using a solar unvented dual coil with a boiler

[What boiler]

I`m looking to install a unvented in my house using a plumber. Some web sites have suggested using a dual coil system which is normally used with two heat sources as in a boiler and solar , however they are suggesting using a single boiler but connect to it to both coils so it reheats the cylinder quicker then just a single coil - any feedback, any issues, extra cost


thanks

 

[thomas donovan]

sounds like a good idea to me but the thing to bear in mind is the volume of water flowing the coils will increase therfore "potentialy" nicking flow from rads. as long as your plumber balances system properly there shouldn't be an issue. may try this myself

 

[What boiler]

thanks for the quick reply but I would not be introducing any new issues as in my mind then same potential issues are there even if you use the cylinder the way it was designed i.e heat from two sources?

 

[SimonJohns]

I would suggest plumbing the two coils as separate circuits.
Then if you don't want too much hot water, you only have to heat the top. Like the old economy 7 set up

EDIT : copyright simonjohns 2012.

 

[What boiler]

thanks, but isn`t that the point of the two coils to heat the cylinder quicker- though I`m jut guessing that a 250Lt cylinder with two coils will reheat quicker then the same cylinder with a single coil ?

 

[Simon F]

I would suggest plumbing the two coils as separate circuits.
Then if you don't want too much hot water, you only have to heat the top. Like the old economy 7 set up

I was thinking the same, this way you have a clear benefit, if you have two coils but your just using one heat source you would be as well getting a cylinder with a better heat recovery.

 

[thomas donovan]

I would suggest plumbing the two coils as separate circuits.
Then if you don't want too much hot water, you only have to heat the top. Like the old economy 7 set up

really like that idea i'm gonna steal it. ;-)

 

[SimonJohns]

Thomas. I wouldn't 😉 lol re-read it

 

[What boiler]

is it a good idea?

 

[Nostrum]

Why would you need to do this?

Surely if your running out of water your cyliner is too small and if your not then there is no need for it? You could fit a W plan for a similar effect. Either way if your hot water demand is that great that you need to heat the cylinder up extra quick you may run into problems in the winter months when your freezing cold because the boiler is concentrating on heating the DHW.

Either that or you will need to oversize your boiler just for an extra coil.