Nibe Exhaust air heat pump help

geocatwest

I moved into a new build one bed flat two weeks ago. I have a NIBE F370. 
I have spent a lot of time reading the manual and watching videos on this, yet it is still very difficult to understand.
These heat pumps have a bad reputation and I'm looking for the most efficient way to set these.
1. I just set it to manual which means I have turned the heating off. Do I need it on in the summer or not?
2. Ventilation - I have found this loud so turn it on periodically during the day. Does it make a difference or not?
1. My water temperature is on 46c and on economy mode. How do I bring this down or off? I set the hot water to off during nights but it is still on 46c?
4. The heating curve, curve offset and flow line temperatures. What is the most efficient setting for these?

matelodave

You may think it's got a bad reputation but generally its because its either been incorrectly specified, not set up properly and, most of all, people dont know how to use them properly. They keep faffing around with the controls without knowing what they are doing and trying to use it like a conventional boiler. So you have to learn how to use it properly.

The biggest problem that most people encounter is that instead of setting back the heating overnight and during the day they end up using the boost/back-up heater to recover the temperature, likewise keeping the hot water temperature too hot which uses the immersion heater.

Why don't you just leave it alone and monitor your energy consumption for a couple of months, taking weekly or even daily meter readings so you can evaluate what is going on rather than faffing around with it. There's no point in tweaking and twiddling until you've got a base line to work from and know how its operating. Make a note of all the settings, so if and when you do decide to have a twiddle, you'll know what it was and how to reset it.

The other thing is to only adjust one thing at a time and then wait a week to see what the effect is (you need to check you consumption daily and ideally check your weather info as well). I'm guessing that now its summer that you aren't actually heating the flat so you wont see whats going on anyway, does it produce hot water for the taps as well.

Regarding the flow temperature, if you reduce it too much then you might find that the radiators (or floor heating) don't get warm enough to heat your flat - so the unit will have to run for a lot longer especially is it very cold. With low flow temperatures it could take ages to reheat the place. My Daikin, which feeds u/f heating has flow temps that vary between 30-40 degrees depending on the weather (weather compensation) but it's never turned off. It has taken more than 48 hours to reheat the place when I let it get stone cold the first winter we had it.
Our minimum indoor temperature is set to 17 degrees with a comfort level of 19-20 degrees. But we are at home all day so it works for us. Likewise our hot water temperature is set to 45 degrees rather than 50 or 60 (most heatpumps can't heat above 50-55 degrees so the immersion or boot heater kicks in and ramps up the running costs

It took the whole of the first winter we had it to tweak it to suit (and i've got a pretty good idea of how it all works). The worst thing you can do is let the place go cold overnight and during the day so turn it down just 2-3 degrees rather than off (assuming that you've got something like programmable thermostats)

The main thing is to ensure that you are on a decent tariff. As I assume it will be running during the day and evening (like my Daikin does) then you'll probably find that a single rate tariff is more suitable  than E7

geocatwest

matelodave said:

You may think it's got a bad reputation but generally its because its either been incorrectly specified, not set up properly and, most of all, people dont know how to use them properly. They keep faffing around with the controls without knowing what they are doing and trying to use it like a conventional boiler. So you have to learn how to use it properly.

The biggest problem that most people encounter is that instead of setting back the heating overnight and during the day they end up using the boost/back-up heater to recover the temperature, likewise keeping the hot water temperature too hot which uses the immersion heater.

Why don't you just leave it alone and monitor your energy consumption for a couple of months, taking weekly or even daily meter readings so you can evaluate what is going on rather than faffing around with it. There's no point in tweaking and twiddling until you've got a base line to work from and know how its operating. Make a note of all the settings, so if and when you do decide to have a twiddle, you'll know what it was and how to reset it.

The other thing is to only adjust one thing at a time and then wait a week to see what the effect is (you need to check you consumption daily and ideally check your weather info as well). I'm guessing that now its summer that you aren't actually heating the flat so you wont see whats going on anyway, does it produce hot water for the taps as well.

