JohnMo Posted December 29, 2023 Share Posted December 29, 2023 Pretty good write up here on condensation theory https://www.heatgeek.com/condensing-boilers-efficiency/ Link to comment Share on other sites More sharing options...
Dee Posted December 29, 2023 Author Share Posted December 29, 2023 So, flow is the red pipe? Rtn is the blue ?? Link to comment Share on other sites More sharing options...
JohnMo Posted December 29, 2023 Share Posted December 29, 2023 17 minutes ago, Dee said: So, flow is the red pipe? Rtn is the blue ?? Could be - if red is hotter than blue, if not then the other way round Link to comment Share on other sites More sharing options...
SimonD Posted December 29, 2023 Share Posted December 29, 2023 Like I said, you've got room to play with as you've got little drop on some radiators and therefore if you spend a bit more time refining the setup, you should see a lower return temp, which is better for effiency. 40C is definitely feasible here. Link to comment Share on other sites More sharing options...
Dee Posted December 29, 2023 Author Share Posted December 29, 2023 6 hours ago, SimonD said: 23 hours ago, Dee said: Cold pipe is 44⁰ hot pipe is 58⁰ So you're not far off. As you've got some rads without much drop, I would be throttling back the flow a smidgen With respect to your pump, do you know what setting this is on? Throttle back? Is that close or open? (Sorry if that's a daft question) How do I check the pump speed? Link to comment Share on other sites More sharing options...
Dee Posted December 29, 2023 Author Share Posted December 29, 2023 6 hours ago, SimonD said: 23 hours ago, Dee said: One rad just refuses to heat up. It did as my previous post but a few days later its gone Cold. I can live with that as I've realised I have taken up way to much of your time chaps. Now I have a great deal of advice snd information thanks to your invaluable input. Link to comment Share on other sites More sharing options...
SimonD Posted December 30, 2023 Share Posted December 30, 2023 16 hours ago, Dee said: Throttle back? Is that close or open? (Sorry if that's a daft question) How do I check the pump speed? Sorry, throttle back is to close it slightly Your pump should have some lights on it when it is running. Older pumps will just have 3 fixed speed settings, newer pumps can have fixed speed settings and proportional speed setting. Upload a photo of your pump and we can tell you. 15 hours ago, Dee said: One rad just refuses to heat up. It did as my previous post but a few days later its gone Cold. I can live with that as I've realised I have taken up way to much of your time chaps. This can be for several reasons, but often if the rad is hot during the initial balancing followed by not getting hot, there's too much resistance so you might need to open up the LSV on that rad a bit. It's so easy to close the valve a little too much when the system is hot and onlyfind out when it heats up again. Otherwise it can be down to the pump speed setting. Here you're just experiencing the reality of balancing a radiator heating system - it is almost never as straightforward as a lot of articles or videos suggest - so back to requiring the patience of a saint and praying for a bit of luck. Some systems are just a total PIA with the worst ones I've experienced having tall column designer radiators. Link to comment Share on other sites More sharing options...
Dee Posted December 30, 2023 Author Share Posted December 30, 2023 All the rads are column type with the 2 kitchen ones tall vertical. The pump on the cylinder has 3 settings and it's always been set on 3 Link to comment Share on other sites More sharing options...
SimonD Posted January 2 Share Posted January 2 Okay ta, not much you can do with the pump as it stands. Link to comment Share on other sites More sharing options...
