Grundfos CH circulation pump - Air Source Heat Pumps (ASHPs) https://renewableheatinghub.co.uk/forums/renewable-heating-air-source-heap-pumps-ashps/grundfos-ch-circulation-pump/ Questions and discussions about renewable heating and heat pumps en-GB Wed, 20 May 2026 22:32:07 +0000 wpForo 60 Grundfos CH circulation pump https://renewableheatinghub.co.uk/forums/renewable-heating-air-source-heap-pumps-ashps/grundfos-ch-circulation-pump/#post-25070 Thu, 21 Dec 2023 09:56:30 +0000 I have a Grundfos UPM2 25-70 180 pump, circulating from a buffer tank with no means of checking or changing speed and I suspect the flow is not balanced to Ecodan.

There is no cable connected to what I suspect is the PWM 3 pin connector.

Could someone please advise on what is required to introduce PWM and thus vary the speed, possibly with speed indication

I am reasonably tech-savy but have no experience of PWM

]]> Air Source Heat Pumps (ASHPs) DavidAlgarve https://renewableheatinghub.co.uk/forums/renewable-heating-air-source-heap-pumps-ashps/grundfos-ch-circulation-pump/#post-25070