Honeywell three port motorised valve - replace the whole thing? And other questions...

[Oxbow16]

Hi again

 

I'm on a roll with the plumbing questions today     So here's query #2...

 

We've not used our hot water for quite some time, and it now doesn't work.  From what I can gather based on what I've learnt in the last hour or two, I think the problem is with the 3 port motorised valve.  When just hot water is selected at the controls, we don't get hot water, but we do get hot radiators.  Just to be clear, that's with hot water selected to continuous, heating off, and the heating thermostat turned right down.  Up in the airing cupboard, I can feel - at the valve - that the pipe going from point B to the cylinder stays cold, while the pipe from point A warms up.  The little lever bit doesn't move and stays in auto position.  So presumably the valve for one reason or another is stuck and no matter what the controls tell it to do, only port A is open.  Does that sound about right?  

 

If so, I wondered if anyone could help with the following please?  

 

1.  We've got some major plumbing work coming up soon, which will require a full drain down.  As such, would it be worth changing the whole unit?  I've seen some try just changing the motor, others just the power head.  But whilst drained down is it worth spending the extra and just replacing the whole thing?  

 

2.  My unit is a Honeywell V4073A1088.  The one you tend to see most is the V4073A1039.  I looked into it and all I could find is the former is 28mm and the latter 22mm.  I presumed that related to the pipes feeding it, but does it?  The reason I ask is because I have 22mm pipes and yet mine is supposedly the 28mm version.  Which has me scratching my head!  

 

3. One forum thread I was reading stated:  "“It explains why you can't use a mid position for your HW and RADS and then add a two port for extra rads or UFH.”  Is that correct?  Is it a blanket statement?  Later in the year we are looking to have UFH installed elsewhere in the house, so I'd be interested to know if it would need changing again at some point.  For reference, the quote comes from here:

 

https://community.screwfix.com/threads/motorised-valves-that-little-lever.173511/

 

4. Is it the heating controls or the room thermostat which control the valve?  

 

Sorry for all the questions, and help with any of them would be much appreciated.  

 

Massive thanks!

 

Some photos in case they help:

 

 

 

 

 

 

 

 

[ProDave]

Honeywell are usually the best, but if the lever won't move the valve mechanism is stuck so you will need to replace the whole lot.  Don't get hung up on model numbers as long as it's 3 port mid position and the correct size pipes.

 

However if you are doing major plumbing I would throw the 3 port valve away, I hate the things, work of the devil.  I would replace it with two 2 port valves and as you say that makes it much easier to add extra circuits, but it will need the wiring centre completely rewiring as well as the plumbing changes.

[Nickfromwales]

43 minutes ago, ProDave said:

However if you are doing major plumbing I would throw the 3 port valve away, I hate the things, work of the devil.  I would replace it with two 2 port valves and as you say that makes it much easier to add extra circuits, but it will need the wiring centre completely rewiring as well as the plumbing changes.

You keep saying that, but this one has clearly lasted yonks, and so will the next. The upheaval of swapping to 2x 2-port is completely unnecessary imo, and even though I also dislike 3-port valves, the OP doesn't NEED to change / upgrade as it has no benefits. If the boiler is doing pump overrun it will actually cause problems, as the 3-port leaves a path from the pump to the rads ( when idle ) for the residual stagnant heat in the boiler heat exchanger to 'leak' away into.

[joe90]

3 hours ago, Nickfromwales said:

and even though I also dislike 3-port valves,

Why is that?, I know @ProDave does not like them. 
 

4 hours ago, ProDave said:

if the lever won't move the valve mechanism is stuck so you will need to replace the whole lot.

I agree and worth doing if your draining down the system anyway. Is it a change over or mid position valve (3 or 5 wires)?

[dpmiller]

that looks like a 28mm valve with reducers to 22mm??

[Nickfromwales]

1 minute ago, joe90 said:

Why is that?, I know @ProDave does not like them. 
 

I agree and worth doing if your draining down the system anyway. Is it a change over or mid position valve (3 or 5 wires)?

One thing dies, two things are lost. Redundancy is doubled with 2 x 2-port. If boiler overrun is required, then a 3-port mid-position is the norm.

Diverter ( either or ) is for W plan and ASHP's, mid position gives heating / hot water / or both simultaneously.

 

All of the above can be achieved with 2-port valves, if designed in from scratch. Conversions may require extensive wiring adaptations, and the OP may not have existing equipment that lends itself to that. 

[Nickfromwales]

1 minute ago, dpmiller said:

that looks like a 28mm valve with reducers to 22mm??

Yup, deffo 28mm.

[joe90]

7 minutes ago, Nickfromwales said:

One thing dies, two things are lost.

But are they? ?, surely if it dies it’s stuck In one mode, either heating or DHW ?‍♂️ If I remember correctly their “rest” position is heating so only DHW is lost! And that could be compensated by using an immersion till a replacement is sourced!

