Pump not active when Heating on - but works in Mid Position

[alienjoker]

Hi all,

Having recently replaced our MA1 with a new unit (old one would push hot water round rads at full heat when just having hot water on and on closer inspection of the old MA1, two springs just fell out when unscrewing) and rewiring as per the previous one, on firing up, the system now behaves differently. When in the H position, the Pump doesn't seem to run. When I run HW only, the pump kicks in - as it does when in Mid position too but the issue I have is that when the Cyl Stat reaches temperature, the Valve moves over to H and the pump powers off. This means that unless I have a cold hot water tank, my heating doesnt work!

The room thermostat clicks when moved above and below room temp as I would expect and used to work with the old MA1 (Honeywell T40 but with only 2 wires). The pump is a Grundfos Selectric.

Any help would be greatly appreciated!

Thanks

 

[seco services]

when the valve is in W, M position the boiler/pump is fed live from the cyl stat.
when in the H position it is fed live from the valve's orange.

check when the valve is in H position that you have 230v on the orange.

if not remove the MA1'S cover and check the m/switch is being activated.

 

[alienjoker]

Hi Seco Services,

Thanks for your very prompt response. I have checked the Orange and it does indeed have 230v when the Valve is in the H position. I'm guessing this is a legacy wiring fault that I've had for some time.

A quick and dirty overview of the Grasslin Tower Control panel and wiriting connections can be seen in the image of the URL below.

http://www.acmcomputers.co.uk/heatingwiring.JPG

Thanks for your ongoing help!

 

[MANDATE]

The boiler/pump relies on power being received from one of two sources.
Both these sources are connected together. One source is the cylinder stat, this used whenever there is a demand for HW. When valve is in mid position and demand is for both HW and CH it still uses the cylinder stat.
This mode will soon change because HW soon becomes satisfied and valve will then move to CH only.
Power can no longer come from cylinder stat, so it now comes through a micro switch in the valves actuator head and out through the valves 'orange' wire.
So there should be three wires in the terminal that contains the 'orange.
One from cylinder stat, One from valve (orange) and one going boiler pump.
I would re check the connection, it may be a poor connection (terminal screw on insulation instead of wire core) or wire not connected.

 

[matt1e]

hi
looking at the image the valve orange needs to be taken out from where it is and put in with the boiler yellow/ cyl stat blue

Matt

 

[MANDATE]

Looked at your diagram.
Cylinder stat should have one input but two outputs. looks like red is input, output to valves grey is the black so the output to boiler is the 'blue' which is connected to boilers yellow.
These I believe are the two wires that should have the orange also connected.
The terminal with the orange has no other wires so power cant be going anywhere.

 

[alienjoker]

Excellent - that's worked a treat. Turns out that as a result of my extremely heavy Stag weekend, my brain ability and vision when it came to connecting up the Orange wire to what I thought was Number 6 on the wiring block was in fact an upside down 9 if the wiring block was mounted 180 degrees.

So a BIG thank you for saving me from even more of a telling off from the other half - particularly as the "No heating" news on top of some interesting antics over the last couple of days would have possibly led to a there being no wedding!

Cheers!