Changed radiator now F&E Tank is overflowing

[JPOxford]

Hi there,

I had to remove and drain a towel radiator a few weeks ago as both valves were leaking and needed replacing. I bunged the system rather than draining it because it's a big house and the refill process takes hours. The water that drained from the radiator contained some black sludge particles but it wasn't too bad.

The valve replacement went smoothly, the radiator refilled and everything seemed fine...

Except that since this operation, the overflow pipe from the F&E tank has been pouring out water when the heating comes on. It gushes for a short time then stops. There is no continuous drip.

I've done some research and it suggests that a blockage somewhere may cause a release of pressure into the F&E tank. The whole system was drained twice last year and this didn't happen so it feels unlikely that a blockage could have occurred in such a short time, plus the water in the rad wasn't too bad. I've bled the radiators so I'm assuming it's not an airlock.

Can anyone suggest the likely culprit here? Any advice appreciated.

 

[Johntheo5]

Gas or oil boiler/
Internal or external circ pump?
If external, post make/model/mode/setting or/and a post of any LEDs when running.

 

[JPOxford]

Thanks for the response!

Oil boiler, Worcester Bosch, 4 years old, regularly serviced. Last serviced end of January. Internal circulation pump located in the airing cupboard, also changed 4 years ago.

No adjustments made to anything else, other than changing the valves and draining/refilling the rad.

 

[Johntheo5]

And the pump details ?

 

[Agile]

When cold what is the depth of water in the header tank?

Only needs to be about 100 mm.

But when hot expansion increases that to about 200mm.

 

[JPOxford]

And the pump details ?

Grundfos UPS3 15-50/65. Three LEDs, when firing the I is green, II and III are amber.

 

[JPOxford]

When cold what is the depth of water in the header tank?

Only needs to be about 100 mm.

But when hot expansion increases that to about 200mm.

My job for tomorrow is to go into the loft and investigate the depth. I wondered if I could have somehow knocked the ballcock when putting in the bung but there's no constant drip, just a spurt when the heating comes on. I will check and lower the level if it's too high.

I've just put the heating on to see how long it takes for the water to come out of the overflow. 30 mins and nothing yet.

 

[JPOxford]

The heating was on for one hour before the water came out. There are 14 rads and it's a fairly big place so that feels to me like it would be down to the water level being too high and the expansion reaching a critical point and driving the level above the overflow.

But just guessing until I go up and look in the tank.

 

[Johntheo5]

Grundfos UPS3 15-50/65. Three LEDs, when firing the I is green, II and III are amber.

Under really no circumstances should you require that UPS3, a giant of a pump, on its max setting of CC3, which, in effect is a constant head of 6.4M up to over 19.0LPM, I'm surprised you're not getting even more carry over and air ingress, CC1, at over 4M should be adequate, one green, if not, CC2 should definitely do the job, over 5M, one green followed by one yellow, suggest trying those settngs, the lowest one first, CC1, if not adequate try the second, CC2.

(Just check again that its not set to PP2, one green, one yellow, one space, then another yellow)

 

[Johntheo5]

The heating was on for one hour before the water came out. There are 14 rads and it's a fairly big place so that feels to me like it would be down to the water level being too high and the expansion reaching a critical point and driving the level above the overflow.

But just guessing until I go up and look in the tank.

Assuming a max of 120L rads+system, the max expansion vol will be 2.5L when fully hot, my 30L F&E cistern, LxBxH, 381mmx254mmx305mm will rise by 10.4mm/liter so 2.5L will cause a rise of 26mm, say just over a inch, not a lot, depends obviously on the cistern dimensions, measure your own.

 

[JPOxford]

Under really no circumstances should you require that UPS3, a giant of a pump, on its max setting of CC3, which, in effect is a constant head of 6.4M up to over 19.0LPM, I'm surprised you're not getting even more carry over and air ingress, CC1, at over 4M should be adequate, one green, if not, CC2 should definitely do the job, over 5M, one green followed by one yellow, suggest trying those settngs, the lowest one first, CC1, if not adequate try the second, CC2.

(Just check again that its not set to PP2, one green, one yellow, one space, then another yellow)

View attachment 408911





View attachment 408909

Ok, I will adjust the setting, thank you for that useful information. TBH the installer messed up a few things so no huge surprise if the configuration wasn't right.

It is not set to PP2 btw, it looks like PP1 from the diagram, green space space yellow.

Really appreciate you looking at this.

 

[Johntheo5]

You said in post #6......"Three LEDs, when firing the I is green, II and III are amber." If it is Green space space yellow then I think it should be flashing, I think all the PP & CP settings have flashing LEDs but maybe thats only while configurating it, its a long time now since I set a UPS3 up.
If it is PP1 then it certainly won't cause any problems as the head will be less than 1.5M but very doubtful if that will give sufficient circulation through 14 rads, so check it out again. If its green space space space amber then thats CP1 which shouldn't cause any problems at a constant 3.0M and will give reasonable circulation.

 

[JPOxford]

You said in post #6......"Three LEDs, when firing the I is green, II and III are amber." If it is Green space space yellow then I think it should be flashing, I think all the PP & CP settings have flashing LEDs but maybe thats only while configurating it, its a long time now since I set a UPS3 up.
If it is PP1 then it certainly won't cause any problems as the head will be less than 1.5M but very doubtful if that will give sufficient circulation through 14 rads, so check it out again. If its green space space space amber then thats CP1 which shouldn't cause any problems at a constant 3.0M and will give reasonable circulation.


View attachment 408952

None of the LEDs flash, they are constantly on.

I checked and it is definitely PP1. The house felt a little chilly this morning. I have increased the pump setting from I to II and will see how that feels when the heating comes back on later. At PP1, should II be sufficient or should it be set back to III?

I will also look at the tank levels today.