Icos M3080 not heating water

[icosowner]

Hi,

I have an icos m3080. It all works perfectly fine, except that occasionally, the water heating does not come on when it's programmed to do so. It can go months without a problem and then suddenly I get a cold shower in the morning.

The timer seems to what it's supposed to, the light comes on at the programmed time, just doesn't start the boiler up. Generally, isolating the mains, waiting 30 seconds and turning it all back on kick the bolier into life, but not always.

I have replaced the external timer (Drayton Lifestyle) and I have replaced the main PCB (but not the front panel). Still getting the problem.

My guess is that, when the timer send to call for heat, something is telling the control unit that there is no need to fire the boiler. But I don't really know about boilers, and am reluctant to replace anything else without more knowledge. Could a faulty control thermistor be telling the control unit that the water is already hot enough?

Any help appreciated!

Icosowner

 

[gas4you]

As the 3080 is a system boiler, your fault, if just on HW, will be an external control, or 3 port/2 port valve fault.

 

[icosowner]

Thanks for the reply gas4you. Hope you don't mind if I ask some more questions. Bear in mind I know nothing about plumbing.

I'm guessing you are referring to the stuff I have in the airing cupboard. I have previously replaced the head of the "Zone Valve Actuator ZA6". That seemed to be sticking, when I replaced it, it fixed the immediate problem.

There is also a "honeywell motorised valve" and a big red "grundfos" thing. Do you think either of these may cause this problem? The Honeywell valve looks like I can simply replace the head (which I am quite comfortable doing myself. The Grundfos definitely needs plumbing skills which I don't have.

Last question, having read other threads on this site, as this system is 8 years old, should I be thinking about having it all replaced and saving a load of strife?

 

[icosowner]

By the way, yes it is only on hot water, the heating seems to work fine all of the time.

 

[gas4you]

As the heating works ok, this eliminates the boiler and pump, so points to the HW zone valve or 3 port zone valve head.

 

[icosowner]

Hi gas4you,

We've never had a problem with the heating, so as you say perhaps we can rule out the pump and the boiler. Am I right in assuming that the "pump" is the Grundfos Selectric UPS 15/50?

The other items I can locate are:

- a Drayton Zone Valve Actuator (ZA6). This was replaced less than a year ago when the water would not stop circulating, that fixed the problem.

- a Honeywell 272848 Motorised valve (same as a V4043) which is on a pipe leading to the cylinder (2 way valve). It's labelled to indicated it's on a pipe with water flowing towards the cylinder.

Do you think the Honeywell valve could stop the water from heating? Is my best bet to replace this? and do you think just a head replacement is most likely, or should the whole thing be changed?

For info, don't know if it makes any difference, the cylinder is a Santon Premier Plus Unvented Hot Water system (210 litres).

Thanks for the continued help!

 

[gas4you]

The Honeywell valve will be the problem. It sounds as if either the motor has had it or the micoswitch.

If it has a raised 'pimple' on one end of the valve cover (top) you will be able to replace just the valve, if it hasn't you will need to replace the complete valve.

One point to bear in mind is that as you have an unvented cylinder, in theory the valve should be replaced by a G3 registered engineer, as this valve also acts as a safety device for the cylinder.

 

[icosowner]

Thanks Dave,

The valve does have a pimple, so looks like I can just replace the head. I'll source the part and get it fitted.

I'll let you know if it works. Thanks for all your help.

 

[icosowner]

Dave,

Just thought I'd get back to you and let you know that I replaced the Honeywell valve and everything seems to be working fine now. Thanks again for your help.

Icosowner

 

[shambolic]

Could we change the name of this thread to I have a faulty 2 port zone valve as we get a bad enough press as it is

 

[gas4you]

Thanks for letting us know the outcome