Thoughts on this system

[Nelson-]

Thoughts on this system, pro's, con's, positives, blasphemy and warrented abuse?
Asuming flow through combi is less than desired for filling bath / shower
vs an unvented system...
Why would or wouldnt you?

sorry if its in the wrong forum, but thought it better in general as its not heating focused as such?

A great many thanks!

 

[sammathias]

Wouldn't be far off the same price as fitting an unvented cylinder.

 

[Nelson-]

Do unvented engineers charge more or not really? How do you think maintenance would compare? Is there anything to be said for the fact if the combi was already there, and the fact this could produce on demand hot water at other outlets? Or is that not really worth it in the bigger picture?

 

[ShaunCorbs]

Can't feed a shower pump off a combi cylinder

 

[Nelson-]

Interesting! why is that Shaun?

 

[ShaunCorbs]

Interesting! why is that Shaun?

Holding tank is too small so can't keep up with the demand also cylinder capacity is normally a bit on the low side

 

[Nelson-]

So the pump would more likely run dry, rather than the user deciding its not hot enough first?

I take your point though, its possible in the first place for it to run dry, where as with a correctly sized tank its not possible, it would just produce cold at least for ages, long enough to decide its too cold.

Thanks for the answer btw that's cracking advice mate.

 

[ShaunCorbs]

Correct need at least 50 gallons for a pumped supply

But if you have a good main pressure and flow you can get away with 35-40 gallons

 

[Nelson-]

Legend great advice.

Say you swapped the combi cylinder, for a separate vented cylinder and 50gal feed tank... (which removes a big advantage because now there's a feed tank again)

Any other areas it would not perform aswel as an unvented?

Would an unvented have miles faster warm up time, or not really?

 

[ShaunCorbs]

TBH my opinion it's a backwards idea your installing a gravity set up and then boosting it other than your water flow and pressure being too low for a unvented set up (only reason to install like your suggesting ) unvented all the way

These days cylinders are the same insulation wise but if you decide the gravity way go for a stainless steel cylinder something like a gledhill unit

 

[Nelson-]

Nice one,

This is just something I'm thinking about in my spare time, keeps me entertained. I'm not a plumber for a living, wish I could be though, find it interesting.

thanks for mentioning the stainless steel cylinder this gives me something else to learn about.

 

[sammathias]

You can use a combi as a system boiler to feed an unvented cylinder.

 

[Harvest Fields]

You can use a combi as a system boiler to feed an unvented cylinder.

As long as the hot outlet on the combi isnpiped to a tap

 

[Ian10261]

Unvented are undoubtedly the way to go BUT they are reliant on a decent incoming supply otherwise they will be a big (and expensive)
disappointment.

 

[sammathias]

As long as the hot outlet on the combi isnpiped to a tap

Ive never personally used one as a system boiler, would you use a frequently used hot tap piped off the combi? why couldn't it just be capped? I was also thinking like certain boilers, Vaillant/glowworm you could put the boiler into p.06 fill mode and just pull the wires on the diverter valve so its open constantly on the heating side.