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fedup · Joined: 25 Jun 2004 Posts: 2 Location: wales

I have solid fuel boiler brand new just installed. Rads are pumped, hot water and 1 rad are gravity fed.Both systems share a common return to boiler via an injector tee. Rads work fine now they have been balanced but don't seem to get very hot due to following problem. Warm water seems to be travelling back up the gravity return pipe at the injector tee thus putting the whole gravity flow system into reverse. Cool water is coming down what should be the gravity feed and entering the top of the backboiler which isn't good as it means the pump is always pumping cooled water round the system and not lovely hot water. There is no hot water from immersion and gravity rad is barely warm I am assuming it is being pumped back up the gravity return by by the central heating pump.
Does this mean the injector tee is faulty in some way. There are no moving parts to this tee, it simply being a restriction in the flow.
Do I need to restrict the flow on the pumped return prior to it becoming common with the gravity return or increase the gravity return flow by removing the injector tee all together. If I remove the injector tee what is to stop the same problem recurring as both return pipes are same
diameter.
Also when I switch the pump off water is expelled into the header tank via the gravity expansion pipe. The water is not hot. I hear gurgling in the gravity rad which then takes in water when pumping resumes. Does this sound like displacement caused by the gravity flow anomally.

All tanks are full, rest of system new, rads balanced. Central heating pump on highest setting. Speed of pump seems to make no difference
Please help the plumber I have employed is baffled and another plumber I called in to look at it also has no idea.

thescruff · Moderator Joined: 03 May 2003 Posts: 4751 Location: Bath

First thing to do is a drawing and email it to me.

A diagramatic showing boiler connections, pump, cylinder, any valves etc.

I shall only be about at the weekends.

scruff

fedup · Joined: 25 Jun 2004 Posts: 2 Location: wales

I will draw up a schematic this weekend and forward it.
But in the meantime I have discovered that the restriction on the injector tee is on the gravity return not on the pumped return.
It restricts the gravity return down to 15mm pipe and the pumped return is 22mm.
From what I can see the injector is constructed of a 22mm tee with a 22 to 15 reducer soldered in reverse on the gravity return so the 15mm pipe projects half way into the bore of the 22mm pumped return. Is this a valid design. If not, how should one be constructed
Should the restrictor be on the pumped return and the gravity left open. I would assume the gravity r. needs a large bore pipe and the pumped r. reduced at the junction to help pull water past the gravity r.