Trouble with balancing after following how-to.

[shaky1105]

Hi All.
Decided to attempt to balance my system, (as it's never been done) following the nice guide on here posted a while ago by D Hailsham. However I've got stuck at the first hurdle (check boiler temp differential according to the guide) as even with my boiler (Worcester Greenstar 9i) on the lowest pump speed and all the LS open, the temp. differential is only just over 2.5°C !
I guess once I start to close the LS, eventually once all done, the TD might be OK but to stop me ending-up chasing my arse around I thought it better to ask on here if there's summat else I should be doing first.
TIA

 

[Madrab]

2 things you are looking to achieve when balancing the system

1) getting the system to heat up quickly and evenly
2) obtaining then relative delta's to ensure that the rads are reaching their designed output and heating the space correctly and that the boiler is running as efficient as possible.

What flow temps are you running and how warm are the rooms to start with? What type of rads are they?

 

[shaky1105]

2 things you are looking to achieve when balancing the system

1) getting the system to heat up quickly and evenly
2) obtaining then relative delta's to ensure that the rads are reaching their designed output and heating the space correctly and that the boiler is running as efficient as possible.

What flow temps are you running and how warm are the rooms to start with? What type of rads are they?

Thanks for replying @Madrab as you've prolly guessed, I'm doing this DIY so I appreciate any help To try and answer your questions. I've set the boiler flow temp at 70°C (it actually measures 63.9° with my differential meter) in an attempt to get the return to about 50°C or so to get the boiler running reasonably efficiently. All the radiators are THIS type of two different sizes sized to the rooms, or at least hopefully they were when I bought them but the CH seems to work OK.

We only usually heat the rooms to 18°C max and the system seems to cope with that no problem but after investing in the differential meter (I noticed the flue didn't have much in the way of a plume coming out of it so decided to check the flow/return temps) and noticing that there wasn't much difference, i deicded to have a go at balancing.

LMK if you need any more info - tks.

 

[shaky1105]

Well, I've spent since 7am this morning trying to do this and all I can seem to achieve is getting a 6°C drop (or thereabouts) across the radiators, apart from the S/Steel one in the bathroom that seems to want to stay at about 2.5°C unless I completely close the lockshield . All the radiators are now also quite noisy with the hissing sound of water being forced through a tiny opening.

I think i will have to admit that this part of DIY has beaten me

 

[Madrab]

Well I can just about guarantee that you aren't managing to get the correct delta due to the type rads you have. Those column rads are really bad at releasing their heat due to their very poor convecting capabilities, therefore the water has circulated through the rad before it has managed to release it into the space. The process for balancing rads makes a few assumptions and one of them is that the rads, in the main, are Type 21/22's. Have you tired to slow the pump speed (flow) down to give the rads longer to release their heat

 

[justigator]

The three downstairs rads in the house I bought in 2019 were all that type; very poor heat output. In summer 2022 I replaced two with ordinary horizontal Type 22s from Screwfix and last winter had much better heating, though still using 100-140 kWh of gas per day in the coldest periods (4-bed interwar semi, North London, solid walls, leaky windows at the time). The third rad survives only because it's on a plasterboard wall and I can't work out where the studs and piping behind it are to replace. Just had new windows and better draughtproofing so will wait and see this winter. I do recommend junking the vertical designer rads though. Even managed to sell mine for a reasonable price second hand.

 

[justigator]

PS have also found balancing very hard, eg one existing rad that used to get toasty very quickly is now very slow to heat, despite all my efforts.

 

[shaky1105]

Well I can just about guarantee that you aren't managing to get the correct delta due to the type rads you have. Those column rads are really bad at releasing their heat due to their very poor convecting capabilities, therefore the water has circulated through the rad before it has managed to release it into the space. The process for balancing rads makes a few assumptions and one of them is that the rads, in the main, are Type 21/22's. Have you tired to slow the pump speed (flow) down to give the rads longer to release their heat

Thanks again for the reply @Madrab . The pump is on it's slowest speed (adjusted on the boiler panel) so there's no "give" there I'm afraid. The annoying thing about this is that I would normally ask loads of questions first to people "in the know"about stuff I'm considering purchasing but this time, I didn't bother. Ah well, you live 'n' learn I suppose ..

