Circulation Pump Question

[John.g]

Cycling on/off every 3 minutes? so if a non modulating boiler, output is only either 8kw or 11kw so something amiss with 18 rads.
If one assumes 25kw total rad demand, then the circ rate required is 30LPM (1.8M3/hr) at a dT of 12C.
Check that the present pump is set to max speed, setting 3 or III.

 

[NorthernLad]

John g - yes pump is currently on setting 3 so getting the best I can out of it.

Firstly I am going to add a 'valve with drain cock' to older part of system and finish the cleaning part of the job. (KOP -Having done the upstairs rads yesterday I can confirm it is time consuming!)
To change that valve and with two F&E tanks I will need four rubber plugs to form a vaccum - Toolstation sell, but theirs have a step instead of smooth cone shape and I read that was better (?) - can anyone suggest alternative?

Once clean I will get the pump changed and see what result I get. This part will take place in the warmer weather and I will let you know because I know you like to have an ending to the story!

Really grateful for all your input.

 

[SJB060685]

Any chance you have a means of measuring the delta T across the boiler? As in what the return temperature into the boiler is and the flow out temperature.

 

[John.g]

Two F&E Tanks, why do you have two?.

 

[NorthernLad]

Any chance you have a means of measuring the delta T across the boiler? As in what the return temperature into the boiler is and the flow out temperature.

I dont, but guess I could get a device to measure that. Any recomendations? What might that show or prove one way or the other?

Two F&E Tanks, why do you have two?.

Good question - Answer is I dont know because I didnt live here when they were installed.
My best guess is this was done at the time of the extension and again only a guess that one ends up at some other point in the system.
The lady of the house at the time was a bit keen on having everything covered up so I cant see where the pipes end up.

The loft had been given fibreboard walls 'to provide a playroom for the kids' and I had to cut the wooden frame and remove a section of this just to get at the F&E tanks. This is just one example.
The buider who did this must have seen the £ signs but the trade guys he used couldnt build a straight line - they actually plastered over wallpaper at one join...

 

[SJB060685]

I have a laser pointer that measures temperatures. You can get clamp on stats that measure the DT but that’s money you don’t really need to spend.
A simple digital thermometer would work and pretty cheap from places like tool station etc.
Being an old non condensing boiler you should be looking at a ΔT across the boiler of about 11-12°c. If it’s more than that that would indicate poor circulation and possibly why you’re experiencing the burner cycling. Poor flow could be due to a fouled heat exchanger or a problem in the system somewhere.

 

[NorthernLad]

Many thanks for that - I will take a look ready for when my cleaning is completed so I end up with the best possible readings.