Ravenheat Diaphragm

[jaymi]

My Ravenheat WhiteStar LS100T combi boiler has been having a problem with the hot water. CH is fine. Basically unless you have the taps on pretty much full blast the boiler does not fire up. The problem has been gradually getting worse as in the water needs to be put on faster and faster in order to get the boiler to fire.

Having done quite a bit of searching on this forum I am putting this down to the diverter valve.

However, it seems I could just buy a new Diaphragm and replace that, but from what I have read the spindle on the Ravenheats are shorter than the standard ones that come in a repair kit.

Questions:

1. Is it possible to buy a diaphragm for a ravenheat that comes with the correct spindle size and if so where from? I have read that you can swap the spindles but it is fiddly.

2. The boiler has excellent access all round so I am wondering if I will actually need to remove the whole diverter valve to do this job?

3. If I will need to remove the whole valve does anyone know what size washers I need to get for this model for when I am refitting?

Thanks very much for your help.

Jamie

 

[Agile]

I would always replace the entire diverter valve for my customers.

You can get the correct diaphragm assembly if you order it as a manufacturer's genuine spare part.

It is possible to change over the common type to the existing spindle but thats fiddly though.

The switch can also fail too but in your case I think that its ok.

Tony

 

[nickso]

the ravenheat should have the long spindle. thats the same diaphragm kit as a worcester would use.

can't remember the part number off hand.

no need to replace diverter unless it's leaking or passing.

 

[oilhead]

Little star and white star use the standard diaphragm, but a shorter spindle and it is totally contained within the valve, so locating it can be tricky. To save disassembling the diaphragm assembly you can cut the new spindle.
If access is good, then removing the pump allows access to the top of the valve to undo the screws.
Try the operation of the switch before you do anything else. It just unclips from the valve body and should be a positive click.

 

[jaymi]

Thanks guys. I wondered about cutting the spindle to the right size.

So I will try the switch first, if that is operational and the diaphragm simply isn't pushing it unless the water is running really fast then I'll try only replacing the diaphragm to begin with (as it is a good be cheaper than the whole valve).

I'll let you know how I go.

Thanks again for your help.

 

[jaymi]

Ok so I checked the black switch on top of the diverter valve and it was fine. I unclipped it and in the unpressed position the boiler kicks in and when I pushed it the boiler stopped. It had a good positive click.

With this in mind I decided to try a little experiment. I turned a hot tap (if you can call it that) on to a medium flow, let go of the switch and let the boiler start. CH was switched off. The tap did become hot, but no where near as hot as it normally would have done before this problem started, however, the boiler did run continuously, so the diaphragm not pushing the switch except when the tap is on full blast is definitely one issue. As the boiler did not stop running I could not understand how the tap was not getting very hot, until I felt the CH feed pipe and that was hot, and the first radiator (very near the boiler) was also starting to get warm. However, CH was most definitely in the off position.

So clearly some of the boilers heating power was being used for the CH even though it was off. I am wondering if this could however, still be related to the diaphragm? Does the diaphragm only turn the switch on and off or does it also have a role in analyzing the flow rate and diverting heating power as necessary? Or do you just think I need a whole new diverter valve?

Any ideas greatly appreciated.

Thanks again,

Jamie

 

[MJN]

So clearly some of the boilers heating power was being used for the CH even though it was off. I am wondering if this could however, still be related to the diaphragm? Does the diaphragm only turn the switch on and off or does it also have a role in analyzing the flow rate and diverting heating power as necessary?

Absolutely. The diaphragm's role is not simply to detect water flow - a simple flowswitch could do that - but also to divert water around the secondary (DHW) circuit rather than the primary (CH). Given that the diaphragm is failing to shift sufficiently it is not moving the diverter enough thus the CH pipes also getting warm (at the expense of the DHW outlet).

Mathew

 

[needyahelp]

For anyone else viewing this, if you've replaced the diverter and find the problem still isn't fixed eg dhw still not as hot but radiator/s then try descaling the secondary heat exchanger. In the ravenheat I have it is quite difficult to get to but was well worth the hassle, once I got it out I placed it in a boiling hot water bath (not allowing the bath water to get into the exchanger) and then filled the exchanger with non corrosive kettle descaler. The amount of crap that came out, with vigorous shakin to help it out, clearly indicated it was pretty blocked. Replaced the descaler a couple of times until crap stopped coming out, rinced well and then refitted. Job done. Oh and its worth emptying the system (flush it if possible) and adding system descaler (one you can leave in) to help reoccurrence.