Balancing my daughters Rads.

[Big Jimbo]

Bit of help from any plumbers, or the Welsh Wizard @Nickfromwales. When i did my daughters house (No previous heating) It was blinking cold, and she was living there with her future husband. Because i was doing room by room as a full house refurb, I mounted the boiler in the old kitchen. From there i ran a 22mm flow and return for the heating. Once i was a few hundred mm from the boiler, i split the 22mm's and ran a flow and return to under the stairs, and a flow and return to upstairs. I put these pipes into a home made manifold. Simple job full bore lever valve on each the flow and return. Then several 15mm flow and return outlets with lever valves to take, and bring back the water to each of the rads.

This basically allowed me to fit a rad to each finished room, as they got done, without me having to drain the system when doing the next room. Now all worked fine, and still does Eight years later. The heat from each of the rads is controlled by a thermostatic valve at the inlet of each rad, and the lockshield valves are all fully open.

Now i have never balanced either the rads or the home made manifolds. the lengths of the pipe runs from the manifolds vary, from say 1.5 meters, to maximum 6 meters.

Due to the pipe runs, i expect the rads on short pipe runs, heat up quicker than the rads on longer runs. Would it be in anybodies opinion, worth balancing either the rads or the manifolds, to balance out the system ? I did size all the rads for each of the rooms, but do have One, (the smallest room) that seems to be a bit cooler than the other rooms.

 

Edited September 8 by Big Jimbo
Missed word

[Nickfromwales]

Just close down the 2 or 3 rads nearest to the boiler, by around 20%, and see what results that yields.

[HughF]

Modulating pump in the boiler?

 

If so just leave them all wide open and let the pump do its thing…. Throttling the rads down will just increase pumping resistance.

[marshian]

49 minutes ago, HughF said:

Modulating pump in the boiler?

 

If so just leave them all wide open and let the pump do its thing…. Throttling the rads down will just increase pumping resistance.

Save a few pence on pump cost and have a house that warms up room by room via TRV’s shutting down to manage temps doesn’t sound to me like a great way to heat a house

 

most balancing valves do very little to increase pumping resistance until almost shut and when they do start to impact flow rates 1/8 or 1/4 turns can change the flow rate massively

[marshian]

I’ve got to balance the rad circuit in a neighbours house - every single balance valve was wide open and TRV’s were the only control on room temps - his main complaint in winter was upstairs warms to fast and downstairs takes an age to warm up (classic short circuit with the water being lazy and taking the shortest path back to the boiler)

[Big Jimbo]

I'm as confused as ever now ! I'm not sure if the boiler has a modulating pump. It's an Ideal esprit eco 30. I'm told a bit of a landlord special ? The  Hot water temp is set to 55 degrees, and the heating to 60 degrees.

[Big Jimbo]

I think in all honesty, that perhaps the reason for One of the rooms being cooler, is because it has Two outside walls. (the box room in the corner) facing North. Although i did oversize the rad in this room, they might just have to live with it.

[marshian]

18 minutes ago, Big Jimbo said:

I'm as confused as ever now ! I'm not sure if the boiler has a modulating pump. It's an Ideal esprit eco 30. I'm told a bit of a landlord special ? The  Hot water temp is set to 55 degrees, and the heating to 60 degrees.

Boiler temps on CH or HW don’t mater - what balancing achieves is an equal distribution of heat to all the rads in the circuit 

 

this is better for condensing efficiency (so cost) boiler cycling (again cost) and house heat up (so comfort) 

[HughF]

6 hours ago, marshian said:

I’ve got to balance the rad circuit in a neighbours house - every single balance valve was wide open and TRV’s were the only control on room temps - his main complaint in winter was upstairs warms to fast and downstairs takes an age to warm up (classic short circuit with the water being lazy and taking the shortest path back to the boiler)

I run all mine wide open on the valves and the lock shields, weather comp takes care of everything. Stat is never satisfied and just calls for heat from September till April. dT of about 3 degrees, but I’m on a heat pump

Edited Wednesday at 15:12 by HughF

[HughF]

6 hours ago, Big Jimbo said:

I'm as confused as ever now ! I'm not sure if the boiler has a modulating pump. It's an Ideal esprit eco 30. I'm told a bit of a landlord special ? The  Hot water temp is set to 55 degrees, and the heating to 60 degrees.

Ouch…. 60 degree rads - that’s burn your skin territory.

[marshian]

10 minutes ago, HughF said:

I run all mine wide open on the valves and the lock shields, weather comp takes care of everything. Stat is never satisfied and just calls for heat from September till April. dT of about 3 degrees, but I’m on a heat pump

 

And there my dear chap is the significant reason why it works absolutely fine for you - ASHP and dT of 3 Deg - heating at low temps and weather comp for the flow temp adjustment - Very likely that your heat pump flows a fair chunk of water

 

On a gas boiler running higher flow temps - you only want the flow that keeps the boiler happy and not over shooting the set point

 

Real rough and ready rule of thumb is 1 litre of flow (per min) for every kW of boiler power 

[JohnMo]

6 minutes ago, marshian said:

Real rough and ready rule of thumb is 1 litre of flow (per min) for every kW of boiler power 

I am flow 4.5L min per kW, doing DHW and 3.5L min per kW, doing heating from ASHP.

