Balancing, a guide to how to make your heating system amazing.

I dont do site visits, I prefer to sit in my mind palace and think about ways to fix far distant heating systems, but this week Ive been dragged kicking and screaming out to look at 2 problem heating systems with my heat pumps on them. Both systems had been in a while and had the same compliant, "My heat pump is broken, my bedrooms are at 21 degrees Centigrade but the lounge never gets to temperature, even if I set the room stat to 30 degrees, send a man".

This cold area problem is caused by a really simple issue which I thought I would try and explain as simply as possible:

Your heating system is piped up with radiators (and or Underfloor heating), every radiator is tubed in parallel like a ladder. The boiler (or heat pump) has a pump in it, it pushes the water around the system, water is lazy it wants to take the easiest way back to the boiler / heat pump. It will always take the path of lowest resistance,

In the system above, if we assume it had no valves anywhere its pretty obvious the water would tend to flow more through radiators C and F than through A and D. So you would get this problem, the rooms dont get hot at the same rate or reach the same temperatures.

Our job as "balancers" is to coax the water to every corner of the house by messing around with the radiator valves. We are supposed to limit the flow in some areas and increase it in others to "balance" the system. Its bloody easy to do, it takes a few minutes but no one bothers, to balance properly you just need common sense and a pair of pipe pliers.

Most systems have thermostatic radiator valves on them. Thermostatic radiator valves open and close as the room temperature raises and lowers and really badly meter the amount of water going into the radiator. The idea being these things will automatically balance the flow around the house.

On the other end of the radiator we have tamper proof or lock shield valves, you are not supposed to touch these unless you know what you are doing.

These valves are designed to limit the maximum amount of water that can go through the radiator. These valves are designed to create resistance to limit the amount of water going through the radiator and stop all the water going through just one or two rads.

In all the systems with colds rooms I find every lock shield valve in the house full open, just for reference a lock shield valve is full open when you turn it 1 turn (anti clockwise) from closed, opening it further than that makes no difference.

Balancing isn't as important on a boiler because if you have a cold spot you can just crank up the boiler and make it work flat out to hide the problem. I liken this to driving a car with handbrake stuck on, just give it more gas and problem solved. If you turn up the water temperature, the roasting water goes to the easiest rooms first, they warm up quickly and the thermostatic radiator valve starts to close, this creates resistance in the radiator so the water seeks out another radiator to flow through. This self balancing works as long as you have high temperatures and radiators which can heat the rooms quickly.

In a heat pump the radiators are run as cold as we can to make the efficiency better and the run cost low. So we never smash hot water into the room and the thermostatic radiator valves never move. Arguably you can throw away your thermostatic radiator valves on a heat pump system but building regs will take a century to catch up, so keep sticking them on to please the man and leave them set to flat out.

On a heat pump or any low temperature heating system we have to balance a lot more accurately so here is how you do it.

Starting at the boiler go to the nearest radiator, shut the lock shield valve fully (clockwise) and then open it 1/2 of a turn, that's it, done. Now go to the next radiator and do the same remembering that as you work your way away from the boiler close then open the lock shield a bit more each time, by the time you get to the last radiators they should not be open more than 3/4 of a turn.

Now leave the heating running for a few hours or days, if any areas get warm to slowly give the lock shield another 1/4 of a turn open, if any areas get hot too quickly close the lock shield down 1/4 of a turn . But always try to remember this, if you open one valve you need to find another one to close down the same amount .The problem comes when you have them all open flat out and you are back to square one.

Of course the really clever way to do this would be if there were flow meters and temperature probes on every radiator so you could perfectly match the design heat load. Or wouldn't it be amazing if it was done automatically for you but this technology is not in heating yet, it wont arrive until we buy the Heatpump, controls, valves, radiators and controls from one manufacturer. (this is what happened in air conditioning in 1990).

And before anyone pipes up "I have Evo home its brilliant", it is, but only if the system was balanced first, even Evo home and its ilk cant balance like Nadia Comaneci.