C&G question bugging me

[dextrous]

This was asked of a mate of mine in his assessment today,and I'm not sure what the answer is:

Conventional cylinder with system boiler. CH turned off, HW on. Radiators downstairs are cold, but upstairs are warm. What is the most likely reason for this? Three of the options were
Cylinder stat faulty
Boiler stat faulty
Pumping over
He can't remember the fourth, which is a pity since can't see how any of the above could be the fault. Enlighten me

 

[sooey]

It was the fourth.

 

[gas4you]

Probably a dv sticking open

 

[EnLiven]

Absent or faulty anti-gravity valve

 

[gas_man_gaz]

ch/3port valve passing? position of cylinder return connection?

 

[ollski]

S plan, y plan, bypass? presume not gravity with a cylinder stat.

 

[dextrous]

So it was the fourth one after all

 

[ollski]

Probably but if you have a faulty cylinder stat (not satisfying) and a bypass, particularly on an s plan, you could have the same fault.

 

[Onetap]

Numpties.

It's the classic upstairs heating return connected to the HWS return. When the HWS is on, the HWS primary return has an alternative return path, i.e., through the upstairs rads' return, out of the flow, into the downstairs rads' flow, out of the return and then back to the boiler. Sketch it out.

You should join up all the heating returns then connect the HWS primary return. Surely you all know that?

If I had a pound for every time I've seen that one, I'd have £4. I don't have £4 because I charge a little bit more than that.

 

[dextrous]

I'll get back to you on that. In the meantime, if you send a SAE to me, your cheque for £4 will be in the post

 

[swbjackson]

Numpties.

It's the classic upstairs heating return connected to the HWS return. When the HWS is on the HWS primary return has an alternative return path through the upstairs rads' return, out of the flow, into the downstairs rads flow and into the return. Sketch it out. You join up the heating returns then connect the HWS primary return. Surely you all know that?

If I had a pound for every time I've seen that one, I'd have £4. I don't have £4 because I charge a little bit more than that.

You've done well if you've only seen it 4 times. It's the most common rookie trick that I come across. Must come across at least one a month.

 

[bengasman]

Absent or faulty anti-gravity valve

Which answer is that: 1, 2 or 3?

 

[Deleted member 105431]

the term is the "common tee" which means the hw return must be last tee before boiler.