Worcester Bosch 30cdi Regular Installation. Greenstar 30CDi Classic System literature Installation and Operating instructions Greenstar. Comfort I RF twin. Installation some information on whether to select a combi or regular boiler installed. I have a Worcester Greenstar 30CDi combi boiler (or is it a 35 - not sure),.

Click to expand.Many thanks, BLOD. However, I understand that the way to convert KW to hours gas rate is to multiply 0.094.

So for 6m3/hr equivlant to 64KW. If I didn't ring up the boiler manufacturer to ask for their gas hourly flow rate, I could just calculate two boiler 30kw+24Kw=54KW x 0.094=5 m3/hr plus 9Kw cookx 0.094=0.84m3/hr. The total would be within 6m3/hr. If you are to issue a Gas Safe Certificate for a landlord, what would you do, do you just calculate the load or check the individual boiler manual? You need to take diversity of use into account as well, below is an extract form BS 6400-1 which tells you how to calculate the actual load Annex A (normative) Sizing of meters A.1 Diversity factor A diversity factor is given to each type of appliance according to the normal degree of intermittence of use. Where there is only one or two appliances (e.g. Combination boiler and cooker) the diversity factor shall have a value of one.

Where there are more than two appliances the diversity factors listed in Table A.1 shall be used. A.2 Meter size calculation To calculate the size of meter required, multiply the maximum heat input of each appliance by its diversity factor, add these figures, convert to megajoules, and divide the total by the calorific value of the gas (typically 39 MJ/m 3 for 2nd family gas). The following is an example of such a calculation.

Table A.1 Diversity factors of appliances for meter sizing Appliance Diversity factor Central heating appliances (other than combination boilers) 1 Unit heaters 1 Circulators 1 Combination boilers 0.8 Instantaneous water heaters 0.8 Sink water heaters 0.6 Room heaters 0.6 Tumble dryers 0.6 Hotplates 0.6 Ovens 0.6 Cookers 0.4 Refrigerators 0 so using your figures and this table you have 30 + (24 x 0.8) + (9 x 0.6) 30 + 19.2 + 5.4 = 54.6 x 0.094 = 5.13m3/hr. To determine the size of the gas meter we require to know the maximum gas flow rate of the Installation. This can be calculated by using the Manufacturers stated GROSS heat input, therefore where the manufacturer states a NET figure we require to multiply this by 1.11 (Natural Gas) Since it is unlikely that all appliances will be on at any one time, a diversity factor is applied where there is more than two appliances depending on each appliances level of use. Where there is only one or two appliances installed no diversity factor is applied with the gas consumption calculated on the total heat input of the installation.

E.g 1st Combi Boiler 30kw gross x 0.8 = 24. 2nd Combi Boiler 24kw gross x 0.8 = 24.

Cooker 9kw gross x 0.6 = 5.4 Total = 53.4 kw 53.4 x 3.6=192.24 Divided by CV of 38.76 MJ/m3 = 4.960 m3/hr. If your figures Above are GROSS. If your figures above are NET: then multiply by 1.11 = 4.960 x 1.11= 5.51 m3/hr but still you are within 6 m3/hr of U6 meter but have no room for any expansion. As I'am a Trainee, Could the experience Gas Engineers tell me if this is correct as I would like to Know if we have been told correct. As I will be sitting my ACS soon or is there another easier way to do it.

Many Thanks for any suggestions, I would appreciate this. Paul Wolfe (topdog). You need to take diversity of use into account as well, below is an extract form BS 6400-1 which tells you how to calculate the actual load Annex A (normative) Sizing of meters A.1 Diversity factor A diversity factor is given to each type of appliance according to the normal degree of intermittence of use. Where there is only one or two appliances (e.g. Combination boiler and cooker) the diversity factor shall have a value of one.

