frost protection

[Franson]

I would like to turn off the frost protection for a radiator controller (HR85 or HR92), is this possible. If not for a radiator controller, is it possible for the entire Evotouch system?

[Richard]

No, evohome will always frost protect at 5 degrees C otherwise things have a habit of freezing and bursting.

[Edinburgh2000]

Can you confirm whether Evohome incorporates frost protection into the hot water (DHW) controls too? I have a Megaflo 210i cylinder which boasts about how well it prevents mixing of the incoming cold water with the water that is already heated, and therefore maintains the temperature of the heated water until that is exhausted. The cylinder provides good stratification leaving hot water at the top of the cylinder and cold water at the bottom.

My problem is that, during the winter months, the incoming cold water is close to 5 degC or below, and my CS92 temperature sensor shows this as the cylinder temperature, even though there is plenty of hot water above it. When the hot water is scheduled to be 'Off' the Evohome controls appear to override this and heat the hot water when I don't want any more hot water. My cylinder can heat at about 24kW and thus acts like a Combi boiler and would provide constant hot water if I don't turn it off.

Does Evohome have a default low temperature override for the DHW? And if so, can I disable that?

[Richard]

My problem is that, during the winter months, the incoming cold water is close to 5 degC or below, and my CS92 temperature sensor shows this as the cylinder temperature, even though there is plenty of hot water above it. When the hot water is scheduled to be 'Off' the Evohome controls appear to override this and heat the hot water when I don't want any more hot water. My cylinder can heat at about 24kW and thus acts like a Combi boiler and would provide constant hot water if I don't turn it off.

Does Evohome have a default low temperature override for the DHW? And if so, can I disable that?

This is the same as any other hot water cylinder. When you have cold water entering the bottom of the cylinder, until it has blended with the hotter water in the upper part of the cylinder the sensor will show this water temp.

The evohome system will frost protect the cylinder (got to otherwise it would potentially freeze if temps in the house were below zero for a prolonged period) and no way to turn frost protection off.

[DBMandrake]

No, evohome will always frost protect at 5 degrees C otherwise things have a habit of freezing and bursting.

Not quite true.

You can't disable frost protection of a heating zone from the controller or schedule, however if you set an HR92 manually to OFF using the built in dial, it DOES disable the frost protection for that radiator.

I was surprised by this, but I have tested an HR92 in a freezer with a dummy valve body attached to it to confirm this... Leave it set at 5 and it does open the valve below 5 degrees, set to OFF and it is still fully closed at -10 degrees. (And below about -10 the display starts to fade out... )

Considering that its very easy to turn to OFF instead of 5 by accident this is something to be wary of. My other half also went through a period of turning spare room zones that weren't needed to OFF directly on the HR92's instead of using a permanent override to 5 on the controller, until I explained to her that that was why several days later those rooms weren't heating up even though they were scheduled to be on (the HR92 ignores the schedule in OFF mode with no indication on the controller) and also that turning it to OFF disables frost protection...

As to why OFF disables frost protection - I assume its for renovating when you have a radiator removed to make sure it can't possibly turn on while it is removed. It's unclear whether it also disables the fortnightly valve pin exercise routine though! Personally I would never trust an HR92 to stay off if a radiator is removed, I would always fit a painters cap on the valve body and probably fit blanking plugs as well!

[Richard]

I don't like the OFF (as DBMandrake has described above it will stop any function) and in normal operating mode (set between 5 and 35) it won't go below frost protection.