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Dinka
12-01-2010, 02:01 PM
We have Mitsubishi Electric (Ecodan) Air to water heat pump for a month. We run it 24/7, at beginning we had 16'C on thermostat, it was nice and warm. When temperatures outside started to drop, it felt cooler at home, so we gradually raised to 21'C. Don't know for how long time, but one day we noticed that the fan has not been working for the whole day, although it was warm in the house. First idea was that there is fault with it. We turned heating off, after an hour and half on again, fan was working. We left it on continuous again and again it was not working! Then we reduced temperature on thermostat to 17-18'C and now it is working fine, but we don't have desired temperatures at home. We have emergency back-up, obviously it was working instead of heat pump, but why would that be that way? Would be grateful for any advice. Forgot to notice- we live in 2 beds new build house.

taz24
12-01-2010, 02:22 PM
We have Mitsubishi Electric (Ecodan) Air to water heat pump for a month. We run it 24/7, at beginning we had 16'C on thermostat, it was nice and warm. When temperatures outside started to drop, it felt cooler at home, so we gradually raised to 21'C. Don't know for how long time, but one day we noticed that the fan has not been working for the whole day, although it was warm in the house. First idea was that there is fault with it. We turned heating off, after an hour and half on again, fan was working. We left it on continuous again and again it was not working! Then we reduced temperature on thermostat to 17-18'C and now it is working fine, but we don't have desired temperatures at home. We have emergency back-up, obviously it was working instead of heat pump, but why would that be that way? Would be grateful for any advice. Forgot to notice- we live in 2 beds new build house.


By fan are you refering to the outside fan?

Because your on air to water the heat pump takes the energy from the outside air
and transfers it through the system into the water that is circulated in the house.

As the weather gets colder you have noticed that you need your heating to be higher
to cope with the extra cold spell. I would say this is normal.

Now as to the fan running or not.
The fan circulates air over the heat exchanger and the transfer is made. The fan only
works if required, it is automatic. It may come on, off and speed up, slow down as required.

If everything was ok set to 20 odd degrees just set it back and let it do its job.

Also to maintain effiency the system warms up the outside heatexchanger to make sure it
does not freeze up. The colder it gets outside the more this will happen, that also results
in the fan being off.

If its working leave it and see what it does.

taz.

.

Dinka
12-01-2010, 02:44 PM
Thank You, Taz.
Yes, by fan I meant outside fan. Well, I understand that pump works as it is required, I just couldn't get why it comes on more often when we turn heating down and doesn't come on at all over 20 degrees. We were worried, as if back-up is turning on, it won't be efficient at all.

NoNickName
12-01-2010, 03:47 PM
Heat pumps are not efficient in low ambient temperature, and back up is required, especially in countries of colder climates, like sweden.
Now, I see you're in the UK which is experiencing very low ambient temp. these days. It may be possible that the unit wouldn't run because of low pressure in low ambient temperature. The reason may be inefficient defrosts or shortage of gas or dirty coils...
There is always a break even ambient temperature for which energy consumed and energy released in a heat pump equates, below which an electric heater is more energy efficient.

Dinka
12-01-2010, 05:06 PM
So does it mean that was only contingency? We'll have to try to set higher temperature again when it gets warmer outside. Must note that heat pump is new, I don't think coils would be dirty. I don't know much about heat pumps, although I have been reading a lot over the internet, anyway I don't know how to spot inefficient defrosts, have no idea about shortage of gas (as we are on electricity only) etc. Well thank You guys for response :)

NoNickName
12-01-2010, 05:41 PM
Shortage of gas in this case means shortage of refrigerant. Surely an electric heat pump is not affected by shortage of fuel.
Also, a coil may be dirty because of snow packing up on the fins.

Dinka
12-01-2010, 06:47 PM
The thing is, our neighbours have the same heat pump, it has worked whole time, even at low temperatures. That made me think that something's wrong with ours. I will try to contact builders regarding this to take a look. Thank you again.

back2space
22-01-2010, 03:53 AM
I suspect you have caught the unit in a defrost mode. If you have set the temperature higher the unit might be working non stop to try to achieve the higher flow temp, this could mean more defrosts that last for a longer time.

If the temperature is below 0C the fan does not run when the coil is defrosting, this is to maximise the defrost, only when it has defrosted would the fan run to then dry the coil out.

When the fan is not running can you here the compressor running in the outdoor unit? In heating it should be noticeable by a humming sound.

When you have set 16C the unit is probably finding it very easy to achieve this temperature as 16C set point is quite low for most peoples comfort level so the unit is probably not doing much work so you will notice that defrosts are few and far between.

If system is working and your house is warm enough at 20C I wouldnt worry about it.

have you observed if there is frost building up on the coil when the fan does not run?

This cycle should only run for maximum of 10-15mins when it is very cold.

THe control panel when it is defrosting will show a defrost symbol, in the same area that it shows heating it will say defrost...

Page 22 of the manual explains the different symbols.

http://ecodanlive.mitsubishielectric.co.uk/pdf/ecodan%20home%20owner%20manual.pdf

If it is displaying defrost when the fan is not running this is normal.

The manual also points out that Heating Eco mode should be used when heating as this will ensure the optimum settings are used based on outdoor temperature. IT will change settings automatically for you so you only need to adjust the room temperature.

Have a read through the manual to familiarise yourself with the system.

Are you setting the temp of 16/21C on the room thermostat or the digital control panel?

fridge doctor
22-01-2010, 12:02 PM
This is all very good advice Dinka, and I realise that you are trying to understand how this equipment works. To be absolutely honest, it isn't technology that you can get to grips with unless you are a technician in the field of refrigeration and heat pumps. There are so many possible reaons why your fan isn't running, and your neighbours is, that we could banter back and forth all day. One very good reaon for there being disparity is simply the location of the outdoor unit. Perhaps there is a difference in terms of sheltering from wind or sun or both? It has been suggested here that the reasons for the outdoor fan not running are either
1/ Because it is not needed
2/ Because it is on defrost
And both of these are correct.

For peace of mind, try this. Turn the system on from scratch - say when you get home, and set it to 21 degrees. When the room gets comfortably warm go outside and check the fan. Keep doing this until you find the fan stopped. When this happens put your hand on the two pipes coming from the bottom RH side of the unit (you may have to pull back the insulation) If they are hot then your fan has stopped because it is not required at that time. If they are ice cold, your system is performing a necessary 'defrost'. If they are indifferent and there is no noise from within the cabinet, the system has quite probably reached 21 degrees and stopped. By all means get the guys back to check it if you must, but it sounds like it is probably OK from what you have said so far.