LG Therma V mono block Air Source Heat Pump

[dpmiller]

I'd go parallel rather than switching between two; the momentary OC might cause a code.

[ProDave]

30 minutes ago, dpmiller said:

I'd go parallel rather than switching between two; the momentary OC might cause a code.

I just tried simulating that and open circuited the thermistor while it was heating the tank.  It throws up a CH08 fault "fault with water tank sensor" after 3 seconds but resets and continues operating when I re connect the thermistor. So I  think it should be okay with a brief O/C while the relay swaps over.

 

The trouble with parallel, is if the hot tank is already very hot, it might cause a reading that is too hot (above 100)

 

Oh and I have just discovered annoying quirk #5 with this unit.  You cannot adjust the set point temperature for the hot water when the heating is turned off. To do that, you have to go and turn the heating on, where upon it will let you set the heating temperature and the hot water temperature, then go and turn the heating off.

 

I get the feeling I am using "user interface version Beta A"

[ProDave]

The temperature probe switchover relay is now installed. With the relay de energised it is connected to my 560 ohm resistor and that gives a temperature reading of 85 degrees which is way above the setpoint so the hot water heating is off.  When I turn the hot water on at my programmer, the relay energises and switches over to the real temperature probe, and the hot water heating turned on immediately, giving a current tank temperature of 38 degrees.  So that appears to be working.

 

I am making some progress on these spurious flow errors I keep getting when everything is idle. So far LG have not been much help in solving this.

 

Yesterday I just happened to be next to the controller when one of these flow errors happened.  What I saw was the "on" light came on very briefly, just for a fraction of a second, and the pump also ran for that very short period. Then a few seconds later up came the low flow error.  It is no surprise it didn't measure any flow as the pump was on such a very very short time.  This got me thinking WHY did it power up for such a short period?

 

As a test, I have for the moment disconnected the thermostat input to the heat pump (this is what calls for room heating when needed) and with that disconnected it has now gone 24 hours without a spurious low flow error.

 

I don't believe it is the UFH manifold controller that is generating a real short demand. That is all very basic relay logic. There is nothing there to glitch like that, and the room thermostats are all mechanical, so again they would not glitch like that.  So I am wondering about crosstalk? Perhaps the thermostat input is a high impedance input with a stupidly sensitive threshold and it sees a small spike from an induced voltage from something else?

 

To test that theory, I am going to re connect the thermostat input, but connect a load resistor and a snubber to try and kill any induced voltage it might be seeing.  I will report back once that test is done.

[newhome]

Saw this on eBay @ProDave

 

https://www.ebay.co.uk/itm/Air-Source-heat-pump-LG-ThermaV/302816426425?epid=25021697740&hash=item468143f9b9:g:iukAAOSwLg5bVh84#viTabs_0

 

 

[ProDave]

8 hours ago, newhome said:

Saw this on eBay @ProDave

 

https://www.ebay.co.uk/itm/Air-Source-heat-pump-LG-ThermaV/302816426425?epid=25021697740&hash=item468143f9b9:g:iukAAOSwLg5bVh84#viTabs_0

 

 

Interesting. That's the split system one, not the monoblock, so there would be a gassing expense to install it, and they should have got it properly degassed not just vented before removing it.  They mention a "pump problem" I wonder if that is the spurious CH14 flow errors that I was getting? I am convinced that if installing one of these a flow meter is essential so you can check the water flow rate you are getting.  This might make a good buy for someone but personally I would stick with a monoblock unit.

 

I can confirm after leaving my unit on for a week now, that the pull down resistor and snubber has cured the spurious flow error problem.  I have sent an email describing what I have have done to cure the problem and suggested they send it to someone technical and consider modifying the unit.

 

What I used in the end was a 100K ohm resistor from the thermostat input to neutral. That was about as low as I wanted to go, and that will dissipate about 0.6 of a watt so I used a 6W wire wound resistor as the next one down that I had was only 1/2W.  In parallel with that was a snubber which is a 0.1uF capacitor in series with a 100 ohm resistor.

