Centrel heating not working

[psf2001uk]

Hi,

HW has been working all summer, but attempting to re-start CH lead to blown fuse (on timer/control/punp/valve circuit) - not sure if this was coincidence or not. Now the HW does not work - boiler won't start (pilot on and running) - no CH either.

After replacing the fuse, I confirmed that the pump is running, by powering it directly. I also suspected the two-port valve (stuck shut?) and tried the manual open switch, but can't budge this past the central position (so I'm not sure if the valve is open or closed). Boiler won't start in any case.

The system is 20+ years old, and the coil in the HW tank appears to have a hole, as I am getting water through the overflow (even though the boiler isn't on...), and is probably full of scale by now. So, I will replace the cylinder and the valve, but would like to be sure there isn't a further problem here that will stop the system working when it is back together (especially as the valve is so conveniently placed behind the cylinder, making future access very difficult).

Any suggestions what else I can try to confirm that a dead valve is really the problem?

Alternatively, am I barking up the wrong tree completely, and if I am, what else do you recommend I check?

Thanks/Paul

[Harry Bloomfield]

[e-mail] expressed precisely :

The just might have failed due to old age.

Did it blow again?

Remove the actuator (the head part of the valve) and see if that operates by itself as you select HW, HW + CH, then CH alone. Then check that you can turn the valve itself with a just a little more than bare finger pressure on the half moon shaped shaft top of the valve.

[Set Square]

I'm not entirely sure from your description what sort of system you have. You mention a 2-port valve - which suggests that you might have a C-Plan system (see

with gravity hot water and pumped heating. Is that what you have?

Or is it perhaps a Y-Plan (or even W-Plan) fully pumped system with a 3-port (one inlet and 2 outlets) valve rather than a 2-port valve?

Once we've established this, we can tell you what to look for.

Is it the small fill & expansion tank which is overflowing, and is the level in this *lower* than that in the main cold water heated tank for the hot water system? If so, it's possible that the indirect coil inside the hot cylinder is leaking - assuming you've eliminated the ball valve on the F&E tank as the culprit.

[Set Square]

Correction

[Don't ask me why I typed "heated"]

[psf2001uk]

Hi,

After a delay, here are some answers to the above questions:

1) The system is type "S" - 2 x 2-port valves - the second valve was under the floorboards. 2) The expansion tank level is lower than the main cold water tank. I have also confirmed that the float/ball valve are regulating water level correctly.

Replacement of the H/W valve restored operation of the H/W side of the system. Setting the C/H valve to "manual on" causes the rads to warm-up. The valve does not appear to work (tried sperate mains connection - nothing happens). I am trying to fit a replacement powerhead (Honeywell 4043), but the "drive shaft" to the valve seems to totate between 10 and 12 o'clock, whereas the powerhead moves from 11 to 1 o'clock (the old one does the same), so although the new powerhead works, the range of rotation it has does not open the valve.

Does this mean the valve itself is faulty/needs replacing?

Regarding the overflow siutuation , the overflow outlet (in the expansion tank) is the same level as the water level in the tank, so water starts to flow when the heating/water is on. Is this standard? I would have expected some "headroom" between the resting water level and the level of the overflow outlet?

Thanks/Paul

Set Square wrote:

[Set Square]

It sounds as if either the wet part of the valve is partially seized - and not moving through its full travel - or else the power head is not compatible with the valve. Is it the same type as the HW valve? If so, what range of travel does that - and its actuator - have?

The F&E tank should only contain 2 or 3 inches of water when the system is cold - just enough to make sure that the pipe in the bottom, which feeds the system, is adequately covered. The level needs to be able to rise quite a long way without overflowing when the system gets hot and the circulating water expands. Remove some of the water, and bend the arm of the ballvalve so that it shuts off at a lower level.