Why is my Mitsubishi Ecodan not heating up the tank?

Hey ​@Jerry05 

I see, still good to have you here!

I did find this page that looks to be France Support specific for Mitsubishi (as long as my Google Translate has helped me correctly) https://fr.mitsubishielectric.com/fa/support.

Do still let us know how you get on, it’ll likely still be helpful to the community!

Hi ​@Abby_OVO , 

Thank you for your help.

My installer should come back to my house some time this week to do a full check on my DHW system, especially the scale trap.
They told me they have a contact at Mitsubishi and should (hopefully) get some answers.

If that doesn’t help, i’ll try and contact Mitsubishi myself directly.

I’ll let you know.

Hi, 

Just a follow-up

The technician came this morning and drained the DHW system and removed the scale trap and the circulator. The problem is definitely limescale.

The scale trap was completely clogged, and the circulator had also started to accumulate limescale... At least now I know where the problem is coming from (water hardness at 28°F).

He was able to clean the circulator a little and ran the trap through the acid about twenty times. After reassembling everything, we recovered some flow. The heat pump heated the hot water to the setpoint, and I haven't received any error messages for now. But he warned me that it won't last too long. I'll probably have to replace the scale trap (pretty expensive...).

He also strongly recommended that I install an anti-limescale system because, without it, the heat pump will continue to clog with limescale quickly (and I'm not going to change the trap, or even the circulator, every two years...).

So I'm going to look into installing a softener, or an Aquabion. I'm not a big fan of softeners, but given the rapid buildup of limescale, I don't think I have much choice. Regarding Aquabion, I've heard about it, but I don't know if it would be effective enough to protect the heat pump.

Do any of you have any feedback on an anti-limescale solution to protect a heat pump (softener or Aquabion)?

Morning ​@Jerry05, I hope you’re well.

I’m happy to hear that the engineer was able to get to the bottom of things for you, and thanks for posting such concise information about this - it’ll help others in the same situation 😁.

I’ve found this web page which has some helpful information, and seems to promote Sentinel products for cleaning and maintenance: https://www.sentinelprotects.com/uk-en/catalog

I wonder whether ​@juliamc might have some advice on this? (Thanks in advance).

No advice from me but now I’m worried !! As far as I know the Daikin doesn’t have a scale trap, but we do have hard water here. Something to investigate.

I must admit I was puzzled by the the scale trap but the arrangement for heating the hot water (if I’ve got the right version) is different from a gas boiler as you can see below.

In a system gas boiler there is a coil inside the HWT which comes from the boiler and it has a fixed volume of water that doesn’t contain any hard water because it is pre-treated and just circulates.

In the Ecodan fresh (hard) water goes into the tank but instead of a coil, water is taken from the tank, goes through a heat exchanger, through the scale trap (the order is important) and back into the tank. So scale will build up in the hot end of the heat exchanger and scale trap. Hard water is circulated in these components whereas in my gas boiler the scale accumulates on the outside of the tank coil. I suppose doing the direct water in/out of the tank avoids the second heat exchanger (the coil I have in my gas boiler) and being a lower temperature system this is probably important because each heat exchanger involves a temperature drop and you are trying to minimise high temperatures in an ASHP system.

​@juliamc I’m thinking you may not have a scale trap if your ASHP feeds a coil in your hot water tank. I do know that at least some ASHPs do it that way (they have a bigger coil than a gas boiler version does) but perhaps operate at a slightly lower efficiency. The diagram does say that scale traps are only used on Mitsubishi Electric made Hydroboxes/Cylinder.

Peter