Balancing rads - help

[Fadburty]

I have recently had a new bathroom done because of this the builder has blocked the radiators on the second floor whilst doing the bathroom and when he had completed he has open the lock shield valves fully.

I have tried to balance them, but I have few questions if someone could help me to fine tune the rads. The setup is as per below.

Living room
Front room rad
Middle room rad
Dining table rad

Second floor
Bathroom
Back Bedroom (next to bathroom)
Front bedroom
Box room

Third floor
Loft bathroom
Loft bedroom

10 rads in total.

The dining room rad gets warmest the first as closest to the boiler.

Then I feel the second floor rads get warm.

Followed by the loft.

Then the front room and middle room rad get warm the last.

I have tried to open the lockshields accordingly.

However, I find the last two rads still take 30-40 mins to get hot as the rads in the second floor whom get hit within 15 mins. Piping hot.

Can anyone give an indication of how much I should open the lockshields valve accordingly.

Secondly isit strange that the front living room and middle living room get hot last?

Bare in mind a British gas engineer did balance them few years ago and he did open the lockshield valve fully on the loft rads?

I just add the loft rad only gets hot when the tvr valve is on 3, not 2 or 1 - any particular reason for this? (I did bleed it yesterday and there was abit if air coming out)

I got a thermostat for to measure the inflow and outflow pipe - but should the outflow pipe be 12 degrees lower? Would this be better way to balance the rads?

Thanks

 

[ShaunCorbs]

Close all the lockshields all the way then open 1/4 of a turn and turn the heating on

If some get hot straight away close them down 1/16 more and if some don’t open them a 1/16 if they still don’t add another 11/6 open etc

 

[Fadburty]

I should add the front room and middle room rad get fully warm when the radiator s upstairs are cooling down after hitting the trv temp

 

[Fadburty]

Close all the lockshields all the way then open 1/4 of a turn and turn the heating on

If some get hot straight away close them down 1/16 more and if some don’t open them a 1/16 if they still don’t add another 11/6 open etc

Thank you for the reply, but isit perfectly normal for the second floor rads to get warm first then the downstairs one?

Also, are you saying there's 16 turns compromising of quarter turns from close?

Not sure I understand the second step if I be honest.....

 

[ShaunCorbs]

Yes as hot water will rise should heat about the same once balanced

No close all lockshield valves then open them 1/4 of a turn then go round with the heating on and see if they all heat evenly if ones still cold / slow open it a 1/16 more

 

[Fadburty]

Yes as hot water will rise should heat about the same once balanced

No close all lockshield valves then open them 1/4 of a turn then go round with the heating on and see if they all heat evenly if ones still cold / slow open it a 1/16 more

Thank you, I guess with 1/16 it's marginally opening the lockshield abit more.

The 4 rads upstairs - not sure which one gets warm first, quite difficult to tell. Should I be assuming on the basis as soon as it's slightly warm and take it from there?

The rad in the loft should that be open fully even though the middle room rad is the last to get warm?

That's my aim with balancing that the rads downstairs should get warm/hot as the same time as upstairs otherwise I have to wait 40 minutes for the rad to be fully hot which defeats the purpose

 

[ShaunCorbs]

I would start with it half way open and go from there

 

[Fadburty]

I would start with it half way open and go from there

Ok, so I will tom:

Make sure all LS are 1/4 turn from close. TVR valves are all on max or 5.

Then I will adjust accordingly 1/16 of a turn.

I read somewhere online saying the LS should all be open fully and tvr 5 then find out which one gets warm the first to least?

 

[Ric2013]

Right. There's a lot of misinformation out there about which radiator warms up first.

The point of balancing is not really about which radiator warms up first, but to ensure each radiator gets the correct flow. This is essentially achieved when the temperature drop across each radiator is the same as the others (with the TRV on max). However, this will usually coincide with the warm up times being approximately the same, and indeed an experienced installer will probably use warmup time and distance from boiler to guess an approximate initial setting to save time doing the final adjustment. Your British Gas engineer probably did a rough balance. You can, if you're a bit geeky like me, spend hours on balancing and get it spot on and if you find it satisfying to do this, then by all means do so. Obviously, once you have got it as good as you possibly can (or quite simply you're reasonably happy), it is then time to stop.

If you want a scientific understanding, the way my brain pictures it is that if a radiator is running 80°C/70°C (as a very old boiler may run - a modern boiler may run cooler but the same principle applies), this radiator is 55°C hotter than the room may be if the room is heated to 20°C. If the flow is higher than needed, that same radiator may run 80/76 because the water is not given a chance to cool before it leaves the radiator. This means the heat output to the room may be a little higher because the average temperature of the radiator above the room is 58° instead of 55°, but it probably means some other radiators are not getting enough flow and might be running, say, 80/60. The other radiators will therefore be only 50° above room temperature, and thus their heat output to the rooms will be reduced. So, as the radiators should be matched to the heat requirements of their respective rooms, getting the balance right means each will have exactly the same temperature drop. As the rooms warm up, the TRVs can then do their jobs of reducing individual radiator average temperatures and avoid overheating of rooms.

