Air source heat pumps (ASHP) and drainage - Why do heat pumps emit so much water?

They do, from the humidity of the outside air. It condenses on the grille and drips off onto the ground or into a drip tray. That water has to be directed away to a drain. On a humid day it’s surprising just how much water runs off.

That’s what can freeze on the grille, which needs the defrost cycle to melt it off. 

Depends on the size of unit and weather conditions. I've seen values of up to 10 litres per hour quoted. Potentially a problem if it just leaks across a path and starts to freeze as the condensate will keep building up in cold weather.

Or as of 3 days ago drips out the front left base of the heat pump as well ! Zero rainfall.

Thanks for your comments on this question. I’ve separated this out into it’s own topic and put it in the public forum so that it can help others searching for this advice. 

So @juliamc @nealmurphy @hambrook does that means every heat pump needs to have some form of deliberate drainage below it? The most common I’ve seen from the trials we’re running is the pump raised off the ground, above loose gravel. But @hambrook doesn’t have this. Will that water be directed below or to the side of that decking? 

What happens if someone's heat pump is going to be placed above tarmac or concrete? 

There should be some drainage (in the same way that a condensing boiler needs a drain). Ours is piped to a nearby drain, although there was a puddle under it this morning so I wonder if the pipe isn't connected properly.

Ours had this drip tray to collect the water which then flows away into nearby drain:

Ours had this drip tray to collect the water which then flows away into nearby drain:

 

Hi Julia

Hi Julia, Re your ASHP drip tray. I’ve just had a Daikin split ASHP installed with a R32 inverter. All working well except for the drips as no tray was installed. My installer doesn’t seem to have a good solution. Are you able to tell me the make of the drip tray or the name of the company who installed yours so that I can hunt down a solution. I would be extremely greatfull. Many thanks Martin 

Hi ​@Martinrthomas Ah ! So that’s where you saw the drip tray. When it was newly installed I thought it was a good idea, now I’ve seen it over a few winters I realise it was completely the wrong thing. It gets filled up with leaves and as the hp is on a slight slope the ice forms in the tray. Also the drainage pipe fro it is ridiculously thin and ices up itself. The correct way to manage the water/ice forming on the unit is to have a proper drain or soakaway and sit the unit on that, no drip tray involved. Should be done before the unit is installed.

​@Martinrthomas 

Further to the above, retrofitting a drip tray on this split system should have been done with the refrigerant removed prior to moving the unit. This wasn’t done in my case, resulting in a significant leak of R32. Long story. 
What surface does your unit sit on ? Can you post a photo of it ?

Thanks for your reply. I would still like to know where the tray came from or who provided it please as I would like one. My installer used a core drill to make. 30cm drain under the pump. The difficulty is without a drip tray the water spills everywhere as there is nothing to collect it to run into the drain under the unit. Your drain tray looks like a genuine Daikin one but we are struggling to track it down so help in finding one for me would be very much appreciated. Thanks 

PS Heating otherwise great