CH system boiling over into header tank. help please

[jonathan63]

We dont use the CH much (its oil fired BTW). In fact it hasnt been on for over 12 months.
I have just drained down the system to fit a new rad on one of the down stairs room (its the lower rad in the house).
All connected now but when i fired up the boiler some of the down stairs rads (new one included) dont heat up and the CH water boils over into the header tank.

Any ideas? it was fine last time it was fired up.

 

[Armo74]

Did you bleed the rads?
If so did water come out?
Did you touch any of the other valves?
Can you explain more about the boiling issue.
Also a bit more info on the system.

 

[doitall]

Did you clean the header tank out before you drained.

IS the boiler banging went it's boiling over.

 

[jonathan63]

thanks for the responses guys.
I bled all the rads until water came out.
All the valves are open.
The system is a simple system I think. We have an Unidare Jetmatic oil fired boiler downstairs (quite cheap through The Farmers guardian about 15 years ago) and little used because of the price of oil. The Grundfos pump is upstairs and the header tank above that in the loft.
I didnt clean the HT before draining down.
I dont know if the boiler was banging when it was boiling over into teh HT; I was up the ladder into the loft as soon as i heard something going on and then dashed to turn the boiler off.

I gave it a few hours (bled all the rads etc again) and fired it up again. It didnt boil over this time.

Could it just have been the Grundfos pump had stuck and then started working again??

Thannks for your help.

 

[Agile]

If some rads downstairs were working then the pump would have been OK.

Just sounds as you had an airlock.

Way to clear that is to run heating into each rad in turn on its own. The extra pump flow will then usually force any air through the system to the vent.

But should I give away these trade secrets?

Tony

 

[doitall]

Not buying into that Tony.

Most likely is a stuck pump, especially if it hasn't been used for a white

 

[jonathan63]

Not buying into that Tony.

Most likely is a stuck pump, especially if it hasn't been used for a white

How very dare you. My pump is not a racist...

Seriously though, I think it was probably a bit of both....sticking pump and air locks from draining down. The house is quite old with downstairs internal walls 2' thick so the downstairs pipe work from 1 side of the house to the other has to travel upstairs, cross from one side to the other and down to the other side of the house. Not ideal.

 

[loafer]

Hmmm! some rads may be working ish... Are they banging hot? If not may just be heating on conduction, not circulation. PUMP!? Possible. If steam is turning the area of your f&e tank into a sauna.... may be pump. Careful it doesn't melt your float cos if it melts your tank will overflow! Just hope that your warning/overflow pipe is solvent welded and secure!!!! And them pesky blighters who put freebie additional rock wool loft insulation in didn't wreck the o/f pipe!!!

 

[jonathan63]

Thanks for the heads up on the overflow and insulation installers. Ill check that tomorrow.

cheers