Open vented system, No HW, CH works fine, BAXI 80HE boiler shows Dry Fire after every restart

[fandyman]

@Harry Bloomfield Thanks for your comment.

If it turned out I need to change the whole lot would it not be possible to use the rad valve change kit to create a vacuum which would avoid draining the system down?

 

[Harry Bloomfield]

If it turned out I need to change the whole lot would it not be possible to use the rad valve change kit to create a vacuum which would avoid draining the system down?

You might be able to close all of the radiator valves, at both sides of the radiators, to avoid draining much of the water out, but that would still leave water to be drained within the pipework. There is no way to avoid draining some water, to change the actual valve.

Cross the bridges, when you get to them - investigate the valve and actuator first, as I suggested in my post above.

 

[Madrab]

If you cant manually latch the 3 port actuator open then there may be an issue with the valve head. Is the head of the valve removable? If so take the head off and then find the mid position of the valve by turning the valve spindle manually using a pair of grips or an adjustable - it will only turn about half a turn end to end, if that, so leave judged half way, the spindle should move easily, if it doesn't then the valve itself could be the issue. Then override the CH system and see if both A and B heat up. You can use the bleed valve until hot water is felt as that signifies that the valve is in the mid position and it's flowing up the bleed, then let the system run. Does the cylinder stat actually click when you turn it to min and back up to max/60deg?

The 3 port should default to B (@ idle) when it's on HW only demand from the programmer. So Only B should get hot right up to the cylinder and then cooler but rarely cold coming out of the cylinder.

 

[fandyman]

Ok this is very strange now. After I turned the cylinder thermostat down a bit to 55C yesterday evening and cranked up the boiler temperature gauge up a bit there is hot water today and I can feel the feed and return of the coil getting warm finally.

I still think there is an issue with the actuator head as I cannot manually latch the 3 port actuator open.

@Madrab I will now try to switch the CH constant ON to OFF position and check that only the B warms up.

 

[fandyman]

This is the setting (attached) I have got at the moment which got my hot water from taps.

This has been like that since yesterday. I know that CH is still on and I now disabled it to OFF position. I have to wait until the system is cold to retest now I suppose.

 

[fandyman]

So two showers later boiler still goes into Dry Fire and with the CH OFF and HW ON on the programmer the flow and return coil pipes are becoming only luke warm again. It seems that the issue persists.

 

[fandyman]

If you cant manually latch the 3 port actuator open then there may be an issue with the valve head. Is the head of the valve removable? If so take the head off and then find the mid position of the valve by turning the valve spindle manually using a pair of grips or an adjustable - it will only turn about half a turn end to end, if that, so leave judged half way, the spindle should move easily, if it doesn't then the valve itself could be the issue. Then override the CH system and see if both A and B heat up. You can use the bleed valve until hot water is felt as that signifies that the valve is in the mid position and it's flowing up the bleed, then let the system run. Does the cylinder stat actually click when you turn it to min and back up to max/60deg?

The 3 port should default to B (@ idle) when it's on HW only demand from the programmer. So Only B should get hot right up to the cylinder and then cooler but rarely cold coming out of the cylinder.

@Madrab The cylinder stat clicks when I turn it to min and back up to 55deg.

 

[Harry Bloomfield]

@Madrab The cylinder stat clicks when I turn it to min and back up to 55deg.

When you do that, with the CH on/boiler running, and HW enabled on the timer - does the actuator show any signs of movement?

 

[fandyman]

@Harry Bloomfield how do I check for sign of movement on the actuator? Are you referring to the movement of the latch there? I do not observe any movement from AUTO position and also it is impossible to latch it into manual setting as it drops out of the slot.

Btw I have taken the actuator out and exposed the spindle. With only hand movement here are the max movement photos each end (about 30 degrees side to side?). I will try with pliers now but should it not go a bit further?

 

[Harry Bloomfield]

@Harry Bloomfield how do I check for sign of movement on the actuator? Are you referring to the movement of the latch on the actuator? I do not observe any movement from AUTO position and also it is impossible to latch it into manual setting as it drops out of the slot.

You will hear the motor run for a minute or so. If you have doubts, with the actuator off the valve - set your system to call for CH, then swap it to a call for HW[1]. The actuator spindle should move, between the two settings.

[1] Set the timer for both CH and HW to ON, with the room stat, and cylinder stat set to minimum. Turn the room stat to max, actuator should move to CH. Change to setting the HW stat to maximum, and it should again move.

Btw I have taken the actuator out and exposed the spindle. With only hand movement here are the max movement photos each end (about 30 degrees side to side?). I will try with pliers now but should it not go a bit further?

I'm not familiar with that valve, so I am unable to comment..

 

[fandyman]

@Harry Bloomfield I have just tested the above and observed actuator moving.

I have actually finally also tested the B side of the valve by manually turning the spindle to HW and turning up the cylinder thermostat from min to 55C and only the B side got very hot so the valve is ok I think.

I also noticed that while the actuator was not powered I could put the latch on MANUAL and also the spring movement seemed fine when release from MANUAL. I suppose when the actuator is powered I should also be able to move the latch to MANUAL which is sth that I was not able to do.

I just wonder where is the problem now...

 

[fandyman]

Would you replace the actuator head in this instance or the valve or look somewhere else?

The boiler seems to be going into DRY FIRE when it remains in the stand by mode (not burning) - not sure that is normal. Maybe the fault is there?

 

[Harry Bloomfield]

The boiler seems to be going into DRY FIRE when it remains in the stand by mode (not burning) - not sure that is normal. Maybe the fault is there?

You keep mentioning 'DRY FIRE' what does that mean?

 

[fandyman]

The boiler goes into DRY FIRE status mode and this is the description from the sticker:

No Water flow or Flow/Return reversed.

 

[Madrab]

I suppose when the actuator is powered I should also be able to move the latch to MANUAL which is sth that I was not able to do.

No and be careful, when the 3 port actuator is in stalled mode - HW and CH calling - then the motor holds the spindle at mid position - Don't ask how it does it as it's a bit of an explanation but the manual lever will not work.