Separating heating loop

[Someuser08]

Hi everyone. Just had a heating engineer over fixing my combi boiler and asked him a few question about replacing it with a new one and he suggested to split CH loop from the boiler and fit PHE and a pump to avoid contaminating the new boiler from the old pipes/radiators( and therefore any boiler would be functioning much better). Sounds l
ike an interesting idea, but I can't find any places where this set up is discussed.

As I think about it there are a few questions:

• Is it going to reduce efficiency by much?
• How is pump controlled in these set ups?
• Are smart control systems like evohome, wise etc able to control CH loop properly?

Thanks!

 

[Dan Robinson]

Nope

Depends

Yes



Comissioned one recently as it happens:

It's not common practice though. This example is a large house with a light commercial boiler so I didn't want to risk an expensive repair from a stroppy company engineer.

 

[Someuser08]

Sounds promising, so how will heating controls connect to the secondary loop?

 

[Dan Robinson]

As normal. It's how you connect to the system pump.

Which depends on the controls and the boiler. Evohome can do it all.

 

[Someuser08]

I'm eyeing up intergas extreme (or may be cheaper intergas). Does it mean that I have to get the set up right from the start or can upgrade controls myself in the future? For example if I initially get some simple thermostat and later upgrade to evohome without rewiring - is that possible specifically with dual loop set up?

 

[Dan Robinson]

upgrade to evohome without rewiring

How do you plan to achieve that?

 

[Someuser08]

I don't know - that's why I'm asking. May be using bdr91 with something other than evohome initially?

 

[Razor900]

There's no point in using the Xtreme as a system boiler the Xclisive is the one for that!

 

[Someuser08]

I'm not planning to use system one - separate loop will be for CH only. DHW would be supplied from the boiler directly...

 

[Someuser08]

At first I'd thought to get a used CM927 with BDR91 now and then just get new evohome binded later when I switch to a new boiler, but I can see I can get a cheap evohome to start with anyway, so will try to do that before moving to a new boiler (that way I'm used to how its supposed to work).

Dan, quick question about the picture - what is the PHE model on it?

 

[Dan Robinson]

Its one we had in stock for ages due to another project changing scope. Can't remember the model but it was huge and was around £700. I would think most houses would be fine on a smaller one. This place was pretty big and drafty.

 

[Someuser08]

Would something like this be sufficient for 36kw boiler?

https://www.manomano.co.uk/heat-exc...plate-heat-exchanger-3214341?model_id=3214341