Drain down....now no heating

[andy24]

I drained down my system in order to move the low point drain. However after refilling I bled as much air out as I could and then fired it up....the boiler came on for 20 secs then went off and stayed off....the pipe coming out the boiler was red hot and everthing elses was cold....except the pump which got v. hot after a while. I drained the lot down again and tried refilling to ensure i hadn't done anything stupid. Same problem except this time there doesn't seem to be any water gone in the radiators and if i open the drain nothing comes out.....I have checked the expansion tank and this is full.......Any idea's....it's getting cold!!

 

[oilman]

If you haven't left a valve on the output from the tank closed, you have a blockage in the pipe which feeds water into the system. Not good for this time of night.

To refill system, you could fit a hose on the drain cock and fill from the cold tap. Don't open the tap much, the system will fill. Bleed everything. If you have a blockege, excess water will come out of the vent pipe and then to the overflow.

This is not a good way to run the system, you MUST sort the blockage out tomorrow. Turn the boiler thermostat down low, and if it won't fire, you wll need to reset the overheat stat.

 

[andy24]

is there a possibility that the water is feeding down as far as the boiler but unable to get any further due to a fault with the pump/3 way valve?? not real sure on the config of this system........any idea where I could get a drawing from?

 

[oilman]

There should be a lever on the valve. Move it to manual or man position. But the radiators should still fill by the return pipe.

If you want a drawing, we need more information, boiler make and type, valve make and type etc.

 

[andy24]

it is a gloworm fuelsaver 2 boiler and danfoss valve. it has 2 open tanks in the loft - one as the heating expansion tank and the other as the cold water break tank for the storage tank. On the timer it has two options water only, or heating and water - it looks to me as if the danfoss valve is just ther to look after the heating (not 3 way type). I have watched this valve and the motor turns ok - I have also tried the manual overide.

 

[andy24]

Thanks to all offering help
Thank goodness after a cold night I attacked the job with a clear head (was so tired the day before!!) I emptied the system again and the header tank was still full - so I summised that there was a blockage down from the header tank. So I isolated the pump and took it out - opened the supply side and nothoing came out. Used a tool for unblocking - a long thin poking device - but to no avail. So ruthlessly cut pipe inbetween header and pump - connected hose that I managed to graft onto a toilet unblocker/plunger - pumped this and was blocked solid!!! A bit of brut force and out came the problem a 4" long slug of black sludgy stuff!! Got this out and flushed out the header tank. Rejoined pipe with a through coupling and proceeded to flush syatem for a while with clean water!!! did this, bled system up and away I went - in fact better than before - radiatirs got hot quicker and the whole thing was much quiter!!

 

[oilman]

Now put some system cleaner in, run it for a couple of weeks, flush and re-fill and add inhibitor, or you will get more problems.

 

[masona]

Out of interest,why does the blockage appears to be in that area most of the time? Is it because there hardly any movement of water for it to solidify with sludge from the F&E supply line ?