navitron
 
Renewable Energy and Sustainability Forum
Welcome, Guest. Please login or register.

Login with username, password and session length
News: Anyone wishing to register as a new member on the forum is strongly recommended to use a "proper" email address. Following continuous spam/hack attempts on the forum, "disposable" email addresses like Gmail, Yahoo and Hotmail tend to be viewed with suspicion, and the application rejected if there is any doubt whatsoever
 
Recent Articles: Navitron Partners With Solax to Help Create A More Sustainable Future | Navitron Calls for Increased Carbon Footprint Reduction In Light of Earth Overshoot Day | A plea from The David School - Issue 18
   Home   Help Search Login Register  
Pages: [1]   Go Down
  Print  
Author Topic: Boiler not producing condensate.  (Read 25877 times)
Norfolk
Newbie
*
Offline Offline

Posts: 8


« on: January 27, 2012, 04:45:06 PM »

Boiler not producing condensate. (Am I worrying unduly?)

I have a 350 litre DPS thermal store heated by an external Warmflow Kabin Pak K90 21-26kW oil boiler. (Currently set up as 24 kW.)
Although it is a condensing boiler and the boiler heats the 350 litre store up from low 20s deg C regularly, to my knowledge it has never produced any condensate to drain in the 14 months since installing it.
The boiler does produce a good plume of steam in cold weather and drips a little from the extremity of the exhaust cowl which is factory fitted.
I try to keep the flow into the boiler as low temperature as possible and often it is about 35 deg C. (we have under floor heating).
Warmflow cannot tell me an ideal flow rate of water through the boiler but I suppose with some power and specific heat calcs I could get an idea.
I have tried all 3 speeds on the circulating pump (Wilo rs25 6-3).
The drain point from the condenser is free flowing if I blow back up it.
The condensate pot is sound and drain is free flowing.
The boiler sits level on a concrete pad..
The inside of the boiler cabinet is dry.
The flow and return are correctly connected.
Flue gas tem is at 90 deg C
Neither the installer nor the subsequent service engineer were that concerned or could offer advice.
I am struggling to solve the issue or am I worrying unduly?
The thermal store can also be supplemented by a Stratford SEB20
Thanks for any thoughts
Logged
A.L.
Hero Member
*****
Offline Offline

Posts: 928

G69, Glasgow


« Reply #1 on: January 27, 2012, 07:08:28 PM »

hello,

Quote
Flue gas tem is at 90 deg C
- to achieve condensing operation the flue gas must be reduced to not more than about 57°C at a maximum within the heat exchanger

as to what is preventing condensing? a low flow could, try to see if the water output is about 11°C higher than the input
Logged
johnrae
Hero Member
*****
Offline Offline

Posts: 764


« Reply #2 on: January 27, 2012, 07:10:20 PM »

90C is far too hot for the exhaust.

If your return water is less than 55C then condensate should be forming.

Are you sure this is actually a condensing boiler ?  Their literature on a google search doesn't appear to mention the magic word
Logged
Iain
Hero Member
*****
Online Online

Posts: 1761


« Reply #3 on: January 27, 2012, 07:14:48 PM »

Hi Johnrae

Quote
Are you sure this is actually a condensing boiler ?
Would have thought so
Quote
The drain point from the condenser is free flowing if I blow back up it.
The condensate pot is sound and drain is free flowing.

Iain
Logged

1.98kWp PV (11 x Sharp 180 and SB 2.5)
20 x 65mm Thermal and 180ltr unvented
Powervault 4Kw - G200 Lithium-Ion (LiFePO4)
9000ltr rainwater storage   Plymouth
desperate
Hero Member
*****
Offline Offline

Posts: 3512


Backache stuff!!


WWW
« Reply #4 on: January 27, 2012, 07:28:59 PM »

Norfolk hi,

What do you mean by "the condensate pot", do you mean the usually clear plastic trap inside the bottom of the boiler? or another separate container?
How do you know that no condensate is draining out? what is the condensate drain connected to and can you see the outlet of it?

Most condensers I am familiar with have a trap in the base of the boiler that gradually fills with condensate and when full it dumps to the drain or whatever and then the cycle repeats, could it be that you have not observed the trap at the right time?

Dunno really

Desp
Logged

www.jandhbuilders.co.uk

still a crazy old duffer!
Norfolk
Newbie
*
Offline Offline

Posts: 8


« Reply #5 on: January 27, 2012, 09:09:36 PM »

Thanks all for replies, 90 deg C for exhaust is in line with the manufacturers specs. Good point on trap emptying its self, will investigate that and put an intercept on the drain. (Desp)
Re exhaust gas temp, I will probably try a smaller jet (0.6) and de-rate the burner to minimum manufactures spec of 21 kW to reduce exhaust temps.(johnrae & Al)
Thanks
Simon
Logged
Philip R
Hero Member
*****
Offline Offline

Posts: 1691

South Cheshire


« Reply #6 on: January 27, 2012, 10:53:58 PM »

You have answerred your own question, Thermal stores do not allow condensing boilers to operate at peak efficiency because the store temperatur has to be maintained above the condensing threshold of the boiler, otherwise, you hot wate(DHW) is not very warm. Been discussed elsewhere on the forum.

Although you heat store from the 20s ( You should get some condensate) Once above the mid 50s ( boiler return temperature) the flue gas plume will be in a form of hot fog blowing out the flue pipe, with little condensate collected in the trap.

My condensing (gas) boiler heats the rads at a flow temp of about 45deg C ( I sized my rads for this). To heat the hot water cylinder, The boiler ramps up to an alternate temperature setpoint of about 75 deg C ( for 25 minutes a day).

When in the low temperature mode, the boiler rapidly modulates down to near minimum o/p. The vapour plume on a cold day is a lazy whisper, with the condensate trap emptying every twenty minutes or so.

With your oil system (pressure jet?) modulation other than by on off is difficult. I have seen it with spinning cup Hamworthy oil burners, but the thermal output of these would kiln your house.

PhilipR
Logged
clivejo
Hero Member
*****
Offline Offline

Posts: 1609



« Reply #7 on: January 27, 2012, 11:31:37 PM »

I also think your return is too hot for condensation to form.  I can hold my hand over the flue on my condensing boiler and it feels like someone breathing on my hand.  Definitely not hot enough to make you pull your hand away.  The return flow is in the region of 20-40C, again same as philip the rads are sized specially for this to happen and the boiler is 'undersized' for rads it drives, but works more efficiently this way. The condensation fills into a small plastic tank and then overflows into a drain (all plastic pipes, as its very acidic and eats through stuff!!)
Logged



DISCLAIMER : I’m not responsible for anything… for anything I say or do. Cos I’m a proud member of clan Eejit who once ruled Ireland.
Philip R
Hero Member
*****
Offline Offline

Posts: 1691

South Cheshire


« Reply #8 on: January 27, 2012, 11:38:32 PM »

Not sure that oil heating qualifies it to be in the Biomass thread. ( Although you can argue it was once biomass).
PhilipR
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.20 | SMF © 2013, Simple Machines
SMFAds for Free Forums
Simple Audio Video Embedder
Valid XHTML 1.0! Valid CSS!