Exhaust Air Heat Pump

SJWILLS91

Hi everyone, will try keep this as concise as possible!

Basically in mid-March I moved into a 1-bed, 3rd (and top) floor, south facing flat. The heating system is a NIBE F730 Exhaust Heat Air Pump. It's connected to radiators only and has 1x sensor in the kitchen/living room area. There are 2 ceiling vents, one in the kitchen and the 2nd in the bathroom. During the past few hot days the indoor temperature has been about 25 degrees but earlier in the year it hung around 21 (even thought I set the temp to 19...). I have the water set on 'economy' mode and there's a schedule set to run overnight 22:00 - 06:00 to maintain a temp of 18 degrees.

Basically my electricity bill for April +1 week of May was £104 and for 10th May to 1st June was another £83 - for a small 1 bedroom flat this seems rather extortionate! And these were mild months, I'm really worried what the costs will be come winter.

Does anyone have any advice on getting it set up correctly so that I'm not paying a fortune each month? I've tried to Google answers but there's just nothing, and the user manual is awful - it just tells you what things are, but not much more about them.

Thanks in advance for any advice!

Steve

matelodave

Have a shufti at the installation manual which might be more educational than the opering manual - https://www.nibe.eu/assets/documents/24233/431700-1.pdf

Reed_Richards

I looked at the Nibe website and found it very difficult to understand how their "Exhaust Air Heat Pump" is supposed to work.  Here is what I can surmise:

You'll be familiar with an extractor fan.  These are wasteful of energy because they take warm inside air and send it outside.  If you are prepared to spend more money you can buy a heat exchange or heat recovery extractor fan that draws outside air in at the same time as it sends inside air out and uses the heat from the outgoing air to heat the incoming air.  What you have seems to extract heat from the outgoing air using a heat pump and use that to heat water, for radiators or a hot water cylinder.  I'm not clear how the extracted air is replaced with fresh air and that would seem to be a critical feature of the design.  In the worst case scenario you cool the air in your house in order to heat water which then warms the air in your house and the whole process is no more efficient than any other form of electric heating with no efficiency gain from the heat pump.  Best of luck.        

Reed_Richards

This is what Wikipedia says about Exhaust Air Heat Pumps: https://en.wikipedia.org/wiki/Exhaust_air_heat_pump

Exhaust air heat pumps have minimum flow rates so that when installed in a small flat, the air flow chronically over-ventilates the flat and increases the heat loss by drawing in large amounts of unwanted outside air.

Again, best of luck.

QrizB

@SJWILLS91 do you own your flat or rent it? As others have said this is an unusual arrangement for a flat and is likely to prove expensive. Heat pumps can be relatively efficient if used to draw heat from outside a property into it, but the device you've got is really intended to reduce heat loss from a property, not add significant heat to it. As a result all the heat input to the system is from electricity.

If you own your flat, you could consider replacing the device. If you rent, you might want to move out again before winter comes!

Reed_Richards

Your best hope is that the description lies about the functionality and it is capable of drawing heat from outside air as well as from extracted air.  But with those big bills I'm not too hopeful.

Cardew

Welcome to the Forum.

I suggest you enter Nibe in the search box above and you will find hundreds of posts - nearly all negative.

iirc nobody got the ASHP working correctly and the company went out of business.

Reed_Richards

Nibe still has a fancy website: https://www.nibe.eu/en-gb

SJWILLS91

Hi everyone,

Thank you for your replies - unfortunately I'm on a shared ownership scheme so the responsibility falls squarely onto my lap. It's developed another alert now which is saying the compressor is blocked, so all my hot water is now being generated from an immersion heater....so looking forward to June's bill! 

I've been in contact with a company to get it serviced as it also turns out in order to maintain the manufacturer warranty it has to be annually serviced by a NIBE-approved partner. My nearest company is around 1.5 hours away so I think the cost of the immersion heater running for a few days will outweigh any emergency call cost!

I think the only option I've got is to have to spend the money getting it serviced and looked over and will grill the engineer for advice on how to use the bloody thing!

Steve

QrizB

SJWILLS91 said:

I've been in contact with a company to get it serviced as it also turns out in order to maintain the manufacturer warranty it has to be annually serviced by a NIBE-approved partner. My nearest company is around 1.5 hours away so I think the cost of the immersion heater running for a few days will outweigh any emergency call cost!

How old is the heat pump, is it still under warranty cover?

Reed_Richards

If you lived in a sauna or a large restaurant kitchen then recovering heat from exhaust air and transferring it to where it can be useful makes good sense.  But in a small flat I cannot believe it is the right tool for the job, even when working properly.