Heat pump / inverter DIY

thechippy

richardc1983 wrote: »

Thechippy, i would like to ask you a question as I am unsure if my system is faulty.

As you can see from my previous posts I have 1 x FM25Ah outdoor multisplit unit connected to 2 x MV12AH (3.5kw) indoor convertible units, (lounge and bedroom)

The outdoor unit is RATED at 1990 watts going down to 1194watts (maintaining setpoint) when both indoor units are on cooling when maintaining setpoint (inverter ramping up and down). This is as per the product specification databook based on certain operating conditions outdoor ambient etc. This figure is pretty spot on though and very accurate.

However in heating mode its a diff situation totally. It says that to have both units turned on in heating and set point of 20C outdoor ambient 7 which is what it has been last few days here in Leeds that the outdoor unit is rated at 2280W, dropping to 1368W (i assume when only maintaining set point)

I checked this yesterday and today and it only ever gets to 1368W if one unit is operating maintaining setpoint. WHich apparently if only one unit is operating it should drop to 800w. It doesnt seem to be ramping down to the 800w so the unit cycles when mainting setpoint. It cycles in cooling but am not bothered because it is costing next to nothing to run.

If both units are running at max power on heating i.e room temp diff of 3C (inverter ramped fully up) the quoted max rating of the outdoor unit is 2500W however its registering on my energy monitor as 2900W even when only maintaining set point, this drops perhaps to the rated input when its maintaining setpoint.

When only one unit is operating in heating mode the max it will ramp down to is 1300W when its maintaining setpoint. This is no where near the 800w mark that is quoted in the specs? So im dissapointed as yes its cheaper than electric heaters but having checked with the energy meter its using more than I was expecting it to. Cooling is very cheap and within the specs quoted, heating is always like 2280W when both units are on and maintaining set point. No where near the 1368W quoted for the min input on the sheets.

We pay 18p per unit of electric and were putting in about £5 a day in coins when were using it both units, and prob about £3 when using just the one unit.

To say an electric heater uses 2kw well this is using an extra 500w when both units are on (yes it heats the whole flat using 2500w as apposed to one room but I want the quoted specs. The units are oversized a little but all doors are left open so it also heats our large hallway so the doors are never closed. Its like it doesnt ramp down early enough so it goes overset point. Cooling mode it sometimes maintains setpoint of .5C but in heating it seems to always be 1C before it clicks back in and 1C oversetpoint before shutting off its not as precise. When its 1C off setpoint it should be pretty much ramped right down but it still doesnt seem low enough for it to go over set point. Once its reached the set point point it stays on until its gone 1C over but doesnt seem to slow down.

For instance it just cycled back on in both rooms and was using 2300W but then cycled back off and didnt seem to ramp down.

Can you shed some light on this for me? The equipment is LG and before u say it has been great in the summer no probs at all, I know LG dont have a good reputation and all that but this is what ive got!

The link is here to the specifications data book. Scroll to my model of outdoor (FM25AH) on the combination tables and you can see the figures for heating and cooling below the cooling. http://mylg.co.uk/data%20for%20site/multi%20f%202008%20outdoor.pdf

The installer who put it in did it as a favour and i got it a lot cheaper than normally but I feel if i keep asking him out and saying its not performing properly in heating that im being a bit ungrateful really. he has connected his ampmeter to it and he says its running properly but I dont think he left it long enough he only measured it on 30C flat out which I think is still using more than it should.

Any help appreciated matey.

Rich.

Hi,

I’ll do my best, but it’s quite difficult to diagnose when the system is not in front of you.
The electronics are very complicated with numerous sensors. The system will be sensing air temp on and off the indoor unit and air on and off the outdoor unit. It will use this to determine the compressor speed and therefore load.

If one of these sensors is faulty, you will have a problem.
As the set point is reached, the compressor should slow down to a point where it tries to maintain that temp. Should the temp continue to rise and go above set point, then the outdoor unit will shut down.

If yours is not slowing right down as the set point is reached, you may have a faulty sensor.

That’s the best I can do without physically being there to have a look, although I’ll try to investigate further. The only other option, is to call out an engineer and get him to call LG technical dept whilst he is on site and able to take readings to pass to them.

Hope this helps.

G.

thechippy

stevehead wrote: »

Here's my setup - I made this today and dropped it on Youtube for U
http://uk.youtube.com/watch?v=79UAPRI6p-M

Nice video,

I'll probably be going Mitsubishi as well, but am awaiting prices.

