My C. Heating comes on ,reaches temp then switches off but doesn't come back on even though 'on' cycle is not finished.It will come on again on new cycle when both HW & CH are requested. Room stat works(clicks). Have tried switching both tank stat & room stat to zero then turning each on with Programmer on constant but boiler doesn't fire up (Potterton Neataheat). Honeywell 3-way MV is in mid position & I can manually open it fully & it returns. Pump is ok. Boiler was serviced 2yrs ago by Potterton.
3 port MV?
- Thread starter retardimus
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Do you have a multimeter (and know how to use it)?
Thanx 4 ur reply. No, i don't have a multimeter. Feared this may b needed. I could just replace head. how is it attached? Do i need 2 drain down?
If the actuator, that's the box on top, has a small bump about 5mm across on the top, you can replace it without draining down. If not, then you have to replace the complete valve, which obviously means a drain down.
But before you rush out to buy a new valve or actuator, there are some simple tests you can do without a meter.
Turn CH and HW stats to min
Set programmer to CH and HW OFF
Turn off the electricity to the system.
Try moving the valve lever from Auto end to Man end. You should feel some resistance as you are opening the valve against a spring. Release the lever and it should move back to the Auto end with a whirring noise.
If the lever has no resistance or does not return, it's because the valve has stuck.
If the actuator is removable, take it off (remove cover - one screw, then undo two screws on opposite corners). This will allow access to the valve spindle ,which should turn easily by hand, but only about 20 degrees. You may need to use a pair of pliers if it is really stiff. Lubricate the spindle with some silicon lubricant, reassemble and test the system.
If the valve is sticking and you cannot remove the actuator, then it means a new valve and a drain down.
If the lever has resistance and returns, the fault is electrical
1. Turn CH and HW stats to min
2. Set programmer to CH and HW OFF
3. Turn off the electricity to the system.
(This resets the valve)
4. Turn HW ON
5. Turn HW stat to max - Boiler should light
6. Turn power ON
The pipe from valve to cylinder should get hot; the pipe from valve to rads should stay cold
7. Turn HW stat to min - Boiler should go out
8. Turn HW stat to max - Boiler should light
9. Turn CH ON
10. Turn CH stat to max
both pipes from the valve should get hot
11. Turn the HW stat to min - boiler should remain on (it may go out and come on almost immediately)
the pipe to the rads should stay hot and the pipe to the cylinder should cool down
12. Turn the HW stat back to max -pipe to cylinder gets hot again
13. Turn the HW OFF at the programmer - boiler should remain on (it may go out and come on almost immediately)
the pipe to the rads should stay hot and the pipe to the cylinder should cool down
14. Turn the CH stat to min -boiler should go out
15. Check the valve lever - it should be loose as the valve is held in the CH open position.
16. Turn the power OFF
17. Check valve lever - it should have resistance as the valve has been reset.
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what happens if you turn the CH on on its own?
DHailsham, thanx a lot 4 taking so much trouble! I have printed off ur reply & am gonna go get down & dirty with the system..well not so dirty. Thanx again.
Great clear steps DHailsham. Thanx. Everything was a 'yes' on ur list (except lever did have resistance, so not stuck valve) until point 11. When I turned HW stat to min, boiler went off but did not come back on even though CH was on and max on stat.Not sure wot2do now. I tried putting CH stat back to zero & then up to max but still no boiler even though I did hear a click on stat.Everything is as point10 at the mo.
Repeat the tests from beginning. When you get to step 11 ignore the boiler going out, continue to the end of the tests and report the results.
Hi DHailsham, did as u recommended. So ignoring step 11,step 12-HW stat back to max & boiler comes on & pipe to cyl gets hot-yes. Then 13. boiler went off but NOT on again. 14. CH stat to min but boiler already off & 15. valve lever WAS loose. 16 power off & after a few seconds there WAS resistance on lever. (Unfortunately the slot in plastic dial on cyl stat is now so manked, it's now virtually impossible to turn;I managed to get it back to 60deg, so no more stat turning on cyl-maybe epoxy another plastic washer on top)
Read more: //www.diynot.com/forums/viewto...fd9f642908d4667aa124c73f9cd1fe7#ixzz1W3Gd5hHH
Read more: //www.diynot.com/forums/viewto...fd9f642908d4667aa124c73f9cd1fe7#ixzz1W3Gd5hHH
So steps 11 and 13 have the same result - the boiler does not light. That means the actuator is almost definitely the cause of the problem. But there's one more check to make.
All the wires from the valve etc will connect into a junction box. We need to check some of the connections, so turn the power off and remove the box lid.
Check that the grey and orange wires from the valve are connected and the terminals done up.
If they are, then it's a new valve or actuator.
Thanx again. All wires are connected. Seems strange to have to replace actuator as it is only a few years since i last changed it..that might mean more than 5yrs..can't rememb.So that's those 2 diagonally opposite posidrive screws on base?to remove actuator I mean. Thanx 4 being so incredibly patient & 4 ur kindness & obvious skill!
Yes.
Honeywell actuators are usually very reliable, you may just have a "Friday Afternoon" one!
Just thought of something else to check (before spending your money!)
The grey wire should go to a terminal which has two other wires connected. One wire goes to the HW stat, the other to the programmer? Are they both present? If it definitely new actuator time.
When changing the actuator, turn the power off (obviously). Then cut the cable of the old actuator so the wires are still attached to the terminals. You will then know which wire goes to which terminal.
While you have the actuator off, check the valve spindle rotates easily by hand.
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