[marshian]

Quick look that the Ideal esprit eco 30 Install manual and it needs a min of 17.4 Litres per min for CH

 

However I would expect that the boiler has been sized for HW demand rather than heating demand so it might be worth range rating the output on CH if it's possible (Min output is 6.1 kW and max is 24.2 kW on CH) 

[marshian]

6 minutes ago, JohnMo said:

I am flow 4.5L min per kW, doing DHW and 3.5L min per kW, doing heating from ASHP.

 

I did specifically say "Boiler Power" Perhaps I should have qualified the statement with "Gas Boiler Power"

 

But it does illustrate the increase in flow required when running an ASHP 

Edited Wednesday at 15:42 by marshian
Edit

[SimonD]

On 08/09/2025 at 21:06, Big Jimbo said:

Would it be in anybodies opinion, worth balancing either the rads or the manifolds, to balance out the system

 

Yes...

 

I have two heating manifolds, one for upstairs, one for downstairs. My longest run however it a lot longer than yours at approx 17m on 15mm pipe and vary from about 3m to 17m across the house. I use the Danfoss self balancing trvs with lockshields fully open. The self-balancing trvs make balancing a dream as you simply download the app, input your flow and return temps together with the size and type of radiator (or required output) and the app will give you the setting on the valve and its equivalent flow rate - it then provides the required flow to each rad. House balanced in 20 minutes rather than 6 hours and then some on following days. Then if you need to increase or decrease the flow to any rads for finetuning its a very simply turn of the self-balancing dial (which is numbered) rather than nuisance lockshields. 

 

Obviously it's a bit of work changing out the trvs but balancing even with lockshields is always going to help - it used to have the normal trvs & lockshield setup.

Edited Wednesday at 16:16 by SimonD

[marshian]

29 minutes ago, SimonD said:

 

Yes...

 

I have two heating manifolds, one for upstairs, one for downstairs. My longest run however it a lot longer than yours at approx 17m on 15mm pipe and vary from about 3m to 17m across the house. I use the Danfoss self balancing trvs with lockshields fully open. The self-balancing trvs make balancing a dream as you simply download the app, input your flow and return temps together with the size and type of radiator (or required output) and the app will give you the setting on the valve and its equivalent flow rate - it then provides the required flow to each rad. House balanced in 20 minutes rather than 6 hours and then some on following days. Then if you need to increase or decrease the flow to any rads for finetuning its a very simply turn of the self-balancing dial (which is numbered) rather than nuisance lockshields. 

 

Obviously it's a bit of work changing out the trvs but balancing even with lockshields is always going to help - it used to have the normal trvs & lockshield setup.

what @SimonD said

 

I’m currently using Drayton TRV4 bodies with 6 flow rate settings so lockshield end is fully open 

 

I moved to TRV4 bodies because my system was a bit of a pig to balance on cheap lockshields and to put decent lockshields with decent linear flow rates on (IME ones) was as much cost as buying TRV4 bodies.

 

I’ve now got Danfoss RB-2 TRV bodies to fit (which is what I should have fitted in the first place) because

 

1. a few rooms I need between setting on the TRV4 bodies (example is a room on 3 is just a little too low a flow rate but 4 is too high)

 

when using a setting with too high a flow rate the dT across the rad drops - the room exceeds target temp and the TRV intervenes which on weather comp I don’t want it to.

 

when using a setting with too low a flow rate the dT accross the rad increases but the room target temp is not achieved

 

the Danfoss ones have a finer level of control with from memory 15 presets. The Danfoss app is a breeze to use.

 

I would have bought the Drayton equivalent but they stated they are not suitable for temps below 45 Deg C when I asked them to update their app to cover lower flow temps - Danfoss are OK with temps down to 35 so I got them

 

 

[Nickfromwales]

15 hours ago, HughF said:

Modulating pump in the boiler?

 

If so just leave them all wide open and let the pump do its thing…. Throttling the rads down will just increase pumping resistance.

Sorry. This is poor advice.

 

Hydraulic resistance, aka the path of least resistance, play a huge role here.

 

Leaving them all wide open will leave the issue to remain. It needs to be balanced, end of. 
 

I suggest the OP tries my suggested cure and reports back. 

[marshian]

Just now, Nickfromwales said:

Sorry. This is poor advice.

 

Hydraulic resistance, aka the path of least resistance, play a huge role here.

 

Leaving them all wide open will leave the issue to remain. It needs to be balanced, end of. 
 

I suggest the OP tries my suggested cure and reports back. 

In fairness @HughF was giving advice based on his experience with ASHP which probably has 3 times the flow rate

 

but I do agree bad advice for a gas boiler set up

[Nickfromwales]

17 minutes ago, marshian said:

In fairness @HughF was giving advice based on his experience with ASHP which probably has 3 times the flow rate

 

but I do agree bad advice for a gas boiler set up

Hydraulic resistance is a law of physics though? 

[marshian]

7 hours ago, Nickfromwales said:

Hydraulic resistance is a law of physics though? 

Yes agreed - perhaps some “gains” could be made with a tweak here an there

 

perhaps circuit is fitted with lockshield with in built restriction I’ve seen some with ~8mm internal path

 

Or maybe the house is piped with first rad on the flow being the last to return and last rad on the flow being the first rad on the return (system would be balanced without any lockshield intervention)

[HughF]

To be fair my system is very simple/small. 2 rads downstairs, three upstairs (usually off), three fan coils and a ufh loop.