rayburn aga banging noises

[bradchop]

Hi guys hope someone can be of help. i have a customer who has a rayburn aga gas run which bangs about every now and then. the system is overheating as the flow pipe is getting dangerously hot!!! at first i changed the pump as the old one was playing up. i am changing the 2 port valve for the hot water (28mm) in a couple of days as it wasnt opening or closing. the trouble with this is that im only solving half of the problem. when i change the 2 port valve it will only stop the cylinder from over heating. after the rayburn will still overheat. the customer rang me up earlier and said a few rads upstairs are getting hot but the ones downstairs and a few upstairs arent.

there is a pipe stat a few feet away from the boiler (on the flow pipe) but it doesnt seem to operate anything at all. pump is on the return pipe, 2 port valve close to the cylinder, no port for the central heating, room stat for central heating. when the boiler is all fired up the only thing that slowly closes the gas valve down is manually operating the 2 port valve??

has anyone else had this problemo??

thanks guys

 

[Roger Welton]

What model cooker is it

 

[diamondgas]

Don't like them, never liked them! An absolute rip off!!! "Here misses have one of these, make you look all countrified and all!!" £10,000 later the house is sweltering in the summer and you still don't know how to manage more than 2 pans at a time!!! :lol:

Saying that though Is the hot water gravity? Coz if the zone valve at the cylinder shuts off you want to hope the pump comes on to dissipate the heat in the Aga That'll be via some stat or other I'd imagine?:38:

 

[tamz]

The pipe stat should be wired to bring the pump on if it gets past the set temperature. The motorised valve should be a motor closed and wire it as a C plan.

 

[bradchop]

it is a royal g33 gas

 

[bradchop]

the hot water is indeed gravity. i have renewed the high limit stat on the flow pipework but still to no avail. mystery this one :juggle:

 

[diamondgas]

Does the pump run at all when just heating the hot water bradchop? The pipe stat you mentioned is usually the item that brings the pump on when the flow gets to a certain temp

 

[bradchop]

the pump only comes on when the heating is called for. if hot water is called for via the cylinder stat then the pump remains off. the stat on the flow pipe does nowt. ive renewed it and still it doesnt seem like its needed. very strange. when i turned off the 2 port valve on the hot water side the boiler gas valve began to shut down as it should, so its sensing something

 

[diamondgas]

My understanding is that the pump should come on to dissipate the heat generated. This is usually done via an external pipe stat like the one you're describing! The stat will override any of the controls. It sounds like it's been disconnected?

 

[bradchop]

i think you may be right on that one. im hoping that when i change the 2 port zone valve that should do the trick. im assuming that as it didnt shut off the boiler was assuming that it needed more heat..hence the banging upstairs and downstairs?? possibility!!?? once ive fitted it i will let you know the outcome. thanks for your help :boat: fingers crossed

 

[diamondgas]

You're welcome It's been a long time since I've messed with a gas aga to be honest bradchop... You'd have thought the boiler stat on them would stop the water overheating but i guess the must store a lot of latent heat?

 

[tamz]

I googled the aga to see the connections to it. It is an old one (suitable for towns gas which went out just before i started working), before the days of motorised valves and the like. Even when it is set for just the oven burner it still produces up to 33,000btu pushing heat to the system which will heat a cylinder of water in a short time (hence the pipe stat fitted to dissipate the heat). Your problem is a wiring one and the motorised valve is making it worse as when it closes there is nowhere for the heat to go. The Aga is not really designed for a motorised valve as it needs a clear route to somewhere even when the heating burner is off.

The pipe stat should be wired off a permanent live and go to the pump live (in beside the room stat). Fit the stat on the HW flow and set it for around 80 - 85 deg. When / if the flow pipe gets above that temp the pump will push the heat to the rads and switch off again when it drops (a few minutes later). It may take a bit playing around to get the pipe stat set properly.

Forget the earlier bit about the motor closed valve, i was thinking solid fuel aga.

The heating side should be wired as a C plan and add in the pipe stat as above.
Some of the upstairs rads may be working on gravity circulation due to how it has been piped which is easy fixed by altering the CH flow to dip .

Here are the MI's in case you have trouble finding them. They also include a bit on how to best operate it.

[DLMURL]http://www.rayburn-web.co.uk/Prodin/Rayburn%20obsolete%20cookers/Rayburn%20G33/Rayburn%20G33.pdf[/DLMURL]

 

[diamondgas]

Mutts Nutts Tamz *bowz* .... Great post

 

[tamz]

I just edited it diamond because i missed a bit :wink:

 

[bradchop]

update. first of all thanks for all your replies. top notch!! i have had to redo the vent pipe as it went from a 28mm pipe to a measly 15mm pipe. also the vent was after the hot water cylinder tee so i moved it to before it. also i put the 2 port valve on the flow before the hot water cylinder so the cylinder wouldnt take in any heat at all. atleast this way the heat will be vented properly. alls thats left to do is wire in the 5 wire valve - which the electrician is going to do as i dont know how to convert a 4 wire to a 5 wire!! that is happening 2moro so hopefully it will all work after that - fingers doubley crossed!! :bucktooth: