Balancing question

[MickyP10]

If I balance all the rads with the TRV heads off and adjust lockshields so they all heat up equally, will this be significantly upset when several of them are in a midway position? For example, I already know I'll be running the bedroom and hallway TRVs on a lower position than the living room, so: a) Will this upset the previous balance and b) If it does, should I be looking at final balance tweaks with these TRVs in the position they'll actually be used?

Many thanks!

 

[BlueLoo]

I don't like the term "Balancing" tbh.
It's fairly meaningless in the modern era of heating with proper distribution and individual radiator controls and dynamic time, temp, and zone control.

In the old days of 1-pipe on-off systems it may have meant something.

Balancing is all about getting the room up to temp in a controlled manner. Trvs are about stopping the room temp from overshooting so balancing a rad is at the front of the heating process and the TRV at the end. Just leave the TRVs on max if you balance the system.

Nobody asks or states what distribution system they have when mentioning balancing. If yours is a manifold system then don't bother unless your rads a massively oversized.

In fact, if its a modern system don't bother at all. Just open everything up and let the TRVs do thier job.
If you have a very non-linear heating arrangement, then you might need to throttle a rad or zone. Unlikely.

Throttling is a better term because that is exactly what you are doing. Do you need to throttle the rads permanently or will the throttling by the TRVs be enough?

I imagine this approach will upset some of the traditionalist on here lol.

But, ask yourself what it is you have. What you want, and what throttling will do or not.

Best if luck.

 

[Gasguru]

Nothing to do with tradition, that's just some really bad advice....that will potentially cause long term boiler damage, excessive gas bills etc.
You recently retired Blue? I'm guessing a keen diyer...

 

[bhm1712]

There is no point having a condensing boiler if the system isn’t to be balanced - is yours a condensing type?

When I balance a system, I refer to the boiler manual and attempt to balance so that the recommended temperature differential (referred to as “Delta T”) across the flow and return is maintained or as close as possible to whatever the manual states it is designed for. There are some things that affect this such as whether the radiators are a suitable size for the room they’re heating etc, but a good rule of thumb is a 20 degree differential across flow and return. For example, a flow temp of 70 and a return temp of 50. This gives a mean radiator temperature of 60 degrees.

On older systems with none condensing boilers, the differential was usually specified as an 11 degree drop across the flow and return.

You must also consider pump speed. Too fast and the differential will reduce and you won’t get the correct heat output from the system, to slow and the flow rate through the boiler will be too low.

Having the modern controls that BlueLoo refers to is great, but the fact is that the majority of homes still rely on a room thermostat, TRV’s on the radiators and a standard programmer to control the heating. Often when I visit homes to deal with the control side of things (I only do controls) I find the system with all lock shield valves fully open and TRV’s set to max and complaints from the homeowner of rooms getting extremely hot, too cold and some radiators not getting warm at all.

Remember that when balancing a dual pipe system, the lock shield valve works to control the flow through the radiator within its first full turn from fully closed. It’s normal to find that the balancing can be done with a lock shield valve open no more than 1/4 to 1/2 a turn.

On a one pipe system, the heating loop should be considered as one large radiator and be balanced on a lock shield gate valve fitted into the return (should be near the boiler) to set the differential and then all lock shield valves should be fully open to allow proper convection through the radiators.

please give us more details about your system!

 

[BlueLoo]

Nothing to do with tradition, that's just some really bad advice....that will potentially cause long term boiler damage, excessive gas bills etc.
You recently retired Blue? I'm guessing a keen diyer...

Engineer and keen diy-er who reads an awful lot and tries to get the latest and best practices when it comes to doing stuff in my own home.
You do what suits your situation i think. Tis hard to know what people do or don't have and i don't give advise, just opinion. (Read my sig).

How will balancing or not potentially damage a boiler or cause excessive gas bills?
Because you are adjusting the outputs of the system out of spec of the inputs? Maybe, maybe not. Most CH stuff isn't designed anyway, its just punted in using old rules of thumb so trying to stick to design rules and norms in that chaotic scenario is impossible anyway.
Are you throttling to limit heat loss? Or balance heat gain? to manage the return temps to a condensing boiler? To manage boiler cycling?
How hot is the boiler set at? what happens when rads or zones shut down?
Many variables.
The CH courses i've read and expert opinion are as i have quoted above. Individual cases can vary.

Of course, "YOu are not a plumber" is a fair criticism, but then again, who is? judging by the posts on this forum, genuine plumbers who keep up to date with modern technology are a rare breed.

 

[BlueLoo]

There is no point having a condensing boiler if the system isn’t to be balanced - is yours a condensing type?

When I balance a system, I refer to the boiler manual and attempt to balance so that the recommended temperature differential (referred to as “Delta T”) across the flow and return is maintained or as close as possible to whatever the manual states it is designed for. There are some things that affect this such as whether the radiators are a suitable size for the room they’re heating etc, but a good rule of thumb is a 20 degree differential across flow and return. For example, a flow temp of 70 and a return temp of 50. This gives a mean radiator temperature of 60 degrees.

