new boiler no steam from flue is this normal?

rarmsby

Hi I have just had a greenstar 28CDI boiler fitted and I am concerned there is no steam at all coming out the flue when hot water is on. My old boiler had plumes of steam when hot water an and when central heating on. Can anybody confirm if this is normal or not in a newer boiler. thanks for any help

BUFF

There are variables - outside air temperature, pressure & humidity; hot water temp & flow rate/amount used; are you using the preheat mode (the boiler will keep a small amount of water already heated).

rarmsby

no not using the pre heat mode it just seems odd there no steam at all coming from flue

grumbler

It's pure physics. Visible steam is a result of hot humid exhaust mixing with cold air outdoors.

Exhaust from a condensing boiler is far less humid and is less hot by definition. The outdoor temperatures are now pretty high.

Bendy_House

Yes, in this very mild (hot!) weather, any plume will be much less visible since any water vapour still exiting the flue will not be condensed before/as it exits like it would be by cooler air.

Also, if it's a very effective condensing boiler, then most of the water vapour produced by the combustion process will have been condensed out by the boiler (and is recovered by the boiler, draining out via the condensate pipe) before it exits the flue in the first place, so there's just less there to be visible.

As someone on here pointed out to me, a boiler in 'full' condensing mode - which would require a return water temp of - ooh - around 35-40oC -  would/should have next to zero visible plume as a result. This would require a well-designed CH system, tho', such as UFH or oversized rads.

I presume your new boiler has been fitted to your existing rads, so you can 'look forward' to some plume when the temp falls enough for you to turn the CH on...

Modern condensing boilers don't send the cold incoming mains through the condenser, do they? Imagine how effective it would be for recovering heat when the cold mains is at ~10oC! I wonder why they don't do this?

 

daveyjp

Perfectly normal at this time of year as the external air temperature is too high.

rarmsby

thank you all