Boilermates 20th Birthday - Need some parts changing

My boilermate will be 20 about now, house was built in 2000. It has been on the whole a superstar over the years (so I might add has this forum), a few outages but all repairable.

I was just starting to have occasional problem with going hot/cold. I have never changed the PHE and live in a hard water area.

So I decided to change the PHE and two wet sensors either side. System back up and running again, will find out today/tomorrow if problem fixed but....

Two questions:

1, I forgot to note the direction of the PHE when removing, from images from the web the logo is on the outside so I just copied this - are they directional? They do kind of arrows on bottom and top but they go in different directions!

2, The new PHE is shallower, by about 10mm than the old one. I checked online and everyone sells this new one with less depth. What happened here?

Ex

Hi at the ripe old age of 20 it might just be worth checking that the control board is functioning correctly, couple of quick checks is the display showing -on or =on? Does the SW2 switch show the correct temperatures when pressed? Is the hot water pump running continuously? If these are not working correctly it may be that the pcb is on its way out. Have a look at my website I have videos that show how to check the pcb out and what to look for to check if it is faulty. I am sure after 20 years you are aware of the above so apologies if a bit of Grandma and egg sucking is going on here! Regards Murray

Hi Murray,
You have fixed two of my boards already over the years - thanks again by the way! Your video is also great to understand the workings.

Board I think is fine at the moment.

Dry Store sensor (not replaced) aiming for around 70, sensor working fine after refill, see it go up steady.

New wet DHW sensor changes when using the hot tap as expected I think,
turn hot tap on, temp goes down to 20's as cold as is going in top, turn tap off, raises again to 40/50 my guess is as the hot and cold water from the pHE mix and it travels back up the pipe

New wet PHE sensor changes when using the hot tap as expected I think,
turn hot tap, PHE sensor then raises to H50's

Any thoughts on the change in size of the PHE or direction of PHE? It is not mentioned anywhere on any forum or the web?

Ex

All sounds well with board and sensors. Plenty of water in header tank? Re PHE size I guess they have improved the efficiency by improved design or maybe realised that the extra capacity was not needed, or maybe it is the chocolate bar syndrome less for the same money!!

Yep, header tank working fine, spent most of sunday keeping an eye on it, for whatever reason when installed the flow into the FHE is very slow and I have a valve on the pipe above the BM that I only open partially when filling otherwise the FHE empties quickly when valve fully open and I always get air locks. Many years of experience!

Will give it a few days now and see if it has helped, initial indications are that showers are not going hot and cold anymore.