Potterton profile 40 mated to a sealed system

[aquabunny]

I have an old(ish) potterton profile 40 which was origional and have replaced the system with a high pressure sealed system. It all works fine except that the presssure switch keeps tripping out on the boiler starting from cold at 1.2b and after many resets (30mins or so) eventually trips out at 0.6b. Is this boiler suitable ? can the reset be adjusted? Boiler thermal trip works as does the tank/room termostats....providing you are happy to keep pressing the underside reset switch. Anyone got any ideas ?

 

[kevplumb]

if you keep having to press the reset your prob is temp not pressure
temp rises so does pressure if its been running for 30 m pressure should be up not down

 

[ChrisR]

A Profile doesn't have a pressure switch. The one underneath is the reset for the high-limit thermostat.

Could it be air introduced into the system that can't get out, causing the boiler to overheat?

 

[aquabunny]

Thank you...so the little reset swtich is for when the boiler reaches its maximum temperature....not pressure ?...in that case if I lower the tank theromstat temperature (currently set to max)...will this cure the problem ?

 

[kevplumb]

we assume you have fill loop expansion vessel prv etc

 

[aquabunny]

Yep I have the filling loop and expansion vessels ( one for the tank and one for the heating circuit) and the system has been charged/fully bled with no problems in that area...the pump works fine and the 'y' system is brand new and works fine too....just the reset switch keeps tripping....though to be honest it will trip out within 30 mins even from dead cold and the tank is 210ltrs and nowhere near hot....though from repeated resets the water gets to the tank higher temp and the boiler cuts out as it should with or without the reset switch being tripped depending at which point the water temp was prior to reseting last time...ie: The tank cuts out the boiler and fires the boiler as it should...only the blasted reset on the boiler is driving me mad.

 

[kevplumb]

i would think the water aint moving thro fasy enuf how hot is the flow pipe before it trips?

 

[kevplumb]

cecck post"boiler shuts down" sounds like same prob

 

[aquabunny]

Thanks...I'll try the pump on a faster setting...but from the other post...what's a 'bypass' ?...where should I have one ?

 

[kevplumb]

either between the flow and return after the pump or i tend to leave the bathroom rad on two locksheilds

 

[ChrisR]

Yes you should have one but the lack of it won't make your boiler cut out before the HW is hot.

There are 2 thermostats on the boiler - the normal one - knob on the front, and the emergency one underneath. There's another as well but for now,...!

The boiler should be controlled by the normal one.
Who did the modifications - was the system cleaned - then or ever?

 

[kevplumb]

sorry the bypass is there to maintain a minimum flow rate thro the heat exchanger to prevent overheating
which sounds like the problem you have

 

[aquabunny]

Phew..that's ok then...the bathroom radiator is connected directly between the flow and return, after the pump and before the y valve....thank's for your help....I'll see if setting the pump speed higher helps.

 

[DP]

If you have an UVHW cylinder, Y plan by itself is not allowed. This type of cylinder MUST have a two port valve

 

[kevplumb]

why? question not a comment?