Central Heating dilemma

[jcarter]

I have what I believe is an open vented indirect central heating system. It has one 2 port motorised valve which gets it's signal via a room stat so it's for the CH. This valve operates visually but does not seem to stop the CH flow, I think it's blocked and I was going to replace it. The controller is an old Glow Worm Mastermind electro mechanical.

I have 4 issues:

1) The system is somewhat scaled up so I was going to drain, treat, run then flush in a week or so. 2) The CH never stops even with Stat on 0 and hot water only on - was going to replace the valve to solve 3) The timer is old and not very useful, was going to replace with Horstmann C27. 4) There is no Stat on the cylinder so HW does not switch off automatically.

Questions:

Any advice on the above?

Would the functionality of the timer be redundant due to the lack of complexity in the system?

Is it normal to add Cylinder Stat in a system with no valve on the HW side? Can't it just break the signal between HW on the controller and the Pump / Boiler shutting it down when the temp is reached in the tank and re-starting it when it drops if the HW is still on?

[malcolm]

Looks like your valve is stuck in the open position or the actuato (the motor) has failed open. With your heating off try removing the actuator fro the valve body,(don't disconnect the power cable) then see if you ca turn the valve by hand. It should turn easily with finger pressure. I you need to use pliers then it's knackered and the valve will need t be replaced. If you can turn it easily the next step is to check the motor. Leav the actuator off the valve and turn it upside down. Note the positio of the 'valve spindle recess' then switch on the CH making sure th room stat is turned up to max. Check the spindle recess. It should mov to a new position and stop. If it does, turn the room stat to minimu and it should move to another new position. (The positions depend o the make of the actuator).Each time the stat is turned up or down th motor will turn. If it does not turn each time or if it turns bu always stops in the same position then the actuator is faulty and need to be replaced.

Issue1) Yes, drain & flush the system.

Issue2) If the valve is stuck open you will get CH even if the syste is calling for hot water only. Check valve & actuator as above an replace as necessary.

Issue3) With an electronic programmer you can time the CH & HW tim intervals independantly of each other and have different programms fo different days. Much better than your old timer.

Issue4) Yes! A clamp on cyl stat will give you better control of ho water but only in the "hot water only" mode. Your system will alway give hot water when the central heating is on. The only way to hav full control is to fit a motorised valve in the hot water circuit an control that with a cyl stat.

Hope this has helped

-- malcolm

[Jimmy5]

Thanks for that, I've fitted a cylinder stat and a new programmer. The valve needs changing, but I'm waiting for a new one to arrive. I can manually stop the flow to the rads by closing the valve further than the spring return seems to, so with a new one everything should be OK. The problem I have now is that when I have HW only, I think due to the excess pressure caused by reduced bore in the pipes of the exchanger etc, I'm getting blasts of steam through the vent into the f & e cistern every 5 mins ! I'm going to try a second chemical treatment and keep it flowing through just the cylinder to try and break down any deposits. Surely it would not be a pipe design issue or a previous owner would have sorted it when the valve used to work, it's not a noise you could live with. Any advice on this one! I previously opened a section on the cylinder return. I used the break to unblock the feed from the f & e cistern with wire, once it was free flowing I used a union to join the break, could the union be restricting the flow? This pipe was considerably reduced in bore size though with black oxide, maybe it's the whole run causing the problem? Do these chemicals work or am I going to have to get someone in? and does that work !! ?