UFH balancing and understanding how it works

[JohnMo]

Few ways to look at flow rates.

 

1. Determine loop length and set flow rate

2. Auto adjust actuators, these read flow and return temp and set flow rate to achieve to pre programmed differential temperature.

3. Mine are set fully open - the highest flow rate (by reading the flow meters) are tweaked down, similar to that as discussed by @Nickfromwales.  I have also further adjusted to get room temp close to where I want.

 

Wouldn't get too hung up on exact flow rate for each length, open flow meters fully.  Set circulation pump to achieve close to 2 to 2.5L/min and leave it at that.  Then adjust any loops that are over 2.5L/min down with the flow meters. Your thermostats will do the rest.

[manoj]

On 13/09/2026 at 19:41, JohnMo said:

Few ways to look at flow rates.

 

1. Determine loop length and set flow rate

2. Auto adjust actuators, these read flow and return temp and set flow rate to achieve to pre programmed differential temperature.

3. Mine are set fully open - the highest flow rate (by reading the flow meters) are tweaked down, similar to that as discussed by @Nickfromwales.  I have also further adjusted to get room temp close to where I want.

 

Wouldn't get too hung up on exact flow rate for each length, open flow meters fully.  Set circulation pump to achieve close to 2 to 2.5L/min and leave it at that.  Then adjust any loops that are over 2.5L/min down with the flow meters. Your thermostats will do the rest.

Will give that ago over the coming weeks. By the way what temp is should the mixer value be mine is at 45 degree. Boiler I think is at 65. Thanks for the pointers.

Edited 11 hours ago by manoj

[marshian]

33 minutes ago, manoj said:

Will give that ago over the coming weeks. By the way what temp is should the mixer value be mine is at 45 degree. Boiler I think is at 65. Thanks for the pointers.

Why on earth is the boiler running at 65 Deg C for UFH?

 

What is the lowest temp the boiler can run at?

 

Is your system doing HW and UFH and is it set up as DHWP?

[manoj]

On 13/09/2026 at 18:24, manoj said:

So I have three zones. Heat source is valiant ecotec boiler. According to the Salus I have to have the flow metres fully open and the let the actuator do it magic. If that’s the case my concern is the the flow rates on the manifold and what they should be set to for all 

Edited 5 hours ago by manoj

[manoj]

5 hours ago, marshian said:

Why on earth is the boiler running at 65 Deg C for UFH?

 

What is the lowest temp the boiler can run at?

 

Is your system doing HW and UFH and is it set up as DHWP?

It does not water tank and also radiators 

[JohnMo]

7 hours ago, manoj said:

By the way what temp is should the mixer value be mine is at 45 degree

Really depends on floor buildup and house heat losses.  UFH is a low and slow heating system so you want the temperature as low as you can get away with, you want long run times.  Boiler flow temp reduced as far as you can while still getting the water temp you need and the boiler doesn't cycle.

[marshian]

3 hours ago, manoj said:

It does not water tank and also radiators 

if rads are sized correctly you can run low temps to rads as well as UFH (same temps even) then with DHWP set up can run elevated temps for hot water tank

 

I'm running 55 deg flow temp when doing hot water tank recharge and rest of the time running WC on rads and even at OAT if -2.5 deg C the boiler flow temp doesn't go above 33 deg C

 

house is 80's detached with CWI and SUDG windows and doors, 300mm of loft insulation and 75mm of kingspan PIR under the suspended ground floor - all I did in nearly all of the rooms was change T11 rads to T22