LG Therma V monbloc DHW recirculator pump not running

[Willits]

Hello All,

I have a Therma V 9kw monbloc installed with a DHW tank and recirculator pump. 

All is working as expected except the recirculator pump is not coming on. 

DIP switch #2 is off and  #3 is on and the pump is connected to TB1 terminals 19 & 20 - water pump C. 

In the DHW menu recirculation time is set to “use” in the controller (for now I have set it at 60 minutes on and 5 off so I can see if it is running). 

My pump is a Grundfos Alpha 1L which uses a maximum of .26 A.

I must be missing a setting or jumper somewhere.

Does anyone have some advice what else to check? 

Many thanks,

Peter

 

  

 

[ProDave]

Are you sure those options don't refer to a split system (unit and outdoor unit) where I think you have a monoblock?

 

Check the obvious first, is power to the pump being turned on?  any errors showing on the controller?

 

And the vital question, is this a newly installed system and the pump has never worked, or did the pump previously work and has stopped working?

[Willits]

Hi Dave, 

 

I am fairly sure the manual I'm reading is for the monobloc I have.  All the other terminal connections matched up with the unit and manual and worked as expected.   

 

The issue is exactly that there is no power being fed to the pump.   It is a new installation and pump has not yet worked.   I did direct wire the pump to a socket to make sure it works and it does.  

 

There are no errors shown on the controller.  

 

I did not find an option on the controller  to test run the circulator pump.  

 

Thanks again.  

 

 

 

 

[ProDave]

It does seem to me a little odd to actually have the ASHP control a hot water recirculation pump.  Most people wire that independent of the heating system with timers, sensors, etc which is a whole other topic how you want it to run.  It might just be simpler to do that?

[Willits]

If I can't get the ASHP control to work that is my plan.    

 

I was trying to avoid adding another piece of equipment.   Especially since the function and connection point is already there.    

 

 

 

[JohnMo]

I would start at the heat pump end, select the pump on, and actually check if the terminals have power, if they don't, it's a setup issue, or that option isn't included in your particular ASHP. If they are powered you have a wiring issue to sort in the house.

[Willits]

Hi John, 

 

What I am not finding is a way to set the circulator pump to on so I can check if the terminals receive power.   

 

The only thing I could find is the DHW recirculation on/off cycling setting.   Which I am guessing when set should enable the power to the pump but in my case does not.   

 

Indeed the manual states series 3 models don't have the option but the series 4, which is mine, does.   

[ReedRichards]

Quote

Therefore, external time scheduler to determine when the recirculation pump should turn on and off is required.

 

Do you have one?  I think the previous sentence misses a "not" so the meaning is inverted.  Should say: 

 

Quote

The recirculation pump should not be operated when the DHW demand is not required

 

I have both a Therma V and a DHW recirculation pump and they function perfectly well completely independently.

[Willits]

Hi Reed,

I fully agree, I can achieve the circulation with an external unit.  

I was trying to take advantage of the built-in function for the DHW circulation since it is there. 

Everything is connected as per the manual and the only issue is it is not turning the pump on and off.  i.e. not supplying power to the terminal block connection points for the pump.  

Thanks

 

 

[ReedRichards]

On 05/11/2023 at 09:25, Willits said:

I was trying to take advantage of the built-in function for the DHW circulation since it is there. 

My reading of the manual you quote is that this built-in function is not intended to work standalone.  So maybe it just throws a switch but requires the pump to be powered independently.  Then you wire it so the live goes to the recirculation pump via the heat pump so the recirculation pump is energised by a switched live as required.   

[Willits]

 Hi Reed,

That is a good point.  I was thinking that the heat pump provides 220 and switching on and off according to the program.  That is how the how the 3 way valve is running.   But the connections acting as a switch makes sense.   I'll check that tomorrow.

May thanks.