Radiator balancing problem, lukewarm rads upstairs.

meelick · 25-01-2025 04:20PM #1

Hi all,
So I'm trying to balance my radiators in a pressurised, single-zone, OFCH system built in 2000. There are 8 rads downstairs, and 7 upstairs. I can get the downstairs rads pretty close. However, most rads upstairs have poor heat and 2 are especially bad and only heat up after the call-for-heat has been on for 20-30 mins or so (maybe longer).
I moved in when house was built, but don't ever recall those 2 rads working properly, so likely a problem there from day 1.
All rads bled and pressure of system at 1bar. Really good circulation pump installed about 5 years ago to attempt to resolve, but didn't make much difference. New tails, lockshield valves, and TRVs on all rads recently (myself), and each rad flushed of black sludge (no magnetic filter on system).
I have temperature probes on the flow/return on the boiler, and these get hot pretty much together, and still the upstairs flow/return pipes at the 'lazy' rads stay cold (when I do a 5 min call-for-heat). The flow/ret could be 50/45deg, but lazy rad flow pipe stays at 17deg. I've tried turning off lockshield valves on all downstairs rads, thinking that the pump would encourage the water upstairs, but the flow/return at the boiler keeps getting hotter without heating the upstairs significantly. The only rads upstairs that get good heat are the one closest to the vertical feed coming up from downstairs (discovered with flir camera), but even then, none of them get as hot as the downstairs rads.
Would it be possible that the last rad on the downstairs loop has incorrect flow/return loop, allowing a "low resistance" path for the hot water around the downstairs circuit, thus closing all the lockshield valves has no effect on encouraging the water upstairs?
I've spent ages with the FLIR and a laser theremometer adjusting valves trying to debug it.
Just get a plumber in?
Thanks for any suggestions in advance.
Dave.

10-10-20 · 25-01-2025 06:40PM

Hi! So if all the rads downstairs are turned off and if you start closing down the upstairs rads, I presume that the two lazy ones eventually start to heat up fully?

Is the house a standard design or layout, or could those two rads be on an undersized extension, or even be connected in series with each other?

meelick · 25-01-2025 07:20PM

Standard countryside two storey, four upstairs bedrooms one at each corner. 2 front bedrooms are the lazy ones.

I should have tried your suggestion before, but turning off all the rest does heat up the 2 lazy, and then slowly opening up the others upstairs allows heat to all upstairs (with all downstairs off). I've now got relatively even heat to all upstairs, but turning on the downstairs causes the lazy to lose heat.

I think I'm a lot closer now, I might need to close down the downstairs more or open up the lockshields on all upstairs, get the ratios right.

I'll start by doubling the turns on all upstairs and see if they keep in balance (with downstairs off), then open up the downstairs.

Someone with balancing experience would probably do this in an hour, I'm just assuming something is wrong with the plumbing, it might that it's 1/8 turn here, 1/4 turn there that will balance it properly. :)

I'll keep ye posted.

Thanks.

10-10-20 · 25-01-2025 08:38PM

The way that I did mine was to close off all rads, then open up the lockshield valves by around 1.5 turns, opening larger rads to around 2 turns and any of the smaller ones to around 1 turn. Then fire up the heating and leave it running for 20min, then adjust any cooler rads up by an 8th of a turn. Worked for me.

jimf · 25-01-2025 10:14PM

does your hot water heat up ok

do you have a balancing valve on the cylinder

John.G · 25-01-2025 11:06PM

What is the pump make/model/mode&setting?.

" Really good circulation pump installed about 5 years ago to attempt to resolve, but didn't make much difference."

meelick · 26-01-2025 10:55AM

https://www.boards.ie/discussion/comment/123099726#Comment_123099726

Pump is a Wilo Yonos Maxo 25/0,5-7 set to mid-speed (II). If I go to III, It doesn't improve the lazy rads, and I can hear the water in the rads late at night, so reverted to II.

meelick · 26-01-2025 11:02AM

https://www.boards.ie/discussion/comment/123099569#Comment_123099569

Hot water heat's OK from boiler. I turn the valve off for balancing, might open up a bit when done, but mostly depend on Eddi (Solar/cheap rate) for hot water.

meelick · 26-01-2025 12:43PM

Good progress here. I first balanced upstairs with downstairs all closed. Then balanced downstairs.

Upstairs had dropped in temp, so doubled the turns on all upstairs. Closed down most of downstairs until upstairs was maintained.

Lazy rads upstairs are now at 1.5 turns, with the rest at about 3/8. Downstairs range from 1/8 open (small toilet rad) with the rest at 1.4 turn open, with the odd one needing a bit more, but none downstairs open more than 3/4 open.

These are lockshield turns, the TRVs are all wide open.

All rads getting up to 60-65 degrees, now including the two lazy ones (house is roasting at the moment).

And the most interesting thing is that the flow/return temperatures are now much more separated. See the diagram here:

Before balancing, the return was pretty much following the flow, but now, there's much more transfer of heat into the rads, so the flow is a lot cooler coming back into the boiler. All upstairs rads were cooler than downstairs, with two below 18deg. Now they're all capable of getting to 60-65deg. Win.

One question though, does that sound like the lockshields are all too constricted, should I be looking for 2-3 turns upstairs and maybe 1-2 downstairs? Am I putting too much strain on the circulation pump?

Now I'll turn all the TRVs down to 3 (out of 6), and leave them sit for a day or two, adjusting where some rooms are cold.

I'm planning on getting a bunch of those cheap Bluetooth temp sensors from Aliexpress and re-flashing so I can use with my home automation setup (node red, etc.), so that I can monitor the temp in all the rooms and watch for cold rooms that should be warm, etc.

Thanks for the interest in the thread so far!

Dave.

10-10-20 · 26-01-2025 12:55PM

Yeah, so I'd say that your rads were all open too wide and the pressure wasn't sufficient to be able to reach the lazy ones. The trick with TRV's is to have one of the rads in each zone as a bypass - that is left without a TRV - so that the whole system doesn't close off and cause pump issues. In my case that's a small 700w rad in the kitchen (zone 1) and a small one in the main bedroom (zone 2). Then my DHW is zone 3 and it's normally closed when the other zones are open.

As for the TH monitoring of rooms… yes, surprised you haven't already! 😁 I have Zigbee and Zwave devices scattered around, mainly Sonoff TH ones. Pop a question into the Home Assistant thread if you want help on that.

meelick · 26-01-2025 01:21PM

https://www.boards.ie/discussion/comment/123100693#Comment_123100693

Great suggestion about one non-TRV rad. I think I had that happen just now, all TRVs down to 3, house pretty warm after all the balancing, call for heat on, boiler temp at max, pump pushing water around but very little place for it to go. Luckily I opened up one TRV fully and it started flowing again, rad got hot immediately.

Shame, I'm after putting new TRVs on all rads, I'll have to either leave one fully open, or go back to regular manual valve. I think I'll do it properly and take out one of the TRVs. I'm single zone here.

Thanks for the suggestion.

Dave.