Thorn Boiler - Help!

[malcolm]

My friend with the new house has a Thorn Olympic 38/50b boiler dating from around 1987. It's making boiling noises and while hot water is fine his central heating doesn't work with just one or two of the upstairs radiators working.

The heating thing smacks of a control valve, but I can't find it. Pump seems to hum. Heating guy who came in sucked through his teeth and said you'll need a new boiler mate.

Anyone in the house know anything about these boilers?

 

[runnach]

I'm certainly NO expert, have your friend check the thermostat, maybe requires a blow out, or replaced, ok there are many other factors, I over heard something similar from our gas guys at work, old boiler, water fine, heat side not so fine, turned out it was the stat in this case.....worth checking?

 

[brightspark]

if a few of the upstairs are working there getting feed of gravity. the pump might be knacked u dont say if its a gravity system or a y plan with 3 port valve. or an s plan with 2 zone valves ? it isnt the boiler if its getting water heated

 

[the snooper]

if the boiler is making boiling noises the the water flow through the boiler is way to slow could be central heating pump pumping slowly the reason for only 2 radiators working not enough flow to reach the rest

 

[malcolm]

Not sure of the technicalities of heating systems. The system has a gas heater boiler thing in the kitchen, one of those heat exchanger tanks in the airing cupboard upstairs, and two hot water tanks in the loft - a big one and a little one. True enough if the valve is closed the upstairs rads wouldn't be getting local heat.

 

[brightspark]

old boilers make a kettling noise due to build up of crap in the heat exchanger u can get scalex to disolve it. add to system but that isnt your problem

 

[brightspark]

Not sure of the technicalities of heating systems. The system has a gas heater boiler thing in the kitchen, one of those heat exchanger tanks in the airing cupboard upstairs, and two hot water tanks in the loft - a big one and a little one. True enough if the valve is closed the upstairs rads wouldn't be getting local heat.

indirect cylinder
?? there either gravity systems or fully pumped

 

[the snooper]

on those types of system ive seen the divertor valve is somewhere near the hot water tank and i have known them to stick but when they have they seem to heat both water and radiators.

one other thought are both the valves on the radiators open or is there an isolation valve near the divertor valve that has been closed as that would cause the same problem

 

[brightspark]

if its a fully pumped system there will be a thermostat strapped to the hot water cylinder on the side if not its gravity . allso if theres 4 pipes from boiler its gravity if only 2 its fully pumped

 

[malcolm]

The switch to change from heating to water only is on the boiler, and I can't see any wires that might go to the divertor valve I can't find.

My friend says it's a gravity system (according to the plumber). It is possible to make out 4 pipes under the pollyfiller. Two in a corner at the back and the other two from the side with the pump on one of them.

BTW - the pump makes an encouraging light vibration like the pump at home suggesting it is doing something. Whether that means it's working is probably another matter.

 

[brightspark]

its more than likely its the pump thats faulty if its humming there generaly 3 speed with a switch on it /try turning it up it should spin the water on full speed. feel the circulation pipes at varoius points to see if water is flowing ok past the pump to manfolds if microbore .or 15mm pipes to rads

 

[brightspark]

this might sound sh ,.,.,./t but tap the pump with a hammer if its stuck it might free it. but if its been left 2 long running stuck it burns the windings out

 

[hunter27]

You can have a fully pumped system with 4 water pipes from boiler as sometimes the expansions and cold feed are run back to the boiler.

Look at the side of your H/W cylinder and where the pipes enter at high and low level from the boiler (not in the middle of the cylinder crown) if the top pipe has a tee in it with a pipe leading up to the feed & expansion tank it should be a gravity H/W system

Does sound like the pump though, it probably has a large chrome or plastic screw or possibly a plastic knurled nut in the middle of the head if its a screw place a rag below the pump remove the screw ( a little water will drip out) and using a small slotted screw driver inside the screw hole rotate the rotor and see if it is spinning when turned on.
If it it a plastic knurled nut unscrew it and pull it out a little it should engage on the rotor and spin when turned on.

Very rare but I have come across pumps where the impeller has detached itself from the spindle and is just free wheeling.
Pete

 

[pedrobedro]

Not sure of the technicalities of heating systems. The system has a gas heater boiler thing in the kitchen, one of those heat exchanger tanks in the airing cupboard upstairs, and two hot water tanks in the loft - a big one and a little one. True enough if the valve is closed the upstairs rads wouldn't be getting local heat.

Are they hot water tanks or header tanks ? One for heating radiators and big one for hot water. The copper storage tank in the airing cupboard holds your hot water for the bath etc. If the water is getting hot it's air stopping the radiators from getting warm, is there a vent pipe to the small tank in the loft and check the ball valve on it is filling it with water ?

 

[GrahamGKD]

For what its worth - my mum's boiler was making a kettling noise a while ago. Her plumber was on about various bits of the system needing re-plumbing. The technical help desk for the boiler said to check the circulation so I took the pump to bits. The pump was working but was furred up and clearly not working to full capacity. We replaced the pump and it has been fine since. Her pump was making the usual humming noise - there was no indication it was below par until I the impeller was exposed.

Hope this helps,

Graham.

 

[Mig-Phil]

In my experience, if the hot water is fine but the rads downstairs are not working then it is the divertor valve. The divertor valve has three positions, hot water, heating or both and it can get stuck cuasing the problems described.

It could be the pump but normally there are a few loud bangs and the boiler turns off.

There is another possibility and that is there is a lot of air in the system which is stopping the water from flowing. In any case it would be worth bleeding each rad and sometimes there is a air bleed valve near the hot water tank in the airing cubboard.

Does the boiler run constantly or does it go on and off for short periods? If it does and there is a minimum/maximun switch on the boiler try setting it to minimim and see if that makes any difference.

 

[malcolm]

Thanks for all the advice there. Does sound like pump or air in the system, or other circulation issue. My friend has just called to say a second plumber might be able to pop around in the afternoon.

So no point me trying to fix it, but armed with the info I should be able to steer the plumber away from the "you need a new boiler mate" routine and get him to just fix it. Will let you know what happens.

 

[tigler]

If the pump had stopped working , was pumping very slowly or the heat exchanger were blocked, more than likely the overheat cutout in the boiler would shut it down. Check the pipe to and from the pump to check if both sides are hot.

 

[rtcosic]

1987?
If Scalex or similar hasn't been used the entire system could be full of corrosion product and general debris. A drain and good long flush may help as well.

 

[malcolm]

Plumber didn't turn up today so I'm going to have a crack at it. Given the house was previously owned by the world's worst DIYer (nothing works) I'll try bleeding all the radiators as an easy first step. If that doesn't work a new pump is worth a shot. I need one for the TIG watercooler anyway. If that gets the radiators working a good flush and corrosion stuff ought to have it good for a while.