Boiler is still pumping over

[doitall]

Our system is not fully pumped but we do have a pump (just for the CH?). Will we, should we, have these motorised valves do you suppose?

Yes she did

 

[Agile]

[At the moment, none of the assumptions that anyone has made here is definitely wrong (except that you were a "he"), but they won't all turn out to be correct.

I have not assumed that she was a he!

An old boss once told me NEVER to assume anything and that was very good advice. It always annoyed him that I was always right even when I could not prove it. He was totally right though that the files should have contained the supporting documents to correlate any actions that I had taken.

When dealing with heating repairs I also have to keep an open mind as to the cause of any malfunction.

In this case she needs a heating engineer rather than a plumber because she is only posting here because the plumber is clearly unable to understand or solve the problem.

Tony

 

[Softus]

Our system is not fully pumped but we do have a pump (just for the CH?). Will we, should we, have these motorised valves do you suppose?

Yes she did

Yup - you got me. I failed to read that part properly, and I apologise unconditionally.
______________________

When dealing with heating repairs I also have to keep an open mind as to the cause of any malfunction.

An open mind?! Unless the OP claims to be short of funds, of course. Or they have an expensive car, or they make a spelling mistake.

In this case she needs a heating engineer rather than a plumber...

Would a rose by any other name still smell as sweet?

...because she is only posting here because the plumber is clearly unable to understand or solve the problem.

Assuming that she's telling the truth and assuming that her interpretation of the plumber's actions and words is correct.

 

[jamesn6]

One last thing. We can only have CH if we have HW so I think that this might mean we don thave these motorised valves.

Re the pipes going into and out of the radiators the wrong way - could this also mean that the pipes are going into and out of the boiler the wrong way - although they go into and out of the cylinder correctly.

Oh and by the way I now have a towel radiator coming off the hot water system by the cylinder cupboard but the pumping over was happening before this was fitted.

 

[Space cat]

This system used to work until the boiler was changed. You can have a motorized valve in a gravity circuit. It's normal to put one in the return pipe from the cylinder coil to close this circuit off when the cylinder is up to temperature. If you don't do this your cylinder will heat up to the same temperature as your radiators, ie b****y hot! Jamesn6, do you have a thermostat on the side of your cylinder? It will be low down.

And now, with due respect to all the comments about guesswork, here's my best guess: The boiler is in backwards. It isn't just the radiator pipes that are the wrong way round; the vent pipe is connected to the bottom of the boiler and the cylinder return pipe, complete with motorized valve, is at the top.

I believe this will give the symptoms as described. Air can escape from the boiler whenever the valve is open, which is quite often. The heating circuit works normally. The hot water circuit works normally when the valve is open. When the heating goes off and the valve is shut you are left with a hot boiler. The only escape for steam is out through the bottom of the boiler and up the feed/expansion pipe.

But that's just a guess ---

PS: Does the boiler always stay on after the pump goes off? It should switch off unless there is a demand for hot water. Maybe it's wired up wrong too.

Edit:

We can only have CH if we have HW

You beat me to the post! Could you have CH on its own before the boiler change?

 

[jamesn6]

Thanks.

I havent seen a cylinder thermostat because there is no electricity in the cylinder cupboard but I am sure that the hot water doesnt get as hot as the radiators.

Will this motorised valve be by the boiler?

I wouldnt be at all surprised if the boiler is fitted incorrectly but the hot water does go into the cylinder correctly. Would this still be the case?

Why the chap who services the boiler every year didnt see this I do not know.

 

[jamesn6]

Oh, and I am certain that the boiler does switch off.

 

[doitall]

Please ignor the post by spacecat, he/she obviously hasn't a clue.

A drawing of the pipework or photo's of the boiler and cylinder pipework will help

 

[Space cat]

When the CH kicks in the pipe going into the cylinder cools down. This is still cool when the CH clicks off. The boiler fires up and gets very very hot then there is an almight explosion and water (?) shoots up the expansion pipe and out of the overflow.

There are two pipes going into the cylinder. Are you talking about the top one - which tees off the vent pipe - or the bottom one?

I am sure that the hot water doesnt get as hot as the radiators.

It's difficult to see how this can work without a valve unless your heating is rarely on and you use the hot water a lot. The valve, if it exists, can be anywhere in the return pipe. That's the one from the bottom of the cylinder to the bottom of the boiler. While you're at it, look for a pipe that runs from the top of the boiler unobstructed by any valve all the way to the vent above the tank. It can run sideways or upwards but never down.

You say the boiler fires up and gets very hot AFTER the heating has switched off. This shouldn't happen unless there is also a demand for hot water.

 

[doitall]

Both the pipes come out of the top of the boiler spacecat.

The cold feed and vent should run back to the boiler and not be connected at the cylinder.

 

[gas4you]

I've come across many a gravity system where the vent is off the primary flow and the cold feed is teed into the primary return at the cylinder.

OP if you turn your ch on from cold which pipe gets hot first off the boiler?

What pipe off the boiler is the pump connected to?

Also sounds asthough something is causing a massive overheat, which if the boiler stat is working correctly, shouldn't happen.

 

[Agile]

Its was the usual method in DIA's days to have the vent continuing up to the loft above the flow to the cylinder coil and the cold feed down to the return to the boiler or on many boilers to a tapping on the boiler itself.

The pressure loss across a large cast iron heat exchanger was very low and irrelevant.

I have never seen a motor valve on a gravity heating circuit before. I dont think that space fellow has seen many heating installations.

The whole concept was the boiler temperature setting controlled the hot water temperature.

Tony

 

[gas4you]

A zone valve on the gravity primary return is very common. Is this not called a 'W' plan?

This then enabled the heating to be used without the HW getting too hot.

 

[chr15]

I have never seen a motor valve on a gravity heating circuit before.

Tony

You definately can have a motorised valve on a gravity circuit tony-working along with a cylinder stat.

 

[doitall]

Yes I argee you can have a valve on the return, provided the copld feedand vent are connected at the boiler, as per the manufacturers instructions