Rayburn overheating (again)

[Burnerman]

Update 12,055.....
When I switched the boiler off, both MV's closed too.
The pump kept on running, but it was noisy - obviously pumping very hot water around the bypass. Opening the bypass valve fully quietens things again but I've turned it back to where I had it before.
So - I've manually opened the CH MV and the pump is quiet, presumably dissapating heat through the rads until the boiler overrun stat tells it to stop.
Is this a stupid thing to do? Will it damage the valve? It seems to be the only way that I can control this thing - without putting an extra rad in the loft as a bypass!
John

 

[ajstoneservices]

Yes no problem.
A spring loaded by-pass valve across the HW cylinder motorized valve which dissipated enough heat to avoid the cut out.

Norcon,

Make and model number please.

 

[Norcon]

I don't remember tbh. It was a few years ago.
A by-pass is just a tap with a spring so any model should work.

 

[Burnerman]

Norcon, would you be good enough to comment on my last post, please?
John

 

[Norcon]

What you outline above is pretty much what the Stanley I mentioned was doing. And as stated the by-pass solved the problem.
Opening the MV won't damage it but I would have thought it will fire up the second burner on the end switch.

 

[ajstoneservices]

I don't remember tbh. It was a few years ago.
A by-pass is just a tap with a spring so any model should work.

Thanks anyway. I'm trying to find a high temperature version to do something similar without any luck so far.

BM, sorry for jumping into your thread.

 

[Burnerman]

OK mate and thanks for that....so at the moment, the rads are all at approx the same higher temp - thats a first - and when the boiler time switches off, the open MV allows the hot water to dissipate into the rads and the overheat reset stays off.
I think - if it works ok tomorrow - I'll leave it at that and see if alls well. I'll tackle the hot water only issue in the summer - should it arrive!
Thanks to all...I'll finally post back tomorrow evening.
Cheers John

 

[Norcon]

I don't remember tbh. It was a few years ago.
A by-pass is just a tap with a spring so any model should work.

Thanks anyway. I'm trying to find a high temperature version to do something similar without any luck so far.

BM, sorry for jumping into your thread.

The Danfoss By-passes are rated at max 100c and the AVDO 120C for short periods.
But I'm guessing this is for solar so you need a higher rated one.

 

[ajstoneservices]

Yes, simple heat dump circuit. I cant find one rated more than 120c.

 

[oilhead]

Is the Rayburn wired up as it should be? The supply to the pump should come from the Rayburn wiring centre and not the motorised valves.
From your description, it seems as though it may never have been wired properly.

Thats the million dollar question, mate....
The main wiring centre is in the Rayburn. From memory, there is a supply to the pump, to which the pump MUST be connected ( Rayburn's capitals), a live, neutral and earth ( from a fused spur), then CH on, DHW on, and DHW off, which is only used if you are installing a frost stat, and a switched live which comes back in from your valve(s). Sounds like someone has wired your pump to the end switch in the valve. The Rayburn wiring centre is either in the burner compartment, on the left, or under the lower oven and is well marked.

 

[oilhead]

Should have added, the switch on the front of the Rayburn looks after water or heating and water. You only get heating on its own if the cylinder is up to temperature, and your programmer on the appliance controls either the boiler or the cooker. If someone has used a non Rayburn replacement, then the water switch will actually control the cooker.

 

[Norcon]

Yes, simple heat dump circuit. I cant find one rated more than 120c.

Why not fit one of these or two in series?
http://tiny.cc/ERvpm or this one http://tiny.cc/uBqQ2

 

[ajstoneservices]

Now that's a good and possibly better idea, I'll give it a try.

Thanks

 

[rayburner]

Hello Experts
I have a Rayburn 480k oil burner and after I had the tank, pump and pipes moved due to house extension work the plumber forgot to hook up the kitchen radiator which was from memory plumbed differently I guess for heat soak.
The problem I now have is that after the boiler has been running for HW or CH the pump over run carries on for ages and is noisy but if I manually open the CH zone valve the pump goes quiet and shuts down quickly due to rapid cooling of the water.
My question is where to plumb in the radiator so it will soak away heat from the overrun automatically without heating up when I just want hot water ?
From vague memory the radiator flow was taken from the return side of the pressure reduction/bypass valve 22mm and the return to the main boiler return 28mm -is this correct and will it do the job ?? Obviously there will be some flow through this circuit when both zone valves are closed and the bypass is working but will the radiator work properly when the central heating is on ?
I thought maybe some device that keeps the CH zone valve open for a set period after shut down would be the best solution
Thanks
Paul

 

[mysteryman]

That's the third thread on bypasses on S Plans today!

The function of pump overrun and a bypass is to dissipate residual heat away from the boiler. There is no point in bypassing it straight back to the boiler. If it is an S Plan layout, there should be a radiator or heated towel rail on lockshield valves fed from the bypass. This will also be heated whenever there is any call for heat from the appliance - which is good for a towel rail. Is that neat, or is it neat?

Another common error, particularly with solid fuel appliances, concerns an external pump overrun thermostat. You use a 3 wire pipe thermostat with the pump connected to the common terminal, the break on rise to the pump supply from your controls, and the make on rise to a permanent live. The overrun 'stat then doesn't back-feed the burner and hold everything on [in the case of an oil or gas burner].