Oil central heating issue

irish bloke

At my wits end here with an oil central heating issue.

Background:

House built in 2007. Oil C/Heating with a firebird S 90 boiler, using a riello burner and a new wilo 6M pump (replaced seized 4M pump).

2 zones (7 rads on each zone) system runs off 2 separate stats. 1 stat upstairs and one downstairs. Both solenoid valves for the stats are in the hot press upstairs.

Problem is I can't heat all my downstairs rads. 3 will fully heat and other 4 will vary from luke warm to cold depending on how the valves are open.

The 7 upstairs rads have the flow on the right hand side.
The 7 downstairs rads have 3 with the flow on the right and 4 with the flow on the left. The flow valves are fully open and the balancing is done on the return side (stopcock side).

Rads that dont work properly are the rads furthest from the boiler downstairs, 3 have flow on left and one has flow on right.

When I open all control and stopcock valves to the max I only get 3 of the 7 downstairs rads working fully.
When I open the control fully and stopcock halfway I still only get 3 of the 7 downstairs rads working fully.
Have tried in vein to balance the rads by incremently closing the half open stop cock valves on the hottest rads and so on.

Never had the heating right and when buying the house several plumbers on site looked at it while never getting it working properly. I even got a plumber out a few months ago who balance the system and it worked for the night but went back to normal again.

Am an Engineer myself so have some idea of what's going on but am no expert in this field.

Have thought blockages, air leaks, under sized pipes, etc, but don't know where to go next.

Any constructive advice welcomed.

Thanks IB

shane0007

If you turned off all rads bar one of the ones that is luke warm, does it hop off the wall with heat or still the same?
Also, do the pipes feeding the downstairs rads come out of the floor or do they come out of the wall?

Also turn off the cylinder coil & see if this helps.

Dtp79

irish bloke wrote: »

At my wits end here with an oil central heating issue.

Background:

House built in 2007. Oil C/Heating with a firebird S 90 boiler, using a riello burner and a new wilo 6M pump (replaced seized 4M pump).

2 zones (7 rads on each zone) system runs off 2 separate stats. 1 stat upstairs and one downstairs. Both solenoid valves for the stats are in the hot press upstairs.

Problem is I can't heat all my downstairs rads. 3 will fully heat and other 4 will vary from luke warm to cold depending on how the valves are open.

The 7 upstairs rads have the flow on the right hand side.
The 7 downstairs rads have 3 with the flow on the right and 4 with the flow on the left. The flow valves are fully open and the balancing is done on the return side (stopcock side).

Rads that dont work properly are the rads furthest from the boiler downstairs, 3 have flow on left and one has flow on right.

When I open all control and stopcock valves to the max I only get 3 of the 7 downstairs rads working fully.
When I open the control fully and stopcock halfway I still only get 3 of the 7 downstairs rads working fully.
Have tried in vein to balance the rads by incremently closing the half open stop cock valves on the hottest rads and so on.

Never had the heating right and when buying the house several plumbers on site looked at it while never getting it working properly. I even got a plumber out a few months ago who balance the system and it worked for the night but went back to normal again.

Am an Engineer myself so have some idea of what's going on but am no expert in this field.

Have thought blockages, air leaks, under sized pipes, etc, but don't know where to go next.

Any constructive advice welcomed.

Thanks IB

Is there a balance valve on your cyclinder? When balancing the hot rads, turn the return side off until the warm ones heat up. Then re open only half a turn. Are your rad pipes coming back to a manifold or tee'd underground?

irish bloke

shane0007 wrote: »

If you turned off all rads bar one of the ones that is luke warm, does it hop off the wall with heat or still the same?
Also, do the pipes feeding the downstairs rads come out of the floor or do they come out of the wall?

Also turn off the cylinder coil & see if this helps.

I havnt tried that but will give it a go tomorrow for all 4 individually. Do you mean open both flow and return fully for each one.

All pipes come out of the wall.
Have turned off the cylinder coil valve to no avail.
Thanks

shane0007

Ok you have a drop down system. Mare of system. Open both sides, but the cause is more than likely sludge. I have come across many of them & the whole house is plumbed in 1/2". Rads on opposite sides of the walls also served off same 1/2". Fitting under floors could have blockages also.

If sludge is the issue, make sure whoever you get to powerflush it has a decent machine. A standard unit will not have the flow rate to shift the muck back up through the walls.

Turn off one of the culprit rads on both sides. Drain & remove it to outside to see if it is very sludged. If so, a powerflush is the only proper solution.

