Help with Ecodan cooling

[Keno]

Hi all, have an Ecodan 8.5 heat pump with preplumbed hydrobox. SUZ-swm80va and box is EHST20D-VM2D. I have switched  the jumper at sw2-4 to on to activate cooling mode. Set flow temp to 12c

 

I now have access to cool the slab via UF pipes, the system works well for 3 minutes or so, the compressor kicks on and the pipes do indeed start to cool, but after about 3 minutes the system throws an error "PL" on unit OC.

 

When I look up the code on mitsu installers website I get

"Abnormal pipe temperature is detected in cooling mode."   

"The liquid pipe thermistor on the indoor unit has detected 75c or more when the system is in cooling mode."

"Check the 4 way valve is operating correctly. Run the system in heating and cooling and check the operation of the valve in both modes."

 

Has anyone run into this issue before, it seems like all the threads Ive searched, most Ecodan owners here just flip the jumper at sw2-4 and it works for them.

 

The part I cant get my head around is "the liquid pipe thermistor has detected 75c or more", when both refrigerant pipes coming in and going out of the inside unit feel very much cold.????

Edited July 18, 2021 by Keno

[dpmiller]

One of the refrigerant pipes should be getting hot tho if it's pumping heat. Water pipes cold yes, but the refrigerant should be carrying the heat. It does indeed suggest that the outside unit isn't switching the whole way over.

Perhaps give the valve a gentle tap while energised and see if it drives farther?

[Keno]

I have located the thermistor on the liquid pipe within the hydrobox inside , the pipe is defiantly cold, there is no way that any pipe within the unit is +75c or even close to it.

 

Still confused  

[Keno]

Issue resolved! For any Ecodan users, this maybe of help for future diagnosis.

 

It turned out that when the compressor is exposed to direct hot sunshine as we are having  now, the thermistor reading would be way off, tripping the PL error, I have simply shaded the compressor from the sun but left ample air flow  around the fan/coils.

 

Flow temp is constant 12c and floors are about 17-18c, will see how long the house takes to cool now.

 

Just wondering how other users are finding the slab cooling method in this heat?

[Happy Valley]

Interesting thread.

 

Please keep us updated as to how it performs.

[Keno]

The slab cooling is performing really well, house is very cool now, as its 30+ outside with bright sunshine. 

 

I have to say Im shocked at how well this works.

[jack]

26 minutes ago, Keno said:

The slab cooling is performing really well, house is very cool now, as its 30+ outside with bright sunshine. 

 

I have to say Im shocked at how well this works.

 

I always say it feels like walking into a large stone church or a cave on a hot day. There's a very different (better!) quality to the coolness compared to air conditioning.

[Wil]

1 hour ago, jack said:

 

I always say it feels like walking into a large stone church or a cave on a hot day. There's a very different (better!) quality to the coolness compared to air conditioning.

Sounds like my old leaky house on a warm day. 

 

It's just that here it feels like we're running slab cooling in the winter too...