Yes it is rather confusing... the boiler the OP provided a link to provides for gravity circulated hot water - although the talk of pressure guages etc does suggest a sealed system. It is possible that it was plumbed as a sealed system and the gravity circulation option simply ignored (or it might be the link posted was to the wrong boiler! ;-) Three port valve fully pumped is what I initially assumed... perhaps if the OP could look at the valve and count the pipes connected to it?
Whatever the case, it sounds like this is a wiring / valve related problem.
Hi, definitely a sealed system, at least that's what it says on the tin (on the boiler).
The valve has one inlet and 2 outlets, the pipe going up is for Heat, down is for H/W.
Questions remaining:
1) Why does the HEAT switch on the wall timer have no effect, and only the H/W switch turns the boiler and radiators on?
2) I note that the pressure does slowly drop, and that there are constant slow drips coming from the hooked pipe outside the property, connected to the boiler. What does this indicate, and how is it fixed?
Did you see my earlier post about the necessary wiring for a Y-Plan system? That explains it.
Is this water - leaking from the safety relief valve? If so, the valve has probably got some crud in it and needs cleaning out or replacing. Or, if you have a condensing boiler, it could be condensate - which is normal, but wouldn't explain the pressure loss.
Thanks, so you're definate I have the Y-plan from what I've said now? If so will take a look at the wiring diagram and my installation.
All I can see is that the water comes out of the safety pipe outside my property, so I assume that is the relief valve? How do I get inside to clean out the crud or replace?
You said "The valve has one inlet and 2 outlets, the pipe going up is for Heat, down is for H/W." In my book, that's a pretty good description of a 3-port mid-position valve as used by Y-Plan. [OK, it just *could* be a diverter valve as used by W-Plan systems, but that is less likely].
I can't speak from first-hand experience on this one - so hopefully someone will be along who can. But I've heard it said that once a relief valve opens, it's difficult to get it to seal again. ISTR that you left your filling loop connected, causing the system to over-pressure and blow off.
There are two types of three port valve. A diversion valve and a mid position one. The diversion valve can be in one position or the other - not between both. Typically the hot water is given priority such that if the cylinder is calling for heat, then it will service that (and only that) output. Works well with rapid recovery cylinders since they can be reheated in short order and the valve then returns the flow to the heating.
The second type is a mid position one. This has the capability to split the flow between both outputs when it gets concurrent requests for CH and HW. Better on slower recovery cylinders since it prevents the cylinder disabling the CH for long periods.
Two possibilities: 1, it has not been wired / setup correctly and hence would never have worked, or 2 something is broken! ;-)
The first task is to eliminate 1, which means some detective work to see how it is wired up. Looking at the outputs from the timer will be a good start - they ought to be labelled with their function (failing that, a manual may be downloadable from the web that will tell you there function.
Once you are happy that the system *could* work, it is a case of working through each stage with your multimeter[1] and seeing what is wrong.
e.g. verify that when the programmer calls for CH that a signal does in fact come out of it.
Verify that the room stat does call for heat when required.
Verify these signals reach the three port valve.
Verify that it moves correctly in response to the signals.
Verify that the micro switch outputs (if present) on the valve that indicate its position are working, and hence if any call for heat that should be passed to the boiler via this route does in fact arrive.
[1] remember that many of these signals are likely to be at mains voltage - so take care. If you don't feel confident that you can do this without electrocuting yourself then this would be the time to consult a competent heating engineer.
It sounds like your pressure relief valve is failing to seat correctly. This can happen when a valve is forced to operate (under normal circumstances it will never open). You overfilling exercise may have caused this. Clean or replace the valve I guess.
If it's a diverter valve, the system will be W-Plan, and if it's a mid-position valve (more likely in my view) it will be Y-Plan. Wiring diagrams for both can be found at
Hi guys, to avoid confusion I have uploaded some pics of the valve:
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I have now identified that the one thermostat in the hall has no effect on the central heating whatsoever. That said, all the rooms (except hall strangely) have a stat on the rad itself. Does this negate the need for a central stat? (Surely not.)
So, to recap, current issues:
1) CH switch on/off has no effect either way. HW switch makes radiators and water hot just fine.
2) Boiler loses pressure slowly.
3) Wall stat has no effect on system. All rads have stats on except hallway.
HW, just CH - or both at the same time. This is the heart of a Y-Plan system.
Even if most radiators have TRVs (thermostatic radiator valves) you still need a central stat to turn the boiler off when the whole house is hot. The radiator nearest to the room stat shouldn't have a TRV - so what you've got is right.
As John Rumm told you many days ago, you have a problem with your mid-position valve. The chances are that the 'wet' part of the valve is stuck in roughly the mid position, but not far enough round to operate the microswitches in the actuator. In this condition, the boiler and pump will be controlled by the HW output from the programmer and the cylinder stat - but whenever the boiler is firing, both HW and CH will get hot. The CH feed from the programmer - which goes via the room stat - will have no effect because that only controls the boiler *after* the microswitches in the actuator have operated.
Remove the actuator from the valve (2 screws). This will reveal the valve operating spindle, the end of which is D-shaped in cross section. The flat of the D will almost certainly be at an angle of about 45 degrees with the body - which is the mid position. See whether you can rotate the spindle through plus and minus 45 degrees. In the unlikely event that it's *not* seized, you should be able to turn it with finger and thumb or - at any rate - with light pressure from a pair of pliers.
Then, with the valve in the mid position, and the actuator still off, put the actuator through its paces. Use the programmer and thermostats to generate all possible combinations of HW and CH demand and see what the actuator does in each case.
Then report back!
Sounds like you've got a leak, like we said earlier.
