SIZING A NEW BOILER

joeduggan

hows it goin lads? i need to buy a new condensing boiler for my house. it will be sited outside the back door. the btu value of all the rads adds up to 124,573 btus. do i need anymore info or is it just the amount of btus from the rads????? thanks.

Joey the lips

joeduggan wrote: »

hows it goin lads? i need to buy a new condensing boiler for my house. it will be sited outside the back door. the btu value of all the rads adds up to 124,573 btus. do i need anymore info or is it just the amount of btus from the rads????? thanks.

I am assuming that you worked out the rads correctly(with the greatest respect) so what I do is add up all the rads and add 20000 btu's for hot water giving you a 150k btu boiler.

There is an arguement that at this level of condensing you would be better off going for a 120k boiler this ensures the boiler constantly condenses. my knowledge is weak on condensing boilers so I would suggest you ask a plumber on this.

However if you asked me in the morning I would say what I said in the first paragraph. 150k burning diesel.

AckwelFoley

Joey the lips wrote: »

I would suggest you ask a plumber on this.

Having worked with and sold materials to many plumbers, if you asked a regular "joe soap" plumber what size boiler you need, dont be suprised if they reply...

*stretches arms out*

"about this big"


The best place to get this information is directly from the boiler manufacturer, ie Grant engineering or a plumber that specialises in fitting and maintaining these units

yoshytoshy

snyper wrote: »

Having worked with and sold materials to many plumbers, if you asked a regular "joe soap" plumber what size boiler you need, dont be suprised if they reply...

*stretches arms out*

"about this big"


The best place to get this information is directly from the boiler manufacturer, ie Grant engineering or a plumber that specialises in fitting and maintaining these units

Thats probably the way for oil boilers snyper ,"most" lads working on gas know their stuff

AckwelFoley

yoshytoshy wrote: »

Thats probably the way for oil boilers snyper ,"most" lads working on gas know their stuff

- they kinda need to, there are far fewer gas installations and due to the nature of gas, one needs special accreditation to work on gas.

items

joeduggan wrote: »

hows it goin lads? i need to buy a new condensing boiler for my house. it will be sited outside the back door. the btu value of all the rads adds up to 124,573 btus. do i need anymore info or is it just the amount of btus from the rads????? thanks.

You have to add in your hot water requirements, standard copper insulated cylinder takes 15,000 btus (30 gallon).

Rads 124.573 and Hot water 15.000 = 139,573 btus

Boiler manufactures work off kWh's (kilo watt hours) their is 1 kWh for every 3.4 btus. Not sure how you sized up your rads, have you allowed for temp of 65c? if so add what you can for hot water based on the above figure. Once you've worked it out you have to factor in boiler efficiency (heat loss) most common boilers run in 80% efficiency.

You can over size your boiler but not a good idea to under size, if you find its hard to get a boiler close to your requirements, you can go for the larger one then adjust the gas setting to lower the kWh to suit your requirement. Its more gas (cost friendly) that way.

Hope all works are been carried out by a RGI.

Joey the lips

items wrote: »

You have to add in your hot water requirements, standard copper insulated cylinder takes 15,000 btus (30 gallon).

Rads 12.573 and Hot water 15.000 = 27,573 btus

Boiler manufactures work off kWh's (kilo watt hours) their is 1 kWh for every 3.4 btus. Not sure how you sized up your rads, have you allowed for temp of 65c? if so add what you can for hot water based on the above figure. Once you've worked it out you have to factor in boiler efficiency (heat loss) most common boilers run in 80% efficiency.

You can over size your boiler but not a good idea to under size, if you find its hard to get a boiler close to your requirements, you can go for the larger one then adjust the gas setting to lower the kWh to suit your requirement. Its more gas (cost friendly) that way.

Hope all works are been carried out by a RGI.

With respect you need to check that figure again

items

Joey the lips wrote: »

With respect you need to check that figure again

Standard Rad 500mm x 900mm = 3300 btus @ 65c. The poster may only have 3 or 4 rads, I am just going with the figure given.

30 Gallon Cylinder = 15,000 btus.

I see the missing 4, apologizes.

Joey the lips

joeduggan wrote: »

hows it goin lads? i need to buy a new condensing boiler for my house. it will be sited outside the back door. the btu value of all the rads adds up to 124,573 btus. do i need anymore info or is it just the amount of btus from the rads????? thanks.

items wrote: »

You have to add in your hot water requirements, standard copper insulated cylinder takes 15,000 btus (30 gallon).

Rads 12.573 and Hot water 15.000 = 27,573 btus

Boiler manufactures work off kWh's (kilo watt hours) their is 1 kWh for every 3.4 btus. Not sure how you sized up your rads, have you allowed for temp of 65c? if so add what you can for hot water based on the above figure. Once you've worked it out you have to factor in boiler efficiency (heat loss) most common boilers run in 80% efficiency.

You can over size your boiler but not a good idea to under size, if you find its hard to get a boiler close to your requirements, you can go for the larger one then adjust the gas setting to lower the kWh to suit your requirement. Its more gas (cost friendly) that way.

Hope all works are been carried out by a RGI.

Ok I am wrong. my glasses clearly see one figure at the start and another figure further down.

Look before I leap????

items

Apology made, been a while since using btus, used to working off lower figures in Kwh. 125,000 is a lot of Kwh's.

joeduggan

items wrote: »

You have to add in your hot water requirements, standard copper insulated cylinder takes 15,000 btus (30 gallon).

Rads 124.573 and Hot water 15.000 = 139,573 btus

Boiler manufactures work off kWh's (kilo watt hours) their is 1 kWh for every 3.4 btus. Not sure how you sized up your rads, have you allowed for temp of 65c? if so add what you can for hot water based on the above figure. Once you've worked it out you have to factor in boiler efficiency (heat loss) most common boilers run in 80% efficiency.

You can over size your boiler but not a good idea to under size, if you find its hard to get a boiler close to your requirements, you can go for the larger one then adjust the gas setting to lower the kWh to suit your requirement. Its more gas (cost friendly) that way.

Hope all works are been carried out by a RGI.

thanks for all the info . i wont have an RGI fella carrying out the work because its an oil installation.

JamesM

joeduggan wrote: »

thanks for all the info . i wont have an RGI fella carrying out the work because its an oil installation.

You can't go wrong with a Grant boiler, if not available try Firebird.
Jim.