I have a condensing boiler and have tried to balance my radiators. However, when I started, all the lock valves were wide open and we didn't have any cold radiators. Is it more effective for the boiler to run with them all open wide, or is it better to have them adjusted for the 10 degree drop across each one?
Many thanks
Jonathan
If decent TRVS are fitted, to an extent they should self balance with those anyway.
Balancing becomes more an issue of differential heating rates of various rooms, than an overriding issue of getting room temperatures normalised.
We do have TRVs fitted that work, so I should probably not worry too much about balancing? Would it be better for the boiler to have the lock valves open?
Jonathan
The "balancing with lockshield valves" thing only has influence when the system is not being controlled by the TRVs (i.e. when you're initially heating the house from cold).
Under these circumstances it will only influence which-room-gets-hot-first.
Once the system has become stable and all rooms are at their TRV-maintained temperature, any 'balancing' with lockshields becomes irrelevant.
My approach is to run with the lockshields wide open and let the TRVs do the heat-controlling:: that way once the house has reached a stable temperature and all rooms are running 'on the TRV' for control, any sudden loss-of-heat from a room [who left the back door open?] will be sensed by the TRV and full heat-flow, unimpeded by a restrictive lockshield, will be available to that room to get it back to temperature ASAP.
In article , Tanuki writes
Failing to balance even a TRV equipped system can lead to long delays in system warmup and failure for some rooms to come to temperature at all.
Without the luck of a naturally balanced system and with lockshields fully open, rads near the boiler will steal all the flow resulting in little or no flow at the far reaches of the system for as much as an hour after startup.
This slows system warmup for 2 reasons:
The bottom line is that balancing a system ensures optimum performance whether TRVs are installed or not.
In article , Jonathan writes
It's more important to have a consistent drop between flow and return on the rads than an absolute value.
eg. A radiator that is dropping only 5degC will be stealing flow from another that is might be dropping 15 degrees resulting in uneven warmup.
It's possible to do a simple balance with your hand. There should be a noticeable difference between flow and return temps but not too much. Generally flow will too hot to keep your hand on but return would be slightly uncomfortable but bearable. If return is just lukewarm then flow in that rad is likely to be less than is should so would benefit from a system balance.
Remember that balancing should be carried out with TRVs set to max and you may need to open windows a bit to avoid some rooms becoming uncomfortably warm (it distorts the balance process too).
To keep the numbers simple, I record the opening of the lockshields as quarter turns from fully closed, that means that you rarely have to record fractional readings. For info, my most distant rads are about half open with closest ones down to 2 quarter turns open. My v smallest rad (small WC) are open only one eighth turn.
See:
Fred's points are valid - up to a point. Lockshield-based balancing can - as stated - lead to a more-even initial distribution of heat when bringing the whole house up from cold - but that's not something we do very often.
Throttling on the lockshield limits the rate at which a single excessively cooled-room can be recovered to its target temperature. [Dogs don't always go-on-demand and you can lose a lot of heat standing with the back door open watching and waiting for them to 'finish'!]
It also means that you can have a startup situation where the TRVs have started to close in quite a few rooms but the lockshields in the not-yet- warm rooms are restricting flow to the point where the bypass-valve is passing hot water back to the boiler. Then you get boiler-modulation or cycling on the boiler's thermostat, neither of which are good. My experience is that just letting the TRVs do their job seems to be the best/least-hassle.
In article , Tanuki writes
Those points are not supported by my experience.
Btw, your text formatting appears to be borked, any chance of fixing it? Perhaps Tools > Options > Send > (News Sending Format) (Plain text) Plain Text Settings - Line length tweak required?
Now I don't as yet have a condensing boiler and prefer it to stay that way as long as possible but as I understand it heating systems intended for condensing boilers have a target 20C drop across the radiators, not
10C. This is because of the need for a low return temperature in order to get any condensing at all. From memory (which might be slightly out) I think the critical return temperature is 53C and you won't get full condensing until considerably lower than that.The easiest way to increase the temperature drop across the radiators is to slow the pump speed down. Alternatively it can be achieved by throttling all radiators back but some degree of balancing may well be required if you are not going to flood the boiler with a too warm return from the near radiators while not getting sufficient heat to the far radiators.
You don't say what sort of controls you have but assuming you have the traditional set-up with a room thermostat and no TRV on the adjacent radiator it is important not to bias the balance in favour of the radiator without the TRV otherwise you will never get the rest of the house up to temperature.
Are you considering a system with a room stat having overall control? If so, unless it is calling for heat, no individual TRV will have any immediate effect.
Chris
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