Ccts conversion and weather comp.

[gingalig]

Aplologies as I've asked before, but would like to clarify, I,ve been asked to convert from oil (Open vent) to lpg sealed, using a viessmann 111w, its being fitted to approx 3kw ufh with electronic actuators at the manifold for each ufh loop, and 7 rads on microbore. My plan is to use close coupled Tees at the boiler with a bypass, (primary circuit) use the boiler pump as a shunt, connect a second pump and zone valve for the secondary circuit (radiator system) and repeat for the ufh with pump, zone valve and blending valve. The system has been power flushed, all the ufh is new and the majority of flow and return primary pipework to the rads is being replaced, My other concern was complying with boiler plus, I usually fit weather comp although I have been informed that adjusting the heat curve will be ok, Any thoughts on the set up would be appreciated. In future I think I will be using a LLH.

 

[ShaunCorbs]

Ok. So say you got CCT and say 4 secondary circuits, say the secondary loop is 28mm, sized to carry full load, you would install 35mm boiler primaries and Tee's to allow this mixing and cross flow? Sorry I'm just trying to familiarise it in my head

boiler primaries depending on load could be 22mm then just upside the tee eg 35mm as your ring is 28mm etc if your ring is 22 you could use 28mm tees but wouldn’t go above 50kw with 28mm tees

 

[gingalig]

boiler primaries depending on load could be 22mm then just upside the tee eg 35mm as your ring is 28mm etc if your ring is 22 you could use 28mm tees but wouldn’t go above 50kw with 28mm tees

Just to clarify, the boiler primaries

boiler primaries depending on load could be 22mm then just upside the tee eg 35mm as your ring is 28mm etc if your ring is 22 you could use 28mm tees but wouldn’t go above 50kw with 28mm tees

Hi, Just to clarify the primaries are 22mm and the loop was going to be in 22mm the boiler max output is 35kw although I would be ranging it down. If I up the tees to 28mm from the boiler to the loop would this be ok, also would the tees for the secondary supply also be in 28mm or would they be ok using 22mm, sorry for all the questions just trying to get it clear before I install. Many thanks.

 

[ShaunCorbs]

Just looking at your drawing again why is the boiler and rads got ccts ?

 

[gingalig]

Just looking at your drawing again why is the boiler and rads got ccts ?

When I first asked the question a while ago on a different thread about mixing microbore on the radiator circuit and UFH you had actually suggested it. I had a concern that the different demands could be counter productive. If I can climb back into my comfort zone and go for a straight install then that would be a whole lot less worry inducing, although my understanding of CCT,s has greatly improved and its been an interesting journey, I will install using them or an LLH at some point. Do you think there is no need for them ?

 

[ShaunCorbs]

Don’t need to do it on the boiler or rad circuit unless you have pump on pump so remove the pump on the rad circuit and you will be fine

but keep your cct on the underfloor heating

 

[gingalig]

Don’t need to do it on the boiler or rad circuit unless you have pump on pump so remove the pump on the rad circuit and you will be fine

but keep your cct on the underfloor heating

Ok back to the drawing board. I'm getting a bit confused. Please correct me if im wrong. Leave the rad circuit and flow and return from the boiler as a standard install, but add cct,s for the ufh. If so where would they be best connected.

 

[SJB060685]

Ok back to the drawing board. I'm getting a bit confused. Please correct me if im wrong. Leave the rad circuit and flow and return from the boiler as a standard install, but add cct,s for the ufh. If so where would they be best connected.

I'm a bit unsure what Shaun is saying as well. Why decide to go for CCT's in the first place? If it's a domestic property and the boiler pump is man enough and the sub systems aren't pulling too much flow rate for boiler then why not install your standard system?

 

[gingalig]

I'm a bit unsure what Shaun is saying as well. Why decide to go for CCT's in the first place? If it's a domestic property and the boiler pump is man enough and the sub systems aren't pulling too much flow rate for boiler then why not install your standard system?

I had a slight worry about the different demands of the existing microbore pipework and the ufh. cct,s sounded like a revalation, subsequent research has proved everyday is definatley a school day, if I can install without and it has little or no impact on the set up then great. although I can see it would be better long term for the actual boiler. Im booking myself onto the vaillant llh and design course as it seems to tie in well with heat pumps ( another little minefield ) and I need to fill in a few holes. In this instance I'm happy to use ccts if needed now that i have better understanding of them but cant quite grasp what Shaun meant.

 

[ShaunCorbs]

Reason to install ccts not enough space for a llh,

You have a big pump on a combi boiler / system eg 25 rads etc (the pump would put too much flow rate through the boiler hex effecting it also both pumps would fight each other),

Ufh when the system is up to temp the boiler would cycle a lot due to low demand eg 0.5kw
with ccts this would help the boiler as if the return is at a usable temp would pinch from this etc
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Ok back to the drawing board. I'm getting a bit confused. Please correct me if im wrong. Leave the rad circuit and flow and return from the boiler as a standard install, but add cct,s for the ufh. If so where would they be best connected.

After the port valve for the ufh manifold is the best place

 

[SJB060685]

So shaun am I right in thinking if sub systems required high flow rate, more than maximum allowed for boiler exchanger then its CCT or LLH time. This allows each sub circuit to have it's on pump

 

[ShaunCorbs]

So shaun am I right in thinking if sub systems required high flow rate, more than maximum allowed for boiler exchanger then its CCT or LLH time. This allows each sub circuit to have it's on pump

exactly so for example but can always help when less flow rate is needed hence ufh when up to temp

worcester 42cdi heat only 25 plus rads on a 15-60 heat doesn’t get to the furthest x amount of rads stick a 25-80 on the system in the airing cupboard on the heating circuits with cct so both pumps are happy and the boiler flow rate is maintained

 

[SJB060685]

Thanks buddy. I have a much better understanding after reading your comments.