3-port valves: Swapping Mid position for diverter valve

[joth]

Backstory: this summer I changed my system from glycol to anti-freeze valves, and enabled freeze protect on the controller.

Now, when freeze protect is running I notice my UVC appears to cool more rapidly, and need more reheats per day. I've long noticed it occasionally runs down temp super quick at other random times too, even with no DHW draw off. The secondary return pump is on a timer and motion sensors, and does not impact this even if disabled.

 

My hunch is that the mid-position valve sometimes lets water by into the DHW coil, even though I've confirmed electrically that it's in the heating-only position. (Neither grey nor white wire energized; it's installed "backwards" so spring return post B is for heating only, and port A is for hot water open when grey+white energized. We never use the mid-position state for obvious reasons. It being backwards makes sense in my mind, as the system is used in heating much more than DHW mode, esp with freeze protect, so this avoid the valve being energized for the majority of the time).  I've confirmed the ASHP controller freeze protect intends to only circulate heating, not DHW. (And this is great as theoretically the cold water from the external pipework will then flow to our bedroom FCU and provide "free" room cooling when it overheats at night: effectively using our excess body heat to stop the external pipes freezing! lol)
 

 

I know @ProDave has a hatred for this mid-position valves, and I agree, I wish I'd put my foot down about my installer using one in the first place, damnit.

 

Anyway questions:

1/ is it likely it's letting water by to port A when in the spring return closed position? It's only 2 years old and the system water is clean, I can't see it is sticking but wdik.

2/ is there an easy way to test if it is letting by?

3/ can I just swap out the head from mid-position to diverter (i.e. from V4073A to V4044 series), or does the whole valve body need changing too, entailing  another system drain down?

4/ is it worth doing this anyway, for piece of mind?

5/ any recommendation for a more reliable make of diverter valve that's a pipe-compatible drop in for the honeywell V4073A  range?

(the primary circulation is in 22mm pipework)

 

cheers

 

 

 

[ProDave]

I think you have to change the whole valve head and body.  And there will be some wiring changes.

 

Personally I prefer the dependability of individual 2 port valves.  As I understand it a 2 port valve is a ball valve.  A diverter is less sophisticated, think rubber bung swings round to block unused port.

[JohnMo]

Why is a mid point valve even installed on a heat pump, goes against every install manual I've read (loads of them). If connected to an unvented cylinder a mid point valve requires a 2 port valve to positively isolated the cylinder.  It should be a diverter and fail to the heating side being open, DHW cylinder being closed unless powered. The other way as @ProDave says is 2x 2-port. But they need to be timed so both are not allowed to open at the same time, which isn't idiot proof.

[joth]

Aye - I got a "great price" on my install and one gets one pays for... there's so much of the system I had to debug/fix/update it's a bit mad.

 

Anyway found a V4044C1288  for 72gbp on fleabay so I'm getting that now. The mid-pos valve has "worked" for 2 years (used just in the end stop positions) but I really don't trust it.