[ProDave]

I have recently made some changes after we had a "ran out of hot water" incident (something I thought would not happen with a 300L tank)

 

It was a perfect storm.  SWMBO had been doing some cooking, which seemed to mean the hot tap running for some time to rinse stuff.  Then she had a shower, not the normal one, but the monthly "put loads of different conditioner in the hair" showers that takes longer.  Then daughter ran a bath, or tried to and got half a bath of hot water.

 

So I was in the dog house instructed to "fix it"

 

The problem was simple.  I had put the temperature probe in the top thermostat pocket, which is about half way down the tank.  Analysing what happened, is half the water had been used up before the probe even knew the hot water was being depleted, and that just did not leave enough for the shower and bath.

 

The fix was simple. Move the probe to the bottom thermostat pocket that is about 1/3 up from the bottom of the tank.

 

It now behaves very differently.  Before it would heat the tank and then do nothing for a day.  Now it heats the tank much more often, but for shorter periods. So it starts to re heat a depleted tank of water much sooner, making the chance of running out much less.

 

A by product of keeping it topped up more often has been I have reduced the set point temperature another couple of degrees.

[Nickfromwales]

17 minutes ago, ProDave said:

A by product of keeping it topped up more often has been I have reduced the set point temperature another couple of degrees.

Got it down to 35oC now eh Dave ?  . 

[Declan52]

Think when Dave goes out for a day in the new boat the wife and daughter will have it cranked up to 55 and be enjoying hot water that would take the skin off a man.

[newhome]

1 hour ago, ProDave said:

Then she had a shower, not the normal one, but the monthly "put loads of different conditioner in the hair" showers that takes longer.

 

See, I'm not the only person who uses the 'leave in hair for 7 minutes' conditioner 

[Sam Barber]

Hi,

 

I live near Kinross in a self-build (or more accurately a custom-build, as I did not build it myself) house with an LG Therma V air source heat pump installation for heating and hot water.  I've also had numerous CH14 flow rate errors on my heat pump.  We've been in the house 2 years now, and have had the problem intermittently since installation.  At first it was only for a couple of hours at a time, weeks or even months apart, and it always just seemed to fix itself.  Recently though it's become an almost permanent issue i.e. the system has been offline more than it has been operational.  At the time of writing, it has been off for over a week and we have no heating in the house.  (We still have hot water, thank goodness, which I assume is the immersion heater in the water cylinder operating by default.)

 

I was hoping you could provide a bit more information about the fix you achieved, in terms of what I could instruct a plumber or electrician to do (I am just not knowledgeable enough about electronics to even attempt to install the fix myself).

 

Thanks

[ProDave]

LG let themselves down badly with information in the installation manual, but their telephone technical help line solved the problem.

 

CH14 comes up when the inbuilt flow switch senses the water flow is too low.  Sadly they don't say in the manual what the water flow rate should be, or how to measure it.

 

I bought and fitted a flow meter and fitted it into the flow pipe from the heat pump, and this showed that the inbuilt pump was not delivering enough water flow.  So I solved it by fitting a second pump inside the house in the flow pipe and that gave me enough flow and the problem has not come back.

 

I wouldn't worry with a flow meter, just buy and fit a second pump and that should solve it.  I just wired my second pump in parallel with the inbuilt pump. But that does mean an extra cable needs to be run from the heat pump to inside.

 

An alternative solution, as yours only tripps occasionally so is almost enough flow, might just be to replace the inbuilt pump with one that gives a higher flow rate.  It is a small Wilo pump they use so just replacing it for a larger type might be all you need to do, but you would first need to look up the quoted flow rate of the pump you have and seek something a little but more powerful.

 

If you are wanting just to get someone in, then I would suggest a plumber, ask him to look and see what pump is fitted already, then specify and supply a more powerful pump to replace it with.  Keep the Wilo pump as a spare, they are nice pumps as they tend to be very quiet, I fitted those to both my under floor heating manifolds because the original ones were too noisy.  But in this case it does not mater if the new pump is a little more noisy as it is outside.

[joth]

I'm guessing this flow rate has deteriorated due to dirt/sludge in the system, so another tack maybe to get the system cleaned?

 

Another thought: is this with radiators or zoned UFH? As an experiment try turning every room up to max temperature on the TRV/room stat and see if it goes away. It maybe that if you're only trying to heat one room there's not enough emitter capacity to get the necessary flow?