Another thing to check is the position of that leaver on the side of the valve. In one position the valve will operate normally, in the other it will be locked into the mid position (thus allowing manual intervention to get some useful operation should the valve control electrics fail in some way).
Also check the room stat does actually generate a signal. With most it is possible to hear a click when you rotate it back and forth around about the current room temp. While the "click" is not a guarantee that it is working, not getting any would be a good indication it is not.
Is your boiler overpressure release valve still leaking? If you are unsure, then tie a small plastic bag round the pipe with a rubber band and see if it collects water.
Who knows?! An electrical screwdriver with neon indicator is about the
*least* reliable way of determining what's live. [In the absence of a voltmeter, copping hold of the bare wire is far more accurate - but not to be recommended ]
With HW-only on and the cylinder stat not satisfied, the *only* live wire should be the orange. When the cylinder stat is satisfied, orange should go off, and grey should come on.
With CH-only on, Grey should be on, White (or brown/white depending on the actuator) should be on when the room stat is not satisfied, and should go off when the room stat is satisfied. Orange should follow white - being switched by the actuator itself.
Don't worry about both together yet - let's sort the basics first!
Not the best of photos, is it! The brown and yellow should *not* both be connected to the same terminal. This is simply by-passing the stat so that it is effectively in the not satisfied state regardless of setting and room temperature. The yellow wire should be one or two places to the left depending on the internal workings of the stat.
Well that just demonstrates how useless an electrical screwdriver is! Brown and yellow are connected togher, so how can one be live and the other not live, for God's sake?
From what I've seen so far, I wouldn't trust *any* of the wiring without going through it with a fine tooth comb and working out exactly what is connected to what - particularly in the 10-way junction box, assuming there is one.
I fear that you're going to have to get someone who knows what he's doing to look at it. What part of the country are you in - someone here might like a challenge, or an excuse to escape from the Christmas spirit?!
This appears to be what happens. We can ignore the "1*" above as I think that means it is picking up a weak signal nearby, not actually from that terminal, so I have:
Valve wire: Blu Org Gry Wht CH On 0 0 1 1 HW On 0 1 0 0 Both On 1 1 1 1
This ties in with you realising that the room stat is permanently satisfied as it had been wired to be so.
I have now tried yellow on both places, and the stat still has no effect on the new valve which remains in the central position at all times, serving both HW & CH.
Sorry, it was implied that Brown was on as it was connected to Yellow, my mistake was at first I thought Brown was on the terminal to left of yellow, which was "0" off.
There is a 10-way box, but I'm not up to analysing it :-S
I'm hoping from the new info above, and that the new valve stays midway even with the stat wired apparently correctly, you will be able to give me some things to try?
Okay, or that option is good :) I'm in SW London (near Richmond, Surrey) if anyone is up for sharing their expertise. Will make it worth their while ;) ;)
I can only re-iterate what I said earlier - your wiring is stuffed. You have a new actuator, so let's assume that that does what it says on the tin. If that stays in the mid-position come hell or high water it must mean - according to my understanding of the beast - that the brown/white wire is live all the time (regardless of the room stat status) and that the grey wire is *never* live - even when the cylinder stat is satisfied and/or HW is turned off at the programmer.
If you are not capable of tracing all the wiring and comparing what is connected to what in the junction box with a standard Y-Plan setup, you'll need to find someone who is.
Afraid I'm 100 miles away - or I'd have a look myself. Maybe there's someone a bit nearer?
Companies like Sentinel and Fernox make both corrosion inhibitors which should be used to prevent sludge in the first place (which is basically bits of decomposed heating system held in suspension!), and also desludgers that can be used to clean a system.
You *must* have the former in there all the time to keep things running well. Whether the desludger is needed will depend on how badly sludged your system is (cool patches at the bottom middle sections of radiators would be a good clue there is a pile of crap in there).
If you use the desludgers you add them to the system for a couple of weeks, then drain down, flush through a few times, refill and add fresh inhibitor.
Might be worth googling back on this group for Andy Hall's posts on a procedure for doing your own system flush.
Great, thanks. Would something like this do the job?:
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assume the current sludge is gone as the system has been emptied a few times due to fitting of new radiator in bathroom, and today's replacement of the 3-port valve.
over half the price - not as easy to add to a sealed system as the cartridge one, but doable with a funnel into a partially drained rad.
Depends on how bad it was. If you were not aware of partial cold bits at the bottom of rads before, then chances are you did not have a really bad sludge problem.
There are some cool bits on the bottom centre of the rads, so I will go the route and do a flush or two with the sludge remover.
On another note, you may remember I have rad stats in all rooms, except the hallway which has a wall stat. However, as this now works correctly and overrides the whole system, I find the hall gets too hot before the other rooms, IOW the hall radiator needs to be turned down. However there is no control on the rad, I suspect for a reason.
Is it as simple as putting a plastic knob on the square turnable shaft that was hiding under the coned white plastic cap, or will reducing the flow to this rad affect the other rads in other rooms?
Advice appreciated on how to reduce the hall temperature, and therefore the temp the wall stat shuts down at.
This rad should be fitted with two lockshield valves - so that it can't be turned off by accident. But you can turn it down - either by using a spanner on the square end of the shaft, or by temporarily fitting a knob.
Reducing the flow through this rad will marginally increase the flow through the other rads. If the system has never been balanced, it would be a good idea to do it now - with the thermostatic heads temporarily removed from the TRVs while you do it. Balancing is important - even when you've got TRVs - because it ensures that the whole house heats up evenly - rather than relying on some rooms getting hot and shutting their TRVs before you get any heat in the remaining rooms.
If the system is already in reasonable balance, you can get away with just turning down the rad near the room stat - using trial and error to find suitable valve settings.
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