Hi everyone,

Need some advice please. We will be installing hydronic underfloor heating in our house in Cape Town - but we are really struggling to decide which heat source to use. Pellet, Heatpump? We've been told by the provider installing pellet boiler that heatpump consumes too much energy and cannot be used with solar energy at all. On the other side we have been told by the provider installing heatpump that it does not consume much energy. So we are completely lost.

Does any of you have water underfloor heating and be willing to have a chat with me - so i can get some feedback and recommendations? And also an understanding of how much electricity bill to expect when heating a 400 sqm house?

Thanks

Meg

 

1 hour ago, Meg said:

Hi everyone,

Need some advice please. We will be installing hydronic underfloor heating in our house in Cape Town - but we are really struggling to decide which heat source to use. Pellet, Heatpump? We've been told by the provider installing pellet boiler that heatpump consumes too much energy and cannot be used with solar energy at all. On the other side we have been told by the provider installing heatpump that it does not consume much energy. So we are completely lost.

Does any of you have water underfloor heating and be willing to have a chat with me - so i can get some feedback and recommendations? And also an understanding of how much electricity bill to expect when heating a 400 sqm house?

Thanks

Meg

 

I don't have water underfloor heating system but I have an electric underfloor heating and also a heat pump that I run only on solar power. 

I can't imagine the installer is being completely honest in terms of the heat pump not being able to run on solar power, unless if he meant that since you would normally switch the underfloor on during the night, it will not be feasible using batteries.

My electric underfloor heating goes up to 30degrees Celsius, if I had water heating, I reckon it would have been much cheaper just heating the water to around 30 degrees using a heat pump.

I also don't have water under floor heating I do have a 5kw heat pump.

It uses around 1200 watts for about an hour to heat 200 litres of water to 55 celcius. I don't even notice that it's on when the sun is up.

If needed I power it from the batteries. As you can see on the screenshot at 5 am.

BTW the 3kw heat pump only uses 800 watts.

On 2021/10/14 at 4:44 PM, Meg said:

Hi everyone,

Need some advice please. We will be installing hydronic underfloor heating in our house in Cape Town - but we are really struggling to decide which heat source to use. Pellet, Heatpump? We've been told by the provider installing pellet boiler that heatpump consumes too much energy and cannot be used with solar energy at all. On the other side we have been told by the provider installing heatpump that it does not consume much energy. So we are completely lost.

Does any of you have water underfloor heating and be willing to have a chat with me - so i can get some feedback and recommendations? And also an understanding of how much electricity bill to expect when heating a 400 sqm house?

Thanks

Meg

 

To size a heat pump you need to do a proper heat load of the building.  But lets say you need about 100W per sqm for heating and you heat about half of the floor area.  That gives you 20kW of heating requirement.  That is a big heat pump unit.

With a 20kW heat pump you are going to need about 7kW of electrical power which will need a big solar system if you want to run it off solar.  The problem is more at night when you still want to heat the home and only have battery power.

Running a heat pump from grid power vs a pellet burner is probably gonna cost you the same in energy usage.  But that is just guessing now.

Edited October 20, 20214 yr by Pietpower

I have underfloor heating (and cooling in the summer) running off a heatpump (home made system in my case rather than commercial). I would recommend underfloor heating to anyone, best heating system I've ever installed).

In my case (North east Spain) I heat the water to typically 32C in winter and chill to 16C in summer, this keeps the house at around 25C in summer and 22C in winter. 

As there is a time delay on the response I use a weather feed and predictive heating based on forecast temperature, always working 2 hours ahead. I also reduce the temperature a few degrees overnight in the winter.

My house is approx 250sq meters and electricity use is between 6000kWh and 8000kWh (depends on the winter!) for a heating season from mid October to mid may.

In my case I have also added (and soon to add more) solar water panels to the system so on sunny days I get free heating from the sun. As the underfloor is effectively a thermal mass the heat is available long after the sun has gone.

Another future plan is to add an extra small heatpump that operates when I have excess solar power. This will most likely only be for summer cooling use and 'emergency' winter use in case of grid failure.

