I have a gravity central heating system (we loose our electricity alot!) connected to a coal fired boiler. All radiators apart from one work well. The one that doesn't is connected (in 22mm) in the loft to the main 28mm pipe, and then comes down the back of the house to a single radiator. from here it runs under the floor to join with the 28mm pipe again.
The pipe gets warm, and if you have the bottom valve of the rad closed and bleed out the water, the rad gets hot. As soon as you open the bottom valve it gets cold. If you close the top valve and open the bottom and bleed, the rad starts to get warm.
It seems that the flow from the loft isn't enough.
I have a hot water cylinder (and two rads) which are fed off a ring, and that has an injector tee where it re-joins the main pipe, is this the answer for this cold rad? How many injector tees can you have in a system?
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