On older systems with none condensing boilers, the differential was usually specified as an 11 degree drop across the flow and return.

You must also consider pump speed. Too fast and the differential will reduce and you won’t get the correct heat output from the system, to slow and the flow rate through the boiler will be too low.

Having the modern controls that BlueLoo refers to is great, but the fact is that the majority of homes still rely on a room thermostat, TRV’s on the radiators and a standard programmer to control the heating. Often when I visit homes to deal with the control side of things (I only do controls) I find the system with all lock shield valves fully open and TRV’s set to max and complaints from the homeowner of rooms getting extremely hot, too cold and some radiators not getting warm at all.

Remember that when balancing a dual pipe system, the lock shield valve works to control the flow through the radiator within its first full turn from fully closed. It’s normal to find that the balancing can be done with a lock shield valve open no more than 1/4 to 1/2 a turn.

On a one pipe system, the heating loop should be considered as one large radiator and be balanced on a lock shield gate valve fitted into the return (should be near the boiler) to set the differential and then all lock shield valves should be fully open to allow proper convection through the radiators.

please give us more details about your system!

The rad rating is something i struggle with as the variability and considerations are quite large. I see that most people give up on trying to figure out how big the rad should be and then just go to a "bigger is best" approach. Big rads give off large amounts of heat which need smaller delta t for comfort which knackers up the return temps to the condensing boiler etc, etc.
I read a report last week that concluded condensing boiler efficiency in the UK is a max average of 80% as they are massively oversized, sat in massively oversized systems with far too large radiators.
Same thing for CH pumps. They are too big and waste huge amounts of energy.

So how to plan a path through all of these badly designed system so that you get a reasonable heating end product?

What i have read, is that balancing is not as simple as is thought. Contemporary thought is that for manifold systems with TRVs, don't do it unless something is amiss. This sounds "right" to me and works well in my situation. Certainly, i don't have any slow radiators on my manifold system. My boiler is non condensing but i still get a reasonable delta t until the system is at heat at which point its irrelevent.

I'd like to see some proper technical papers on radiator set up. I certainly have never found any. A few odd comments in boiler manuals and old fashioned best practices but nothing contemporary which includes considerations for condensing boilers, manifolds, variable speed pumps, well insulated housing etc.

Post a link if you have something.

 

[bhm1712]

You think the design of gas fired central heating is a problem…just wait until the heat pump takes dominance.
Jesus Christ wept.

Totally agree. There are very few boiler installers and heating fitters who actually take the time to calculate the proper requirements, radiator sizes etc. Part of the problem is the customer themselves as there are not many people who want to hear “you need to replace the radiators too” in a lot of cases. It’s hard to justify the cost of a properly designed upgrade when the customer simply doesn’t want to know. It’s my belief that this is by and large the greatest problem.

As a result of this, you get new boilers fitted to existing (incorrectly sized) radiators, bad pipe work design and the solution is usually to fit a large boiler to overcome any potential Avenue for customers to complain about things not working right.

 

[BlueLoo]

You think the design of gas fired central heating is a problem…just wait until the heat pump takes dominance.
Jesus Christ wept.

Totally agree. There are very few boiler installers and heating fitters who actually take the time to calculate the proper requirements, radiator sizes etc. Part of the problem is the customer themselves as there are not many people who want to hear “you need to replace the radiators too” in a lot of cases. It’s hard to justify the cost of a properly designed upgrade when the customer simply doesn’t want to know. It’s my belief that this is by and large the greatest problem.

As a result of this, you get new boilers fitted to existing (incorrectly sized) radiators, bad pipe work design and the solution is usually to fit a large boiler to overcome any potential Avenue for customers to complain about things not working right.

I've updated my Sig to make it clear that i am just posting my thoughts and opinions and that its not advise.
Hard to know where to draw the line on the forum and i am still learning. I would have thought its obvious to do your own research. I'll change my posting style.

Yea, Heat pumps, how on earth does one manage them?
You will have plumbers treating them like normal boiler systems no doubt.....

 

[ericmark]

I have to agree with @BlueLoo the setting of the lock shield is more than balancing with a modern gas boiler.
A TRV takes time to open and close, so the flow through the radiator needs to delay it heating up fully long enough for the TRV head to act.

I also agree big radiators are good, as it means you can speed up the heating of one room when required.

I trimmed the lock shield by starting at closest to boiler upstairs, turning radiator off, then once pipes cold, on a little until one pipe got a little warm, and repeated moving out from the boiler, but this was only a start point.