 

[Jeremy Harris]

FWIW, our Carrier ASHP is also really sensitive to flow rate.  The water pump on ours is a three speed one, so it can be adjusted as one way to try and stop it tripping out on low flow, but the thing that finally fixed the low flow error trips was fitting an adjustable pressure bypass valve.  This opens a "short circuit" between flow and return if the pressure in the flow pipe is momentarily too high (the ASHP seems to sense flow rate indirectly by measuring pressure) and by opening it lowers the flow pressure and stops the ASHP tripping out.  It needed a bit of fiddling about to get it to work, though.

 

The cause in our case was that the ASHP is running UFH, and the actuators take a fair time to open when the system is turned on, so the ASHP is initially working against a heavy flow restriction.  I changed the main actuator valve to a Salus temperature controlled servo operated one, that helps, as it only takes about 30 seconds or so to open, but that's still a bit marginal, as the ASHP seems to trip out after about 20 seconds or so, as far as I can tell.

[ProDave]

Yes an automatic bypass is essential. In my conversations with LG I think I found it needs to sense sufficient flow within 10 seconds otherwise it will trip.  Even a standard 2 port motorised valve will barely open in 10 seconds, so a bypass is essential.

 

In the case of the LG heat pump it is an actual flow switch which consists of a weighted flap that triggers a hall effect sensor when it moves to the "open" position.

[Sam Barber]

11 hours ago, ProDave said:

I bought and fitted a flow meter and fitted it into the flow pipe from the heat pump, and this showed that the inbuilt pump was not delivering enough water flow.  So I solved it by fitting a second pump inside the house in the flow pipe and that gave me enough flow and the problem has not come back.

 

I wouldn't worry with a flow meter, just buy and fit a second pump and that should solve it.  I just wired my second pump in parallel with the inbuilt pump. But that does mean an extra cable needs to be run from the heat pump to inside.

 

Thanks very much for your response.  I may have misunderstood the previous posts on this thread; it seemed to me that after fitting the second pump you still had some reoccurrence of the CH14 which you then remedied by fitting some electronics - your statement that "the pull down resistor and snubber has cured the spurious flow error problem".  Would you mind explaining the purpose of the resistor and snubber in that case? 

 

Thanks again

[ProDave]

9 hours ago, Sam Barber said:

 

Thanks very much for your response.  I may have misunderstood the previous posts on this thread; it seemed to me that after fitting the second pump you still had some reoccurrence of the CH14 which you then remedied by fitting some electronics - your statement that "the pull down resistor and snubber has cured the spurious flow error problem".  Would you mind explaining the purpose of the resistor and snubber in that case? 

 

Thanks again

Ah yes, you jogged my memory.

 

That was a separate issue.  That was a design fault causing the heat pump to very briefly turn on when it was not commanded to be running, which then triggered the "10 second check for flow" only the spurious demand had gone by then, so there was no flow.

 

So just to clarify.  Does yours trip with CH14 when it is running and actually heating hot water or space heating?  Or are you getting it tripping with CH14 when it is idle?

[Sam Barber]

5 hours ago, ProDave said:

Does yours trip with CH14 when it is running and actually heating hot water or space heating?  Or are you getting it tripping with CH14 when it is idle?

 

It's hard to say unfortunately, as I've not really seen it actually trip from working to not working.  Actually my setup has been unusual from day one, in that the little orange light on the control panel was almost always illuminated, even when there was no call for heating and the outside unit wasn't running.  The supplier seemed to think the light should only be on when the unit is actually providing heat, but the builder (whose electricians installed it) said it had been done right according to the wiring diagram he'd been provided with.  I have no idea whether the light constantly being on is any kind of issue or is contributing in any way to the flow rate errors.  In any case I would guess that the error trips when there is a call for heating, but I can't prove that.  

 

[ProDave]

Do you know how yours is configured?  In particular are you using the "room thermostat" input?

 

There are two ways you can run this unit.  One is entirely from it's own control panel. In that case there is a room temperature probe built into that control panel and that would in effect be the room thermostat.  If that is how you are using it, then this spurious input issue won't be your problem.

