Hot water but no heating

[chetenham08]

Ideal Logic 24 boiler.


There are 3 circuits, hot water, under floor heating, radiators.


When the hot water calls for heat the boiler fires up fine and water heats up. When either or both of the central heating systems calls for heat the boiler errors with error code Fd, no water flow.


When the boiler is heating up for the hot water and either of the central heating systems is on, then water is pumped to them fine, the radiators and / or underfloor heating warms up.


The water flow sensor was replaced only 3 months ago when we had the reverse problem. Heating but no hot water. We have not tried using the central heating since then.


The person who came and replaced the water flow sensor has been to have a look but is at a loss as to what the problem is. He has spoken to Ideal who are saying it is not a boiler problem.


It is now being suggested we have a complete system flush, but I can't see how this will help if the water is circulating round the central heating system without a problem.


Any thoughts on where we should go from here?

 

[Armo74]

What other controls do you have?
Valves?

 

[chetenham08]

What other controls do you have?
Valves?

There are 3 x 2 way zone valves. One to hot water and one for each of the heating circuits

Valves opening and closing correctly.

 

[MANDATE]

sounds typical of a 3port mid position valve problem, where it goes to mid position so you get both HW and heating, but you can't get heat only.
This being due to either
(a) valve will not move beyond mid position due to incorrect wiring or micro switch failing to make contact in actuator head so failing to power the motor, via the 'grey' wire
(b) Valve does move to heating position but boiler fails to light due to 2nd micro switch failing to make contact and failing to allow power out from the valves 'orange' wire

 

[MANDATE]

Obviously its not what I thought!