Underfloor Heating - Cold Rooms

[conorpmc]

Hi all,
New to this site and looking for some advice.
We built our house 11 years ago and had underfloor heating installed upstairs and down.
I have been more than happy with the system in general, although it was sore on oil for the first year or two until the house was fully dried out.
Our system is zoned with a manifold on each floor and each room in the house has a stat. Our system runs off a standard oil boiler. I have noticed over the last couple of months that some of the rooms are hard to heat so I finally got around to checking the system today. My initial thoughts were that I had a couple of faulty actuators but have taken them off and they are opening and closing as they should. There is plenty of hot water coming in and 4 out of the 6 rooms on the manifold are heating perfectly. On the two rooms that aren't heating, the outflow pipe to the room is hot when it is calling for heat but the return pipe is cold. On the rooms that are working, both pipes are hot with the return pipe being slightly cooler, as they should be. There is two bleed valves on top of the manifold but there is no sign of air from either of them.
Is is possible that there is a blockage within the loop in these rooms? Is is a big job to flush out an under floor system?
Any help or advice would be much appreciated.
Thanks and Regards,
Conor

 

[Neil K]

When you took the actuators off did you check the pins on the valves, they could be seized stuck in the closed position

 

[conorpmc]

Neil,
Thanks for the reply. The pins on the valve were out when I took the actuators off and I assumed this is how they shoud be. The actuators are Honeywell z100 bge. I didn't try them all but I was able to push the pins on a couple of them in with a screwdriver and they sprang out again. The heating was on when I was doing this and even with the actuators off and the pins out and the stats turned up in the effected rooms the return pipes were still cold.
Regards,
conor

 

[Neil K]

Try shutting down the other zones to see if you can push it to the 2 that aren't working. I don't know which make of manifold you have but a lot of them you can manually shut down xones with an allen key

 

[conorpmc]

what i done yesterday was to shut down all the other zones via the stats and only send heat to the 2 effected rooms. the out pipes to the rooms were hot but the rooms weren't heating and the return pipes remained cold. I ran the heating for over an hour like this. i have attached a pic of my manifold. https://www.dropbox.com/s/1iu7b3e4ucqm3s6/manifold.jpg?dl=0

 

[Neil K]

Sounds like you've got an airlock or a blockage then. Best thing to do is set up a hose at the manifold and flush it out. If you feel confident enough to do this well and good. If not then best get a pro in.

 

[Ermintrude]

Also add some AF10 don't want Spider-Man growing in your ufh