 

The other way is as I use mine.  I have the "room thermostat" input enabled. That is something you do at setup as you have to set a switch on one of the boards in the unit and it then uses this input, in my case from the under floor heating manifold to tell it when to do heating.

 

I am pretty sure if the orange light is on all the time you are not using the room thermostat input, my orange light only comes on when the heating is calling for heat via the room thermostat input.

[Sam Barber]

7 hours ago, ProDave said:

Do you know how yours is configured?  In particular are you using the "room thermostat" input?

 

The control panel is in the garage so definitely not using the temperature probe in the panel.  There are a number of heating zones in the house, each with its own thermostat.  Each thermostat activates an underfloor heating circuit.  This doesn't necessarily cause the heat pump to operate though; my understanding is that it will only do that once the temperature of the water in the water cylinder overall falls below a certain level.  So the operation of the heat pump is only indirectly linked to the thermostats.  (As a side note, I've noticed that when the heat pump is offline due to the CH14 error, the underfloor heating loops still operate when activated by a thermostat, but they don't pump hot water round as you'd expect, only water around 20 degrees or so.)

 

Hope that answers the question.

[ProDave]

It sounds like you have a buffer tank.  Perhaps a tank cylinder stat in the buffer tank drives the "room thermostat" input.

 

Is there any chance you could find this out for sure by taking the panels off the outside unit of the heat pump and look for something for me?

 

[Sam Barber]

Sure, I can do so tomorrow.  I had the front panel off the outside unit the other day to look at the pressure gauge (it was reading under 1 bar).  

 

In the boiler room there's a big water cylinder and also a smaller one, I think they called this a low-loss header.  Is that the same as a buffer tank?  

[ProDave]

Yes the low loss header is the buffer.

 

In case you don't have it here is the service manual http://www.solfex.co.uk/uploads/downloads/Installation_MFL62567801_8_130520.pdf

 

What I want to know is, are there any cables connected to terminal block  2 , terminal 17?

 

Oddly enough water pressure does not bother these units, I only run mine at about 0.5 bar.

 

 

[Jeremy Harris]

A low loss header is really just a way of making a bypass valve without needing any moving parts.  It doesn't usually have enough capacity to be useful as a buffer.  They work by using two hydraulic switches, in effect.  The flow in and out pipes are in line, as are the return in and out pipes, so flow normally runs straight across the header, in line with the pipes.  If the flow is restricted on the downstream side, then the upper hydraulic switch trips the flow downwards to the return end of the header body.  They work well for dealing with the case where the flow can be restricted by a slow to operate valve, or closed thermostatic valves, as they allow a bypass in much the same way as a bypass valve.  The only slight issue with them is that they partially rely on the temperature differential between flow and return to maintain a reasonable degree of separation between the two sides.  With a heat pump this temperature differential may be a bit low, so separation may not be quite as good as with a boiler. There are larger LLHs made specifically for heat pumps, like this one:

 

 

[Arvyd]

Hi, guys my name is Arvydas, at first I will tell that I am from Lithuania and sorry if my english is not so good. Now about 2 monts I am lucky ? owner of Therma v R32 9kw. I sent this heat pump from Italy and installed it at my self. Before I heatet my house by wood.  At yet I am not answered for some questios about how it will working for my self. On internet is not so many forums where guys talking about these pumps, seems that you are a more qualified than others in their discussion.

Maybe you can answer how this pump should working. I mean that if I right understand,  the best algorithm for heat pump is if it working all the time without shut downs. But my heat pump is heating the house  to as example 23 degrees ant shutting down, then working just water pump. After some time when temperature decrease heat pump turning on , and thats all the time. I did not find the answer or thats will be or not. Maybe you can help me to answer to this question. 

 

Edited December 4, 2019 by Arvyd

[ProDave]

I am not familliar with the R32 version, but if we assume it is the same as mine then the programming unit has timer functions built in.  But I found it a very complicated thing to use and set, so I decided not to use it for anything other than setting up parameters.

 

My unit has a hardware input for a "room thermostat"  To enable that you have to flick one of the DIP switches on the control board.  I use this, in conjunction with an ordinary central heating programmer to determine the on and off times of the heating.