Joining the Renewable Heating Hub forums is completely free and only takes a minute. By registering you’ll be able to ask questions, join discussions, follow topics you’re interested in, bookmark useful threads and receive notifications when someone replies. Non-registered members also do not have access to our AI features. When choosing your username, please note that it cannot be changed later, so we recommend avoiding brand or product names. Before registering, please take a moment to read the Forum Rules & Terms of Use so we can keep the community helpful, respectful and informative for everyone. Thanks for joining!
Rads warm when heating not on but ASHPs heating hot water
Hi All
Some of our rads are warm when the ASHPs are heating our hot water. The 3 port valve which controls where to send flow from the ASHPs is set to the hot water cylinder only. when not set to heat water, the 3 port valve sends water from the ASHPs to the rad and UFH circuits where that is ocntroledd by 2 x 2 port valves according to heat demand. The 2 port valve in the loft which opens and closes the radiator circuit is closed ( controlled by room stat which is not calling for heat ). The UFH circuit 2 port valve is closed. No sign of any warmth in the UFH system on the Ground floor.
Could the 3 port valve be leaking some hot water to the rad circuit?
Or more likely, the 2 port in the loft is allowing hot water from the ASHP primary circuit to leak through into some of the rads?
Any ideas gratefully received. Hope the above makes sense.
Cheers
Alan
It’s a bit left of field but could your 3 port valve be a mid position three port valve? Does the CH side of it get hot when DHW is on?
House-3 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
6.9 kWp of PV
10kWh DC coupled battery
Blog: https://thegreeningofrosecottage.weebly.com/
Heatpump Stats: http://heatpumpmonitor.org/system/view?id=60
Is it the orange Belimo 3-way valve?
🔥 Britain’s Heat Pump Shitshow
How Installing a Heating System Became a National Nervous Breakdown
Free UK shipping.
Rewritten and updated for 2027
📘 From Zero to Heat Pump Hero
🛠️ Bodge Buster
New to heat pumps?
Take the Heat Pump Fundamentals course and use INTRO50 at checkout for 50% off.
Posted by: @alanbHi All
Some of our rads are warm when the ASHPs are heating our hot water. The 3 port valve which controls where to send flow from the ASHPs is set to the hot water cylinder only. when not set to heat water, the 3 port valve sends water from the ASHPs to the rad and UFH circuits where that is ocntroledd by 2 x 2 port valves according to heat demand. The 2 port valve in the loft which opens and closes the radiator circuit is closed ( controlled by room stat which is not calling for heat ). The UFH circuit 2 port valve is closed. No sign of any warmth in the UFH system on the Ground floor.
Could the 3 port valve be leaking some hot water to the rad circuit?
Or more likely, the 2 port in the loft is allowing hot water from the ASHP primary circuit to leak through into some of the rads?
Any ideas gratefully received. Hope the above makes sense.
Cheers
Alan
How warm are the radiators and do they remain warm? Are the radiators warm before the system changes to DHW heating?
What is the temperature setting of the thermostat for the radiators?
- 27 Forums
- 2,775 Topics
- 65.4 K Posts
- 1,004 Online
- 7,180 Members
Join Us!
Installer Finder
Degrees of Separation
Latest Posts
-
RE: Review your electricity provider
Happy to add Scottish Power and the review 'dont touch ...
By JamesPa , 45 minutes ago
-
RE: Who's your electricity provider and what's your tariff?
@rob-of-york i know about G98 cert. My PV installer ini...
By AgentGeorge , 51 minutes ago
-
RE: Analysis of the economics of switching to an A2W ASHP compared to other heat sources
@rob-of-york Very sound analysis, albeit for a curre...
By JamesPa , 17 hours ago
-
RE: Is it just me, or does tradesperson timekeeping and communication drive you absolutely mad?
Yes, and I would suggest likely to get worse with more ...
By Batpred , 2 days ago
-
RE: Electricity price predictions
This topic seems more suitable for this thread... I a...
By Batpred , 2 days ago
-
RE: Why are ASHP installs so expensive?
It is clearly difficult to say, there must be cases whe...
By Batpred , 2 days ago
-
RE: Panasonic Free Multi Z and Etherea Internal units.
@dgclimatecontrol Thank you for that information and re...
By Toodles , 2 days ago
-
RE: My Kronoterm Adapt 0312 ASHP is finally installed!
@editor It was serendipitous really. Both my wife and I...
By tomasmcguinness , 2 days ago
-
@mrkfm, I'd also suggest that whenever you're ready, st...
By Mars , 3 days ago
-
RE: Are you planning to use a wood burner to supplement your central heating this winter?
I use my stove daily for backup and comfort. Definitely...
By Margarethomas , 3 days ago
-
@rob-of-york Thanks. I wish I'd started on this site as...
By mrkfm , 3 days ago
-
RE: Solar Power Output – Let’s Compare Generation Figures
@downfield I just checked this morning and OE just r...
By Papahuhu , 3 days ago
-
RE: Passiv Smart Thermostat - Help & Forum Support
Thanks Will. I'll probably be a week or so before get...
By Singlespeed , 4 days ago
-
RE: Cooling using an air to water heat pump
From experience this summer, a single-split A2A unit on...
By Rob of York , 4 days ago


