Hot Water Zone Valve Problem !

[Monkey Wrench]

I have an ongoing problem with a hot water zone valve that I've currently been unable to resolve despite replacing it twice ! The customer has an S plan system connected to a gas fired rayburn and called me because they only had hot water when the heating was ON. I checked the zone valve (Honeywell 4043) and found that when the hot water circuit was switched on, there was no power from the zone valve orange wire to the boiler/pump. I therefore replaced the zone valve head, turned the hot water circuit only on and the boiler/pump fire-up...... problem solved, or so I thought ! I switched the hot water circuit off (at the programmer) tidied my tools away and then swicthed the hot circuit back on as a final test.... Nothing ??? I therefore checked the zone valve and, once again, found no power from the orange wire to the boiler/pump.

I've fully tested the hot water electrical circuit and found both the programmer and cyclinder stat to be working fine. I therefore replaced the new powerhead with another new powerhead I had removed, switched the hot water circuit on and it worked fine. Turned the hot water off then on again at the programmer and nothing ! In all cases when the hot water will not come on, the only problem is no power from the zone valve to the boiler/pump. The programmer is sending power to the cylinder stat, the cylinder stat is sending power to the zone valve (calling for heat), the zone valve is opening but in most cases there is no power from the zone valve (orange wire) to the boiler/pump.

I have tried installing two new powerheads and checked all the connections in the junction box (all ok) but neither have resolved the problem. Sometime the zone valve (new or old) sends power to the boiler/pump but most of the time it doesn't. I hope this makes sense to someone as I really haven't a clue what the problem can be possibly be and so any help would be much appreciated. Thank you.

 

[Ch4 plumbing]

Sounds like you need to change the brass body aswel, sometimes the motor can't move the valve over enough to make the micro switch.

 

[Monkey Wrench]

Sounds like you need to change the brass body aswel, sometimes the motor can't move the valve over enough to make the micro switch.

Thank you for the post Ch4 plumbing. I turned the spindle on the valve body several times before replacing the powerhead and it moved freely enough but, as you say, may be just not enough to be activating the micro-switch. I guess replacing the valve body is the next thing to try as I can't think of anything else it could be. The only problem is that both the CH & HW zone valves (and the pump) are under floorboards on the first floor landing just above the kitchen and access is not great (but definitely doable). I'm going to see if I can hire a freezer kit (rather than draining down) to save time. Thanks again.

 

[Masood]

An easy test is to take head off the 2-port valve then turn the water on and off. If the boiler fires reliably then it's confirmed that wiring, synchron motor and microswitch are all fine, just the valve itself not moving far enough over to make the switch.

 

[Monkey Wrench]

An easy test is to take head off the 2-port valve then turn the water on and off. If the boiler fires reliably then it's confirmed that wiring, synchron motor and microswitch are all fine, just the valve itself not moving far enough over to make the switch.

That's great, thank you Masood, I hadn't thought about trying that one !

 

[Masood]

That's great, thank you Masood, I hadn't thought about trying that one !

A technique I learned from my old man!

 

[gassafe]

Yep, there's only so many times we can put a new head on an old valve lol... Sometimes it's nice to have a nice new valve in there also