Lockshield valve adjustment for EvoHome controlled radiators

[Teaboy]

I’d really like some advice about setting the lockshield valves on my radiators. I’ve a gas boiler and hot water storage system inherited with the house. The boiler was replaced 5 years ago and I also replaced the control system to the original EvoHome (monochrome) system at the same time. Subsequently I upgraded to the colour screen and internet gateway. I’m an electronics system engineer – so installation and set up of the EvoHome was no problem – but I have always had difficulty with the practicalities of balancing my rads for 2 reasons:
1. I cannot confidently work out which rad is closest to the boiler, and which is next in the plumbing “circuit diagram” and this knowledge always seems to be a pre requisite in any balancing instructions I’ve read.
2. I can’t help wondering if balancing in the conventional way is the best idea for a system using EvoHome rad valves.

Broadly speaking, I have the living areas heated in day time between 7:30a.m and 10:00pm and the occupied bedrooms heated from 10:30 – 11:30 at night.
Unoccupied bedrooms are on frost protect. The dining room is set to 12°C and I manually change the setting if we plan to use that room.
A few rooms (utility room, cloak room, study) don’t have EvoValves – just conventional Thermostatic Rad Valves set to frost protection. These rooms pick up enough heat from the heated rooms.
The two bathrooms each have a heated towel raiI. I’m advised by my plumber (who is a great guy, but thinks my control system is the work of Satan!) that these are there as a kind of 'safety valve' to remove heat if all the other rads are shut off. I can see the sense in having this arrangement. However, for most of the day, the towel rails are very hot and I wonder if opening the check valves in the living areas would make them heat up more quickly and reduce the temperature in the bathrooms.
I sometimes wonder if all the lockshield valves on the rads with EvoHome valves should be fully open since my schedule never has the living areas and sleeping areas heated simultaneously - but that might be a step too far!
In the event of the house lying unoccupied in winter, I can see that if there was a very cold snap such that all the EvoHome valves and all the traditional thermostatic valves opened, then the system might not be well ‘balanced’ in the conventional way, but surely there would be enough heat in the house to give adequate frost protection.
My objective is to put more heat into the lounge in particular. It’s set to 19°C (sensor is the EvoHome controller) and there are two radiators.On cold days it can take 90 minutes to get from 14°C in the morning up to 19°C. The radiators are ‘quite hot’ – but not as hot as the bathroom towel rails. Would it be a rash idea to open the lockshield valves on the lounge radiators without resorting to a full ‘balancing act’? (I can borrow clip on pipe thermometers from my plumber if that would help.)

[Richard]

The term 'Balancing' refers to temperature balancing of the flow and return of your heating system. Balancing radiators ensures the temperature drop across the heating system is sufficient to ensure efficient operation of the boiler. You don't really have to know which radiator is the 'closest' one, just find out which one gets hottest first when all valves are fully open then start with this one.

Modern condensing boilers require a temperature differential of 20 degrees (for example a designed flow temp of 75 and return 55), however this is rarely achieved when the boiler is a replacement and the previous radiators were not designed to achieve a temperature differential of 20 degrees. In this situation, you may only achieve an 11 degree differential therefore reduction of the flow temp to 66 degrees would keep the boiler in condensing mode longer.

To not balance the system at all will mean the boiler will not operate as efficient - evohome or not.