No HW when only HW system is ON, HW available when CH is ON

22 May 2004
Reaction score
United Kingdom
Could someone please advise on the possible root cause of this problem, as well as tell me where the solenoid valve actuator might be located?

* Potterton Profile L Bolier
* Grundfos pump
* 1x Landis & Gyr, 1 x Honeywel Motorised Valves
* Honeywell strap-on cylinder thermostat
* Indirect HW Cylinder, (with Immersion heater NOT switched ON)
* Landis & Staefa HW & CH timer
* Digistat 1 wirless thermostat (Timer and Digistat connected in Series)
* Have two water tanks in the loft

1. When the CH is ON I get CH & HW. (CH feeds the HW Cylinder)
2. Haven't yet tried having only CH ON and not HW on timer. (Will try tonight)
3. When only the HW is ON, I get NO HW
4. Have turned UP Digistat to max
5. Have turned UP & DOWN thermostat at cylinder until it clicks on/off while HW is turned ON. Also checked thermostat continuity (power off and unplugged at time)
6. When HW system is set to ON the boiler does not kick in, even when HW is in use

a) If the problem was the solenoid valve actuator then I should always have either (HW) or (CH) or (HW & CH) at all times, I think.

- Any idea where the problem is?

- Also I can't find the solenoid valve actuator in the cupboard where the boiler & cylinder are, or under the floor when a few of the pipes disappear. (Does there need to be one?) Any ideas with this one?

Only been in the house 1 year. Was newly plumbed 2 years ago.

Thank you. :LOL:
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You won't have any solenoids. Is the hwell motorised valve 2 port or 3 port?
Both Honeywell and Landis are 2 port. The Hwell manages flo to the HW cylinder and radiators directly... but the Landis is connected to the same pipe as the hwell anyway.

Checked today, when CH is on and HW timer is OFF, I get HW.

Boiler---------------<--Pump-------<-+--------- (Overflow in loft I think)*

(Ignore the yellow, I needed them to get right spacing)

Seems like more piping added so they added a Landis value for that. If either value opens then all radiators will get HW as well as the HWCyl.

I don't recall ever having to turn off each radiator last summer, anyway 3 of the radiators can't be turned off. We had 36dec last summer and it wasn't because of them.


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