Heating/HW control problem

[martin69]

I have a fully pumped gas CH system with Horstmann Centaur Plus C27 programmer and Honeywell V43073A1088 motorised valve.

When HW or CH are on separately each work fine, and motorised valve (with cover off) can be observed moving from one side to the other accordingly as Boost/Advance are pressed, or programmer kicks in.

Problem arises when 2 are operated together, as follows:

If Boost and Advance are pressed simultaneously, valve moves to mid position, and both HW and CH work. However, if Boost is pressed when Advance is already activated (or programmer is programmed for HW to come on after CH) valve doesn't move from CH side and we get no hot water.

In all above cases tank stat and thermostat are switched up high, but both work correctly.

Any thoughts? Is this a wiring problem or motorised valve problem, or is there a simple test?

Many thanks for any ideas!

 

[matt1e]

Problem arises when 2 are operated together, as follows:

If Boost and Advance are pressed simultaneously,

Why are you doing this? for what purpose?

the boost button boosts the HW for an hour and the advance button advances the CH

the boost button is a toggle so if

If Boost and Advance are pressed simultaneously

the HW will turn on and the CH will advance
then

if Boost is pressed when Advance is already activated (or programmer is programmed for HW to come on after CH) valve doesn't move from CH side and we get no hot water.

pressing boost again will toggle HW back off if

programmer is programmed for HW to come on after CH

this seems normal to me(depending on time settings)

A better description of the problem would help what is exactly wrong with the water/heating?

matt

 

[martin69]

Sorry, I'll try to explain more clearly:

If HW and CH are programmed to come on at same time (or done manually with Boost and Advance buttons) valve moves to mid position and we get HW and CH.

HW or CH will operate separately correctly - either by timer or Boost/Advance - in this case valve can be seen to goes to appropriate position.

Problem occurs if HW is programmed to come on (or Boost pressed) when CH is already on (programmed or by Advance) - in this case valve does not move to mid position, so we get no HW. So, if CH is on all day, and we press Boost to heat the water, we get no HW even after an hour. To get it we have to turn CH off!

Hope this is clearer.

Thanks

 

[Tipper]

Sounds like a problem with the valve to me so might need a new valve motor head to be fitted.

Also a very rare problem is the Horstman programmers fail and appear to get confused.

 

[martin69]

Thanks for that. Is there any way of testing the valve, or is it trial and error?

 

[jackthom]

When the system is set for CH only, both the White and the Grey wires to the valve should carry mains voltage.

In this situation when you also switch DHW ON, the Grey wire should no longer be live while White remains at 240V as it was.
This lets the valve fall back to the mid-position for DHW & CH.

 

[martin69]

Thanks for that.

Spent happy afternoon checking wiring, in course of which discovered plumber who'd wired it up originally hadn't done it right, with result that boiler and motorised valve weren't properly earthed, and one earth wire from timer was live!

So rewired properly according to Y plan design and rechecked.

Discovered that, when DHW comes on at same time as CH system works properly, and readings are as expected. However, if DHW comes on AFTER CH the output from the HW OFF terminal of timer remains at 240V and there is only a trace output from HW ON terminal of timer, meaning motorised valve doesn't move as it should. From this I deduce timer is knacked.

If anyone has similar problems, there is a v helpful fault finding guide on honeywell uk website, which helps establish which components are working properly.