Why is my heat pump cooling my DHW?
Just wondered -can you lower the temperature when your hot water reheat starts?
You seem to only have a 5 deg drop. That also means the start of the reheat is at 43 degC which might be a bit high.
I’ve got an 8.5kw HP and have the temp set to 48degC with reheat kicking in at 38degC. That means it’s got a 10 deg drop and so, not switching continually to DHW. And perhaps equally importantly the reheat temp starts when pipe temps roughly match the radiator temps if they’ve been heating the radiators.
I hope this is of interest
Posted by: @sunandair“The cylinder seems to hold the temperature quite well. The problem happens when the system is totally idle, no demand for space heating, no use of hot water. When the temperature drops to 43 (due to normal loss) and the HP starts up to reheat the DHW back to 48, that's when it does the sharp drop.”
I think I’ve encountered something similar. Your paragraph above seems to describe my thoughts.
If HP was idle then the primary pipes are probably cold. HP is slow to build temp up so while water is circulating it’s re absorbing heat from your DHW cyl. This could be confusing for the system (for a while) since the return will be warmer than the flow.perhaps try to coincide DHW reheat while the space heating has been running then the primaries will already have some heat in them. Just a thought from a newbie.
My DHW has always been like this, it drops about 7 or 8 degrees if I recall correctly when it starts heating, I attributed it to what SUNandAIR describes. Since summer I have it set to only heat at midday for an hour and do a manual start if more is required, so its not as noticeable because the tank is mostly cold anyway and I don't watch it like I did when it was first installed.
Mitsubishi Ecodan 8.5kWh
4.4kW Solar PV
5.2 kWh Battery Storage
1983 build, 300mm loft insulation, cavity wall insulation (beads)
- 22 Forums
- 2,096 Topics
- 46.1 K Posts
- 74 Online
- 3,383 Members
Join Us!
Trusted Installers
Struggling to find a reliable heat pump installer? A poor installation can lead to inefficiencies and high running costs. We now connect homeowners with top-rated installers who deliver quality work and excellent service.
✅ Verified, trusted & experienced installers
✅ Nationwide coverage expanding
✅ Special offers available
Latest Posts
-
RE: Commencing on an ASHP Installation Process
I should perhaps have mentioned this in my post, as I'd...
By Sheriff Fatman , 2 hours ago
-
RE: Mitsubishi cycling while on chilled water output
@jamespa you are so much faster than me, happy to see g...
By ASHP-BOBBA , 3 hours ago
-
@jamespa Thanks for the advice - very helpful. I had al...
By abam48 , 13 hours ago
-
RE: Weather compensated secondary circuits with Biomass
Hi @andycoo we do an LK 110 standalone weather compensa...
By Sune , 13 hours ago
-
RE: Adding battery storage to SolarEdge PV system
@chandykris No need to apologise at all! I forgot to ad...
By Toodles , 1 day ago
-
RE: Say hello and introduce yourself
Yes please do Suggesting a loss in the region...
By JamesPa , 1 day ago
-
RE: Surface mount or bury primaries for heat pump installation?
Can we have some links to those you're considering plea...
By Transparent , 1 day ago
-
As I have reported elsewhere we turned on the cooling o...
By downfield , 2 days ago
-
-
@el3b Hi, sorry to hear that, it is advisable to instal...
By ASHP-BOBBA , 3 days ago
-
RE: Difficult positioning of air source heat pump
@rikiarn Out of intrigue, the thread reads as though Ai...
By Sheriff Fatman , 3 days ago
-
RE: Mitsubishi Ecodan Fails to Heat Water despite temperature drop
@m1kegibson If you are able to access the service me...
By HarriUp , 3 days ago
-
RE: When will heat pumps and install prices come down?
... which of course is impossible because the world mov...
By JamesPa , 4 days ago
-
RE: Battery storage to run Heat Pump.
I would be surprised if the battery chemistry is going ...
By Transparent , 4 days ago