Rads not heating fully

[Millsy 82]

1st you need to swap the 3 port valve for 2 x 2 port valves or at least put a 2 port in front of the unvented.

How many radiators are there? If there are loads then look at the pipe sizing, boiler size etc. physically take a couple of radiators out and flush them out. if everything is ok then maybe a low loss header with a larger pump on it?

 

[jonnyswamp]

Take off one of the rads with just the front panel working and temp support it and turn it around,reconnect and refill, see what happens
Are the rads round top type? if so they will have a bleed point for each panel

 

[PaulMartin]

yes there is only 3 port, no safety cut out 2 port. Not sure how that would affect flow to heating.
There are about 19 rads...It's 28mm from boiler through 3 port and 15mm to rads and a 35kw boiler.
I did flush out a basement rad that was not heating fully and it was totaly clean.
The problem has existed since entire system was installed 4 years ago.

 

[stevetheplumber]

pipework is under sized a three port valve is realy only good for 50000 btus max you need to remove that and get a 28mm valve for heating and a 22 for ho****er

 

[AWheating]

Do you time the hot water separate to the heating?
When was the boiler and unvented cylinder last serviced?

 

[Neil K]

If it's an unvented cylinder then it should really have it's own dedicated 2 port zone valve controlled by a cylinder stat. Is there a gate valve on the Hw primaries so you can turn them off completely and see if the rads heat up? After which you can balance it right down. Also is it possible to lift floors in the house to look at what way it's piped? Had the same problem a few years back where we went in after another plumber because him and the builder had a falling out. Turned out the flow and return on the rad circuit were linked under the floor, so it was short circuiting and the rads weren't heating up properly.

 

[Neil K]

If it's an unvented cylinder then it should really have it's own dedicated 2 port zone valve controlled by a cylinder stat. Is there a gate valve on the Hw primaries so you can turn them off completely and see if the rads heat up? After which you can balance it right down. Also is it possible to lift floors in the house to look at what way it's piped? Had the same problem a few years back where we went in after another plumber because him and the builder had a falling out. Turned out the flow and return on the rad circuit were linked under the floor, so it was short circuiting and the rads weren't heating up properly.

And apart from that "mistake" (did he do it on purpose, who knows!) he had done a cracking job.

 

[Best]

And apart from that "mistake" (did he do it on purpose, who knows!) he had done a cracking job.

Believe it or not, I came upon that same problem in a large house. My job was to fit new radiators to the two big living rooms before oak flooring was going on top of the wooden floors. As the pipes were fairly poorly done below the joists, I repiped both rooms entirely. The original soldered tees were swept branch type, but system was a 2 pipe job.
When I filled & tested the heating, it virtually didn't work at all. Then I discovered a 3/4" copper pipe bypassing below the floors. I eventually plugged it off & system working amazingly well. It was the original from 1968 & had been for a 1 pipe loop for one bedroom!!

 

[Neil K]

Believe it or not, I came upon that same problem in a large house. My job was to fit new radiators to the two big living rooms before oak flooring was going on top of the wooden floors. As the pipes were fairly poorly done below the joists, I repiped both rooms entirely. The original soldered tees were swept branch type, but system was a 2 pipe job.
When I filled & tested the heating, it virtually didn't work at all. Then I discovered a 3/4" copper pipe bypassing below the floors. I eventually plugged it off & system working amazingly well. It was the original from 1968 & had been for a 1 pipe loop for one bedroom!!

That makes sense. In my case however it was a complete repipe, brand new first fix. We filled it up after lunch on a Friday afternoon (it's always a Friday afternoon isn't it.....) and 2 older much more experienced men than me were losing the will to live by 5pm as to why it wasn't working. We threw in the towel, came back on Monday and lifted every board in the house and eventually found it. Just as well you found yours before the oak floors went down!

 

[PhoenixServices]

yes there is only 3 port, no safety cut out 2 port. Not sure how that would affect flow to heating.
There are about 19 rads...It's 28mm from boiler through 3 port and 15mm to rads and a 35kw boiler.
I did flush out a basement rad that was not heating fully and it was totaly clean.
The problem has existed since entire system was installed 4 years ago.

if it's 15mm supplying 19 rads it needs a full re-pipe. It will never work properly. Needs at least 22 maybe even 28mm depending on the pipe runs.

 

[Taffman]

Check all rads vented on both panels, if they are sounds like a pump problem.

 

[Bolty123]

Do you know what sort of kW your getting out the boiler? I think fan speed for ch can be adjusted on these.

 

[Bolty123]

Unsure if I am allowed to suggest such things still learning ropes here.