Rad slow to heat up fully

[Johntheo5]

Can't remember how many rads you have?.

It will take a lot of balancing to get that rad hot, you will probably have to compromise and accept a fairly slow heat up in this rad to allow reasonabe heat output from the remaining rads, the target flow temperature will probably also have to be increased to 70/75C, very unsatisfactory overall IMO,
All Vallient boilers (apart from the "4" series) have a internal bypass, the boilers come with this set to 250mbar, 2.5M, so this is the maximum head available (at this default setting) to circulate through all the rads, relatively quite low. it can be adjusted to a maximum of 350mbar, 3.5M which will be quite adequate for most systems, it may be worth looking at this but requires your installer to change it and also talk to Vallient re changing pump settings.

 

[ZakUK]

Can't remember how many rads you have?.

It will take a lot of balancing to get that rad hot, you will probably have to compromise and accept a fairly slow heat up in this rad to allow reasonabe heat output from the remaining rads, the target flow temperature will probably also have to be increased to 70/75C, very unsatisfactory overall IMO,
All Vallient boilers (apart from the "4" series) have a internal bypass, the boilers come with this set to 250mbar, 2.5M, so this is the maximum head available (at this default setting) to circulate through all the rads, relatively quite low. it can be adjusted to a maximum of 350mbar, 3.5M which will be quite adequate for most systems, it may be worth looking at this but requires your installer to change it and also talk to Vallient re changing pump settings.

Wow. Id say a bit too much hassle for little reward. Id rather leave as it is and not mess with the boiler ...

 

[Bod ...]

Not read all the replies.

What I'd do is thst I'd get the system hot.

Turn off radiators closest to the boiler or cylinder. Via the lock sheilds

Feel if said radiator is getting hotter. If not turn another radiator off then another if need be.

With the but of a hammer or a rubber mullet tap where the vertical and horizontal panels meet. Not too hard as you don't want to mark the Finnish, but hard enough.

Feels the heat come through.

Then go back and gently crack open lock shields open little at a time furthest rads first until you feel heat to the flow side. Leave to heat up then move on.

 

[Bod ...]

Wow. Id say a bit too much hassle for little reward. Id rather leave as it is and not mess with the boiler ...

You really should get the builders plumber to come and do this if your not sure. Ultimately its their responsibility.

 

[Bod ...]

From my experience it can be sludge particles blocking up the small ports where the vertical meets with the horizontal.

I like to flush these sort of radiators before I install as there generally is alot of manufacturing swalf left in side + I think they are poorly manufactured.

 

[Johntheo5]

Wow. Id say a bit too much hassle for little reward. Id rather leave as it is and not mess with the boiler ...

A 20 min job for any GRI and regularly done, you will certainly find it far easier to balance with a 3.5M head vs a 2.5M and also run with a lower boiler return temperature to give greater boiler efficiency.

 

[Madrab]

Balancing issue ?

yep

 

[ZakUK]

Got it. Thx for your wisdom everyone. Will see what builders will have to say and take it from there !

 

[ianmcd]

as @Madrab correctly says , you have a balancing issue, forget all the crap about changing boiler paramaters, water is like everything, it is lazy and will always travel the easiest path, so will happily circulate around the nearest small radiator than take the harder path to a large radiator, your installer should have balanced the system when adding that radiator

 

[ZakUK]

as @Madrab correctly says , you have a balancing issue, forget all the crap about changing boiler paramaters, water is like everything, it is lazy and will always travel the easiest path, so will happily circulate around the nearest small radiator than take the harder path to a large radiator, your installer should have balanced the system when adding that radiator

Thx. Will defo make sure he starts with balancing to solve the issue.

 

[Madrab]

In the short term, you could do a quick balancing exercise. Did it take for all the other rads to be off to get that one or did you take your time and wait and check the column with one after another?

A quick process would be, with the system cold, keep the column full open, turn all the others off at their lockshields and then just open the lockshield on the furthest away rad just enough to allow enough flow to start heating the inlet valve. Then start opening the lockshield by a 1/4 turn until the rad warms up properly. Every adjustment though you need to wait and give the rad time to heat up. then move onto the next and keep checking the column isn't cooling down, this isn't a quick process.

 

[ZakUK]

I switched them all off except the column one and thats when it heat up whole. Didnt do one by one.
Ill try your suggestion on my day off as it seems like a longish process
So lets say i start opening one by one and then column starts cooling down after the third one. What does that mean and what im supposed to do then ?

 

[Madrab]

That's why I suggested to turn them off one at a time ande once the column heated up properly then the others could be left alone. It would have been an easier balance with less rads to work with.

So lets say i start opening one by one and then column starts cooling down after the third one

As suggested take your time with them. Open the lockshields just enough to feel the valve heat up, then leave it 5 mins, if the rad doesn't heat up to the top properly, then crack the lockshield another 1/4 and wait another 5 mins, repeat that until you feel the rad warming up to the top properly.

I would be quite surprised if you get to the point where the column goes cold with only 7 rads and the boiler on default but if it does then it would then be looking at pump settings. How old is the boier?

 

[ZakUK]

That's why I suggested to turn them off one at a time ande once the column heated up properly then the others could be left alone. It would have been an easier balance with less rads to work with.

As suggested take your time with them. Open the lockshields just enough to feel the valve heat up, then leave it 5 mins, if the rad doesn't heat up to the top properly, then crack the lockshield another 1/4 and wait another 5 mins, repeat that until you feel the rad warming up to the top properly.

I would be quite surprised if you get to the point where the column goes cold with only 7 rads and the boiler on default but if it does then it would then be looking at pump settings. How old is the boier?

Boiler installed new in 2021.

So what result are we looking for ? If heating is ON, all rads (except column) fully hot and i start turning TRVs off one by one every 15mins. Lets say after 2 rads column heats up fully, what will that tell us ?

 

[Madrab]

It will tell us that the system isn't wildly out and will only need the minimum of adjustments to get the column heating up properly. If it takes more then a more extensive balancing exercise will be needed.
If they all need to be off and there are only 7 rads then that column has a problem with either it's supply or the rad itself. A 2 year old combi on default settings should easily supply all those rads albeit with a bit of setting up.