# Popcorn noise from boiler

Are you thinking the current pump is too large or too small?

I'll look over the pipework indexing guide.

Cheers,

iep

Your pump is fine!

Microbore is largely self balancing because the flow and return pipework to each radiator has a resistance which is effectively in series with the low resistance of the radiator.

Translate it into an electrical circuit and if you apply 100v to a 50 ohm resistor in series with a variable resistor the range of currents will never exceed 2 A.

On the other hand if you have a fixed resistance of 10 ohms then the current can vary up to 10 A.

Similarly a microbore limits the maximum flow through each rad. In many cases if the pipe length per rad is say at least 1-2 m then balancing is hardly required at all although obviously some balancing would be better. Thats the basis of my comments that with balancing problems opening every lockshield just 3/4 turn will give an aproximate balance point.

With a microbore system the manifold connection method usually used ensures the pipe lengths are all reasonably long.

On a traditional system if the first rad is not restricted then hardly any flow will get further down the system as it effectively short circuits the distribution.

Tony

Are you thinking the current pump is too large or too small?
It's not so much the size of the pump but the shape of the working curve which is wrong, i.e it is cannot deliver the correct flow at the actual head.

However, something you said earlier has set me thinking.

In your original question, you said: For the record, when operating with the CH zone valve open, there is a normal 10 degree drop across the system.. I assume, from other things you wrote, that this is on speed 2. So you have a 17.58kW boiler running with a 10C drop. This gives a flow rate of 17.8/(4.18 x 10) = 0.42 litres/sec.

Looking at the pump graph on the Screwfix link, a flow rate of 0.42 l/sec on speed 2 is equivalent to a head of about 1.1m. But, using the boiler resistance graph, the head at 0.42 l/sec (25 l/min) is also about 1.1m. This means that the pump would only be able to have enough oomph to handle the boiler on its own; there would be nothing left over for the heating circuit.

I then checked the pump curves I have for the 15/50 and they are completely different. At the same flow rate on speed 2 the current 15/50 has a head of about 2.3m, which would leave 1.2m for the rad circuit.

So the question is: which version of the 15/50 do you have?

The P/N, on the right just below "Grundfos" is the key. What is this number?

That would certainly explain the confusion. I'll have a look tonight (unfortunately, the pump etc are behind my dishwasher which needs to be un-plumbed in order to be moved out far enough to see the pump, so didn't get a chance to look at it yesterday).

Cheers,

iep

btw when you finally get around to changing the heat exchanger let me know, I might have a spare one in the garage

Do you mean the primary or secondary heat exhanger? If it's the secondary one I might take it off your hands anyway as the condensation tray (integral to the secondary heat exhanger) in my boiler is already badly corroded and looks like it might be ready to pinhole.

Cheers,

iep

Do you mean the primary or secondary heat exhanger? If it's the secondary one I might take it off your hands anyway as the condensation tray (integral to the secondary heat exhanger) in my boiler is already badly corroded and looks like it might be ready to pinhole.

Cheers,

iep

I'll have a look, later, having a clear out and the scrap man is coming. I did have about 5 at one time in various conditions(its not a common fault honest gov ). Will let you know. I may have an old one, but with a bit of treatment it can probably be cleaned up.

Boiler part number:

988123

Seems like this might be an older model. Can't find a copy of the manual anywhere. Anyone have one?

iep

thats the serial no, hence the 98 the year of manufacturer. I've got manuals for both variants the 60 and 60P, look for the GC number on the label it will be either 4131974 or 4131971
I've got manual for both

oooops, bit tired when I wrote that.

I wrote boiler part number but I meant pump part number (still trying to find a manual that will help me set the bypass valve correctly).

So, looking for manual for grundfos pump ups15-50 part number 988123, IP42.

Cheers,

iep

D_Hailsham, I should also explain the 10 degree drop I reported in the original post. At the time, I had not fitted the aluminium plates ot the send return pipes and was trying to measure off of the pipes themselves. The results were very variable so I made a best guess. With the aluminium measurement plates for trhe IR theremometer I get a consistent 6 degree figure.

iep

So, looking for manual for grundfos pump ups15-50 part number 988123, IP42.
Are you sure it is a Grundfos?

I have just looked at mine and the only numbers are the P/N (59525600) and, just below P/N) the PC (9943). The Screwfix link shows these as

There is a table on the left showing the Watts and Amps for the three speeds. What are the numbers? This can also be used to identify the pump.

There is a considerable difference between the older 15-50 and the current model (see table below), so you need to know which one you have.

[code:1]
Old model New Model
Speed Revs Watts Revs Watts
1 800 40 1700 35
2 1200 65 2100 45
3 1900 95 2300 50[/code:1]

Deinitely a Grundfos, tis writ large across the face plate of the pump.

However, having seen the face plate of newer pumps, mine looks nothing like them so I'm guessing it is pretty old. I have trawled the net for a photo and found one that looks like mine.

As you can see, the power figures bear no relation to those from the two versions that you posted. In fact, assuming a similar pump efficiency, this one is more than 2x as powerful as the current new model!

Unfortunately, I can't find a manual that reflects these power figures anywhere.

Cheers,

iep

As you can see, the power figures bear no relation to those from the two versions that you posted. In fact, assuming a similar pump efficiency, this one is more than 2x as powerful as the current new model!
The older pumps are nothing like as efficient as the modern ones. I suspect that the pump is even older than your boiler. I am just guessing, but is the Energysaver the original boiler or has a new one been installed? The reason I ask is that old cast iron heat exchanger boilers had a much lower resistance compared to modern boilers, so the pumps did not have to be so powerful.

Good guess, the system itself is over 30 years old but the energysaver was installed about 10 years ago (approx).

iep

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