Worcester bosh gas rates

[Danv44444]

Has any one else noticed that when you do a gas rating on these boilers with the hot tap running the gas rate is always approximately 10 kw out? I tried on a 42cdi and only got 29kw and on a 30 si and only got 21 kw? I know how to do a gas rate properly before anyone asks.

 

[andyg0507]

you are putting the boiler to max rate rate then??

 

[Danv44444]

im am running the hot tap flat out

 

[andyg0507]

no are you setting the boiler in chimney sweep mode and making the boiler go to maximum, the hot tap should also be opened fully like you have said.

 

[Kev the gas]

Never had a problem myself.

I only install Worcester boilers, are your calls always 10 kw out ?

What method are you using for the calculations?

 

[SafeGasInstall]

undergasssssssssss

 

[Kev the gas]

Never had a problem myself.

I only install Worcester boilers, are your calcs always 10 kw out ?

What method are you using for the calculations?

Edited calls for calcs

 

[Kev the gas]

undergasssssssssss

Understand your thought Stan, but 10kw out most times sounds like a decimal point in the wrong place. ?? Hence why I asked what method he is using.

 

[SafeGasInstall]

to op what was wp at the appliance and Meter ?

 

[GrahamM]

Just about every day I work on one of these and am always well within 10%.

Open all TRV's, turn up room stat and read MI's about service/chimney sweep mode.

 

[Danv44444]

i havent done the chimney sweep mode, maybe thats where the problem lies?

 

[Halesowen1]

What difference will turning up the stat do??
The boiler fires on max or min when in chimney regardless of the stat.

One word of advise when starting the boilers up in chimney sweep, if its not a combi make sure you start up the heating/water on the programmer to open up the valve/valves otherwise the boiler will instantly overheat.

 

[andyg0507]

maybe you should sit down and have a read of mi's before doing the job, just out of curiosty is this installs or servicing?

 

[Danv44444]

the formula i use is time 2 mins check 2 readings on meter. 2nd reading minus first reading x the difference by gas cv then xthat by 30. then divide by 3.6 = the kw

 

[Danv44444]

installation, i have had the right result before i assumed that having the hot tap running would be the same as chimney sweep. i was wrong obviously

 

[andyg0507]

i think so my friend

 

[andyg0507]

just another query what inlet wp are you getting at boiler? think this has already been said but just wanted your results.

 

[glenno1]

Always good to have the corgi slide rule handy

 

[AWheating]

if you gas rate in hot water mode the boiler will modulate to suit. Put the boiler in service mode with hot taps open and you should get full rate. Check the Manufactures Instructions and it tells you how to perform the gas rate correctly.

 

[ambrosia]

If you get it 10% out are you doing FGA as well, I think CO should be 9.2 -9.8 on those boilers

you are distinguishing between input and output kw, not that that will account for 10% out

also i know there are different ways of gas rating, but try 2min x30 x10.7 for newer meters
and 3600/ by time for revoultion x1040 /3412 for older meters

if you gas rate in hot water mode the boiler will modulate to suit. Put the boiler in service mode with hot taps open and you should get full rate. Check the Manufactures Instructions and it tells you how to perform the gas rate correctly.

if only all boilers were as good as worcester

 

[mikeygas]

Setting up boiler to Gas rate it = Set boiler to chimney sweep mode, open a hot water tap and turn the central heating stat to maximum as well, simples.

 

[GQuigley67]

chimney sweep or not, you should not be that much out, never had a problem

 

[topdog]

Take 1st reading from 2nd reading = Answer,
Then times that by 3600= Answer,
Then divide by seconds taken=Answer
Then Times by the C.V (i.e)38.76=Answer
Then divide by 3.6 = Answer KW GROSS,
Then divide by 1.11 = ANSWER KW NET.

 

[tamz]

There are a hundred "correct" ways to work it out. Use whatever one sticks in your head.

 

[topdog]

it would be great to "NO" the other ways for me to know in the future