More practically, what Shaun has suggested is a perfectly reasonable approach to get you there. As lockshield valves are a very crude control (but good enough for the job in hand), they only really start to do anything to the flow once they are 1/4 turn from fully closed, hence Shaun's suggestion. If you are able to measure the inlet and outlets of the radiator accurately, then aiming at a 12 degree temperature drop would probably be a reasonable way of checking if a radiator is getting too much flow (less degrees drop) or too little flow (more degrees drop). You might want to open the radiators which most tend towards insufficient flow, but in practice the difference between being 1/2 turn from fully closed and being fully open will probably not be noticeable.

What you are experiencing with your middle room getting hot once the TRVs shut down elsewhere is the result of the TRVs balancing the system for you (sort of). But letting TRVs do the balancing is not a valid approach if you tend to switch your heating on and off (which you should of course be able to do) rather than run it continually. The radiators should be all heating through in approximately the same time.

 

[Fadburty]

Right. There's a lot of misinformation out there about which radiator warms up first.

The point of balancing is not really about which radiator warms up first, but to ensure each radiator gets the correct flow. This is essentially achieved when the temperature drop across each radiator is the same as the others (with the TRV on max). However, this will usually coincide with the warm up times being approximately the same, and indeed an experienced installer will probably use warmup time and distance from boiler to guess an approximate initial setting to save time doing the final adjustment. Your British Gas engineer probably did a rough balance. You can, if you're a bit geeky like me, spend hours on balancing and get it spot on and if you find it satisfying to do this, then by all means do so. Obviously, once you have got it as good as you possibly can (or quite simply you're reasonably happy), it is then time to stop.

If you want a scientific understanding, the way my brain pictures it is that if a radiator is running 80°C/70°C (as a very old boiler may run - a modern boiler may run cooler but the same principle applies), this radiator is 55°C hotter than the room may be if the room is heated to 20°C. If the flow is higher than needed, that same radiator may run 80/76 because the water is not given a chance to cool before it leaves the radiator. This means the heat output to the room may be a little higher because the average temperature of the radiator above the room is 58° instead of 55°, but it probably means some other radiators are not getting enough flow and might be running, say, 80/60. The other radiators will therefore be only 50° above room temperature, and thus their heat output to the rooms will be reduced. So, as the radiators should be matched to the heat requirements of their respective rooms, getting the balance right means each will have exactly the same temperature drop. As the rooms warm up, the TRVs can then do their jobs of reducing individual radiator average temperatures and avoid overheating of rooms.

More practically, what Shaun has suggested is a perfectly reasonable approach to get you there. As lockshield valves are a very crude control (but good enough for the job in hand), they only really start to do anything to the flow once they are 1/4 turn from fully closed, hence Shaun's suggestion. If you are able to measure the inlet and outlets of the radiator accurately, then aiming at a 12 degree temperature drop would probably be a reasonable way of checking if a radiator is getting too much flow (less degrees drop) or too little flow (more degrees drop). You might want to open the radiators which most tend towards insufficient flow, but in practice the difference between being 1/2 turn from fully closed and being fully open will probably not be noticeable.

What you are experiencing with your middle room getting hot once the TRVs shut down elsewhere is the result of the TRVs balancing the system for you (sort of). But letting TRVs do the balancing is not a valid approach if you tend to switch your heating on and off (which you should of course be able to do) rather than run it continually. The radiators should be all heating through in approximately the same time.

Thank you for taking the time out with a very helpful response.

I really do want to get this right, so apologies if my understanding is wayward.

I got a digital thermostat, my understanding is that the outflow pipe should be -12 degrees from the inflow pipe? Is that correct?

When I had a look at the front bedroom, when the trv is at 5, the temp was 40 degrees and the outflow too.....I have dining room rad (first to heat at 1/4 turn) then the upstairs back bedroom between 1/4 and 1/2 and the front badroom was at 1/2 turn on LS. However the outflow and inflow temp was the same? This is what has confused me.

 

[Ric2013]

A few variables there. Firstly it would be interesting to know what type of boiler you have and whether the pump is internal to the boiler or external.

The old gas boilers (and most modern oil boilers) had a fixed rate at which they burnt gas and the burner was on or it was off. The traditional temperature drop was 'around' 11°C, simply because that was 20°F which was a nice round number that was a reasonable compromise between being too high a drop (result being colder radiators and greater thermal stress on the boiler heat exchanger) and too low a drop (the circulation pump would be oversized and noisier, use more electricity etc). The 11°C drop was with the boiler running at maximum temperature (usually 80-82 degrees) on the flow and firing continually, with the rooms up to temperature.

