Balancing radiators in a 2 zone system

[cstumoo]

Hey everyone,

Looking advice on balancing the radiators in a 2 zone (+hot water) system.
I know you should open all valves and then close the one that heats up the quickest and open again by 1/4 turn, following this pattern for the rest radiators.

Is it the same process for a 2 zone system or do you do upstairs and downstairs independently i.e fastest rad upstairs open by 1/4 then start again downstairs and fastest rad open by 1/4 turn?

Thanks

 

[Ric2013]

Since the idea is to have all the radiators with the same flow and return temperatures (not, strictly, that they all heat in the same amount of time), I'd run the 2 zones together when balancing.

 

[SJB060685]

The idea of balancing a system is to try and get the pressure drop of all circuits equal to that of the index circuit. The index circuit is the section of system that poses the most frictional resistance foe the flow of water. The index circuit is usually but not always the stretch of pipework furthest from the boiler. Once you have got the pressure drop in all circuits equal to, or as close as you should have equal flow and temperatures at each radiator.
Balancing should be done with both zones open and the boiler running at optimum temperature.
Be aware the boiler will eventually cycle on and off, so completely balancing may take some time.

 

[cstumoo]

I wasn't sure that even with both zones open, say all upstairs radiators are balances with the final one taking 1 1/2 turns, do you then start on the downstairs and the first radiator there beginning at 1 3/4 turns or do you start back 1/4 turn.

Thanks for the info

 

[SJB060685]

I would have both zones open and the boiler close to optimum temperature and balance the closest rad first on each circuit slowly making your way through to number 2, then 3, then 4 on each circuit if that makes sense?
Is it a condensing boiler? Your DT (delta t) across the rads is vital for what type of boiler you have.

 

[cstumoo]

yes that makes sense, so really no 1 + 2 could be upstairs followed by no 3 downstairs and so on.

yeah its a condensing boiler. Had been reading about getting the 20c drop across each rad also, with some saying its not always possible

 

[SJB060685]

No 1 upstairs, then no 1 downstairs, then no 2 upstairs and then no 2 downstairs and so on making your way back to the furthest rads on each zone.
You're aiming for a DT of 20°c across each emitter but as long as you get close you'll be fine.
The quality of the valves on the radiators play a big part in the ability to balance systems, many refer to this as valve authority, which ultimately represents the affect on pressure drop for every 1/4 turn for example. Some valves are just outright c@$p and are a nuisance when balancing.
Just to make you aware there are now auto balancing TRV's on the market, notably some Danfoss ranges which when used with the phone app will affectively balance the system for you, although I'm not suggesting forking out the expense. The old fashioned manual way can be just as good.

 

[cstumoo]

ah right ok got it. Actually getting a plumber to fit TRVs on our downstairs (for some reason only the upstairs was done when house was built) in the next month or 2. Will have a look into those and maybe let him do the balancing after

Thanks for the info on this

 

[SJB060685]

Any reputable plumber will be more than familiar with balancing hydronic systems, so should be able to do for you.
Everything I've said above will get you heading in the right direction though and to be fair with a digital thermometer or laser gun etc then you should be more than capable yourself, which would save you an unnecessary plumbers bill.
Remember though an unbalanced system can affect your modulating boiler output if the return temperature is mixed and too high. It's not something one would usually find on oil boilers (which I'm qualified in) but can affect modulating boilers, such as your mains gas appliance.