Hot Water gets too Hot

[paulb69]

Hi Guys,

Worst type of post -- amatuer heating engineer warning !!!!

I have a five year old house with a Gloworm F55 boiler and Danfoss controls. It's a system with a mid position valve control. Recently the hot water has been scalding hot, the system seems to function normally apart from this with CH and HW running OK. Therefore thought this was the Danfoss AT cylinder thermostat failed so after testing it ( It didn't switch off at all) I replaced it with a Landis & Gyr (Wickes) type.

Wiring diagrams are a bit useless as the original installers have wired the main terminal block back to front ( e.g. the connectors run from 10 back to 1 rather than the other way round. However, I THINK I've got the connections right as the thermostat switches in when I raise the temperature with HW only switched on, it calls for heat and switches off again when temperature set on the thermostat is reached. However, when the CH is also switched on, it seems to keep pumping hot water to the tank! Could this be a mid position valve problem? I can hear it switching from time to time, but can't easily identify if it's switching the right way round. Also as the connection block is the wrong way round it's difficult to check the wiring in case I have inadvertantly wired something the wrong way round.

Any help would be greatly appreciated.

Regards

PaulB69

 

[Agile]

Yes, you are right about the amateur heating engineer!

I can only suggest that if you have wired the thermostat correctly then its likely to be the three port valve.

However I think that you have probably connected the new thermostat wrongly. They are a SPCO switch and different manufacturers put DIFFERENT numbers on the contacts! If you connect it from an electronics approach then it will probably work.

Since you seem to be phased by the connector block numbering then I suspect you have wired it "by numbers" and introduced an error.

If you were a professional you would encounter systems wired with taped twisted joints and others that use four terminal mains power connectors. And of course motor valves which are powered to return. Much more fun!

Tony

 

[ArtfulBodger]

Check that you are getting 230 volts to the grey wire to the 3 port valve. If you are, then it is likely that the valve is at fault. However, since the only change has been the stat wired in by you, it is more likely that you have introduced a fault in the system. Best of luck.

 

[bab]

on a cyl stat for a 3port the live in to the stat is quite often connected to C if it has one & the other 2 wires can be switched around to rule out the fault. It wont damage it as they are all live terminals.

 

[paulb69]

Thanks for the help. I've tried reversing the two wires in the stat and i'm sure that it's correct. If I reverse them then the pump switches off if I turn the stat temperature down. So having established that it's working the right way round, can any one advise a simple test to see if the mid position valve is working the right way round? ( Remember I said amatuer so no multimeter)

At the moment the wire from terminal 2 on the stat connects to the orange wire on the valve and terminal 3 goes to the grey wire. Is it possible that I somehow reversed these wires in the terminal block?

What fun on a Sunday afternoon!

 

[ChrisR]

I've tried reversing the two wires in the stat and i'm sure that it's correct.

I'm not

If I reverse them then the pump switches off if I turn the stat temperature down.

That's what's supposed to happen!

Your connections sound right for a Landis though, but have you got the wire people leave out - from the HW OFF terminal on the programmer (could tellyou the pin if you gave the model) to the grey wire?

 

[paulb69]

Sorry Chris, didn't explain that very well, I'm obviously an amateur at that also.

When I reversed the connections, and then turned on the power again, although the water was now hot, the pump was running but turned off when I reduced the stat to 20 degrees. The "right" connection works in the opposite way. e.g. the pump comes on if I raise the temperature and goes off when I reduce it.

My problem is that it all seems to work OK until I switch on the CH. I then try reducing the stat temperature setting and expect the valve to switch to CH only but I can still feel hot water travelling through the pipe that goes into the tank. My expectation is that the motorised valve should switch to CH only until the stat calls for heat again but I can't tell if that is actually happening.

My simple logic tells me that this is maybe why I'm getting hot water in the tank rising to the boiler temperature setting and not being controlled by the cylinder stat at all.

 

[paulb69]

Chris sorry the programmer is a Danfoss Fp 715

 

[ChrisR]

Without a meter you can't tell much, except for the model/number of the programmer and the valve if you can see it, and whether the wire I mentioned appears to be there.