Edited August 21, 2021 by joe90

[Nickfromwales]

Just now, joe90 said:

But are they? ?, surely if it dies it’s stuck In one mode, either heating or DHW ?‍♂️ If I remember correctly their “rest” position is heating so only DHW is lost!

The actuator needs to travel to and activate the internal microswitch, so yes, no go = no show. If it jams in the hot water position then the heating can come on when DHW is called for, and the cylinder stat will be ignored.

Design them out at the outset by all means, but you can't tell someone to delete one unless the full ( existing ) system requirements are identified and understood.

[Eric]

My heating system has the same valve, I have just been doing some maintenance & checked the little lever & it feels stuck.

I waited for the hot water to heat up then switch to underfloor but the lever didn’t move.

 

Should I investigate it further or leave it alone?

[MikeSharp01]

8 hours ago, Eric said:

My heating system has the same valve, I have just been doing some maintenance & checked the little lever & it feels stuck.

I waited for the hot water to heat up then switch to underfloor but the lever didn’t move.

Was the underfloor calling for heat? It may have just stayed put at DHW as it didn't need to move for the UFH - depends on how your controls are organised.

[Eric]

Yes, the UFH was calling for heat, I will keep an eye on it, everything is working well but I’m sure it used to move before.

[Oxbow16]

Many thanks for the great replies and explanations.  I've got to admit, I love learning about this kind of stuff.  Not that I always fully understand it though!  

 

If I could bother you with some more questions please...  

 

- Is there no way UFH could be added - as a separate zone - to my current system with 3-port valve?  100% not?  Appreciate this is a naive question, but can it be on a completely separate feed from the boiler itself, or does the boiler just have a single flow and single return?  

 

- The reason I ask is because we're not sure if we're going to have any UFH heating yet or not.  If we do go for UFH, it would seem a shame to put in a new 3-port unit now only to have to change it all again soon.  But if don't end up with UFH, it would be an unnecessary waste and expenditure changing to two-port units.  

 

- Which leads me onto seeing if my existing unit is fixable, in which case we can continue using that until we've decided on UFH or not and then have a new unit(s) installed accordingly.  So tomorrow I'll re-read the above, do a little more googling, and watch a couple more vids to see about diagnosing the fault with the unit.   

 

- This is more for my curiosity...  I don't mean to be thick, but where exactly does the change from 22mm-28mm take place?  I'm pretty sure that when I measured the visible pieces of pipe where they go into the unit they were 22mm.  I can take a photo tomorrow.  So is the reducer/adapter out of site or am I just not getting something (something which is no doubt extremely obvious to everyone else)?  

 

Right, that's enough excitement for tonight!  

 

Cheers 

[joe90]

1 hour ago, Oxbow16 said:

where exactly does the change from 22mm-28mm take place?

If you look at your original photo, the bottom pipe shows it best, the adapter goes into the nut union, pipe swells just 2 1/2 mm each side before disappearing into the nut.

 

 

[ProDave]

If you want to try fixing your old unit, turn the power off, remove the cover from the actuator head and buried deep down at the bottom you will find the 2 screws that hold the head onto the bottom, remove them and lift the head off.

 

Then see if you can turn the shaft on the actuator head, chances are after a long period of non use it is seized and getting it to move with a pair of pliers and exercise it until it is free might be all that is needed.

[Marvin]

I always give the port valve in this situation a resounding tap just in case it frees it up. I have often had success on circulation pumps the same way after not being used all summer..

[Oxbow16]

Thanks for the continued great help.  I really do appreciate it.  Didn't get the chance to check the unit today but will...

 

Seeing as I brought up UFH in my last post, I was just wondering if all boilers are suitable for it?  A bit off topic I know but it got me to thinking...  I have a Worcester Danesmoor 20/25 (oil).  Can anyone confirm if there's any reason UFH wouldn't be compatible with that boiler?  

 

Cheers

[ProDave]

On 23/08/2021 at 00:48, Oxbow16 said:

 

- Is there no way UFH could be added - as a separate zone - to my current system with 3-port valve?  100% not?  Appreciate this is a naive question, but can it be on a completely separate feed from the boiler itself, or does the boiler just have a single flow and single return?  

 

As I have eluded to, the 3 port valves are complex things with a couple of microswitches resistors and diodes.  As well as being able to stop and mid position, they also create the "call for heat" signal to the boiler.

 

In principle you could connect a 2 port valve direct to the boiler flow and return to power the UFH independent of anything connected to the 3 port valve.  However there would be 2 issues doing that.  Firstly the 3 port valve at rest connects to the DHW port, so whenever the UFH was on, water from the boiler would flow through the tank coil and also ignore the cylinder thermostat in the process.  And secondly you would probably have issues if you just connect the call for heat from the 2 port valve in parallel with the call for heat from the 3 port valve.  Feeding 230V into the 3 port valve like that might have some unexpected complications.

 

So i still say replace the lot with 2 port valves.