I think the proper way is to measure in and out temperatures, I tried with one of these they can be set to read object temperatures, but the results fluctuated wildly so did not work. Using the electronic head I get current and target, so I used that for the final little bit, if current exceeds target then close a little, once done I was surprised how well it worked, the model of TRV head I used was OTT with anti-hysteresis so set at 22°C at 7 am and 20°C at 8 am or it would take to 10 am before fully warmed up, and it could not stop morning sun in bay window causing over heating, but in the main once set it was spot on, no need for a wall thermostat to control room temperature, although still need one to turn boiler off to stop is cycling on a warm day.

On removing the electronic heads now lock shields set, and replacing with liquid filled mechanical type, they also worked spot on, but hard to set with those heads, as *123456 means nothing.

The liquid filled TRV has a range, as at 20°C it will be wide open at around 3.5 and shut at 2, so 20°C is some where between 2 and 3.5 so would say best option is get one electronic with target and current displayed and move it radiator to radiator to set them.

I have 9 electronic heads, and I can set them so before coming home first kitchen warmed, then dinning room, the living room and finally bedrooms to speed up the heating of rooms being used first, but this does not work with geofencing.

I find geofencing a pain, it will for what ever reason not detect my phone, and turn the heating off. It did work last year OK, may be because now turned to google control rather than nest, first went wrong when high winds damaged EE mast, but since then done it many times.

 

[BlueLoo]

I have 9 electronic heads, and I can set them so before coming home first kitchen warmed, then dinning room, the living room and finally bedrooms to speed up the heating of rooms

That is a bloody clever idea if you have a undersized boiler or rads!
The wiser system has "Comfort mode" which learns the heat/loss profile of the room/rad/zone and will advance the start of the heating before your set time so that the room is at temperature when you expect it to be, rather just starting from cold at the set time.

Quite clever really.

 

[ericmark]

My Nest Gen 3 has an Eco setting, this can be set, so when I leave the house it auto turns down, but not off, however it has gone wrong, it should detect either my wife's or my mobile phone is home, and not go into Eco mode, but this years it has repeatedly dropped into Eco mode, at first I blamed the failure of the EE mast in high winds, but even after repaired unless I walk past the thermostat, if has been putting us into Eco mode, I have now disabled the function.

The TRV (Energenie MiHome) also have the ability of geofencing, but unlike the Wiser system, they don't have algorithms to work out when to close, and the anti-hysteresis is OTT so in mothers house when setting changed to 20°C it would heat room from 14°C to 18°C fast, but 18°C to 20°C was painfully slow, so would set to 22°C for one hour then back to 20°C.

But this returns us nicely to the trimming of the lock shield valve. This house not trimmed in very well, on my to do list, the radiator over shoots, it gets to full heat before the TRV starts to close, and actually they work better, this over shoot counters the OTT anti-hysteresis software.

Oddly the cheap (£15) bluetooth eQ-3 heads work better than the expensive (£37) wifi Energenie, the door open function works very well, if the TRV is cooled fast it assumes the outside door has been left open, and it delays heating for the time set by me, ½ hour, so when we get home with shopping we can leave open the kitchen door while unloading with minimum waist of energy.

It also has a boost function, one press of the button and it goes wide open for a short time, and also single button Eco/comfort so walk into the room and one press turns up heat, no need to mess around with mobile phone. Seems odd only on the cheaper electronic head.

However the Energenie has two sensors one for water and one for air, and compensates for the heat from radiator.

The problem is you need to read the instructions carefully to find out about these features, and some features change, I was told when getting Energenie they worked with Nest, however it seems support has been withdrawn, also seems to work wrong way around, Nest tells Energenie not Energenie telling Nest.

It is the little things that matter, Hive for example has a limit of 22°C on the wall thermostat after which "demand for heat" from the TRV stops working, so the wall thermostat needs to be in a room normally kept cool. Also needs a TRV in the room to ensure that room never exceeds 22°C. So all this about not fitting a TRV in same room as wall thermostat is a load of rubbish.

Even with other makes, the idea of wall thermostat and TRV in the hall works well, the TRV allows fast recovery, but slows down the heating before it turns off the wall thermostat, allowing time for other rooms to heat up, the wall thermostat should only turn off when there is a change of scheduled temperature or on a warm day with a modulating boiler in most homes.

There is always an exception, my first house was hot air, since the air was circulated throughout the house, one thermostat was enough. Second home open plan, i.e. very few doors, arch between living and dinning room, again one wall thermostat between the two rooms was good enough, however neither of those houses had a modulating boiler, so didn't matter anyway.

But it is easy to say you should do XYZ without realising in the home involved for some reason that would not work, be it a regular used stand alone fire, bay windows getting the sun, or a cold wind in one direction cooling one side of the house, this is why the people installing heating and ventilation are called engineers, to me engineer means over level 3 trained, i.e. University. And it needs a lot of skill to work out what is required. OK any tom, dick, or harry can install the top of the range all singing dancing units, but to work out that room needs a linked TRV, and that room does not need a linked TRV takes more skill, so you pay more for the designer and less for the controls.