worcester 240 combi

[carljb]

I have a worcester 240 combi situated on upstairs landing.It pumps to 2 large rads downstairs and 4 medium rads upstairs.How do I know or can anyone tell me if it`s powerful enough to pump to another rad above in the loft

thanks

 

[breezer]

I am not a plumber or heating engineer.

I would be interested in the answer too. Reason being this.
If the boiler is on the 1st floor it has to pump the water downstairs then back up so that is say 3 metres (water finds its own level so you only have to pump it up)
Then you have the room it is in say 3m high and obviously to get to the loft the pipes must run up.
That makes a total of 6 metres, and as most pumps can only pump to a 6m head, i would err on the side of caution and say that it would need an 8m head pump.

You could always look at it the other way if the boiler is downsatirs it would have to pump up the first floor (3m) and into the loft (3m)

You could say that if the boiler is say 1.5 m up the wall it has to pump less, but i would say its too close to be sure and a bigger pump would be better.

lets see if i am wrong or right.

 

[dave448]

You miss the point .. the boiler heats water .. the pump pumps it .. so the pipe lenth and bore and the pump rating will be the limting factors ... the boiler will chuck out the heat .. if the pump cant distibute it as fast as the boiler generates it .. the boiler will over heat.
Yhe radiator sizes are not a factor .. if its too cold .. turn up the circulation temperature.

so ... again .. its about frow resistance .. which has two main components .. pipe run lenth and pipe diameter .. by far the most important factor is bore diameter in increasing resistance to water flow ...it keeps the velocity of the down...

Water pump head is the vertical distance it will squirt water and is a measure of its pumping power .. notice its a curve .. so different volumes at different heights....
so having a pump at the top or bottom of a system has no bearing at all... you just dont want it near the header tank and the header tank need to be a meter or so above the pump .. wherever it is

... so 22mm bore is fine for the distances you are talking about

 

[ogoshi]

sorry to say it dave,but its you thats missed the point not breezer!
A worcester 240 combi doesnt have a header tank.The rad sizes are an important factor as the boiler may be operating to its maximum btu output.
I dont understand the "velocity" bit,im a 39 year old plumber and have always worked to pressure and flow rate,my dictionary definition of velocity is simply the speed which something is travelling,and is measured in mph,inches per second etc,thats not relevant to the question asked,which was would the boiler supply rads on the floors above and below it.Thats a question of pressure,is there enough pressure to reach all the rads when the water is being split 2 ways.
The easy way to find out if it will work is to run a pipe into the loft from the flow pipe,(use 10mm,forget 22mm as you want pressure not flow because water is heavy,heavy means more work for the pump).
To save draining down you could use an aerosol freeze kit and conex tee(22x22x10mm).fit a conex blank on the end of the 10mm in the loft,let the pipe thaw,turn on the heating and CAREFULLY crack open the blank in the loft (with towls/dustsheets around the pipe).Dont fully undo the blank as you will not get water straight away,air first followed by water(hopefully).if it doesnt work at least you havent had the expense of buying a rad and valves!

 

[dave448]

Okaaaay ... point by point then
I assumed the thing had a header tank .. whether it has or hasnt is immaterial
The circulating water temp is relevant ... as its the temperature drop across the rads that gives the heat output
Velocity means you get circulation sounds from the system if it is too high. flow resistance increases a great deal with increasing water 'velocity'... flow resistance is a function of water velocity and pipe diameter.
Pressure is a static measure .. it has nothing to do with resistance to flow...
water .. is indeed heavy ... but the pump does NOT see that .. it works against a head ...or resistance to flow .
..
its all Physics ...
Oh .. yep .. I too have installed C heating systems ... but thats not the point either

Have you actually calculated what the flow rate would be through a 10mm pipe?

 

[breezer]

Perhaps I can help before this becomes too heated (no punn intended)

Dave448 you are talking about the Physics of the subject.
ogoshi and myself are talking about the praticalites of the subject as to if his (carljb) boiler could get hot water (at a suficiant temperature) in radiators in his loft.

all carljb wants is a yes or no, and if no what can i do answer. Not a big debate.