At least they do actually warm the house up when they're required to, even before I tried to balance them so I'll prolly just leave as is and live with it. Our gas bills aren't astronomical anyway, we use about 8.5k a year so it's not exactly life-threatening I suppose.

I might have a faff with them in a couple of days if I see fit as I suppose a 6°C drop is better than the 1°-2°C drop they have when both valves are fully open.

PS have also found balancing very hard, eg one existing rad that used to get toasty very quickly is now very slow to heat, despite all my efforts.

As I found out to my cost ‍ although having next to no patience these days doesn't help..........thought you were supposed to get calmer as you got older

 

[Madrab]

I think there are 2 things that I would consider if I was looking at that system.

1) A central heating system is only as good as it's rads, (car and tyres spring to mind), I can be relatively sure that if you had standard convecting rads your system would be more efficient and space heat up times would be shorter = lower bills
2) If you had convecting rads you would be able to run the system at a cooler temps with a similar space heating outcome. Balancing would be easier with a lower return temp, so condensing would be more effective, bringing the boiler closer to optimum efficiency = lower bills

At the moment with those rads, for them to be effective, you will have to run the system hotter and for longer to achieve a comfortable space.

It's all moot though as you say, it all really comes down to what you are happy with.

 

[shaky1105]

It's all moot though as you say, it all really comes down to what you are happy with.

Yeah, I know where you're coming from buddy and with hindsight (what a wonderful word - lol) I should've done a bit more research before buying them all. Being a DIY'er, I thought I was being fairly clever, making sure I got the correct size rad that will give the correct output for the room size at a ΔT of 50°C................hmmmm, obviously not .

I won't be replacing them as basically the whole house refurbishment heating pipework was based around the design of these rads and it'd be a major upheaval to swap them for the more efficient, standard types but as I mentioned earlier, the system works and heats our house up perfectly well. The main reason for attempting the balancing was to see if I could get the system running a little more efficiently.

I do appreciate your input @Madrab and at least you've saved me the time I'd have wasted chasing my ass trying to get them balanced.

 

[ericmark]

I also tried to balance radiators, I did improve them to what they were, but clearly not right. I found that if the flow it too low, they don't heat the room, which is what one expects, but if too high the TRV can't adjust in time, what would happen is the radiator would over shoot, then I would get a hysteresis rather than a smooth radiator heating and cooling as the room required. I am sure one can set the lock shield using a differential thermometer, I have now found mine, but not the thermocouples, so a bit useless, and most people simply don't have one.
So I used the target and current temperature reported by the TRV head, both heads show target and current, and if current exceeds target then the lock shield is open too much, with a modulating boiler, does not seem to work very well with an on/off boiler, I turned the wall thermostat up full so that was doing nothing, set the temperature required, and just kept tweaking the lock shield until current never exceeds target.

I am just an electrical engineer not anything to do with heating and ventilation except for stress relief, it is just what I have learnt trying to get the 4 houses I have lived in working. Late mothers house was only one with a modulating boiler, and the TRV's once set worked A1 in her house, they have not worked so well in this house, but main problem in this house is where the wall thermostat is located, in the hall, which is about central to house, but cools too slowly. I can set heating speed with lock shield but not cooling speed.

 

[Madrab]

making sure I got the correct size rad that will give the correct output for the room size

It definitely was the correct approach but unfortunately it was thwarted by the characteristics of these rads as they're not ideal. The reason behind it is the way they heat the space.

Optimum process to heat any open space is by convection, therefore standard convecting rads are design to output their heat @ 90% convection and 10% radiation, their delta's are designed around this. Column rads like those operate @ 30% convection 70% radiation therefore whilst their output may be adequate for the space they are in, the way they heat that space isn't as efficient at all and it takes a lot longer for them to release their heat, ergo lower Delta's. Longer heat up also means larger bills as the boiler has to run for extended times to satisfy the stat.

As you say, at least the house isn't cold