Condensing Boilers - what volume of codensate is discharged

[Rob Foster]

When a 25 kw condensing boiler is going full tilt in the winter what volume of condensate water might be discharged per hour ? Obviously an overflow pipe will cope. Anybody any ideas. It could be 20KW or 30 KW I am looking for a ball park volume. Many thanks

 

[Scott_D]

What's the reason you need to know?
I don't think many boiler are condensing 100% of the time

 

[Rob Foster]

customer asked my mate, he didnt know and asked me ,neither did I so I asked you !

 

[ShaunCorbs]

Would say under a litre an hour

 

[Scott_D]

I think sone boiler have an amount listed in the manual

 

[fixitflav]

customer asked my mate, he didn't know and asked me ,neither did I so I asked you !

For 25kW output, I make it theoretical water production about 2.4 litre/h , but not all of that will condense.

 

[Rob Foster]

Hi fixitflav thanks for that - how did you calculate it may I ask - in awe of you on this one

 

[rpm]

Rob, when you had 20 fitters working for you what sort of work were you doing?

 

[Rob Foster]

Types of work ....1 Contract ch installation new build, 2 medi-gas contracting, 3 local plumbing/domestic ch installs but in a quite tight area - no adverts just word of mouth so we knew the customer and they us. 1st 2 profit is all down to margins and speed 3 is down to reputation word of mouth. Beware you have to get from one man (you) to over 5/6 very quickly or you end up not earning anything yourself Young men for 1, steady fellas for 3 and anybody who was prepared to work xmas easter and bank holiday for 2

 

[fixitflav]

Hi fixitflav thanks for that - how did you calculate it may I ask - in awe of you on this one

Originally I used a hand calculator and seem to have dropped a cod, it's actually more like 3.8 l/h.
Calculation below. I used Mathcad, but pleasantly surprised it copied in OK. Don't worry about apparent lack of conversion factors etc, Mathcad takes care of that for you. I've made one or 2 assumptions, as natural gas is not pure methane, but it won't be far out for water produced. Be interesting to compare with maker's figure, to get an idea about what fraction condenses. Come back if you need more.

 

[Rob Foster]

thank you gobsmacked -

 

[ShaunCorbs]

Originally I used a hand calculator and seem to have dropped a cod, it's actually more like 3.8 l/h.
Calculation below. I used Mathcad, but pleasantly surprised it copied in OK. Don't worry about apparent lack of conversion factors etc, Mathcad takes care of that for you. I've made one or 2 assumptions, as natural gas is not pure methane, but it won't be far out for water produced. Be interesting to compare with maker's figure, to get an idea about what fraction condenses. Come back if you need more.

View attachment 34144

2.347m3/hr not 2.429

also that figure is a constant 25kw on a heat/system boiler which even at the middle of winter wont run constantly on full

if its a combi that figure will be lower also due to the output

 

[fixitflav]

2.347m3/hr not 2.429

Depends on the makeup of the gas and the assumed boiler efficiency, but either is near enough in practice.

also that figure is a constant 25kw

OP said "when the boiler is going full tilt".

 

[sammathias]

Honestly I think I've read closer to 3l/h somewhere. Maybe a vaillant manual.

 

[sammathias]

28kw vaillant 1.9l/h...
30kw vaillant 2.5l/h
God I'm sad.

 

[ShaunCorbs]

Depends on the makeup of the gas and the assumed boiler efficiency, but either is near enough in practice.

OP said "when the boiler is going full tilt".

Yes but I would be surprised if it went for longer than 30 mins on full tilt will modulate down to half power

Also return temp matters a lot

 

[sammathias]

Based on a 50/30 temp them figures are.

 

[Rob Foster]

Rob, when you had 20 fitters working for you what sort of work were you doing?

Rob, when you had 20 fitters working for you what sort of work were you doing?

I did not mean to end up with 20 or so. I had semi retired at 40 ish , myself and 2 others did really well in the late 80's + 90's building and property. I was stood in a pub ! fella next to me was doin xword and asked whats a greek cheese ? conversation ended with him asking me to help him with a ch installation next day. When we did it he was impressed and asked how much I wanted - I told him - Jimbo said he didnt earn that rate himself. So it ended up with me getting the work for him and about a score of his really experienced older pals at my idea of rates - it worked. wacky story but all true

 

[fixitflav]

whats a greek cheese ?

And whats a greek urn?

 

[fixitflav]

Yes but I would be surprised if it went for longer than 30 mins on full tilt will modulate down to half power

So would I, but my calc is for an instantaneous rate. Reminds me of introduction to rates of change and differential calculus a few (!) years ago. Sir told a tale of a woman being stopped by a cop and told she was doing 45mph. Don't be silly, officer, she said, I only bought the car 10 minutes ago.
Just out of curiosity, how do you get 2.347m3/hr in #12?

 

[ShaunCorbs]

So would I, but my calc is for an instantaneous rate. Reminds me of introduction to rates of change and differential calculus a few (!) years ago. Sir told a tale of a woman being stopped by a cop and told she was doing 45mph. Don't be silly, officer, she said, I only bought the car 10 minutes ago.
Just out of curiosity, how do you get 2.347m3/hr in #12?

25/10.65

 

[fixitflav]

25/10.65

OK thanks. The 10.65 must include a number of factors, notably assumed boiler efficiency, which could be different from those I used. But clearly not much different.

 

[townfanjon]

Hard to estmate but depends totally on delta T .