So ogoshi and myself are just saying that carljb should err on the side of caution and a pump with an 8m head would be a good idea.

___________________________________________________________

The answer to your question
"Have you actually calculated what the flow rate would be through a 10mm pipe?"

it depends (as you said, on the velocity) but if we assume a velocity of 1.5 ft/second the flowrate would be 2.1545043 litres per minute.

Now let us stop "debating" and help carljb PLEASE!

 

[dave448]

oh .. I am trying to deal with facts... I am interested to see how you got 2.1545043 l/min ...


here are some tables
Note that the flow rate is gallons per hour, not feet per second.

Flow (galls/hr) head loss (inch water gauge per foot run)
15mm tube 22mm tube 28mm tube
5 0.01
10 0.02
15 0.03
20 0.05
25 0.07
30 0.10 0.01
35 0.13 0.02
40 0.16 0.02
45 0.20 0.03
50 0.24 0.03
55 0.28 0.04
60 0.33 0.05 0.01
65 0.38 0.06 0.02

The columns dont match up .. go to
http://www.diydata.com/planning/ch_design/pressuredrop.htm
Whilst your there you .... should read the rest

you will see that 22 mm gives a low loss high capacity flow rate
...
water temperature losses on pipe runs are negligable .. what matters is water flow and temperature drop across the radiator
take a good look at this site .. how practical can you get?
Physics has everything to do with the real world ... it underpins it ... its the basis for rational thought...

its not a debate .. im dealing with facts.....
As for advice
I would use 22 mm pipe for the extension .. a high out put rad to limit the size needed .. as space wb at a premium in the loft and fit a thermostatic valve

 

[breezer]

as i have always said i am not a plumber or heating engineer, i looked it up on the web, thats what it said the anwser is.

 

[ogoshi]

Carl would you please let us know if it works.I have fitted a rad in my sisters loft conversion and she has the boiler in the bathroom (which is now the middle floor since loft conversion).It supplies all three floors with no problems.The boiler is a potterton combi but i cant remember what size pump is fitted in it.
ps.....i piped up to it with 10mm microbore.

 

[dave448]

oh.. ive used 8mm on short runs ...like i said ..it depends on the heat output required as dictated by the temperature required in the room and the thermal losses (amount of insulation) of its construction , the curculating water temperature .... and crucially the speed the water ts being pumped along by.......
there is no law against using 8 , 10, or whatever bore pipe ...using small bore over long runs though ..inceases the pumping effort ..shortenening the pumps life and increasing electicity bills... and you will get a noisey system at high circulation rates.
My whole point is that this can be calculated quite easily and not left to guesswork and the benefits of using larger bore pipe are considerable.
...
remember... you will need to rebalance the system afterward

 

[ogoshi]

My sisters house is 1940 something,not well insulated,full of microbore and the heating system has been in for years and is still very quiet.
I doubt if carl is interested in physics,more interested in getting his loft warm,so shall we leave him to decide whether he wants to check it out scientifically using your methods,or practically using mine and breezers methods?after all thats what diy is all about,doing it yourself.

Carl you must let us know if its successful.

 

[dave448]

ahhh ha haa .. MY house is a 40s semi ...full of microbore (two manifolds) ... BUT the mains are 22mm.....
Physics is the way of making sure your loft is warm.....
practical methods rely on trial and error ... and not understanding why it went right when it does

small world

 

[carljb]

Thank you so much for all your advice but the solution is now as clear as mud!!!! I have enjoyed reading all your comments and they have made me chuckle but I still don't know whether it is going to be safe for me to put a radiator in the LOFT. So I think I will try an ELECTRIC HEATER and I will let you know how I get on.Thanks to you all again, Carl.

 

[ogoshi]

Good luck carl.

 

[carljb]

Well guys i have finally plucked up the courage and gone for the rad in the loft .
HEY PRESTO it works a treat. Well worth all the agro.
Thanks again .
carljb.