G.

richardc1983

thechippy wrote: »

Hi,

I’ll do my best, but it’s quite difficult to diagnose when the system is not in front of you.
The electronics are very complicated with numerous sensors. The system will be sensing air temp on and off the indoor unit and air on and off the outdoor unit. It will use this to determine the compressor speed and therefore load.

If one of these sensors is faulty, you will have a problem.
As the set point is reached, the compressor should slow down to a point where it tries to maintain that temp. Should the temp continue to rise and go above set point, then the outdoor unit will shut down.

If yours is not slowing right down as the set point is reached, you may have a faulty sensor.

That’s the best I can do without physically being there to have a look, although I’ll try to investigate further. The only other option, is to call out an engineer and get him to call LG technical dept whilst he is on site and able to take readings to pass to them.

Hope this helps.

G.

Yes theres no way of telling what it is really, the indoor sensor was faulty on one the units, shutting off late in cooling so the sensor was 1C out. However the return sensors are working as these have been checked. So the outdoor unit must be the problem, however its fine in cooling and very efficient, this is what I dont understand!

U see I cant really afford at the minute to get a different engineer out, and dont really wanna keep asking the same installer back out cos if i start saying theres a problem and he says there isnt its like im telling him his job. The system was only installed in June so has all its parts warranty etc.

Do u ever get up to Leeds? Would I be cheeky in asking if you could check things for me?

Kind regards
Rich.

richardc1983

stevehead wrote: »

Here's my setup - I made this today and dropped it on Youtube for U
http://uk.youtube.com/watch?v=79UAPRI6p-M

Steve

Good video, What temps do you get in the lounge and the bedrooms?

Do u leave the units on 24/7? HOw well insualted is the house?

Love the lights in the lounge around the coving.

thechippy

Hi Rich,

I'm about 4 hours from you unfortunately, otherwise I would have a look no problem!
I'm still investigating, so maybe have an answer for you soon.

Take care

G.

richardc1983

Ok thank you Chippy.

What is it your investigating??

Im on another forum too and have put a post on there. This is the response I got on there...

http://www.refrigeration-engineer.com/forums/showthread.php?goto=newpost&t=16465

thechippy

richardc1983 wrote: »

Ok thank you Chippy.

What is it your investigating??

Im on another forum too and have put a post on there. This is the response I got on there...

http://www.refrigeration-engineer.com/forums/showthread.php?goto=newpost&t=16465

I'm a member on that forum. I posted a copy of your query on there.
Although I have installed (and repaired) many heat pumps, vrv's, vrf's etc - I don't do it all the time. I also install a lot of large commercial coldrooms. I thought I'd pose your query to those that do this 100% of the time.
A good friend of mine is a trouble shooter for a very large a/c company - he is popping around tomorrow night for a glass of wine and I will show him your query as well.
However, I still think it's a sensor fault at this stage.

G.

stevehead

richardc1983 wrote: »

Steve

Good video, What temps do you get in the lounge and the bedrooms?

Do u leave the units on 24/7? HOw well insualted is the house?

Lounge is kept at 22 daytime, 24 nighttime; everywhere else sits at around 21-22.

The aircon is only on all day if the sun don't shine and it's a northerly. Normally, it's on upstairs 7am-9am then 4pm-10pm and downstairs 7am-10am and 4pm-1am.
This varies, and I only use the timer to start the system and turn it off up/down manually.

My house is well, but not very well insulated. The draughts have been delt with, and loft and cavity walls sorted - but v old double glazing remains to be done. Hey... Rome wasn't built in a day!

richardc1983

Your house stays at a pretty decent temperature really doesnt it.

My ground floor flat which is in a converted victorian house has thick walls and large bay windows and double glazing but does not have any insulation in floors etc. There are draughts under the winidows despite double glazing and if outdoor temp is about 2 or less the inside can drop to 14C overnight easily.

Do you set the timer each day and night before u go to bed etc as mine is only a 1 event timer, so once its been on and off u have to set it again.

stevehead

richardc1983 wrote: »

Do you set the timer each day and night before u go to bed etc as mine is only a 1 event timer, so once its been on and off u have to set it again.

I've never tried timed on/off Rich, just on before bed for the warm morning effect. Currently the house drops to 17/18 by 7am.

I use to live in a victorian flat and I always miss the larger room sizes, especially the tall ceilings. Bound to be harder to insulate, especially if a rental. Killing all the draughts will drop your bill.
Y'know what I'd love to do? Give the place a once-over with a thermal imager and see where the heat's escaping. There's some good FLIR pics on the web from Thermographers showing missing insulation, duff double glazing panels - really useful to know.