Faulty diverter valve on Potterton Gold Combi HE28

Joined
3 Dec 2005
Messages
96
Reaction score
1
Location
Surrey
Country
United Kingdom
My Potterton Gold Combi HE28 is misbehaving. I have it set to hot water only, but when I turn on a tap it makes a banging noise and the radiators start to get hot. I do get some hot water from the taps, but it's not right. Could it be a faulty diverter valve? Or could it be that the plate HE is partially blocked, and the divertor valve is opening up to the radiator feed under the pressure? As I understand it, it's designed to work the other way round, such that the plate HE acts as a bypass for the heating.
 
Sponsored Links
Turn a hot tap on and feel the heating flow pipe under the boiler (left hand side), if this gets hot you have a diverter issue. Depending on what sort of banging noise it is, it could be a pump/circulation problem (likely).
 
Thanks for the reply.

I think the banging is probably kettling due to a partially blocked plate HE. Yes, the heating flow does get hot, but my real question is this: Because both parts of the diverter valve are sprung, is it possible that a partially blocked plate HE would cause a build up of pressure such that the bottom part of the valve(the part that controls the flow to the rads) is forced open?
As I understand it, the top part of the valve is designed to work that way, i.e. if all the rad are turned off or the flow or return are blocked or turned off, then the water from the main HE opens the top valve against the spring and the plate HE acts as a bypass.
 
Sponsored Links
Yes, if badly blocked the it can cause the diverter valve to leak due to excess pressure.

Quite clever of you to work that out when some engineers sont seem aware of that possibility.

Although i always think that in London we have some of the worst installed/maintained boilers!

Tony
 
Just going on what the service manual says:
"14.20 Plate Heat Exchanger (Fig. 98)
1. Drain the boiler primary circuit and remove the gas valve
as described in section 14.23.
2. While supporting the heat exchanger undo the screws
securing it to the brass manifolds.
3. Withdraw the heat exchanger upwards, taking care not to
damage any wires or controls.
Seals
4. There are four rubber seals between the manifolds and
heat exchanger which may need replacement.
5. Ease the seals out of the manifold. Replace carefully,
ensuring that when the seal is inserted into the manifold it is
parallel and pushed fully in.
6. When fitting the new heat exchanger note that the left
hand location stud is offset towards the centre more than the
right hand one.
7. Reassemble in reverse order"
 
Yes, if badly blocked the it can cause the diverter valve to leak due to excess pressure.

Quite clever of you to work that out when some engineers sont seem aware of that possibility.

Although i always think that in London we have some of the worst installed/maintained boilers!

Tony
Thanks for the compliment, although I have to say that I have the advantage of having a diverter valve repair cartridge on my desk here, which I bought on eBay for 14.99. Little did I know that it only fits the slightly later Gold Combi HE28A, not the HE28. So I've had plenty of opportunity to consider the problem.
 
Never took a plate out of the gold, but done loads on the promax and duotec's and the instructions are exactly the same. As Baz says, no need to take the gas valve out. The way i do it is close F&R valves and drain primary water in the boiler, turn stop tap off and drain hot taps (open ALL the taps). Place a paint tray or similar under boiler and crack the plate gingerly, when it stops dripping take bolts fully out and turn the plate holes down to catch water. When the last drips are out, turn plate holes up and manouvre out of the boiler (cover electrics as it WILL get in where the cables enter the pcb). Use a good cleaner and replace.
 
Thanks.
I'll take another look, and see if I think I'm competent. Make sure I've got the necessary spanners...

What's a good cleaner to use?
 
Only just got round to doing this, what with being on holiday and various other committments. Anyway, I bought a replacement HE to be on the safe side(wife and daughter have proper jobs, and they'll not be happy if they can't have a hot shower). Finally managed to wiggle the old one out, cutting myself in the process on the razor sharp back seam. Oh dear, the new one's quite a bit deeper(back to front dimension)! I somehow managed to manoeuvre it into place, it was a bit like one of those annoying bent metal puzzles from a Christmas cracker.

Seems to work fine now, and I haven't spotted any leaks, so I just wanted to thank you all for your help and encouragement.

Oh, and it seems I was right about the divertor valve, as the CH flow stays nice and cold now when the DHW is being supplied.

John
 

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Sponsored Links
Back
Top