Heating control box problem

[JayTee]

Hi, I fitted a new hw tank before chrismas along with new 3 way motorised valve, tank stat and timer control box. There is a stat on the hw tank but no room stat.

All has been working fine until recently. The heating and hot water are set to come on in the morning but when the water reaches temperature the heating then stops aswell, the indicator light on the control unit is still lit but the circulation pump stops and the boiler goes out. to get it running again I have to set both to off and then pull the fuse and reinsert it and then put heating and water back on to the timed setting.

What do you reckon? Take the control box back and swap it for new or could it be somoething else?

The control box is a Gasslin Towerchorn QE2.

Thanks, James.

 

[Terrywookfit]

Is the H/W off connection connected?

Check diagram and check voltages!

Fault finding is not guesswork!

 

[JayTee]

I will check all the connections again but if it worked fine for three months it must have been connected right and it seems to be an intermittent fault now, for the last couple of days it has worked fine. This is why I thought it may be a faulty unit rather than wiring.

James.

 

[D_Hailsham]

no room stat.

Why not?

Presumably the MV white lead is connected to terminal 4 of the Grasslin?

The heating and hot water are set to come on in the morning but when the water reaches temperature the heating then stops aswell, the indicator light on the control unit is still lit but the circulation pump stops and the boiler goes out. to get it running again I have to set both to off and then pull the fuse and reinsert it and then put heating and water back on to the timed setting.

Could be a faulty Mid-position valve.


Read Mid-position valve working and Diagnostics.

When CH and HW come on in the morning, the boiler is powered via the Cylinder Thermostat. The MV is held in mid-position by 240v on the White lead.
When the HW reaches temp the cylinder stat switches over so that there is now 240v on the Grey wire. This will drive the MV over so only the CH port is open. This then supplies 240v to the Orange wire, which keeps the boiler alight. If this is not happening there are only two reasons: the Cylinder stat is incorrectly wired or the MV actuator is faulty.

Shutting everythng down resets the MV to the HW only position. In this position the MV does nothing; the boiler is powered via the Cylinder stat.

 

[JayTee]

no room stat.

Why not?

Hi D, because the house didn't have one when I moved in. All the rads apart from one have thermostatic valves. I was thinking about putting one in.

Thanks for the info, I'll have a read of the link ref the valve, although from what you say regarding the incorrect wiring of the cylinder stat or the faulty valve - I would think it was the valve as it has been working fine wired as it is for so long. I'll have a poke around with a multimeter when/if the fault reoccurs.

Thanks, James.

 

[D_Hailsham]

no room stat.

Why not?

Hi D, because the house didn't have one when I moved in. All the rads apart from one have thermostatic valves. I was thinking about putting one in.

A good idea, apart from the fact that Building Regulations now expect one.

What a pity you did not do it when you put in your other new bits. A Honeywell CM900 type would have done the job of the Grasslin and provide optimized heating control. OK you would need a separate single channel timer for the HW, but they are dirt cheap or your old timer would probably have done the job, provided it was not u/s.

 

[JayTee]

What a pity you did not do it when you put in your other new bits. A Honeywell CM900 type would have done the job of the Grasslin and provide optimized heating control. OK you would need a separate single channel timer for the HW, but they are dirt cheap or your old timer would probably have done the job, provided it was not u/s.

hmm nice idea. Oh well maybe next time - I'm on a steep learning curve TBH the whole systems a bit crap and has been messed about with by the previous owners, but we don't plan on staying here too long so I just wanted to sort what didn't work / leaked. Will probably fit a simple room stat though as I have been thinking about it for a while - Should fix this problem first though!!