It may affect the ability to remove an airlock. Most motorized valves have a lever on the side which allows one to put the valve into a manual "drain" position in the absence of power, to cover the situation you are describing. It would be worth removing the boxing and trying that.
First of all thanks to John Rumm and Set Square for previous related assistance.
Last night I tried to bleed one radiator and one towel rail both of which struggle to manage warm when the rest in the house are reasonable temp (both fed from same plastic 15mm feed).
With the following result:
First of all the towel rail:
Attached hose to top connection and opened each valve in turn. With only the return valve open I get reasonable flow from the hose. Closing the return valve and opening the flow valve, I get much less flow so I suspect the valve is stuck closed(ish).
Next the Bedroom Rad
Tried the same process - remove bleed connection and attach hose. Same thing occurs, good flow with return valve open, good trickle only when only flow valve is open.
Presumably this suggests either an air lock or blockage rather than two blocked valves. The motorised valve for the heating side is boxed in and not accessible. But I wanted the heating off before messing last night.
So I have one or two questions:
Does the fact that the heating is off mean the motorised valve is closed and therefore flow will be lower from the flow side valves anyway? OR Would the make up water (which is teed into the return from the hot water cylinder) pass from the return to the flow side in the rest of the system, so that flow from either valve on bleeding should be approximately equal?
If this is an air lock, any tricks on how to clear this? On recommendation, I tried leaving the valve open at both the towel rail and rad (one at a time not simultaneously) for a while to bleed out the air lock, but didn't get more than a steady trickle!
So what next? Any suggestions gratefully received
TIA
Phil
Yes, if the motorised valve is closed, it will certainly make it difficult to get any water to the rad on the flow side.
Remind me, are we talking about an S-Plan system with separate 2-port valves for CH and HW? If so, you somehow need to open the CH valve - either using its manual lever or electrically. You clearly don't want the heating on while you do it - so if you go for the electrical option (because the valve is difficult to access physically) you'll need to disable the boiler and pump and *then* turn on the heating.
[If it's a Y-Plan system with a single 3-port valve, you'll need to force the valve to either the mid or CH position. Again you have manual or electrical options, depending on which is easier]As a matter of interest, have you run the system after your less than 100% successful attempt to bleed it. If so, was there any improvement?
That ought to eliminate the plastic pipe, and the amount of head the system has from the equation then...
Yes - probably. It will depend on the type of valve, but a solenoid driven valve will close on removal of power, as will a sprung motorised one.
If you think about it, with the valve closed the only path from make-up water to flow side of the rad is collectively through the other rads by drawing water out of their feed connections.
One solution is using mains cold water from a hose to force water back into the affected pipes. You need to be sure that there is a clear path back to the vent before doing this though. The water you force in should end up in the header tank ultimately.
I get the impression that the motorised valve is looking like one suspect - does it feed all of the rads, or just the problem ones?
Yes S Plan
Whilst it will mean unboxing, I am inclined to go the manual route as the current wiring arrangment is a bit hairy!
Wouldn't this maybe help to move an air lock with the pump running and the motorised valve open?
Bit late finishing last night, so not sure if there has been any change. I would be very suprised if there had, as the bleed rate didn't improve from either rad or towel rail during test.
Thanks again
Phil
True
I thought as much
Have you tried this yourself?
No there is only one motorised valve on the CH side so this isolates all rads. As I think I may have mentioned many mails ago, this was making some nasty noises some months ago, so may be presenting more restriction than it should. Maybe this, combined with the reduced 15mm pipe size upstairs is causing the pump over.
Unfortunately we have visitors this weekend so I don't think I will be allowed to start unboxing in the dining room to expose the problem valve. This treat may have to wait till next week.
Thanks again for help
Phil
I was thinking from the point of view that, if you're bleeding a lot of water out of the rad, you don't want this to be uncomfortably hot. On second thoughts, it *may* help to bleed with the system running - at least the valve should then be open, and the pump should be adding a bit more urge. If you try this, I would turn the boiler stat down quite low to avoid getting scalded.
I wouldn't have thought so. With an S-Plan system, the *valve* switches the boiler and pump on - and only does so once it's fully open. Also, I presume that the valve is on the *output* side of the pump so that, if the valve
*were* creating a restriction, it would be throttling the flow and making it *less* likely to pump over.Another random thought: I have never tried this but it *might* work. You said that, when trying to get some flow through the problem radiators, if you turned off the other rads and turned up the pump speed, the system then started pumping over but *still* didn't heat the problem rads.
Unless anyone comes up with a compelling reason why it is a *bad* idea, I would then try temporarily (for a couple of minutes or so) bunging up the vent pipe with a cork. This would stop the pump-over and would give the flow nowhere else to go other than through the problem rads - and might just clear any air locks which exist. [The air should collect in the top of the rads concerned, where it can be bled out]. Worth a try?
Never had a need to... Had to do it once many years ago on my mum's hot water cylinder though.
My vented system (when I had it) only got drained twice in my recollection - once to move a rad, and it refilled ok after that, and the second time when I ripped it out! (it did not ever recover from that!)
Could be... in fact I would suspect the valve contributing more than the pipe - the pipe is probably just tipping the balance.
Funny things women ;-)
Something to look forward to then...
(handy tip, small metal detector thingies are quite good for working out where the screws are hidden under filler and paint on boxed in pipes etc)
Think I'll try this option first, before stripping out to find motorised valve!
Thanks
Phil
Yes I believe so. I think the system has pumped return through the boiler, then the heating mot valve straight after. Again this is all covered by boxing, but I am fairly confident that's the layout.
Sounds a touch hairy for my liking. Without electrical jiggery pokery, it will be necessary for the boiler to be running and heating the water for the pump to run and valve to open. Sounds like it may pressurise the system generally?
Phil
Set Square's point about the switch making only when the valve is fully open would tend to dispute this. Unless the valve can be so damaged/worn that the switch can make without the valve internals opening correctly.
Actually the visitors are 3 (yes three!) French boys about 10 yrs old. A return exchange trip for my lad's visit earlier this year. Where did I put that French phrase book?
Thanks again John
Phil
On further thought, it's probably best to do the flow side with the pump running, and the return side without.
Can you turn your boiler right off on it's own stat - so that it doesn't fire even when given a demand? [Mine will do that] If so, you can simply circulate cold water while you do this dastardly deed. I don't think you need to worry about pressurising the system - the pump generates damn all pressure in absolute terms because it only needs to overcome flow resistance rather than having to lift water to a great height. [A typical CH pump only produces about 0.5 bar even when running stalled at its highest speed]
Yes, in fact I expect he is right thinking about it... so unless the valve is also partially blocked with debris of some sort, you can discount what I said.
I was thinking more along the lines of the rhetorical question and tone of voice that goes with: "you are not going to start pulling the house apart _now_ are you"?
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