occasional excess PV during winter), but that isn't possible with my current setup.

 

Depending on the rate at which my slab can absorb energy, the solution may be to just increase the flow temperature across the weather compensation curve. That might be enough to get me over the line. The problem I have is modelling all of this. I may just need to try it out when it gets colder.

 

 

I've thought about using this in the past, mainly for when there's excess PV but the house is already up to temperature. The main issue is the very long time constant of my slab. I'm sure there's a way to program in some guardrails to make it work though.

 

Ah got it makes sense, yes my brain wasn't fully engaged.

I managed to do what you're after with my ecodan, using the Home Assistant MELcloud integration to set the flow temperature. Problem is that goes via cloud and WiFi and only updates once per 30mins (assuming the server is online..) so I have up with it. Direct connection is possible by wiring an ESP32 into the WiFi adapter port but I've not ventured there yet, and will lose the use of the cloud portal for performance monitoring. (which is pretty poor tbh but I have 3 years data there now so feel bound to it)

 

The Panasonic has an optional modbus gateway, depending on the model number you have, which would very cleanly allow Loxone to directly control the flow temperature.

 

PAW-AW-MBS-H supports H generation onwards, via the CN-CNT port. 

 

[Johnnyire]

18 hours ago, jack said:

I have a home automation system and I haven't bothered using it to do anything other than act as a thermostat for our ASHP. It works fine in our highly insulated house with a single downstairs UFH zone.

 

The only thing I currently wish I could do (without having to hack into the ASHP's external temperature sensor to make it think the weather is colder) is to bump up the UFH supply temperature when energy is cheap. With an Octopus EV tariff, I can get 6 hours of cheap energy overnight. I use two hours of that for DHW heating. It'd be nice to bump up the UFH temperature during the other four hours so I can pump as much energy into the slab as possible.

 

I understand that's possible with more advanced controls, but for my Panasonic Aquarea unit, they were hundreds of quid more than the standard controller.

Hi Jack,

 

Is it not a simple solution to just increase the temperature on the loxone schedule during this period of low cost tariffs?

[joth]

Just to riff on this a bit more, what I've effectively done now is create a WC curve that allows my heatpump to put in a day's worth of energy requirement in about 4 or so hours runtime. I have octopus go so having Loxone boost  the room target temp between midnight to 4am pretty much ensures the ASHP just runs during cheap rate, and again a bit sometime during the day if solar gains are low. This works well enough I'm not so motivated to mess with direct control of the UFH flow temperature 

[JohnMo]

I have two very different spaces to heat, the house and have UFH in the summer house (it is used most days by the wife) the UFH manages the min temp set point (10 deg), a direct electric heater does the rest. If I batch heat the house overnight I end up spending using the electric heater to keep the summer house above 10 deg.

 

My heat pump has minimal inputs similar to @jack. But I do have a double set point input - unfortunately it's a multi purpose input and I use that for cylinder heating thermostat call for heat.

 

Last night, on cheap rate, I used the immersion to heat the cylinder as a trial, cylinder was at 48 degs this morning and heated in 45 mins. So that works ok.

 

I have another option to connect the cylinder via a PT100 probe, but is just about impossible to route the cable, so would need a wireless option (new thread I think). That would leave the dual set point connection open to use.

 

So dual set point - have one set point set high to batch charge the floor, once up to temp use the thermostat to switch to the lower setting and ASHP circulation pump would continue, but as the flow temp would be pretty high the ASHP would be unlikely to start up, summer house borrows heat from the house.