marshian Posted January 4 Share Posted January 4 On 02/01/2024 at 10:26, SimonD said: Okay ta, not much you can do with the pump as it stands. Sorry but why would you say that? In a well balanced circuit the faster the pump speed the higher the return temp is going to be as you are forcing water thro the rads before it's had chance to shed the heat to the room. You are also using more electricity - for that pump Speed 1 45W Speed 2 65W Speed 3 90W So Speed 3 is twice the consumption of Speed 1 and unless you have a very large circuit you are likely to get a lot more system noise Appreciate that the OP may well not have a well balanced circuit from the original post but you want to balance the circuit with the lowest pump speed possible IMO I'd be dropping it to speed two and seeing if all the rads still get hot - if they do drop down to speed 1 and then just check that when the boiler is firing the temp doesn't overshoot the set point too quickly. Right now my boiler is running at 48 Deg Flow temp - I'm getting a return of 32 - 34 and the whole house is up to temp (11 rads and 2 towel rails) The lower the flow temp you run the lower the delta between the two will be Typically your return temp should be 70% of your flow temp so table below gives a pretty good guide to the delta you should aim to achieve at various flow temps Flow Temp Return Temp Diff 80 56.0 24.0 75 52.5 22.5 70 49.0 21.0 65 45.5 19.5 60 42.0 18.0 55 38.5 16.5 50 35.0 15.0 45 31.5 13.5 40 28.0 12.0 More info can be found here https://www.heatgeek.com/do-we-really-need-dt20/ On warm up I can run the pump on speed 1 but as the TRV's start shutting down the boiler short cycles too much because the boiler overshoots the flow temp set point so I compromised and run speed 2 all the time. Link to comment Share on other sites More sharing options...
marshian Posted January 4 Share Posted January 4 Oh forgot to add - on all 11 rads and both towel rails the lockshield valves are wide open - I use Drayton EB TRV bodies - the balancing is all done on the presets. Most Lockshield valves have terrible valve authority which means all of the closing is done in the last 3/4 of a turn - once open more than 3/4 of a turn they are effectively wide open from a flow perspective Have a watch of this video - it will explain why some lockshield valves really don't help you balance the system easily Link to comment Share on other sites More sharing options...
marshian Posted January 4 Share Posted January 4 On 27/12/2023 at 17:47, Dee said: Aha! I have 18 hot rads!! My concern is though the temp diff varies massively from 1⁰ on rad #11 upto 23⁰ on rad# 9! On 14 rads the TRV pipe is hotter than the LSV side and the LSV on rads furthest away from the boiler are open no more than 1/8th if that. In fact I would state that all the LSV are open open no more than 1/8th. Does any of this matter? Hope you all had a peaceful Xmas....Dee Doesn't matter if the hot end is a TRV or a lockshield end (provided the TRV bodies are bi-directional - if they are unidirectional it maters) Were these temps taken during the warm up phase or when the rooms were up to temp? Can you list the rads type/size and the flow and return temps for each rad you are getting If you are counting towel rails as rads they are terrible for having a decent difference between flow and return - at best I can just scrap a 2 or 3 deg difference On your vertical rads do they have diverters built in? Link to comment Share on other sites More sharing options...
Dee Posted January 5 Author Share Posted January 5 I'll get back to you...I appreciate the input Link to comment Share on other sites More sharing options...
SimonD Posted January 5 Share Posted January 5 (edited) 13 hours ago, marshian said: Sorry but why would you say that? Is the boiler cycling? No Is the boiler showing a low flow situation - e.g. rapid flow temp rise/low return temp? No Is the boiler showing a low differential temp? No - with rads rebalanced but not quite there it's at about 14C which is pretty good Were/Are all the radiator getting hot? No Does the pump selector setting just apply to flow rate? No, it also applies to the overall pressure drop across the system. So the process of commissioning a system is to balance the boiler flow and return and adjust the pump for adequate flow. If you read the whole thread, you'll find it's not too far out and the answer is a pragmatic one. If I was going to be picky I'd say junk the constant speed pump because that should not have been installed on a system with trvs and a pump with proportional pressure settings should be installed instead -cost is hardly any different. But how often do I come across proportional pressure pumps installed and set up on fixed speed? All the bleedin' time and I set them to proportional... Edited January 5 by SimonD Link to comment Share on other sites More sharing options...
marshian Posted January 5 Share Posted January 5 13 hours ago, SimonD said: Is the boiler cycling? No Is the boiler showing a low flow situation - e.g. rapid flow temp rise/low return temp? No Is the boiler showing a low differential temp? No - with rads rebalanced but not quite there it's at about 14C which is pretty good Were/Are all the radiator getting hot? No Does the pump selector setting just apply to flow rate? No, it also applies to the overall pressure drop across the system. So the process of commissioning a system is to balance the boiler flow and return and adjust the pump for adequate flow. If you read the whole thread, you'll find it's not too far out and the answer is a pragmatic one. If I was going to be picky I'd say junk the constant speed pump because that should not have been installed on a system with trvs and a pump with proportional pressure settings should be installed instead -cost is hardly any different. But how often do I come across proportional pressure pumps installed and set up on fixed speed? All the bleedin' time and I set them to proportional... You missed one Is the circuit noisy I'll leave it to the OP to answer - my bet is as soon as a few rads that are too open start to shut down it is PS 14 deg at the boiler at the flow temps stated is not really good at all Link to comment Share on other sites More sharing options...