In an ideal hypotherical situation, the old boilers would be running continually and the flow temperature would reach 80°-82°C and then not get any hotter because the heat lost to the rooms by the radiators matched the heat put into the water by the gas being burnt at the boiler. In this situation, balancing is fairly easy.

Modern condensing gas boilers are usually quite happy running at a 20 degree drop, radiators are larger to allow the boiler to run cooler (often 70/50). They may vary their flow temperature to try to limit the drop to a maximum of 20°C. Or, if a new boiler is coupled to an old system, then the radiators may remain at 80/70 or 82/71 to allow for sufficient output. The flow temperature can still be reduced in warmer weather.

The problem with balancing is that boilers often have a heat output that has been set to a rate greater than the total output of all your radiators put together. In this case, it is sometimes hard to get the boiler to fire continually as setting the gas burn rate is a boiler adjustment that isn't really for DIY or even for someone like myself that is not a registered gas installer, so the boiler has to switch the burner on and off to avoid overheating the water. A modern condensing boiler may ramp down the gas burn rate to allow them to run without cycling on and off, but many old boilers will cycle on and off, and many modern condensing boilers may not cope with the load they are being asked to give and will tend to cycle too.

Logically, if you find yourself in this situation, then you are probably better off paying more attention to the return temperature and trying to get that around the same for each radiator. How much cooler than the flow? If it's a condensing boiler that can vary its burn rate 'modulate', then I'd be looking to get it within 20 deg C, whereas if it's an old boiler, I'd be aiming at 11 deg C, and no more than 12. But if your radiators receive their flow at 65 instead of 80, then you might consider that 12 degrees is an excessive drop as the 11 degrees figure was for a flow of 80. If you find the difference is only 7 degrees, say, with a flow of 80 degrees, you may be able to slow the pump down and see if that gives you a better drop, but it doesn't really matter too much and I doubt this will be the case in your circumstances.

If the boiler is switching on and off then the flow temperature may fluctuate. In this case, I try to take the peak flow temperature as being the reference to measure against, but I'm not sure this is universal practice and other plumbers may have different ideas.

On to your 40°C question. I am guessing you are measuring the temperature with the boiler not yet having reached its maximum temperature (because it seems unlikely you would run a boiler this cold). How does the the flow at the boiler outlet compare with the temperature at radiator inlet and vs other radiators? If within a few degrees, then it seems to indicate that the boiler is not yet up to temperature. If, on the other hand, the boiler is getting hot and the radiator is not, there could be a partially blocked pipe (sludge or air) or a fundemental design issue. I have seen additaional radiators piggybacked off other radiators in an existing system with the result that the water starts to cool before it gets to the radiator: there isn't much you can do in that case unless you want to start increasing pipe diameters within the system. The fact that the radiator is running without a temperature drop suggests it is receiving excessive flow and needs throttling back, and you might find that you have a modern boiler and that it is reducing its flow temperature (or even slowing down the pump) to try to compensate for the fact that it sees that no heat has been lost by the water it has sent around the radiator system.

Back to our hypothetical situation from paragraph 3. As soon as you add TRVs, this situation becomes unsustainable. As the temperature outside rises above the -1 to -3°C that the system is probably designed to work at, the heat losses from the house fall and the radiators start to overheat the rooms. The TRVs shut down the radiators, the boiler is running at part load, and the drop across the radiators increases. As such, there is a certain amount of truth in the idea that TRVs will self-balance a system. The problem is when you first switch on the system and find some radiators are taking 45 mins to warm up, or someone turns a TRV to max and starves other radiators. By manually balancing the system, what you are avoiding is that, but the TRVs will usually take over control of the balancing most of the time. So, if the number of variables means that the hypothetical ideal is not sustained, it doesn't really matter because you'll have achieved a good enough balance, even if absolute perfection was not possible.

Does this help?

 

[Timmy D]

I haven’t read all the posts by lockshield valve are fine for the job they need to do.

However you need to understand that they really only do anything within the first rotation from closed to open.

There’s no difference in 2 turns open to 4 turns open.

If you want a better understanding of this, look up “valve authority”.

 

[Knappers]

I'm a bit late but this is how I 'balance' a system quickly.

Open all TRVs and open lockshields as follows:
-1/2 turn for small rads and medium rads close to boiler
-1 turn for all others

Turn on heating and run around feeling heat as it percolates through rads. The idea is that they should heat evenly so I catch them all when 1/2 warm.
For the first couple of slow rads I'll open 1/4to1/2 turn then I'll check for the ones that start to heat at the base first and turn them down 1/4 to 1/2 turn.

Then I turn off heating and have a cupa while I respond to some msg's.

Then I fire it up and repeat adjustments.

I do this untill I'm happy that they all heat evenly.

Not very scientific but it works for me and over time you get better at guessing and so make much less adjustments.