Posted by: @adamba

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Hi All, I’m looking for some advice please.  I had an ashp from Earth Save Products which recently failed and I have just replaced it with a Mitsubishi Ecodan 11.5kW.  The ashp provides heating to my ufh only.  My hot water is generated by a separate system.  The ashp feeds a buffer tank for my ufh and I have stats in each room which call when heat is required.  The stats activate the flow pumps for each zone and these are connected to the Mitsubishi control panel via a volt free contact.  This all works perfectly and I’m achieving good results.  My confusion is that the circulation pump which is installed in my utility room next to the buffer tank runs 24/7. It runs when heating is not being called by the system and when the ashp outside is not running.  I have monitored and it runs all the time, not just an overrun when the ashp has just switched off.  Outside air temps have been between -4 and +7 deg C and no difference.  Clearly this is not normal as it should only run and circulate water when heating is called and the ashp is running + a short overrun.  Does anyone know where I should have this pump connected to in the control panel?  Maybe we have it wrong or are missing a signal?   Any help would be great.  Thanks.  Adam.

Where is your water pump connected at the moment? Photo's may be useful.

Hi, here is a photo of the circulation pump.  Thanks.

@derek-m - thanks.  Here are some photos.

@adamba @Derek-m My frost protection - used to be set to activate the pumps at 12 degrees C I’ve since set it to 3c now. Since we don’t have glycol. The next setting below 3c was zero. 

Hope this helps

add... we have an Ecodan 8.5

@sunandair hi, thanks for your input.  I’m new to the Mitsubishi system, so please can you tell me where and how to adjust the Frost protection?

I assume this is Frost protection of the ashp outside?  I have glycol at about 20%.  My thought is I wouldn’t need a high temp for the Frost protection?

thanks.  Adam.

@adamba If you are familiar with the buttons on your FTC main controller you can check what your ecodan freeze function is set at? This is a quick check which may be all that is wrong.

If you have access to your controller here is a sequence of screens to access the 

Freeze Stat Function

1. press the left Menu Button
2. select the Service Button
3. enter password = 0000
4. Select Operation Settings (accept yes to shut the heat pump down temporarily) then re-select Operation Settings
5. Select Freeze Stat Function

in that screen you will see 2 windows

FlowT and Ambient

your set outdoor temperature which will trigger the pumps to come on is shown in the “Ambient”window.

Can you write down and confirm what temperature does the Ambient window show?

you can exit the Operation settings by pressing the back- arrow button twice then leave the service screen. Press the YES button. Then press the back-arrow button again to get back to a blank screen.

Then to restart the heat pump press the round on/off 🧳 key

@sunandair excellent thanks - I’ll try this tonight and will confirm.  

As a separate thought - does the internal circulation pump have to be set on the keypad to only run when the ashp runs?  I guess this would be the only other reason the pump doesn’t stop/start with the ashp?  I’m not sure if it can be set to permanently on?

@adamba hi 

Since you’ve got glycol you could set your frost-protect down to zero if it’s not already set to that temperature *But please let us know what temperature it’s set at currently before you change anything if you don’t mind 👍

The HP needs to switch the circulation pump/s on at various times - such as defrosting when the grills ice up, or to pre-circulate the water before it starts the heat pump. They really are very clever at looking after themselves. The problem you are hinting at would be if the installer has done something unusual for some reason.

@derek-m is already checking via your pictures what else might be going on with your assembly. He has far More extensive knowledge of variations in systems than could hope to know.

please report back what you find when you get back home, let’s hope it just needs an easy adjustment.....

@sunandair  - thanks both for all your help so far.  Here is a pile of photos just taken.  Will wait to hear your thoughts.   Thanks in advance.  Adam.

Hi @adamba

thanks for the information you’ve sent.

Regarding the Freeze Stat Function.You can adjust this down to a lower temperature without affecting other settings. However looking at your setup I can see you’ve got underfloor heating in four zones so I think this system is more efficient to operate continuously but at a low flow temperature.

The way under floor heating works is to gently warm large mass floor areas which if set up properly is the most efficient way to use your Ecodan heat pump. 

So while you can lower your freeze stat function the heating method may still be better operating continuously at low heat output.

hope this helps

@sunandair My freeze Stat settings are as yours (20c Flow @ 3c ambient) and my pumps are spinning 24/7.