whole house calculation

[Steve ski]

Hi guys, I am pricing for a large heating job and looking for some advice to aid my confusion!!. The new extension is considerably larger than the existing cottage, and materially very different, I intend to use the whole house calculation to size the boiler my head is swimming because the new and the old will require very different heat requirements, would it be better to separate the two buildings, I am commited to getting the right system for this job, I am sure I will raise many more questions so apologies in advance, thanks guys!:willy_nilly:

 

[oz-plumber]

Set the system up with 2 thermostats - old and new.
Run 2 sets of piping - old and new.

Set the boiler up with 2 zones - old and new.

You will find it less difficult to balance the system and maintain even temperature throughout the house if you set the system up this way.

It will cost the customer more for the installation, but just explain why you are doing it and the benefits that it will achieve

 

[Steve ski]

Thanx oz the old part is 200 yr old granite cottage has never had central heating installed it will have ground floor and first floor as will the new build are you talking about zoning the old part separately as I would like the boiler to provide heat for the whole house. Or would it be better to have two boilers 'oil' to provide for the new and the old ??

 

[missplumb]

Have one boiler and zone the two systems, you could also use a low loss header to aid the balancing of the two different heat loads.

 

[plumben]

One boiler and minimum two zones set up as old and new although you could have more I'E old living area, new living area, new sleeping area, old sleeping area

 

[Nostrum]

Don't use the whole house method, do a room by room heat loss calculation. Size the rads and size the boiler off the combined heat loss.

 

[ShaunCorbs]

Don't use the whole house method, do a room by room heat loss calculation. Size the rads and size the boiler off the combined heat loss.

+1/3

 

[Rckape]

Last December I finished a job that sounded a lot like this. 200+ year old cottage 2 up 2 down but brick not stone. With modern extension to the back and side. They'd insulated the old building with 60mm celotex backed plasterboard on 40mm timber battens.

I calculated room by room heat loss and it all went swimmingly.

 

[Steve ski]

Thanks so much everyone, really helpful, I will do heat loss room by room and work it out this way, A low loss header sounds good and I may look into this. I will come straight of the boiler with a common flow, this will divide into two each with its own zone valve to old and new. New going to airing cupboard (unvented) and space heating, old space heating only with seperate stat and time control. I will do the same with the return, a common return with return from cylinder and new build heating and return from old part heating should I be concerened about reverse flow with this set up ???

 

[oz-plumber]

I calculated room by room heat loss and it all went swimmingly.

Did you have the same problem I had once?
Turned the ground floor of a property into a 55C indoor swimming pool.
The owners weren't very happy as they already had an outdoor swimming pool.

 

[Rckape]

At least they weren't cold!

 

[missplumb]

but if you do a whole house calculation, how do you decide what size emitters to put in each room???. if you do a room by room calc, you size the rads to emit enough heat for that load, therefore you shouldnt have uneven heat distribution. a well sized and designed system will have no problems