Largest Rad Not Getting As Hot As Others

[planemad]

Merry Xmas to all

can you please help me chaps, i'm a sparks by trade and have limited practical plumbing knowledge!


System is a heat only pressurised system.
S Plan (two x 2ports)
18l pressure vessel in airing cupboard
Vaillant 418.
Pump - Grundfoss Alpha 3 (model b)
system is a very clean system, rads are modern (8 years old) has always had inhibitor in the system and the magma clean is always quite clean.

4 bedrooms - (6 rads upstairs)
Upstairs = 4 rads with Drayton TRV4
1 towel rail (non TRV)
1 rad in on suite (non TRV)

downstairs 6 rads
4 rads with TRV4s
1 rad in downstairs (non TRV)
1 rad in hall where main stat is located
(non trv)

the issue is the living room rad is the largest in the house and is the only double panel with double connector.
it's just does not get hot enough.
the top is warm (not hot) and the bottom is luke warm, the flow pipe get hot but the return pipe is barely warm

it's not a sludge issue as of i turn all other rads off in the house and have 100% flow around this rad it gets perfectly hot all over in a uniform fashion.

the system is generally well balanced in respect that the returns upstairs are cracked right down 0.5- 1 turn open and the returns downstairs are 1-2 turns open, i try to leave the largest rad return fully open but it's still no good.

any ideas chaps on where i can go with this, as the living room is uncomfortably cold for my family.

thanks all in advance!

 

[terryplumb]

Your system isn't balanced as well as you think , as the rad in question heats fully when others are turned off.

 

[cross thread]

Depends on rad size in kw and size of and length of pipe supplying it.

 

[BlueLoo]

What makes you think that sludge will move out of the way if you isolate the rad?.

Remove rad. Flush in back garden with hose.

If it continues, then move onto other issue's

 

[DP]

I am with Terry on this one.

 

[planemad]

Had a local heating engineer over yesterday and the balancing was fine.
the problem was the stat in the hall was being satisfied far earlier than the other rooms in the house.
it's a honeywell stat and he went into the config and adjusted the temp read out so that it reads a 1.5 degrees lower than the actual hall temperature.

this is more akin to the rest of the house temperature and now warms the living room up very well.

 

[foxhole]

Had a local heating engineer over yesterday and the balancing was fine.
the problem was the stat in the hall was being satisfied far earlier than the other rooms in the house.
it's a honeywell stat and he went into the config and adjusted the temp read out so that it reads a 1.5 degrees lower than the actual hall temperature.

this is more akin to the rest of the house temperature and now warms the living room up very well.

Don't know why people put stats in the hall when we never live in them.

 

[DP]

Had a local heating engineer over yesterday and the balancing was fine.
the problem was the stat in the hall was being satisfied far earlier than the other rooms in the house.
it's a honeywell stat and he went into the config and adjusted the temp read out so that it reads a 1.5 degrees lower than the actual hall temperature.

this is more akin to the rest of the house temperature and now warms the living room up very well.

what setting did you have the hall thermostat set to?

 

[planemad]

21c morning (05:00-09:00)
20c during the day (09:00- 17:00)
21c in the eve (17:00 - 21:30)
17c overnight (21:30 - 05:00)

 

[planemad]

with a data logger he used with a digital display when the hall was 21c (confirmed on the data logger and the stat display) the main living area was 19c.

the largest rad in the house takes longer to warm up and was just having a chance to warm up.

now with the new settings and without any balancing we get 63c on the flow to the rad and circa 40c return back to the boiler.

 

[BlueLoo]

The bit that caught me out was the timeline.

8 years.

How come this happened after 8 years if nothing changed?

Note to self: 1st question should always be. "What did you do"

 

[DP]

now with the new settings and without any balancing we get 63c on the flow to the rad and circa 40c return back to the boiler

That is not a hall radiator issue but a balancing issue or pipe feeding the BIG radiator is UNDERSIZED. Temperature differential is too large