Do I need to empty radiators while changing Honeywell Motorised 2 port valve?

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Hi All

Background: DHW is not hot anymore. My boiler engineer can come on coming Wednesday. Tried to contact local heating engineers. 3 of them said that they are fully booked over the weekend and the earliest appointment is Tuesday. I have two young children and moaning Mrs and getting constant pressure to get it changed for the sake of the kids.


Can I pick your brain?

We have a system boiler Vaillant Eco Tec 630 plus and connected to Hive. Things have been perfect however, DHW is cold now.

I have ruled out Hive (as it turns on DHW light) but the boiler is not turning on. The boiler is new and only 4 months old.

That leaves the Honeywell Motorised valve as a culprit. I have moved it to manual and then auto a few times and that alone turned on the boiler (while the hive booster for HW is on). However, after a few minutes boiler turn off. I have turned the valve to manual position and the boiler is not kicking in now.

I have concluded that it's Honeywell motorised valve (22mm). I have gone to a local plumbing shop and bought a new one.

My abilities:
I can drain radiators, refill, bleed and work out any minor issues.
I have worked out the wiring of the Motorised valve and confident in changing it (I installed Hive myself).
New valve is exactly the same as old so hopefully, no extra work is required.


My questions:
-Looking at the pipework, the pipe from DHW Honeywell valve is going to CH valve as well. If I switch off the boiler / whole heating system, that means the CH valve will be closed. Do I need to empty radiators? Or considering the above, I can change the valve after I empty DHW pipework.

Will appreciate any help/pointers in the right direction.

PS: Pipework is shown in the photo. The valve which is closer to us is DHW valve and other one is for CH. Immersion tank heating filament is faulty (that is what I have been told).
 

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As a temporary solution ,you could put heating on with hw valve latched open. Then wait for a professional to do the replacement
 
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You could do as suggested above ,but if you really want to do it yourself ,draining the central heating systems water to a level below the position of the motorised valves is required. Domestic hot water doesn't need to be drained.
 

CBW

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That looks like an unvented cylinder, which I’m not sure if you’re allowed to change the head on the hot water valve, unless you’re G3 qualified.
 
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1. If the DHW works for a while after setting the Honeywell DHW valve to manual, then there is not likely to be anything wrong with the brass valve itself. If the valve is the problem, the fault will lie in the actuator.
2. The actuator head is removable without any contact with water:
2a. Turn off all power in the house, unless you can guarantee to electrically isolate the valve and all boiler / hot water systems connected to it.
2b. Undo the screw just above the white label, its in line with the dimple on top of the cover.
2c. Remove the cover and undo the two screws inside (more or less in the corners) which secure the actuator to the valve body.
2d. Fit a new actuator head. Its can be cheaper to buy a whole valve and discard (or keep as spare) the actual brass part.
2e. Attach the wires from the new actuator to the exact same positions in the wiring centre as the wires from the old valve. An old trick is to cut the old wires about an inch from the terminal in the wiring centre, then one at a time remove these stubs and replace with the same coloured wires from the new valve.
3. That is an unvented hot water cylinder, and you have to be G3 registered to work on it. Whether the two port valve is part of the cylinder might be arguable, but it forms an integral part of the 3 layer safety system, and in my view should be considered part of the system.
 
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As a temporary solution ,you could put heating on with hw valve latched open. Then wait for a professional to do the replacement
I have already tried that. Kept it open on manual and it doesn't allow HW heating on.
 
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Have you removed the head and moved the pin manually?
 
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I have already tried that. Kept it open on manual and it doesn't allow HW heating on.
The central heating has to be on ,that Fires up the boiler ,and you manually latch open the domestic hot water motorised valve,to heat the water in the cylinder.
 
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I have already tried that. Kept it open on manual and it doesn't allow HW heating on.
If you manually latch the valve open you will have to switch the CH on at the same time with the Hive demanding CH to power the boiler, latching the HW valve to manually open will only open the valve, it wont tell the boiler to fire , to replace the actuator you dont need to drain anything, you have removable actuators, so simply an electrical job, no water involved
 
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Does the cylinder have an electric immersion heater installed?
If it does, just switch that on for hot water and get the valve or whatever fixed next week.
 
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Does the cylinder have an electric immersion heater installed?
If it does, just switch that on for hot water and get the valve or whatever fixed next week.
Apparently the OP has been told the immersion " filament" is faulty .
 
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Have you removed the head and moved the pin manually?
No.
The central heating has to be on ,that Fires up the boiler ,and you manually latch open the domestic hot water motorised valve,to heat the water in the cylinder.
CH to power the boiler, latching the HW valve to manually open will only open the valve, it wont tell the boiler to fire , to replace the actuator you dont need to drain anything, you have removable actuators, so simply an electrical job, no water involved
Yes tried it after turning on the heating (booster on hive) and then putting it into to manual settings. It fired the heating twice and then didn't work.


1. If the DHW works for a while after setting the Honeywell DHW valve to manual, then there is not likely to be anything wrong with the brass valve itself. If the valve is the problem, the fault will lie in the actuator.
2. The actuator head is removable without any contact with water:
2a. Turn off all power in the house, unless you can guarantee to electrically isolate the valve and all boiler / hot water systems connected to it.
2b. Undo the screw just above the white label, its in line with the dimple on top of the cover.
2c. Remove the cover and undo the two screws inside (more or less in the corners) which secure the actuator to the valve body.
2d. Fit a new actuator head. Its can be cheaper to buy a whole valve and discard (or keep as spare) the actual brass part.
2e. Attach the wires from the new actuator to the exact same positions in the wiring centre as the wires from the old valve. An old trick is to cut the old wires about an inch from the terminal in the wiring centre, then one at a time remove these stubs and replace with the same coloured wires from the new valve.
3. That is an unvented hot water cylinder, and you have to be G3 registered to work on it. Whether the two port valve is part of the cylinder might be arguable, but it forms an integral part of the 3 layer safety system, and in my view should be considered part of the system.
Sir you are a legend!

Followed it and you couldn't have made it any simpler.

HW is on now. All, I have to do is to get a professional in and double-check the installation. I am not sure what is professional (G3 registered) going to do but always good to have professionals on the case.

Thank you all... You are saviours. Kids will be happy and moaning Mrs can mind her business.
 
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1. Unvented hot water systems come under Section G3 of the Building Regulations Part G. The cylinders are pressurised, and in very extreme circumstances can explode.
2. To reduce the risk to nearly zero, they have pressure release valves, temperature and pressure release valves, and thermostatic controls of the heating temperature (electric and oil / gas). There are a good number of do's and dont's involved in installing and maintaining them.
3. Because of the slight risk / high impact nature of severe fault conditions:
3a. They may only be installed, altered and / or maintained by someone who is a current member of an approved G3 accreditation scheme.
3b. They require an annual service.
4. Gas Safe offer a G3 accreditation service for qualified members, as do a number of other organisations, such as NAPIT.
5. Someone with Gas Safe Registration is not necessarily G3 accredited - its a separate qualification.
6. All schemes issue cards with the operatives picture, and the details can be checked on-line or by 'phone with the accreditation agency listed on the card.
 
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If only the head is faulty you can get replacement heads ( made by other firms which fit Honeywell ) and do not need to mess with any water.

Sold by Toolstation and Screwfix.

But first you need to ensure the valve shaft is moving reasonably freely ( using a small adjustable spanner and not pliars )
 

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