Central Heating - 3 Port Valve Question
Discussion
System:
Two story 80's build house.
Bosch Greenstar Boiler about 10 years old located in garage.
Y-Plan, vented, pumped, conventional CH system (not combi).
Header tank in loft
Honeywell 3 port valve, pump and hot water cylinder in the airing cupboard within the upstairs landing.
Symptom: Radiators get hot even though heating not requested.
Diagnosis steps so far:
Timer working, thermostat working, motorised valve head working - i.e the motor responds appropriately to the various call signals from the system controllers and the override lever moves correctly, responds correctly and is loose when in heating mode, whilst resistant and self returning when forced into the manual open position if heating not called. Switch normally left in auto position.
I manually closed the gate valve post the port valve to the radiators and as it fully closed, I heard a slight change in pump load as the flow to the rads finally stopped as you'd expect, however this was when the heating wasn't called for and the valve should have already prevented flow to the rads.
This indicated to me that the 3 port valve was not closing correctly, despite the correct efforts of the motorised head unit.
I removed the head and found the valve spindle very stiff to move, requiring pliers and a (very) little force. I waggled it open and closed repeatedly for a good while until it was free to twist by hand to both extremes of movement with a definitive 'stop' felt at both ends of the travel, albeit more positive in the heating on position than the heating off end of travel.
I double checked the movement of the actuating socket in the head of the motor which slides over the top of the spindle and observed it moving correctly both when manipulated by the lever and also by the motor under various call demands.
With the spindle on the 3 port valve now free, I reassembled everything and cycled the controller a few times, however water is still making it's way to the rads - confirmed by a) the ongoing hot water supply to them, and b) despite the valve being in the closed (no heating) position, when I again closed the gate valve, as it fully closed, I heard the slight change in pump load again which shouldn;t (by my logic) occur if flow is already blocked by the 3 port valve.
My diagnosis is that the rubber ball is not seating and sealing correctly in the valve either due to wear, debris, or both, and likely needs changing?
Is my diagnosis correct based on the above?
If so, what is the prescribed method of isolating the valve given that the only gates I can see in the vicinity are post valve to the rads, and one a few feet of pipe away that is from the boiler hot feed, although this T branches to a smaller pipe that goes elsewhere to an unknown destination and cannot be isolated from the 3 port valve.
Additionally, the feed from the 3 port to the hot water cylinder is not gated, therefore I'm assuming that even though I can isolate the 3 port on the rads side, I still have a water feed from the coil return to the boiler within the cylinder and also the mystery T-juntction off the boiler supply feed pipe, post gate valve to somehow isolate? Therefore my logic says that to elements could spill and unknown quantity of water without isolation if I remove the valve?
Or is that normal, and actually not an issue by some other system design that prevents water back flowing through those two non-gated pipes?
I'm trying my best to apply common sense and logic but don't want to start draining the system down or removing the 3-port if my diagnosis or system understanding is flawed.
Thanks in advance for any guidance advice or observations.
Two story 80's build house.
Bosch Greenstar Boiler about 10 years old located in garage.
Y-Plan, vented, pumped, conventional CH system (not combi).
Header tank in loft
Honeywell 3 port valve, pump and hot water cylinder in the airing cupboard within the upstairs landing.
Symptom: Radiators get hot even though heating not requested.
Diagnosis steps so far:
Timer working, thermostat working, motorised valve head working - i.e the motor responds appropriately to the various call signals from the system controllers and the override lever moves correctly, responds correctly and is loose when in heating mode, whilst resistant and self returning when forced into the manual open position if heating not called. Switch normally left in auto position.
I manually closed the gate valve post the port valve to the radiators and as it fully closed, I heard a slight change in pump load as the flow to the rads finally stopped as you'd expect, however this was when the heating wasn't called for and the valve should have already prevented flow to the rads.
This indicated to me that the 3 port valve was not closing correctly, despite the correct efforts of the motorised head unit.
I removed the head and found the valve spindle very stiff to move, requiring pliers and a (very) little force. I waggled it open and closed repeatedly for a good while until it was free to twist by hand to both extremes of movement with a definitive 'stop' felt at both ends of the travel, albeit more positive in the heating on position than the heating off end of travel.