@Acuario Do you have a storage tank for the hot water from the solar panels and what is the volume in litres. Also are your heating pipes embedded in the floor slab or in an isolated concrete layer above the floor slab. Perhaps you would be so kind as to describe the your hydronic floor heating system a bit more comprehensively. I did embed pex pipes in my concrete floor slabs when building the house and am trying to figure out the most effective way of producing the required hot water. In the Western Cape Province of South Africa, where I live, we have a fair amount of sunshine in winter but our electricity infrastructure has been badly neglected and willld probably fail at some stage. We are already having frequent rolling blackouts and electricity prices keep escalating. So I think it is time I put the pipes in the floors to work.

The system I have was retrofitted in most of the house but the principle is the same. I had tiled floors that were on top of a weak cement/gravel layer, that was on top of a concrete slab. I removed the tiles and cement/gravel down to the concrete. I then used insulating panels like these to support the tubes. On top went a layer of cement with a plasticiser and then new tiles on top of cement layer.

My heating/cooling system (all home made and mostly from recycled items...) consists of:

I built my own controllers for both the solar controller and heatpump controller.

As an (almost) last resort I can run the oil boiler and circulating pump from my solar system if I don't have power to run the heatpumps. As an absolutely last resort we have a woodburner..

For anyone interested in building their own system like the above there are details on the Eco Renovator website, along with many other designs both of mine and other people.

@Acuario Thanks a lot for your drawing and details of your underfloor heating system. It will be of much value to me.

I only saw this now. All I can add I have wired in a Sonoff at the PCB in the relay circuit. I wonder what is the "damage" caused if not started or shut down by the controller. If there was then it means if the pump was running during load shedding damage is caused.

Sonoff has 2 starts a day and been in service for more than a year.

Lastly still just as happy with my ITS 4.7KW installed under rebate 10 years ago as when it was 1st installed.

On 2022/05/20 at 10:18 PM, Scorp007 said:

I wonder what is the "damage" caused if not started or shut down by the controller. If there was then it means if the pump was running during load shedding damage is caused.

It shouldn't cause any damage. These devices are designed with the possibility of a power cut in mind so if they were to be damaged then that would be really bad news.

The design will have a power fail start up delay programmed in so if there is a power cut there is a delay on the compressor re-starting. If this isn't there then if the power cut was short (a few seconds for example) then the compressor would try to re-start while under compression - which it wouldn't be able to do, so would over-current (and possibly long term) suffer damage. 

The old (non inverter) machines simply had a solenoid to turn on/off the compressor, no slow wind-up/down, just on/off. There was a time delay built in for cold (from no power) starting to prevent the above from occurring.

 

@Acuario

Thanks for the detail operation of the unit. I am sure that my inverter start unit will have all the protection housed on the PC board.

It's been running fine with the Sonoff at 2 starts a day and more than a year with 3 starts a day when I used the Sonoff to drive a relay to switch the heat pump as well as my 2nd geyser which still uses an element. They are too far apart and the 4.7kw unit will battle to heat 300L in our cold winters. I have never used the element back up on mine.

We had a heat pump installed to my father's cottage but with loadshedding he often has no hot water. I understood from a plumber recently that his geyser will not have an element as it is purely a storage unit. Is that true or wil the geyserchave an element?

Maryke Roberts

1 hour ago, Maryke Roberts said:

We had a heat pump installed to my father's cottage but with loadshedding he often has no hot water. I understood from a plumber recently that his geyser will not have an element as it is purely a storage unit. Is that true or wil the geyserchave an element?

Maryke Roberts

How will the normal geyser element get power to heat the water during LS. 

This cannot be a negative for a heat pump. 

A heat pump uses the same geyser for hot water storage. 

In 1989 I installed a Daikin heat pump.  A regular copper geyser with a 3kW element was used 

A drawback was that the limit was 63 deg, due to the refrigerant used.

I fitted a temperature switch that would come on at 20h00 if the water was under 45 deg.  The geyser's thermostat was set to 55 deg

The heat-pump was in the,upstairs roof and worked perfectly until 2018

Fitting a replacement seemed to be beyond 5 different plumbers I consulted, so I fitted a dual voltage PTC element and the low voltage (72VDC) leg is powered by 2 PV panels and a Geyserwise ECO controller 

Our daily electricity useage is under 6 units most of the time

Thsre are also 6 PV panels and a 7.2kW inverter and 10.2kWH battery