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blownagasket · Joined: 07 Mar 2008 Posts: 10 Location: Grimsby

Right,..... overflow was dripping (central heating expansion tank in the loft, (if its of any consequence, its a common overflow with the hot water feed tank and that is ok)). On investigation, found that when I switched the heating on, hot water started dribbling from the vent over the expansion tank. Same happened when I switched the hot water on. Same when I switched em both on. when I switched them off , there was a momentary surge of hot water from the vent and then it stopped.
Now I would assume that if water was being pushed out of the heating system via the vent, it would be replaced via the feed from the expansion tank, but this is not happening hence the dripping overflow. It seems to me that the pump is pumping against a head whichever service is selected, and that it would indicate a blockage somewhere. I managed to force some water (via a small plunger type hand pump) down the cold water feed, and this came straight back out of the vent. I have injected fernox L3 superconcentrate into the system to try to de-sludge it but no joy yet.
The system is an 'S' plan fully pumped with two motorised valves (one for heating, one for hot water, which are both working fine, and are switching the pump on ok). the boiler is an Ideal W2000 (yeah I know its an old one) and was in the house when I bought it. Any suggestions?

thescruff · Moderator Joined: 03 May 2003 Posts: 4659 Location: Bath

Is it an combined cold feed vent and where do they join the system

blownagasket · Joined: 07 Mar 2008 Posts: 10 Location: Grimsby

the vent and the cold water feed are connected within about 1 inch of each other to the pipe that feeds the pump suction (inlet) just below the pump.
Just a little more info. The pump is on setting 1, if I raise to 2 or 3 the flow of hot water from the vent increases accordingly. I suspect a blockage at the boiler but I have no manual, so don't know what hardware is under the cover (i.e. valves, non-return valves etc....) and don't want to go exploring until I've exhausted the theoretical side. Scary thing is, if there is water coming out of the system, and apparently non going back in, whats gonna happen?

thescruff · Moderator Joined: 03 May 2003 Posts: 4659 Location: Bath

ave you got an by-pass valve either auto, or an gate valve, and are they open.

It sounds like the cold feed maybe blocked, but check the motorized valve by opening them manually and checking to see if it still pumps over.

blownagasket · Joined: 07 Mar 2008 Posts: 10 Location: Grimsby

the only valves I can see are two gate valves, one in the cold water feed from the hot water tank above the cylinder to the cylinder, and one at the lower outlet from the coil in the cylinder. I suspect these are more to do with isolation for removing the cylinder than anything else.
I've tested the boiler stat (in case of overheating), and it seems to shut off at the required preset and come on again when I increase the setting. All the radiators are getting hot eventually, the hot water side warms up (I've lowered the boiler stat as a safety measure), but I have noticed a rushing sound at the pump every now and then. I've already checked the manual levers on the motorised valves, and can physically feel them moving over and closing again when the heating/ hot water comes on and off, and hear them switching the microswitches to the pump. I've just had the boiler cover off (electrics/ gas isolated) and found a drain cock, when I drained water from this it started off black and quickly cleared. I did this twice with same result. And, the expansion tank level went down.

thescruff · Moderator Joined: 03 May 2003 Posts: 4659 Location: Bath

I think the problem is to do with the motorized valve, you say you have two so I assume they are 2 port valves On an S plan.

Is there a pipe teeing off the flow pipe between the pump and the valve, this is the heating pipe we should e looking at

Can you post a pic

blownagasket · Joined: 07 Mar 2008 Posts: 10 Location: Grimsby

the valves are indeed two port 22mm honeywell v4043's. From the pump outlet at the top of the pump (pump is mounted vertically, with the arrow on the casting pointing up), there is first, the isolation valve, three inches above that is a tee that feeds back down for about 10 inches to the motorized valve to the heating (no other branches off this). Three inches above that tee is another tee that feeds back down for about 1inch to the motorised valve to the hot water coil in the cylinder (it feeds to the top of the coil) the pipe carries on vertically for another 8 inches to an automatic vent (there is also an automatic vent on the lower connection to the cylinder coil, and I bled both of these to make sure that there was no air lock). I have changed the motorised valve to the hot water cos it looked very old and I thought it might be a problem (and it is the right flow direction and the wiring was like for like), and the valve for the heating looks like a recent Honeywell with the silver motor cover (incidently, both the manual levers are at the top). Because the problem exists with the hot water and/ or the heating, I'm assuming the valves are ok.
Will try my hand at getting a pic. to you, but don't hold your breath, my I.T. skills are worse than my plumbing!

thescruff · Moderator Joined: 03 May 2003 Posts: 4659 Location: Bath

I shall be out for the rest of the night but will give that some thought later.

To post a pic save it in Photobucket or similar, then copy and paste the IMG tags to here.

blownagasket · Joined: 07 Mar 2008 Posts: 10 Location: Grimsby

Update, I drained the system today to clear the fernox cleaner out of the system (I drained from both the rad. drain cocks in the hall and kitchen, and the drain on the boiler). Then let the water run through for a bit to flush. Refilled and bled all the radiators. and put the whole thing back to work (at the same time I bent the arm on the ballcock in the expansion tank, to lower the level a bit in the tank, to see if it made any difference, you'll know why Scruff). Problem almost the same, put heating on BUT DIDN'T DRIBBLE, turned heating off, momentary surge. Same with the hot water. Now, as the water got hotter, the problem seemed to get worse (expansion?). So let me run this by you...the vent is throwing water out of the heating system into the expansion tank, but is not going back into the system from the expansion tank (as I said before), so I asked myself, where can the heating system get water from?... The hot water cylinder!.. I dismissed the idea before because the expansion tank header is so much higher than the hot water tank header, and so thought the pressures were wrong, but having thought more, there is a lot of water in the cylinder creating quite a squeeze... what do you think? am I now verging on the realms of insanity? It's doin' my head in!

thescruff · Moderator Joined: 03 May 2003 Posts: 4659 Location: Bath

Did you get the pics, if you cannot post them you can always send them to me.

blownagasket · Joined: 07 Mar 2008 Posts: 10 Location: Grimsby

hopefully there will be images...

thescruff · Moderator Joined: 03 May 2003 Posts: 4659 Location: Bath

Would be handy if you stand about 5-6 feet back Laughing

I need to see the pump and fittings in one pic.

blownagasket · Joined: 07 Mar 2008 Posts: 10 Location: Grimsby

Best I can do (stubborn furniture)...first photo on the last post shows a close up of the cold feed (15mm) and the vent/ inlet to pump (the pipe with the creases). The two pipes on the back wall (white ones) are the vent and the cold water feed.

thescruff · Moderator Joined: 03 May 2003 Posts: 4659 Location: Bath

I can only see one pic the rest didn't come out Laughing

I'll email you mine and you can send them to me.

john

blownagasket · Joined: 07 Mar 2008 Posts: 10 Location: Grimsby

I've tried again, I will get the hang of it!!!!!! third photo is the close up of the vent/ supply from the boiler(22mm with creases), and cold feed(15mm). They then go to the inlet of the pump.