I double checked the movement of the actuating socket in the head of the motor which slides over the top of the spindle and observed it moving correctly both when manipulated by the lever and also by the motor under various call demands.
With the spindle on the 3 port valve now free, I reassembled everything and cycled the controller a few times, however water is still making it's way to the rads - confirmed by a) the ongoing hot water supply to them, and b) despite the valve being in the closed (no heating) position, when I again closed the gate valve, as it fully closed, I heard the slight change in pump load again which shouldn;t (by my logic) occur if flow is already blocked by the 3 port valve.
My diagnosis is that the rubber ball is not seating and sealing correctly in the valve either due to wear, debris, or both, and likely needs changing?
Is my diagnosis correct based on the above?
If so, what is the prescribed method of isolating the valve given that the only gates I can see in the vicinity are post valve to the rads, and one a few feet of pipe away that is from the boiler hot feed, although this T branches to a smaller pipe that goes elsewhere to an unknown destination and cannot be isolated from the 3 port valve.
Additionally, the feed from the 3 port to the hot water cylinder is not gated, therefore I'm assuming that even though I can isolate the 3 port on the rads side, I still have a water feed from the coil return to the boiler within the cylinder and also the mystery T-juntction off the boiler supply feed pipe, post gate valve to somehow isolate? Therefore my logic says that to elements could spill and unknown quantity of water without isolation if I remove the valve?
Or is that normal, and actually not an issue by some other system design that prevents water back flowing through those two non-gated pipes?
I'm trying my best to apply common sense and logic but don't want to start draining the system down or removing the 3-port if my diagnosis or system understanding is flawed.
Thanks in advance for any guidance advice or observations.
GasEngineer said:
Try running it with the actuator head off* and hold the valve spindle manually turned to the hot water only position to see if it still lets by.
*(make sure you have the cover back on the actuator before you switch the power on as live components).
Thanks, I should have said that - I did try that and observed that despite holding the port valve closed, the gate valve still made a difference to pump load when fully closed, indicating it was getting past.*(make sure you have the cover back on the actuator before you switch the power on as live components).
Buy the service kit for the valve, comes with a new ball mechanism and seal. The balls are just rubber so harden & distort with time.
Seems to be at least two versions of kit (maybe for different valve types), one does the ball and one is a repair/conversion with the whole plate/arm/etc.
Latter is only £20 and replaces everything that isn't the cast valve body or the motor head.
Give the body a good scrub while you're at it so the seats are clean.
I used one of the kits and it basically gives you a new valve, much cheaper than a full replacement.
Seems to be at least two versions of kit (maybe for different valve types), one does the ball and one is a repair/conversion with the whole plate/arm/etc.
Latter is only £20 and replaces everything that isn't the cast valve body or the motor head.
Give the body a good scrub while you're at it so the seats are clean.
I used one of the kits and it basically gives you a new valve, much cheaper than a full replacement.
119 said:
Must admit if you have to drain the system to replace valve parts, i would just replace the whole thing!
A lot less money and effort in just taking the top off, undoing 4 bolts, pulling the guts out and replacing it than in doing the whole thing. It's not like the body deteriorates, it sounds like the head is fine and the kit replaces everything else. Less likely to leak as you haven't touched the joints, no need to wire the new head in and assuming you're buying genuine Honeywell not Ebay knockoff it's 1/5 the cost.
So less work and less money and fewer problems, only Charlie Mullins would see that as a bad thing.
JoshSm said:
119 said:
Must admit if you have to drain the system to replace valve parts, i would just replace the whole thing!
A lot less money and effort in just taking the top off, undoing 4 bolts, pulling the guts out and replacing it than in doing the whole thing. It's not like the body deteriorates, it sounds like the head is fine and the kit replaces everything else. Less likely to leak as you haven't touched the joints, no need to wire the new head in and assuming you're buying genuine Honeywell not Ebay knockoff it's 1/5 the cost.
So less work and less money and fewer problems, only Charlie Mullins would see that as a bad thing.
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