A2W Nibe Heatpump optimal settings

Denisoftus

Just wondering what settings people use to run air-to-water heatpump with UFH.

I have just one installed and plumber put all the settings on, but I'd like to become more familiar with it and be able to adjust settings in the future by myself with a good knowledge what I'm doing.

So at the moment I understand that the unit only adjust flow temperature by using outside thermostat and ignoring inside thermostats. Having said that I assume that colder outside, the warmer flow is, no matter how warm is inside.

Also at 5C outside it kicks in the immersion, which increase the power consumption by 4, if I'm not wrong. So literally the pump is only effective above 5C outside and during the cold weather we are going to see the spike in the energy bills.

Any thoughts?

Thanks.

BigGuy82

For a well insulated air tight new build the heating curve is usually set at either 4 or 5. It takes a bit of adjusting to find a setting your comfortable . With a passive house your looking at curve 3 with a flow temp of 30deg or so. That's not true about inside stats being ignored by the heat pump. Whenever a room stat is satisfied it shuts off the heat to that room (end of) when all rooms are satisfied the heat pump goes into stand by mode.
In cold weather yes it's not as efficient but if the heat pump is struggling to get up to temp it turns on the built in immersion to give it maybe a kW or two of energy to give the extra boost.

So try curve 4 with a flow temp of 40 deg and monitor the progress. If you have a night rate meter ( half price at night) you could let the pump work at night and have the best in the floors for the following day.

soundskin

the immersion will only come on if the heat pump output does not match the heating load for a sustained period of time (ie struggling to heat the house). This is based on a degree minute calculation.

You can check your "add heat hours" quite easily of that is a concern.

Your heating curve is where you set your heating for your house. Only you and your house can determine the curve to suit. Typically 2-6 for UFH.

Stats are only there to keep rooms lower than what your HP wants to keep your house, ie bedrooms at 17 degrees or what suits your needs. Typically on Nibe units there is no comm between stats and HP. There can be a central room sensor. It is very important to have plenty open circuits in your UFH. Insufficient open circuits will cause cycling of HP and shorten the life of your compressor. A conversation you don't want to have for 10 plus years.

samdeluxjones

I have built an airtight (.56 ach) super insulated 230mm external wrap, insulated slab and triple glazed windows.

My Nibe air to water pump working UFH is set at curve of 3 with offset 0.

It is heating 300m2 to 20-22 degrees.

My last bimonthly electric bill was €400+ Can I get this down?

I know it was colder than normal for these months but I was surprised at that bill.
I was expecting around €300

heating, compr. only 8272.0kwh
heating,int. add. incl 8272.0kwh

Do these figures mean I haven't used the immersion yet to heat the house?

Maybe this is normal for heating a passive house in winter and my expectations in the theory were far higher than the reality of things..

KCross

samdeluxjones wrote: »

My last bimonthly electric bill was €400+ Can I get this down?

First thing to check is, is that bill or the previous one to it using an estimate for the meter reading?

If either of those bills had estimates in them you will have an inaccurate view of what it actually cost you.

samdeluxjones

Previous one was estimate but not far off, I've also been keeping a record of the meter box units.

May to Aug average of 17 units/day bimonthly bill was €180 odd with heating off.
Missus bakes a lot so ovens bump that up.

Dec to Jan average of 33 units a day with very little baking

I take random readings subtract it from last reading and divide by number of days since last reading.

Turned heat pump on last February and until it turned itself off for summer it clocked up 1450kwh.
It turned itself on last October sometime and now it's 8272kwh

These do not correspond to ESB kwh but that's some feckin jump and the winter ain't even over yet..

samdeluxjones

Flow temp never goes over 30.

In cold weather it's about 28-29 with a return of 22-23

So once it's up to speed it only ever has to re-heat the water 6 degrees which is feck all.

soundskin

samdeluxjones wrote: »

I have built an airtight (.56 ach) super insulated 230mm external wrap, insulated slab and triple glazed windows.

My Nibe air to water pump working UFH is set at curve of 3 with offset 0.

It is heating 300m2 to 20-22 degrees.

My last bimonthly electric bill was €400+ Can I get this down?

I know it was colder than normal for these months but I was surprised at that bill.
I was expecting around €300

heating, compr. only 8272.0kwh
heating,int. add. incl 8272.0kwh

Do these figures mean I haven't used the immersion yet to heat the house?

Maybe this is normal for heating a passive house in winter and my expectations in the theory were far higher than the reality of things..

Turn down your hearing curve or temp offset is how you reduce your heating bill. Reducing heat output reduced costs. Assuming correct installation and configuration then that is your means of reducing costs

samdeluxjones

Installer has app for at least 10 other systems on his phone for that particular model so it wasn't his first.

Turning down heating curve or temp offset will also reduce the supply temp no?

I will try this when installer puts valve controllers on downstairs valves as the are all currently open. We live upstairs..

soundskin

samdeluxjones wrote: »

Installer has app for at least 10 other systems on his phone for that particular model so it wasn't his first.

Turning down heating curve or temp offset will also reduce the supply temp no?

I will try this when installer puts valve controllers on downstairs valves as the are all currently open. We live upstairs..

Yes turning down the curve will reduce the heat, ergo costs.

I’d limit the number of stats, actuators, zone valve etc on the system. You’ll only increase compressor cycles and decrease Compressor life span. I saw 3 compressor failures this week on Heat Pumps and that can be one or the main causes, that and incorrect coil size for DHW (not an issue in your case). Compressor replacement can be up to 2k. The more open circuits your heat pump can distribute its heat to the better.

You could have stats in your bedrooms but they rest of the house should be open circuit.