What do you mean exactly by frost protection?

Hi James

Frost protection is the mode to prevent the water in the pipes from freezing (no glycol).

Vaillant also have the De-icing mode to clear the ice build up on the rear.

Many thanks

Kevin

Ok, just trying to clarify.

So what you are experiencing if I understand you correctly is that when there is no call for heat and the outside temperature is less than 8C it's switching on and heating the water to 30C.  Is that correct and for how long.  Also what is the circumstance when it's less than 8C and there is no call for heat.  Also you give 'from' temperatures above, how do those arise?

I have a Vaillant also so trying to understand the detail in case it helps with a diagnosis or solution.

@jamespa 

Yes the house is warm enough so no call for heating.  So when the outside temperature falls below 8oC, the HP will kick in and elevate the flow from 14oC to 30oC.  it monitors the flow for 30minutes and kicks in when the flow reaches 14oC.  Typically it runs the heat pump for 10/15minutes.  If the outside temperature is still 8oC or below the cycle (monitoring the flow temperature) starts again after about an hour or so.

Hope this makes sense and apologies for the confusion.

From Vaillant

the trigger points for frost protection are:

1. outdoor temperature drops below 4C, which is followed by monitoring of the flow and return temps from the heat pump for 30 mins
2. if the flow / return temps are 6C or below, the frost protection kicks in, and will run unti9l the flow / return reaches 12C
3. if the flow / return exceeds 6C after 30 mins, the heat pump will run the hydraulic pumps for a couple of minutes then reset the 30 min timer

The timer will shutdown if any heating demand is received by the heat pump.

We might need to unpack this to work out whats happening.

Here is an extract with the paper manual which came a couple of months ago with my unit (the manual currently online is different, suggesting this stuff is still being tweaked!)

I suspect 'regulate the target room temperature' means 'adjust the flow temperature according to the WC curve as if this were the target room temperature'.  Depending on how they wrote the software it possibly also means 'respect the minimum target flow temperature as set on the unit'.  What is your minimum target flow temperature (its an installer setting).  This might explain the reason it ramps FT up to 30 which I think is thew factory default minimum flow temp, also the flow temp it gets to will be affected by the minimum output available from the machine.

This doesn't however explain why it kicks in at 8C.  Of course we dont know which sensor Vaillant are using - where are you measuring 8C and what temperature does the Vaillant OAT sensor register.  There is also a sensor at the back of the unit (effectively an inlet air sensor), in your specific situation is it possible that reads lower than the OAT sensor?

I think the unit may be trying to ensure that the house doesn't freeze, not just to protect itself.  What room influence mode are you running in or are you running pure WC.  From where is the call for heat coming (external thermostat or something else?)

Its worth bearing in mind that most of the heat generated will go into the house so its not all wasted.

Many thanks for this much appreciated. 

The minimum flow temperature is 15oC. The set back mode is eco, but thinking moving to normal, to see if frost protection kicks in less.

Room temp mod was inactive,  changed to expanded.

We use the sensocomfort indoor controller as the main thermostat 

When the frost protection started kicking in all the time, I moved the outside sensor indoors.  This seemed to stop the number of frost protection starts.  As you noted the air inlet sensor appears to be the second trigger point.  I can only assume they read slightly differently I.e. air inlet triggers 7oC. Outside sensor triggers 8oC.

I would just like the frost protection to work sensibly,  ie initial trigger 4oC. Elevate flow 6 to 12oC.

Thanks again for your help 

Ok. 

How do you know frost protection is triggering (as opposed to just normal operation)?  With the outdoor sensor indoors how can WC work.  I'm a bit confused as to what your setup is and what you are seeing.

FWIW I have found this heat pump extremely simple to operate.  Disable room influence, remove TRVs in most rooms, tweak the WC down until house is at right temperature, leave.  I probably wouldn't notice frost protection because its on 24*7 hence why Im a bit confused whats happening in your case.

@jamespa 

From the vwz indoor controller,  then looking at the live monitor. 

 I have been playing with settings and did think I hopefully resolved it. So put the outdoor sensor back outside sunday. The heat pump was in frost protection mode , more or less all night. So I have moved it back in Monday morning. Also it was elevating the flow temperature to 38oC.  

Posted by: @kentuk

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@jamespa 

From the vwz indoor controller,  then looking at the live monitor. 

 I have been playing with settings and did think I hopefully resolved it. So put the outdoor sensor back outside sunday. The heat pump was in frost protection mode , more or less all night. So I have moved it back in Monday morning. Also it was elevating the flow temperature to 38oC.  

Sunday night was very cold where I am: - 2, I would definitely expect frost protection to kick in in this circumstance and be very worried if it didn't!  Obviously I don't know about where you are so your temperature may have differed.

Have you got a heating schedule set that means it may not be supposed to heat when its cold outside.  Also I don't understand how WC is working when the outdoor sensor is indoors.

Can I suggest you

• reinstate the outdoor sensor to its correct location
• turn off room influence so its working on WC only
• see what happens

If it goes into frost protection mode then record time of day, the outdoor, indoor and flow temperature shown on the sensocomfort, and how long it switches on for before switching off again.  

Obviously if you already have this information from a previous occasion then just post that.

Many thanks attached some diary notes containing that information.  

Thanks again for your thoughts and assistance

OK.  Im still not clear what is actually happening.  Can you confirm, on 6/12/24 and 7/12/24 at those times,

what were you expecting it to be doing and why?

what are the two flow temperatures recorded

how long did it switch on for

on each occasion was it showing 'frost protection' on the controller

what does the annotation 258-DHW mean

Also, when you move the outdoor sensor indoors, what happens to the actual heating (Id expect it to switch off completely or oscillate assuming that weather compensation is active)