@cathoderay Re your ‘rant’ - I have shouted at the radio when Tim Harford has made spurious claims about baby boomers being supported by generation whatever-letter-it-is-at-the-moment, and I shouted at the TV on a regular basis during the Brexit crisis, but not because the BBC as a whole is biased. But targeted ads and what is deemed “relevant to me” are my particular bete noir.

Re Freeze Stat setting: Heating Engineer has been and checked glycol. It is good to -12 degrees. As per usual a verbal explanation has not stuck in my mind with precision….basically what he said is that Freeze Stat setting prevents the coils from freezing - at 3 degrees the pump reverses its action and heats itself. This is the one that I am most interested in but now I think it will be OK. AND - if the coils do ice over as with my neighbour’s Ecodan, it is OK to trickle luke warm water over them, avoiding the wiring on the left hand side of the unit. Freeze protection is separate, where the pump senses as you say that oops the weather is getting too cold and it switches itself on. This happens regardless of the Freeze Stat setting. All dependent on a power supply existing. A prolonged power cut will be a problem under either circumstance. A couple of years ago there was a power cut which lasted two days here and about 11 days in parts of Aberdeenshire. So it does happen. Some systems don’t have glycol in them eg Daikin. 

One thing you don’t want to have is anti-freeze valves in your pump - these open up and drain the system. And then after that apparently it costs £££ to have it refilled, and after that the valves never really close again properly, so your system is leaky. 

I'm not sure if this will help anyone, but I made a "roof" for my Samsung HP I noticed that the rain/snow was freezing up as it ran down both the intake and exhaust sides of the HP. The roor extends out by about 6 in from the front and rear of the HP and  allows the rain and  snow to remain clear of the HP and drip to the ground and thus the HP operates with a clearer airflow and less defrosting required. Normally our HP runs all the time from October to April, controlled by a hive thermostat and unless the temp drops below -15C outside we can leave the weather comp. at -5C which puts water temp at 32C, keeping the house at 18-19C. I suspect the "roof" also has a slight effect on cold nights, when the pump isn't running, keeping the temperature slightly higher much like a car port does.

New member here based in the UK. I've got 2 Mitsubishi Ecodan 11.2kW R32's set in cascade. My installer says it's impossible to record the efficiency of the units because they are in Cascade. There's apparently no way to get the power created data.... (I can see how much electricity they are using as each pumps a monitor attached to its feed on the consumer unit). 

I find this hard to believe....anyone have or installed Mitsubishi's in cascade and worked out how to do it please?

my FTC6 controller doesn't have the reporting screen...its missing.

thanks all 👍 

@iancalderbank just had explanation from Heating Engineer. Freeze Stat function triggers the pump to reverse cycle at 3 degrees, heating itself to prevent the coils from icing up. My Freeze Stat is effectively set to OFF. This is OK because the glycol in the system is sufficient protection down to -12.

Posted by: @amanda1

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@iancalderbank just had explanation from Heating Engineer. Freeze Stat function triggers the pump to reverse cycle at 3 degrees, heating itself to prevent the coils from icing up. My Freeze Stat is effectively set to OFF. This is OK because the glycol in the system is sufficient protection down to -12.

Did your Heating Engineer clarify which pump is reverse cycling, the water pump or the heat pump?

The water pump will not operate in reverse and neither will the compressor. What I think that your 'heating engineer' was referring to was when the refrigerant gas flow is reversed within the heat pump unit, when it performs the defrost cycle. This has nothing to do with the Freeze Stat.

When enabled, I would expect the Freeze Stat function to operate in the following manner:-

If the outside air temperature falls below the setting of the Freeze Stat, the heat pump unit and water pump will be started, but only if the Leaving Water Temperature (LWT) from the heat pump is below 20C.

When the LWT increases above the 20C fixed value, the heat pump and water pump will stop.

If the outside air temperature remains below the Freeze Stat setting, and the LWT again falls below 20C, the heat pump and water pump will again be run to raise the LWT above 20C.

When the outside temperature increases above the Freeze Stat setting, this function is deactivated.

When operating normally during the heating season, it is unlikely that the LWT would fall below 20C, so activation of the Freeze Stat function would have no effect. It may be possible that if the outside air temperature falls below the Freeze Stat setting during an overnight indoor temperature setback, the LWT could possibly fall below 20C and cause the heat pump to operate for a short period of time.

I hope that this answers your query.

@amanda1 my, oh my

Welcome to the forum

A 6kW Ecodan doing 7+kW at -8C with a few defrosts

If for whatever the reason(too much boiler flue steam from the neighbour) the outdoor unit looks like this, the defrost can do so much, slow warm water is key.

@derek-m No. The Freeze Stat setting relates to the refrigerant coils at the back of the Unit icing up. And at the Freeze Stat temperature setting of 3 (or whatever you have set it to) heat being delivered back to the unit to deal with this.

And he was a heating engineer. I understood him correctly but I am not a scientist and I have not yet got to grips with the technical vocabulary for ‘reversing the cycle’ 😂 I think (in non-technical terms)  he said something about the pump taking back some of the glycol solution from the heating system to help defrost itself. And this concurs with what I found this morning on a Heat Pump installer’s website about how this Freeze Stat functions. It triggers the Defrost Cycle.

• Once the system has recognised ice building up on the heat exchanger coils (usually with temperature sensors outside), the defrost cycle will automatically activate.
• The system switches a reverser valve, essentially turning the process on its head. High temperature liquid from the buffer tank passes back through the compressor, creating a large amount of high temperature, high pressure gas. (In the meantime, either the immersion heater or some other secondary heating system will kick in to provide heating for your house.)
• This high temperature gas passes back through the external heat exchanger coils, quickly thawing the ice.
• The ice melts, and water droplets start filling up the soak way beneath the heat pump unit. Once the outdoor thermostat reaches a certain temperature (or the built-in timer finishes depending on your heat pump), the system returns to heating mode

@amanda1 please, enjoy the lecture(use the search function)

https://library.mitsubishielectric.co.uk/pdf/book/Ecodan_ATW_Databook_R32_Vol5_5

@fazel thanks for that - your KWh consumption looks promising.

@fazel yes thanks I had seen that before.

@transparent what exactly are you trying to say there? If it’s “Bullshit”, your ruminant is the wrong gender.