Popcorn noise from boiler

[mickyg]

don't want to sh1t on the parade cos everyone is sounding really smart, but you've got an energysaver, guaranteed it will be one of the heat exchangers with carp in it bouncing around. Most likely the burner(that will confuse some people )

 

[Agile]

When balancing the rads, in an ideal world the lockshield valve would be set to achieve the 11° desired.

In a real world a rad will take about 20 min to stabilise after further adjustments have been stopped.

The heating coil on the cylinder can also be adjusted for that differential too.

BUT the setting of the heating and of the hot water will be different when either or both are in use! So I would set the heating primarily on CH only. Similarily the HW on HW only. I would then see how the HW and CH are diferentially balanced together with both on.

So the reality of balancing is that its a compromise. But an experienced professional would use a degree of skill to achieve the balance.

I would always use a contact thermometer and not an IR unit !

Tony

 

[iep]

I guess that I could take the bypass out and reinstate the gate valve.

However, the reason I took the gate valve out was that, in order for the pump overrun to work correctly, the gate valve had to be so open that it was stealing a significant amount of flow under normal operation.

The auto-bypass should (in theory) remian closed (or only be very slightly open) during normal operation and then open fully during overrun. Or that's how I understand it.

iep

 

[D_Hailsham]

Close the bypass valve, open all lockshield and wheel valves and remove any TRV head.

Set system to CH only.

What temperature differential do you then get on each of the three pump speeds?

Looking back at you first topic, I see you say that the rads are connected individually, by microbore pipe, to the main 22mm flow and return pipes - there are no manifolds. What size is the microbore?

 

[iep]

Microbore is 10mm or 8mm, not totally sure I'm afraid. Longest runs are actually longer than I had initially suspected (I've lifted a few floor baords to check stuff out since then) and can be up to 4m from the main 22mm pipes.

I will be out until quite late tonight so won't have a chance to do the test you describe until tomorrow but I will definitely get it done then. I will also measure the gas usage (didn't get home until 1am last night so haven't yet done this).

Is it definitely safe to run the pump on its lowest setting? Don't mean to doubt your advice but am not sure what might happen to a boiler if the flow through it is too low.

also, I'm guessing the usual procedure of running the room and boiler 'stats at full will apply during this test?

Thanks again,

iep

 

[D_Hailsham]

Microbore is 10mm or 8mm, not totally sure I'm afraid.

That's OK. I was just checking that it was microbore. Some posters on here have referred to 15mm as microbore and, as you said there were no manifolds, I thought it worth checking.

Is it definitely safe to run the pump on its lowest setting? Don't mean to doubt your advice but am not sure what might happen to a boiler if the flow through it is too low.

It's OK for a short while, but not continuously.

The object of the exercise to to check that you can achieve the correct 11C differential when the circuit resistance is at a minimum (all rads fully open). The differential should decrease as the speed rises. If you can't even achieve 11C on the lowest speed, there is something wrong.

I'm guessing the usual procedure of running the room and boiler 'stats at full will apply during this test?

Yes.

PS which pump do you have - 15/50 or 15/60?

 

[Agile]

Microbore is largely self balancing on the rads if ALL the rads are fed with microbore of the same size. The pump usually needs to be on the maximum speed.

A non-microbore fed cylinder heating connection usually needs to be closed down considerable on the lockshield unless you will accept a virtually total hot water priority.

Tony

 

[mickyg]

hows all this balancing gonna unblock the heat exchanger?

 

[iep]

The pump is the 15/50. I'll carry out the test as you describe. Until I get to the bottom of this, I don't think I'll be able to sort out any final niggles with the system.

Agile, all rads are on microbore but there are big differences in how long the microbore runs are (some as little as 30cm, some as much as 4m). Unsurprisingly, the 30cm rads are the ones that need to be throttled back the most.

It's an interesting point that you rais about the cylinder getting priority. There is no lockshield (or similar) on the HW circuit and, as you say, the CH is pretty poor when the HW circuit is on. This was the main issue with the heating system when we moved into the house as the HW zone valve was jammed permanently open. As a result the rads took ages to get warm and the ones furthest from the boiler only got up to 50 degrees. It was damned cold in our house back in March.

iep

 

[iep]

I'm pretty confident that the heat exchanger is not blocked as we live in a very soft water area and the system has always run with an inhibitor (which I tested using theold nail in cup technique when we moved in).

When I recently drained down the system the water was totally clear and the intenrals of the zone valves were also very clean.

Also, there is no kettling and, if anything, the flow in the system seems to be too high rather than too low. Unless you have picked up on something I am missing here?

Cheers,

iep

 

[mickyg]

Unless you have picked up on something I am missing here?

yeh, you've got an energysaver. A guinea pig of a boiler. The burner is prone to blocking. At first it will materialise as a bit of occassional noise like yours. it will slowly get worse. If you haven't already replaced the heat exchangers at some point then feel yourself lucky!

 

[Agile]

Just for other readers, living in a soft water has no relevance to dirt building up in the heating system. Its based on metal oxides and not calcium compounds.

Calcium in the water does modify the nature of the dirt though and certain wrong operation or commissioning can produce a build up of calcium in the boiler ands particularly in the heat exchanger.

Most of the problems in heating systems however are caused by the metal compounds.

The originally stated problem was noise caused when the pump is on over run and seemed to be associated with the operation of the auto bypass. I do not find these to always be very quiet.

Tony

 

[mickyg]

The originally stated problem was noise caused when the pump is on over run and seemed to be associated with the operation of the auto bypass.

when its running around the bypass the pressure/flow on the return will be higher and more likely to affect particles stuck in the heat exchanger waterways. There's 3 small bore heat exchangers in this boiler, any dirt going in doesn't come out again!

 

[D_Hailsham]

Microbore is largely self balancing on the rads if ALL the rads are fed with microbore of the same size.

Why should they be self balancing? Each rad will still have to be adjusted to give the correct flow, which depends on the size of the rad. Are you assuming that the rads are all the same size and fed from manifolds? This is not true in the OP's case as each radiator is connected separately to the 22mm main flow and return.

10mm can carry a max of about 2.5kW and 8mm about 1.5kW.

 

[D_Hailsham]

I am beginning to wonder if the correct pump has been installed. There are two ways of finding out: try a different pump (expensive) or calculate the index circuit (takes time) and size the pump from manufacturers' literature.

Copper Tubes in Domestic Heating Systems explains how to calculate the index circuit.