Regarding the flow temperature, if you reduce it too much then you might find that the radiators (or floor heating) don't get warm enough to heat your flat - so the unit will have to run for a lot longer especially is it very cold. With low flow temperatures it could take ages to reheat the place. My Daikin, which feeds u/f heating has flow temps that vary between 30-40 degrees depending on the weather (weather compensation) but it's never turned off. It has taken more than 48 hours to reheat the place when I let it get stone cold the first winter we had it.
Our minimum indoor temperature is set to 17 degrees with a comfort level of 19-20 degrees. But we are at home all day so it works for us. Likewise our hot water temperature is set to 45 degrees rather than 50 or 60 (most heatpumps can't heat above 50-55 degrees so the immersion or boot heater kicks in and ramps up the running costs

It took the whole of the first winter we had it to tweak it to suit (and i've got a pretty good idea of how it all works). The worst thing you can do is let the place go cold overnight and during the day so turn it down just 2-3 degrees rather than off (assuming that you've got something like programmable thermostats)

The main thing is to ensure that you are on a decent tariff. As I assume it will be running during the day and evening (like my Daikin does) then you'll probably find that a single rate tariff is more suitable  than E7

When I moved in the flow temperature was around 55c but I brought it down to 35c. Is this OK?
I have turned the heating off - yes hot water still runs without the heating function.

matelodave

.gocatwest said:

I moved into a new build one bed flat two weeks ago. I have a NIBE F370. 
I have spent a lot of time reading the manual and watching videos on this, yet it is still very difficult to understand.
These heat pumps have a bad reputation and I'm looking for the most efficient way to set these.
1. I just set it to manual which means I have turned the heating off. Do I need it on in the summer or not?
How do you get hot water if you set it to off 
2. Ventilation - I have found this loud so turn it on periodically during the day. Does it make a difference or not?
Yes - the heat pump relies on air flowing through the heat exchanger to extract heat from the exhaust air - if you turn that off the only way it can get heat is from the back-up/boost heater which could treble your costs. You are also likely to increase the likelihood of condensation.
1. My water temperature is on 46c and on economy mode. How do I bring this down or off? I set the hot water to off during nights but it is still on 46c?
If you try and reheat the water in short bursts with the heatpump off then it's likely that the immersion will do it rather than the heatpump - costing you about three times as much
4. The heating curve, curve offset and flow line temperatures. What is the most efficient setting for these?
Hopefully they've been correctly set by the installer and should be matched to suit your heating system - see what I said above about faffing without understanding whats going on. Even default levels (whatever they are) should be fairly close until you understand how the system is operating.

matelodave

"When I moved in the flow temperature was around 55c but I brought it down to 35c. Is this OK?
I have turned the heating off - yes hot water still runs without the heating function."

It will be fine at this time of the year because your heating isn't being used BUT make sure that your hot water isn't being heated by the immersion if you've turned the heatpump off - have you got a smart meter to see what is going on.

My heatpump heats my tank with about 1 kwh of energy at this time of the year (to 45degrees) - it would take 2-3kwh if the immersion heater was being used instead.

A heatpump extracts heat from the air using a heat exchanger and fans to draw the air through. In my case, two big ones in an outside unit because the air is cold so it has to work harder to get heat from colder air. In the case of an exhaust air heatpump like the Nibe the air is drawn from inside the house, so it's already warmish., Consequently the fans, compressor and heat exchanger aren't as big or powerful as an outside one.
(Looking at the NIBE specifications, reducing the ventilation airflow reduces the efficiency of the heatpump - so shutting it off might stop it working properly and cause the immersion/boost heaters to operate more often than they should)

If you only heat the place intermittently then the air is colder and so the heatpump, has to work a lot harder. In in some cases will turn on the back-up heater to assist it (I've got both my back-up heater and immersion heaters disabled so that can't happen even if the outside temp goes down to -20 - it's supposed to kick in at -5).

You will only find out if  a flow temperature of 35 degrees is enough when its around zero degrees outside because it depends on how much heat the radiators or underfloor heating can deliver with only 35 degrees. The heat output of a radiator is proportional to the flow temperature so 35 degrees is only about a third of what the radiator is specified at which is 70-80 degrees - that's why you have big ones or underfloor heating. 

It could be OK but the heating has to be on 24/7 especially if your heating relies on recovering warm air from inside the rooms to function properly.

There's lots of info here but be very wary about tweaking - keep a careful record of what you do so you can go back if it all goes wrong and only adjust one thing at a time to see what effect it has before jumping straight in. https://www.nibe.eu/assets/documents/23212/431428-1.pdf

Looking at the specifications it's only a low power heatpump so might rely a lot more on using the back-up heater if you get the settings wrong or don't operate it correctly (around 2kw as a heat pump but with a 5 or 8 kw back-up heater)

It's also worth noting that an engineer can plug in a USB drive to check what's been going on so if you cods it up and have to get an engineer in, he'll know what you've been up to