Central heating: What circulation flow rate?

[JohnD]

I have a Spirovent on the 22mm return to my boiler. The installer thinks it is slowing down the flow too much. I have found a graph of flow resistance in the Spirovent documentation, (it has a logarithmic scale and is difficult to follow) which seems to say that at a flow of about 0.5 litres per second (which seems low to me) the pressure drop is about 2 kPa (what's that?)

in the tech spec table it says "Flow Rate 1 m/s: l/s 0.35

which I presume means 0.35 litres per second

but I don't know what "1 m/s" means

or whether these figures mean it applies "a lot" of flow reduction or "not much" flow reduction.

the pump is a new Grundfos Alpha + with 28mm gate valves.

The head from F&E to boiler is about 5m (so about 0.5 bar pressure)

If I were to move the device to a single radiator, what sort of flow should a radiator have?

 

[mickyg]

never had to concern myself with such technicalities! Why does he think its affecting flow?
If you have 28mm flow+returns and a 22mm spirovent then yes its possible it could affect flow. Take it out and see if it makes any difference.

 

[JohnD]

the boiler has 22mm F&R

It joins into my existing 28mm pipework (up to pump and 3-port) which is in place from the old boiler)

He suspects it because
(1) the boiler has an error code 0b which signifies air in exchanger, or flow switch faulty, or flow too low
(2) he has I think never seen a Spirovent before

 

[namsag]

Surely your not having trouble already with the boiler that certain people on here said was the best thing since sliced bread.

 

[JohnD]

haven't started having trouble with it yet

installation not finished (!)

installer just back from hols

luckily I haven't paid anything


Edited: What can you tell me about flow rates?

 

[mickyg]

John as I understand it you also have a magnaclean?? Why not just take out the spirovent and fit a 28mm line strainer in its place?

 

[JohnD]

no, I put the Magnaclean on my mum's system.

Anyway, I have this great brass thing, it would be a shame not to use it.

View media item 3406

 

[mickyg]

ok, well not sure whats best then, other than just try it without it. i don't think getting into the science of flow volumes etc is gonna get you any answers, its all very hypothetical, doesn't always add up in real life.
Personally I always fit the magnaclean and if I had concerns about the system(old rads/pipework etc) I would add a line strainer.
One thing I don't like about the spirovent is that although it seperates dirt and air quite effectively there's nothing stopping the odd stray particle here and there getting through. Also I think it is possible it might cause a dead spot in the flow( I might be wrong).

 

[namsag]

Must be some heating job . Started on 29th july and here we are a month down the line and its not finished why ever not thought it was just a boiler change.
I would have thought a boiler coming up with an error code would mean its not working as it should otherwise an error code would not appear?

 

[doitall]

I have no idea what boiler we are talking about, but if your having flow problems it could be down to.

Grundfos Alpha + with 28mm gate valves

 

[JohnD]

why?

 

[doitall]

why?

Because its a variable duty pump, any resistance and it slows down

 

[JohnD]

just tried it on non-variable setting "II"

it does the same

 

[doitall]

just tried it on non-variable setting "II"

it does the same

You haven't told us what its doing

 

[mickyg]

(1) the boiler has an error code 0b which signifies air in exchanger, or flow switch faulty, or flow too low

oooh yes he did