Diagnosing heating system fault

[engineerSteve]

Hello, I have a situation that may resonate, I think there could be two faults:

Situation: excessive oil being used in heating/hotwater system, pump never turns off, radiators often hot even when programme is set to off/off.

There is a drayton motorised valve on a Y valve

Often one can hear a rapid clicking like a relay while the valve poistion remains pretty much in the mid position. I understand that the motor is held in mid by pulsing the motor against the internal spring however I have not hear the consent clicking before does that lead one to think motorised valve at fault or the physical valve or the programmer or the thermostat(s).

If it were not that the pump doesn't turn off i would have looked at the motorised valve as the culprit, and questioned if the actual valve is working freely or to full deflection ( there is only a very small amount of travel of the lug that engaged with the motor maybe 20 degrees max )- is this deflection normal?

The programmer has been changed recently by a heating engineer who came to do the annual service of the boiler ( waste of £50 plus labour as if anything the problem has got worse ( £500 oil used in three months)

So, all comments and suggestions very welcome, the Pump is a grundfos UPS 15-50 and there is a honywell wireless thermostat on central heating which appears to demand heat according to temperature settings so I dont think that there is a fake demand signal causing any issues, at least not from the CH, I dont know how to check the hot water stat,. the system was fitted by an animal really shoddy work the control box is an utter mess I am slowly going through the connections to at least get an idea of how it has been worked out, as this was a renovation by a very dodgy developer ever corner has been cut so I can not say even that the system was ever correct.

Happy to answer questions and receive the benefit of engineers with experience in this area, this is not my area of expertise and after three attempts of calling on local heating engineers by the SWMBO I am fed up with the head scratching lets replace a part and get out quick approach to the problem.

cheers

 

[picasso]

Is there a frost stat fitted to your system ?

 

[oilboffin]

Could be the micro switch in the actuator has stuck and is holding the system on.Bob

 

[Gasguru]

Drayton zone valves are notorious for failing. When dealing with Y plan faults is often much easier to just replace the actuator rather than work out what the problem is with it.
The spindle doesn't move that much on the Drayton as it's just shifting a paddle to close the ports.
In mid position the motor is stalled by applying half wave rectified mains.

 

[polesapart]

^^ ^^
Wot they said.

Otherwise out with the multimeter and follow page 8
www.honeywelluk.com/documents/All/.../Wiring%20Guide%20Issue%2016.pdf

Valve wire colours are the same as Drayton

 

[engineerSteve]

Thank you all for your comments, family emergency took me away from the problem however I have swapped out the Drayton mid point actuator and that has cures all but one issue. The pump still runs all the time. I have now documented all the connections and find that the pump is always on because doh ! It isn’t wired to LNE at the back of the programmer so electrically no surprise!

My thought is move the L to a calling line feed rather than the common L. There seem to be two schools of thought one says output from the boiler another says output from the valve actuator. As I don’t have good access the the boiler and it is two floors away in a bunker, I would fondness the job mich easier to do if I pull the pump feed back to the wiring centre. (Euphemism as the animal who put this in only twisted the connections couldn’t even be bothered to put terminal blocks behind a wall box)

The other reason for choosing to not switch L from the pump is that there seems only to be LNE going to it so no call circuit which is what the wiring diagram says is required from the boiler manual.

I’ll tell you what if the bloke that did this worked for me - he wouldn’t work for me !

Also thanks for the comment about the movement on the physical valve very useful!

 

[engineerSteve]

Oh yes to Picasso no frost stat

 

[D_Hailsham]

The correct connecting point for the pump live will depend on the boiler. If the boiler has pump overrun, it connects to the pump Live terminal on the boiler. If no overrun, it connects to the boiler switched live (same terminal as valve orange and HW stat Call).

Which boiler do you have (make and exact model)?

 

[engineerSteve]

Hello thanks for looking at the thread. Here is the information you asked for: Boiler is a Grant Vortex Eco 26-35.
https://www.grantuk.com/wp-content/...rnal-installer-DOC-0081-Rev-3.1-June-2015.pdf

The wiring diagram is on page 37 fig 27.

I have searched the document for the word overrun and there is no mention so I have made the assumption that it is not an over run type.

As far as I can determine without confirming this at the boiler end there are three connections running from the wiring centre to the boiler: in a three core cable Brown, Black and grey. Connected as follows:

Brown > Brown from programmer ( LP112 )
> Brown from Fused spur

Black > Orange mid position valve ( Drayton MA61)
> Blue to cylinder Thermostat ( Honeywell 642 ) blue is connection 1 in the thermostat

Grey > Blue fused spur
> Blue mid position valve
> Blue to programmer

As far as I can see from the various wiring diagrams the pump should have its live feed from the wiring centre position 8 which is the orange, boiler live and HW on. this appears to correctly be connected to the cylinder stat via T1 ( blue cable mentioned above )

The programmer LP112 is connected directly to the pump LNE on the LNE common terminal - while clearly the reason for the pump running continually I just dont see what benefit this has over having the pump ( grundfos UPS 15-50 )

My inclination is to simply rewire the pump to the wiring centre rather than take its supply from the back of the programmer as far as I can see should be simply L to WC 7 connected to mid position orange and cylinder stat T1, N to common N and E to common E.

Very grateful for the help.

 

[Terrywookfit]

Wire it to m/v orange.
It should only be live with a demand from m/v NOT Programmer.

 

[engineerSteve]

Finale:

First thank you to each of you that contributed your knowledge to my question.

I was going to just rewire the pump but when I disconnected the LNE from the programmer I was curious as to why only CH on and OFF were wired to well any thing! I know most configurations have CH OFF T2 unused but HW ON T1 I would have expected to be connected to the cylinder thermostat. Anyway I decided to junk the old and redo everything also a good opportunity to tidy up the wiring as well. Pleased to say everything now works perfectly and hopefully we will save money from not having the pump on continuously.

If anyone can tell me if adding a connection to HW ON was unnecessary I would be interested to understand the original logic I think with out the programmer enabling the thermostat to call for heat the system would have literally been able to demand heat for the HW 24/7 regardless of what the programmer was set to. This was probably why during the really cold spell we had the boiler was burning through oil so fast but un-noticed as the boiler is external to the house and not in sight so we would not have even noticed steam coming from the flu at odd ties and put two and two together earlier.

I also cant help saying what a bloody awefull design the drayton LP522 terminal connectors are, I have been trying to think of a worse way to design them but I really think they have it nailed!