Improving heat pump efficiency : circulation pump on Mitsubishi Ecodan

Sorry for my ignorance, there is water circulating between indoor and outdoor? I thought is refrigerant

I think monobloc pumps don’t circulate refrigerant outside the pump, making them simpler to install, so it’s water or water+glycol running to it.

I think PUHZ-SHW140 is a split unit, so does circulate refrigerant?

Thank you @mjr and @Timbones. How can I tell if it refrigerant or water circulating and ultimately if it’s safe to turn off freeze stat?

@pcman you can confirm for yourself in the data book

As @Timbones confirmed PUHZ-SHW140 is a split system.

I have a PUHZ-W112 which is a packaged unit and it has two insulated water pipes which run from the external units to supply the heated water to the indoor pipework. You should keep freezestat on if you don’t have glycol (I’m doing the same).


I took a picture of the water circuit diagram of indoor unit installation manual. My model is EHSC-VM6D so I believe it matches E*S* from this photo. My understanding is that I am running refrigerant between the inside and outside unit. Am I wrong?

The manual for the PUHZ-SHW140 does mention a refrigerant pipe…

And EHSC-VM6D is the accompanying “Hydrobox”, which monoblocks don’t have.

I’m pretty sure it is a split system.


Assuming it’a a split system, should I turn off freeze stat or there is something else I am not seeing. During winter, I have negative temperatures, sometimes -10 C

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@pcman listen to @Timbones, he knows his stuff. Turns out my packaged unit is a PUHZ-W112!

I’ll edit my original post so as not to mislead anybody else :slight_smile:


Thank you all. I turned off freeze stat and now my system consumtion is 25W when not heating

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