Feed & Expansion Tank Q

[pte440]

Hello All, following on from my post about boilers...

Our system has been pumping over for quite a while, most rads are sludged! I have identified the problem as the pump is sucking water from the F&E tank, the cold feed to the system joins about 12" from the pump. It is a single pipe system, rated about 250kw, the vent pipe is on the flow from boiler.
We have fitted a speed controller on the pump, but that made no difference,
I have thought about converting it to a sealed system, but given the age of it (75yrs) i thought best not too.
Any ideas how to stop this problem?
Thank you as always
Peter

 

[keego]

It would take a brave man to convert that to a sealed system. Pressurizing a system like that could pop a few joints, if it was me I would rip the lot out & renew the whole system.

 

[Onetap]

I'd look at changing the system from (making some assumptions here) one pump serving the entire system to a primary/secondary system with;

i) a primary pump serving the distribution system and;

ii) a secondary pump dealing with flow from the primary system, through the boiler and back into the primary system.

The boilers cold feed and open vent connections are probably (more assumptions) on the return and flow connections respectively. The (single?) pump has to deliver the flow rate through the distribution system at the pressure differential/head required by the least-favoured circuit, so it will have a high differential pressure. A primary pump would only have to deal with the flow through the boiler, a big old boiler like that would have a very small hydraulic resistance; so the boiler/secondary pump could have a small head, small pressure differential across cold feed and open vent connections and much reduced likelihood of pumping over.

You need to stop the pumping over as a matter of very high priority, it will wreck the entire system.

 

[Axel]

Did they really have heating systems like that in 1935?

 

[Whitespirit66]

Probably referring to the rad circuit.

 

[Onetap]

Did they really have heating systems like that in 1935?

It probably started off as a gravity circulation coal-fired system. The boiler might be a Beeston (Senior?)???

 

[pte440]

yes, it was a coal fired gravity system, but (apparently) in the late '70s the boiler was converted to oil fired and a hot air blower installed, using the hot water. I guess a pump was added at this time.

 

[Onetap]

, the cold feed to the system joins about 12" from the pump. Any ideas how to stop this problem?
Thank you as always
Peter

Now I think of it, the arrangement is probably cold feed connection, pump, boiler return connection, boiler flow connection, open vent.

Re arranging it (so that the cold feed is on the return just before the boiler and the open vent on the flow just after the boiler) would probably be adequate to stop the pumping over.