Where there are more than two appliances the diversity factors listed in Table A.1 shall be used. A.2 Meter size calculation To calculate the size of meter required, multiply the maximum heat input of each appliance by its diversity factor, add these figures, convert to megajoules, and divide the total by the calorific value of the gas (typically 39 MJ/m 3 for 2nd family gas). The following is an example of such a calculation. Table A.1 Diversity factors of appliances for meter sizing Appliance Diversity factor Central heating appliances (other than combination boilers) 1 Unit heaters 1 Circulators 1 Combination boilers 0.8 Instantaneous water heaters 0.8 Sink water heaters 0.6 Room heaters 0.6 Tumble dryers 0.6 Hotplates 0.6 Ovens 0.6 Cookers 0.4 Refrigerators 0 so using your figures and this table you have 30 + (24 x 0.8) + (9 x 0.6) 30 + 19.2 + 5.4 = 54.6 x 0.094 = 5.13m3/hr. To determine the size of the gas meter we require to know the maximum gas flow rate of the Installation. This can be calculated by using the Manufacturers stated GROSS heat input, therefore where the manufacturer states a NET figure we require to multiply this by 1.11 (Natural Gas) Since it is unlikely that all appliances will be on at any one time, a diversity factor is applied where there is more than two appliances depending on each appliances level of use. Where there is only one or two appliances installed no diversity factor is applied with the gas consumption calculated on the total heat input of the installation.

E.g 1st Combi Boiler 30kw gross x 0.8 = 24. 2nd Combi Boiler 24kw gross x 0.8 = 24. Cooker 9kw gross x 0.6 = 5.4 Total = 53.4 kw 53.4 x 3.6=192.24 Divided by CV of 38.76 MJ/m3 = 4.960 m3/hr.

If your figures Above are GROSS. If your figures above are NET: then multiply by 1.11 = 4.960 x 1.11= 5.51 m3/hr but still you are within 6 m3/hr of U6 meter but have no room for any expansion. As I'am a Trainee, Could the experience Gas Engineers tell me if this is correct as I would like to Know if we have been told correct. As I will be sitting my ACS soon or is there another easier way to do it. Many Thanks for any suggestions, I would appreciate this. Paul Wolfe (topdog). To determine the size of the gas meter we require to know the maximum gas flow rate of the Installation.

This can be calculated by using the Manufacturers stated GROSS heat input, therefore where the manufacturer states a NET figure we require to multiply this by 1.11 (Natural Gas) Since it is unlikely that all appliances will be on at any one time, a diversity factor is applied where there is more than two appliances depending on each appliances level of use. Where there is only one or two appliances installed no diversity factor is applied with the gas consumption calculated on the total heat input of the installation. E.g 1st Combi Boiler 30kw gross x 0.8 = 24.

2nd Combi Boiler 24kw gross x 0.8 = 24. Cooker 9kw gross x 0.6 = 5.4 Total = 53.4 kw 53.4 x 3.6=192.24 Divided by CV of 38.76 MJ/m3 = 4. Lec Translator 15 World Premium Edition 2011 Chevy here. 960 m3/hr. If your figures Above are GROSS. If your figures above are NET: then multiply by 1.11 = 4.960 x 1.11= 5.51 m3/hr but still you are within 6 m3/hr of U6 meter but have no room for any expansion. As I'am a Trainee, Could the experience Gas Engineers tell me if this is correct as I would like to Know if we have been told correct. As I will be sitting my ACS soon or is there another easier way to do it.

Many Thanks for any suggestions, I would appreciate this. Paul Wolfe (topdog). Many thanks for all your reply.

Apparently the meter can push through more than 6m3/hr, but I am told that new boilers are very sensitive unlike old ones, if the pressure drops to certain level, they will automatically shut down. So during peak hours or extremely cold weather, the boilers might not function properlyy. Also I am told that I will fail the Gas Safe Certificate check. But then again British Gas engineer said the max they would allow is 6.3m3/hr. Very confusing!

We are looking at two system boilers with an unvented cylinder not combi boilers, I don't know whether this makes any difference. The house currently has two vented boilers 18years old at 30kw and 24kw, a gas cook and a gas fire. Originally we were looking at them being replaced by two 30kw but concerned about the load. It may be of interest.

But prior to about 1970 we used Town Gas in the UK. It was manufactured usually from coal or oil.

The amount of heat each cubic foot of gas contained could be altered either up or down, so long as it never fell below a government set minimum level. They watered it down using steam if it was too rich. Usually coal or oil had a higher CV than that sent out.

And coal or oil was expensive to use, so bulking it out to reduce the CV was money saving. Its why on old systems you have water drain off pockets. The Natural Gas we have now can vary as Tamz says and that shows once again that using set formulas without checking are only a guide, the CV can change depending what is in the gas.

