3 Way valve problems

[a1exh]

Boiler = Radiation FuelSaver 12
Control = HoneyWell Sundial Y-Plan
Pump = Grundfos 15-50
Radiators = 7 singles with double entry valves
Pipes = Microbore

At the moment the CH is not getting hot when the system comes on.

The Pump activates. The light on the control panel is on. The room thermostat has an effect if you turn it down low of switching off the pump but regardless the boiler doesn't fire.

If I put my hand on the head-unit of the 3-way valve it is warm, probably indicating that the motor has been running for a long time.

If I listen very carefully to the pump I can hear slight noises, possibly particulates or bubbles.

It to me sounds like the valve is not fully opening and so the motor stays on and without it getting to it's final position it does not tell the boiler to activate?

Switching the entire system off then on sometimes helps to bring it to life.

It is only two years ago since a plumber replaced the entire 3-way valve & head unit for a similar fault.

So what could be the cause after only 2 years and what are my solutions?

I have no maintenance valves either side of the 3-way valve (just ones around the pump) so last time, instead of draining the system, the plumber used freezing to replace the valve. (Possibly the wrong choice, draining may have prevented this?)

Could it be that the system is so full of rust & sludge that it has clogged the valve? I've lived here (which is a hard water area) for 4 years and I admit I have never added any inhibitor to the system perhaps that is a big contributor?

Would adding an agent to the system at this point, to dissolve the rust & sludge potentially work? (recommend any?) Drain the system after a month of use (if it works that long) and then re-fill including inhibitor?

Would it be foolish not to replace the 3-way valve at the same time while the system is empty?

How much should a plumber charge these days for such a job and how can I get the best value for money? I take it that draining the system probably takes a long time? If the plumber hangs around should I be telling them to go to another job and come back?

 

[Nige F]

Put the valve into manual with the lever on the side If you told me to " go to another job " I wouldn`t come back at all

 

[a1exh]

Thanks for the advice.

I moved the switch to manual and it does allow the boiler to fire. Unfortunately it does not stay in place and when the timer activates it moves back to auto. I guess if I go away I could perhaps leave the CH on but the thermostat dialled down. I didn't really want to leave the system on all the time if there was no-one around. Just a couple of hours every day to warm the house and prevent anything freezing.

There is no catch on my unit as depicted in some diagrams

I know this is not a long term solution. Any suggestions as what to do after xmas?

Several of the plumbers I called were suggesting a chemical followed by a power-flush. Is this wise or effective on an old microbore system with radiators with double entry valves?

 

[gas4you]

Flushing microbore, especially with double entry valves, is often not very successful.

I would expect you to pay around £180 ish for a new 3 port valve fitted.