Ideally monoblock aren’t suitable for cold climate where severe weather conditions are expected in the winter ! Install split type and all worries are out the window ! Please make sure all refrigeration pipe work is well insulated . For example we use pipe work with 9mm insulation but then we add on additional 17mm pipe insulation all the way between indoor and outdoor unit! By doing this we minimise heat lost from primary’s … And off course when choosing your heat pump do consider Midea, Midea is amazing technology at affordable prices!

Vailant offer a heat exchanger that separates the Glycol circuit from the water + inhibitor CH circuit. It will cost around £700 so I guess you should only fit one if it is really needed. I don't know if there are any downsides to using one. Perhaps others can comment.

I think that's what I have installed by the house developer. It works well, but you do need to play with the switch over temp

The pump will always run in heating season. It should be weather compensated

@@HeatGeek do the ASHP’s know the system is not using glycol to do this? I don’t understand how weather compensation stops the water from freezing. Thanks.

There is no internal unit.. unless you mean the controller?

@@HeatGeek Yes, I meant the controller and possibly a hot water cylinder.

Heatpump is half at best the temperature of a standard house at 60c to 70c radiator temperature...half the temperature =double the radiator surface area and pipes to suit. The lower the Heatpump target temperature the more efficient.

@@benburton3496 That's the beauty of going hybrid. Even if it's absolutely impossible to set the flow temperature below 60°C without losing comfort when it's -5°C outside, that's only a fraction of the heating season. Most of the heating season it's around +10°C or more outside. Most of the heating season a gas boiler is switching on/off and/or modulating way down in power in order to provide the adequate amount of heat. If you would take an average of the flow temperature and power output of the boiler per day, you would see most homes only need a flow temperature of 40-45°C and just a few kW of heating power during 90+% of the days in the heating season, which is perfect for a heatpump. Since an ASHPs COP only drops near or below the freezing point when you don't use it in a hybrid setup, and it should be ideally dimensioned for the demand during the rest of the heating season, the SCOP of an ASHP in a hybrid setup should be greater than that of a more powerful standalone unit serving the same home. This greater SCOP, combined with the lower investment (in an existing home with an existing serviceable condensing gas boiler) of the smaller ASHP and not immediately having to upgrade radiators and piping, easily offsets the price of still using gas during the coldest winter days and to provide hot water (in some cases even only the legionella-cycle needs to be gas powered). This makes it a perfect, often easy upgrade to an existing home for many years to come. Then in the future, when parts of the house get renovated, piping, radiators (or underfloor) and insulation can be upgraded gradually to prepare for the time the gas boiler becomes unserviceable or too expensive to run. By that time, if enough focus was put towards insulation, air tightness and heat recovery, it's very likely the ASHP you were using in the hybrid setup meets the heating demand of the home during the entire heating season, so going stand-alone is just a matter of shutting off the gas. Ofcourse you could just do all the upgrading/insulation at once, but that means not being able to live in the house for a while and spending the cost all at once, probably taking shortcuts to speed up the process and stay within budget.

It's not like mixing oil and water. There's other issues before the freeze juice was added

It's "and capable"

It's a British (maybe southern? british) thing... where and is contracted to 'n'. Like "Fish n Chips", "Bread n Butter" etc Just unfortunate that the word after is one that can be negated with "in".

Incapable of installing is not only extremely poor English it means the engineers can’t do it. Exactly the opposite of what he means.

“and capable” - it can’t be that hard to have worked out that’s what he said..

It's obvious he said "and capable"

The anti-freeze valve is only a back-up, as long as there is no power cut during freezing temperatures, it should never open as the ASHP will keep the pipes from freezing as long as there is power.

Insulation and trace heating are one solution, but the heating can only work if there is power. If there is long power cut, AFVs would avoid damaging the expensive ASHP. There is definitely a case to add insulation, trace heating and AFVs if you are specifying a monobloc ASHP.

@tlangdon12 still a power cut will disable the trace heating and pop goes the pipes

Corrosion