Pumping over into header

Mike2007 · 6 May 2015

I fitted a new condensing oil boiler and the manufacturer states it must be fully pumped. Well their integral pump is on the flow from the boiler and thus it tends to pump over, causing corrosion.
Do you think its system design or could the boiler actually work semi-gravity instead as it can't stay like this

St0rmer66 · 6 May 2015

Combine cold feed and open vent and you're sorted.

45yearsagasman · 6 May 2015

What's semi gravity? If it's pumping over its either system design or a blockage. Either way it needs sorting quickly as if left it will stuff your new boiler. Was it really a DIY install?

Mike2007 · 7 May 2015

St0rmer66 said:
Combine cold feed and open vent and you're sorted.

Really? T both together

St0rmer66 · 7 May 2015

Mike2007 said:
St0rmer66 said:

Combine cold feed and open vent and you're sorted.

Click to expand...

Really? T both together

Yes... Very common. Needs to be in at least 22mm all the way. Either eliminate the open vent pipe completely and have a 22mm cold feed or tee the existing 15mm cold feed into the existing 22mm open vent pipe and cap off the old cold feed lower down (nice to put a manual air vent on it).

simond · 8 May 2015

Some oil boiler manufacturers, such as Worcester Bosch, do not permit combined CF and OV.

You could go for a make up tank and expansion vessel, or a conventional sealed system.

I would look first at how the CF and OV are attached to the pipework , most condensers have a higher flow resistance than an old boiler and a close coupled arrangement is best suited.

If it had a cold feed at the boiler and an OV at the cylinder and you've done an S plan or similar, pumping over is not unlikely. I lose plenty of jobs to other installers who are happy to corrode a customers system to bits by not changing the pipe configuration when doing a new boiler.

This is another example of customers who just see the bottom line price; they will pay many times over if their system blocks up with sludge in the following years, long after the cheque clears. Anyone who has needed powerflushes and has sludgy radiators will know what I mean.

Mike2007 · 8 May 2015

simond said:
Some oil boiler manufacturers, such as Worcester Bosch, do not permit combined CF and OV.

You could go for a make up tank and expansion vessel, or a conventional sealed system.

I would look first at how the CF and OV are attached to the pipework , most condensers have a higher flow resistance than an old boiler and a close coupled arrangement is best suited.

If it had a cold feed at the boiler and an OV at the cylinder and you've done an S plan or similar, pumping over is not unlikely. I lose plenty of jobs to other installers who are happy to corrode a customers system to bits by not changing the pipe configuration when doing a new boiler.

This is another example of customers who just see the bottom line price; they will pay many times over if their system blocks up with sludge in the following years, long after the cheque clears. Anyone who has needed powerflushes and has sludgy radiators will know what I mean.

The other poster said you could seal it but it causes leaks with extra pressure, have you found this problem?

St0rmer66 · 8 May 2015

Semi sealed then?

Use existing header tank, combine cold feed and open vent then put a non-return valve on it. You'll then need a 3bar Pressure Relief Valve and expansion vessel as per a normal sealed system. Advantage is that you don't have mains pressure filling it so less chance of leaks but with all the advantages of a sealed system too.

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Pumping over into header

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