marshian Posted January 12 Share Posted January 12 One more thing that came to me today - may or may not apply Before I fitted Drayton EB4 TRV bodies and was balancing the circuit on the lock shield The higher the pump speed on my system the more sensitive the lockshield valves were to adjust and harder it was to get the system stable My logic (may or may not be correct) was that with a higher pump pressure smaller adjustments on the lock shields had a much bigger effect (think of the finger over the end of a garden hosepipe small movements dramatically change the flow and spray pattern and it's really hard to get a consistent result) - when pump speed is lower changing the lockshield setting has a much lower impact ad the circuit pressure is lower (restrict the flow to the hose pipe and the changes to the spray pattern aren't as great) Food for thought..... Link to comment Share on other sites More sharing options...
JohnMo Posted January 12 Share Posted January 12 Lower pump speed, give less system head (pressure) for a given flow rate. High pump speed give a higher head for a given flow rate. When you close a lock shield you increase pressure drop at that location and decrease flow rate, a pump running at too higher speed, will just find somewhere else to dump the fluid and keep causing imbalance. Higher the pressure the easier the water can push it's way though small gaps. For an efficient system (least pump power), you need as little restrictions as possible, while having system balance and so allowing lowest pump speed. Link to comment Share on other sites More sharing options...
marshian Posted January 12 Share Posted January 12 32 minutes ago, JohnMo said: Lower pump speed, give less system head (pressure) for a given flow rate. High pump speed give a higher head for a given flow rate. When you close a lock shield you increase pressure drop at that location and decrease flow rate, a pump running at too higher speed, will just find somewhere else to dump the fluid and keep causing imbalance. Higher the pressure the easier the water can push it's way though small gaps. For an efficient system (least pump power), you need as little restrictions as possible, while having system balance and so allowing lowest pump speed. Surely higher pump speed gives higher flow rates as a result of increased pressure? The only reason I run my system at pump speed two is that my boiler needs a min of 15 lpm and even if I free off the rad circuit as much as I can whilst still keeping it in balance the flow rate on pump speed 1 is too low for the 10 - 15 kW that the boiler throws at the heat exchanger.......... I really need a buffer in the system but I'll change the boiler rather than install a buffer Link to comment Share on other sites More sharing options...
SimonD Posted January 12 Share Posted January 12 Don't forget that flow rates change the resistance within the circuit: If you double the flow rate this quadruples flow resistance and requires eight times the power. Link to comment Share on other sites More sharing options...
marshian Posted February 1 Share Posted February 1 On 19/12/2023 at 17:25, Dee said: Stuff Any update Dee? Link to comment Share on other sites More sharing options...
Dee Posted February 27 Author Share Posted February 27 (edited) Sorry for the radio silence but I've become obsessed with building a bathroom....I need a life! System is now running perfectly! The random rad in study that was limping along suddenly heated up weeks after I gave it up as dead....all good so I've now turned off 10/18 rads to save me from the poor house 😳 Edited February 27 by Dee Spelling Link to comment Share on other sites More sharing options...
marshian Posted February 27 Share Posted February 27 8 hours ago, Dee said: Sorry for the radio silence but I've become obsessed with building a bathroom....I need a life! System is now running perfectly! The random rad in study that was limping along suddenly heated up weeks after I gave it up as dead....all good so I've now turned off 10/18 rads to save me from the poor house 😳 Turning off rads can save you very little........... The balance of the circuit on the remaining rads is no longer correct Unheated rooms steal heat from heated rooms so those rads have to work harder The circuit volume is reduced so the boiler short cycles which is bad for efficiency 1 Link to comment Share on other sites More sharing options...
marshian Posted February 27 Share Posted February 27 Explained well here Link to comment Share on other sites More sharing options...
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