Potterton C80 overheat CH

[steve28]

Hi,

I have a Pott C80 thats developed what looks like an overheat problem.

The CH fires up and the rads all get hot. However the temp rises and the pressure goes thru the roof until the pressure valve gives and all the water drains out the boiler. That shuts it down until its filled again manually.

The problem is related (I think) to the CH overheat sensor 10/18735 or the Boiler overheat sensor 10/18761.

Can someone confirm that the Boiler sensor is NC and tell me what temp it goes (should go) open at?
Also the CH sensor I believe this should have a cool temp resistance of between 8k to 15k, going open once its value is reached.(?)

The latter is very cheap so I will probably just replace it as a step in diagnosis, but the boiler stat is expensive to just swap incase so I want to try and test it first. Is there an easy way to check this is working ?

Another question, has anyone considered using the stats sold by Radio spares? The seem to be the same thing and are very cheap.
(www.rswww.com)

Any help or advice as ever appreciated.

Steve

 

[B.O.B DOLE]

well i think it is the expansion vessel vessel

 

[steve28]

All

Since I posted, Ive been trolling the site looking for inspiration and it appears that a possible reason for pressure increase Im seeing could also be caused by faulty or blocked pressure vessel.

The temp sensor has a warm resistance of 3-4k and its rising as the system cools. The overheat boiler stat is a dead short (NC). SO I think this proves there OK and not the primary cause at least of my problem.

So, whilst Im anxious to see what you guys advise, I,m going to revisit the system and check the vessel connections are not blocked.

One thing I omitted to mention in my first post was that one RAD near the end of the system was sludged up. Its been removed, but the presence of sludge is a reason for concern over the working of the vessel.

 

[steve28]

BOB Dole

I hope great minds think alike.

I did check and theres no water in the vessel so its not busted, and I did infact pump it up a bit so there is def pressure in it, but I have to check for a blocked(sludged up) connection.

I'll do that when I get home tonight.

cheers

 

[B.O.B DOLE]

All

Since I posted, Ive been trolling the site looking for inspiration and it appears that a possible reason for pressure increase Im seeing could also be caused by faulty or blocked pressure vessel.

The temp sensor has a warm resistance of 3-4k and its rising as the system cools. The overheat boiler stat is a dead short (NC). SO I think this proves there OK and not the primary cause at least of my problem.

So, whilst Im anxious to see what you guys advise, I,m going to revisit the system and check the vessel connections are not blocked.

One thing I omitted to mention in my first post was that one RAD near the end of the system was sludged up. Its been removed, but the presence of sludge is a reason for concern over the working of the vessel.

try checking the presure is ok

 

[steve28]

I did check and theres no water in the vessel so its not busted, and I did infact pump it up a bit so there is def pressure in it, but I have to check for a blocked(sludged up) connection.




I will take a Tyre pressure valve and get a reading. 10-11psi?

If its not that, I,m back on the overheat sensor I guess.