heatpump wont heat when below -5 C outside temp

Im a commercial ref tech from Denmark and havent really played with heat pumps before but today
I was sent out to a chinese heat pump (type Andes) that wont heat when outside temp falls below -5 C. There is a red light on the indoor unit that flashes and the unit blows cool air for a while before it starts up again.

When I run it in cooling mode i get a suction pressure of 3 bar eff. The system run R410A so thats about
-5 C . The outside temp was about -8 and the condenser (outdoor unit) fan was running 100 ( couldnt find a fan speed controller ) at the time so i think the charge it right and the low suction pressure is because of the low ambient temp.

After i ran the unit in cooling mode for 20 min I swiched to heating and surprise surprise it started heating .

Is it because of the low ambient temp that the unit can heat ?

Quote:

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Originally Posted by hlogp

Im a commercial ref tech from Denmark and havent really played with heat pumps before but today
I was sent out to a chinese heat pump (type Andes) that wont heat when outside temp falls below -5 C. There is a red light on the indoor unit that flashes and the unit blows cool air for a while before it starts up again.

When I run it in cooling mode i get a suction pressure of 3 bar eff. The system run R410A so thats about
-5 C . The outside temp was about -8 and the condenser (outdoor unit) fan was running 100 ( couldnt find a fan speed controller ) at the time so i think the charge it right and the low suction pressure is because of the low ambient temp.

After i ran the unit in cooling mode for 20 min I swiched to heating and surprise surprise it started heating .

Is it because of the low ambient temp that the unit can heat ?

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3 barg on 410a is nearer -20 not -5.

I think somthing is wrong with your readings or system.

taz

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Heating at -5°C for most Chinese non inverter system is prety much impossible mission. Swich it OFF and don't use untill outdoor ambient is above 0°C. It is cheaper to heat with electric heaters and you wont damage compressor.

Agree with Nike. The reaon you got it to work AFTER running on cooling for a while, is that you had put some heat into the outdoor condenser. Switching then back to heating would temporarily 'fool' the system (control board) into thinking that the outside ambient is not so low as IT ACTUALLY IS. Sorry, but at those temperatures a heat pump ceases to be useful.

Are you refering to the outside ambient temperature? Where I live pretty much well every H/P is set up to lock out aux. heaters until -15c outside temp. Still providing 85c-95c supply air temps.

Quote:

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Originally Posted by HvacKevin

Are you refering to the outside ambient temperature? Where I live pretty much well every H/P is set up to lock out aux. heaters until -15c outside temp. Still providing 85c-95c supply air temps.

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I mean F scale not Celsius for supply air temps

')

I'm sorry to hear about the trouble.But,in China,the technology is mature now but only for some brands heat pump which can work well with the ambient temp. -5℃ So a good choice is upper important.

By the way,"Andes" should be Japanese brand......

I did some testing with a Bunch of Chigo Units from China and i was able to still get 105-110 degree F (43 degrees C) discharge air when it was -3 degrees F(-19 degrees C)....

I have NEVER seen any heat pump that could sustain 85-95 degrees C at the vents for any length of time... that would seem to spell a crash for the compressor!!
-Christopher

When you do these runs, strap a thermocouple to the compressor discharge (150 mm from compressor) & monitor the discharge temperature.

If it gets up into danger territory (nominally 107-110'C), that will be your limit of safe continuous operation. For short periods, excursions of 110 - 115'C can be tolerated, but watch the time over temperature.

its madness to say that just because something is from china (or anywhere else) it 'cant' do this or that.

What DOES happen is, installers put their rose tinted glasses on and expect kit that is less than half the price to do the same.......er thats why its half the price. Usually this is backed up by the test data....which again mostly gets ignored.

I have a made in china heat pump on my victorian vicarage. All through the nightmare of last winter (we didnt get above -4 for nearly 3 weeks) it kept us going. Maybe some would not have, maybe some would have done it better, but we got value for money.

I've fitted viessmann ground source units that have not worked out of the box. On those days, I would have given my right arm for a unit from china that worked.