Click to expand.Graham M. Many thanks for your reply. We intend to use two Worcester boilers one Greenstar 30CDI (30KW) the other Greenstar 24i system (24kw). Worcester told me the gas flow rates for both are 3.4m3/hr and 2.59m3/hr. I don't know whether they are gross or net.

I can ask again. Bitdefender System Repair Download on this page. The gas cook is 9KW.

Don't know the flow rate. The boilers are not connected, they serve different zone, i.e one serve Ground floor and second floor, the other serve first floor and hot water. I don't know whether diversity can still apply in this circumstance. Will the above information sufficient to do the precise calculation. Click to expand.Midge, you are absolutely right. Change to U16 is neither straightforward nor cheap, we are low pressure, but have a built in U6 which is recessed into the wall whilst U16 can only be installed flush with the wall. So the gas supplier can't just change the meter, We have to have the southern gas network to change the meter position before the gas supplier can change the meter.

The network has tested the capacity and told us that the max load is 77kw. But as nowdays U16 tend to have a 2inch plastic pipe, they want to upgrade the pipework, which means that they will dig up the road to relay the pipe to connect to the main. Further complication, their drawings don't show where the main is. I will get the quotation from gas network next week. I imagine it will be anything between 5-10k. Gas supplier has already quoted £900 just for chaning the meter. Many thanks for all your reply.

Apparently the meter can push through more than 6m3/hr, but I am told that new boilers are very sensitive unlike old ones, if the pressure drops to certain level, they will automatically shut down. So during peak hours or extremely cold weather, the boilers might not function properlyy. Also I am told that I will fail the Gas Safe Certificate check. But then again British Gas engineer said the max they would allow is 6.3m3/hr.

Very confusing! We are looking at two system boilers with an unvented cylinder not combi boilers, I don't know whether this makes any difference. The house currently has two vented boilers 18years old at 30kw and 24kw, a gas cook and a gas fire.

Originally we were looking at them being replaced by two 30kw but concerned about the load. Many thanks for your reply. We intend to use two Worcester boilers one Greenstar 30CDI (30KW) the other Greenstar 24i system (24kw). Worcester told me the gas flow rates for both are 3.4m3/hr and 2.59m3/hr. I don't know whether they are gross or net. I can ask again. The gas cook is 9KW.

Don't know the flow rate. The boilers are not connected, they serve different zone, i.e one serve Ground floor and second floor, the other serve first floor and hot water.

I don't know whether diversity can still apply in this circumstance. Will the above information sufficient to do the precise calculation. Click to expand.Yes the house has a gas fire at the moment. We bought the house 2 months ago and didn't realize the problem. The reason I am looking so closely on the max load is to avoid changing the meter given how difficult it is. We are going to change the gas fire to electric one to save the capacity foe others.

I am even looking at heat & loss calculation to see whether 2 new 24kw boilers can replace the old 30kw and 24kw as the new ones has 90% efficiency whilst old one only has 75%. Maybe the money saved dor changing meter can be used to insulate the property better. Graham when you say our load is in the region of 6.3m3/hr did you use the manufacturer gas flow rate or use the 0.094 conversion rate?

The gas transporters work with a 65kw rule of thumb. With only being a little over why not down size one boiler a little.

What method did u use to workout the power u need whole house or room by room? Just as a wee story had a massive house with 22 rads and 3 floors =3x heating zones and a solar cylinder (sans solar). I sized the house with the whole house method and worked out i needed 2 boilers 45kw ish i think. The customer said no cuz his last place had a 35kw and 35 was what he wanted 2years and some bad winters later his house it fine throu the awful weather we have had. Thought I'd drag up an old topic instead of a new one.

Just read about the diversity factor above, am I right in saying that if there are only two appliances, the diversity factor is 1 for both appliances? I'm pricing a job in which a customer wants an additional combi boiler fitted to the extension (don't ask!) The existing boiler has a gross heat input of 31.5Kw and the new one for the extension has a gross heat input of 37.7Kw. Obviously if the diversity factor is 1 for two appliances, it'll have a requirement of 69.2Kw, which is too high. The guy at Gas Safe Technical told me the max is 63Kw for a U6.