Dtp79

shane0007 wrote: »

Ok you have a drop down system. Mare of system. Open both sides, but the cause is more than likely sludge. I have come across many of them & the whole house is plumbed in 1/2". Rads on opposite sides of the walls also served off same 1/2". Fitting under floors could have blockages also.

If sludge is the issue, make sure whoever you get to powerflush it has a decent machine. A standard unit will not have the flow rate to shift the muck back up through the walls.

Turn off one of the culprit rads on both sides. Drain & remove it to outside to see if it is very sludged. If so, a powerflush is the only proper solution.

Would it sludge up after only 5 years ? I too agree that " drop systems " are rubbish. Proud to say I never did one! I usually find air the biggest problem in them.

irish bloke

Dtp79 wrote: »

Is there a balance valve on your cyclinder? When balancing the hot rads, turn the return side off until the warm ones heat up. Then re open only half a turn. Are your rad pipes coming back to a manifold or tee'd underground?

Yes. Balancing valve on the cylinder.
3 pipes connected together going downstairs. 2 have the solenoid valves connected to them and the 3rd pipe goes into the lower section of the cylinder. Pipe coming out of the upper section of the cylinder has balancing valve on it. This goes to 2 places:
a) to a varem expansion vessel which is teed into a pressure gauge and pipe coming from attic to downstairs. Pipe has shut off valve on it lower then the vessel..
b)downstairs.

Tried closing the returns on hot rads fully but made little difference to problem rads.

Not sure re manifold or teed underground, how can I tell.

Tks.

shane0007

Dtp79 wrote: »

Would it sludge up after only 5 years ? I too agree that " drop systems " are rubbish. Proud to say I never did one! I usually find air the biggest problem in them.

Absolutely. You will also probably find it as a so-called "semi-sealed" system with a failed non-return valve from either if you are lucky it's own tank or worse, into the cwst. This will constantly expand & contract into the tank bringing with fresh oxygen. It could also have a leak fed from an auto fill valve (pressure reducing valve).

shane0007

irish bloke wrote: »

Tried closing the returns on hot rads fully but made little difference to problem rads.

Sludge so, or blockage in a fitting serving those rads.

Dtp79

shane0007 wrote: »

Absolutely. You will also probably find it as a so-called "semi-sealed" system with a failed non-return valve from either if you are lucky it's own tank or worse, into the cwst. This will constantly expand & contract into the tank bringing with fresh oxygen. It could also have a leak fed from an auto fill valve (pressure reducing valve).

3 babies of the boom.... Auto filling valves, drop systems and semi sealed systems!!

irish bloke

shane0007 wrote: »

Sludge so, or blockage in a fitting serving those rads.

Can I also add I got a thermal imaging camera off one of my mates to see if I could see cold spots or blockages on the rads and they looked ok. Could also see the the flow side of each rad with this camera.

If its a dodgy valve, what's the best way to diagnose?

Dtp79

irish bloke wrote: »

Can I also add I got a thermal imaging camera off one of my mates to see if I could see cold spots or blockages on the rads and they looked ok. Could also see the the flow side of each rad with this camera.

If its a dodgy valve, what's the best way to diagnose?

Is there a gate valve on the coil to the cyclinder?

shane0007

I also powerflush with the aid of a thermal image camera. You will not see the sludge until you can get the rad upto temperature to see the temperature difference between the top of the rad and the bottom where the sludge is located.
Your issue is not a dodgy valve or 4 dodgy valves for that matter!

irish bloke

shane0007 wrote: »

I also powerflush with the aid of a thermal image camera. You will not see the sludge until you can get the rad upto temperature to see the temperature difference between the top of the rad and the bottom where the sludge is located.
Your issue is not a dodgy valve or 4 dodgy valves for that matter!

Can you recommend anyone in the limerick area for a proper flush?

Tks

irish bloke

Dtp79 wrote: »

Is there a gate valve on the coil to the cyclinder?

Yes gate valve on top half of cylinder, not the pipe on the very top of the cylinder, ie pipe going to taps

Dtp79

irish bloke wrote: »

Can you recommend anyone in the limerick area for a proper flush?

Tks

Don't know anybody unless Shane himself would travel down south!!

frankdefinger

On the off-chance that you have an airlock I would try to force the water through to your problem radiators, one at a time!
First, shut off every radiator (feed valve only) except the downstairs one which you describe as been furthest from the boiler.
Shut off coil valve. Turn up downstairs thermostat. Switch on heat and set circulating pump at III (highest setting). If you have an
airlock on the radiator this process should clear it. Repeat for the other rads.