Servowarm system

[Chris S]

Hi
I am trying to solve a problem for my elderly father who has a “marvellous” old Servowarm-type system (central heating only, Potterton Flamingo) with the open non-plumbed tank in the attic and 10 mm hard rubber piping. I recently put a new rad in for him (while keeping all other rads turned off to protect the MB1 already in there). The problem is that there would appear to be a large air block in the system. I have tried to approach the problem by isolating the rad nearest the boiler and opening the pump screw. I was able to get that rad hot. I then tried to go round the house in turn. All downstairs rads are full however nothing (gas or water) is coming out of the upstairs ones (yet this phenomenon occurred for a couple of them last winter despite their being red hot all the way through!). The problem remains after a whole day of trying: the boiler comes on for 3-4 min each time and then cuts out. It had a service a year ago. I allow 10-15 min each time for the system to cool down so it comes on again through the thermostat. In the early stages liquid did come out of the pump intermittently but not later on (some high pitched gurgling resulted when some of the downstairs rads were turned off). I am assuming that things get easier if the boiler is on all the time as the air will get pushed round quicker? And that cold water + air in the system is not? The pump would appear to be working OK (I used it on the highest speed). The attic tank is full and the new downstairs rad filled up in less than 20 sec so I am not sure if there is a blockage problem as there are upstairs and downstairs manifolds supplying all rads. There is a bleed point on the lowest (copper) pipe near to the boiler (which I would imagine is part of the boiler system, being copper) which lets out liquid as soon as it is opened (and is close to a microbore pipe from the tank that is attached to the copper pipe).



I am afraid that my father at the age of 88 is so set in his ways that there is no question of replacing the system so I am hoping that there might be some low-tech remedies to solve this save of bringing the plumber in.


Many thanks!

[John t]

Sounds like trial and error Chris. Did you have any luck? Did a 'simple' job this week and one of the rad valves that I hadn't touched became blocked!! Next time I drain a system I am going to plug the hole in the expansion tank (instead of just isolating it) to stop any crap falling into the system.

[mcmoby69]

I am assuming that things get easier if the boiler is on all the time as the air will get pushed round quicker?

hi chris, dont assume anything with central heating systems. they are like women , they defy all logic and laws of physics!
try bleeding the rads upstairs with the pump off. do them one at a time. if this doesnt work. you could try opening up the rad valves and running some water off. the system could also be airlocked on the feed to the sytem so you will have to run some water off until you have removed any air bubbles. if this fails you will have consider using the mains pressure to blast a way thru the air lock or blockage in the pipework dont forget to blank off the vent pipe (dont forget to remove it after) you will also have to 'fernox' the system again! try shutting all the rads then open one and try to bleed it, if that doesnt work switch the heating on and try it that way. if this works you will need to repeat it until all the rads are bled.

[Chris S]

Finally solved the problem with the last ditch dramatic hose backfill from the kitchen sink tap. However I have now had to do it again within the space of a few weeks, having been alerted by the boiler going out, which naturally happened after I bled a large airblock in the rad next door to it. My new enquiry is therefore why I had to do the fill a second time, is it because heating up the fresh water created new bubbles?

Thanks!

[wiggikins]

Blocked cold feed??