When is Cold Fire Boiler not a good idea?

Reply

  #1  
Old 10-01-12, 06:55 PM
Member
Thread Starter
Join Date: Jan 2012
Location: Canada
Posts: 2,739
Received 16 Votes on 15 Posts
When is Cold Fire Boiler not a good idea?

I've been reading about this cold start concept (firing up the boiler only when the t-stat requires it) for a bit now. My boiler system has been retrofited over and over so it's likely it is not the most efficient setup.
That being said, I'm looking at the cold fire concept and wondering when it is not suggested to go this route?
I do not have DHW feeding from my boiler (coil is still installed, but not used). I know my aquastat would not support it, but I think my boiler might (with the correct aquastat).
Currently running;
The oil burner unit is a Riello 40 Series
Boiler is a Kerr Comet 145 Oil Fired hot water boiler
Honeywell Triple Aquastat Type L8124L (came with the boiler when it was new)

Currently both zones (t-stats) control the seporate relay boxes which control two circulation pumps. The aquastat has no direct contact with the t-stats.
From my understanding, I can connect the t-stats to the aquastat and have them fire the boiler, but the boiler will (with the current aquastat), maintain a minimum temp of 100'F.
 
Sponsored Links
  #2  
Old 10-01-12, 07:46 PM
lawrosa's Avatar
Super Moderator
Join Date: Dec 2010
Location: Galivants Ferry SC USA
Posts: 17,962
Received 37 Votes on 32 Posts
I believe the only reason to keep your aquastat, is if the boiler leaks converting to cold start. The theory is a warm boiler likes to be warm all the time if its been that way for years. Make them go cold start, and they weep. Hence keeping it warm. If not, cold start for efficiency.
 
  #3  
Old 10-02-12, 05:52 AM
Member
Thread Starter
Join Date: Jan 2012
Location: Canada
Posts: 2,739
Received 16 Votes on 15 Posts
I believe the only reason to keep your aquastat, is if the boiler leaks converting to cold start. The theory is a warm boiler likes to be warm all the time if its been that way for years. Make them go cold start, and they weep. Hence keeping it warm. If not, cold start for efficiency.
From what I know, the boiler has been shut down during the summers only over the last 2 or 3 summers. Previously, they where aquiring DHW from the boiler, so it would have run all summer as well.
A lot of the work done in this house has been out of need, and not a lot of thought had been put into "If I do this, I should also do this". With the boiler, they installed an eletric hot water tank, but left the boiler as is. Added a new expansion tank, but left the old one in place. Added two pumps instead of one and moved the controls to the relay boxes, leaving the old control valve in place.
A lot of the work I have to do as a result is look at what is there, figure out what it was for, and why it's no longer in use.
I guess I'll find out how well the boiler will do with a cold or barely warm start. Last years oil bill would have bought me a new boiler.
 
  #4  
Old 10-02-12, 08:48 AM
Member
Join Date: Nov 2011
Location: USA
Posts: 418
Received 2 Votes on 2 Posts
Another thing to keep in mind is that, from a cold start, your oil-fired boiler will be operating at lower temperatures for longer periods of time. During these low-temp periods there is greater risk of flue gas condensation. Some boilers are worse than others in this regard, a lot depends on design and how well-tuned the system is.

Related to that, when an oil burner fires into a cold chamber, conditions are less than ideal for a "complete" burn, which can cause some of the vaporized oil to not get burned during the combustion process, which can lead to more smoke and soot accumulation over time. In short, your boiler may get dirtier sooner than if it remained a warm-start.
 
  #5  
Old 10-02-12, 09:07 AM
Member
Thread Starter
Join Date: Jan 2012
Location: Canada
Posts: 2,739
Received 16 Votes on 15 Posts
Good to know Rockledge.

Would condensation be as much of a concern if the boiler is in the basement (~65'F temp average) as well as the oil tank? The stack goes horizontal for ~8ft in the basement before exiting the wall and going straight up.
 
  #6  
Old 10-02-12, 11:13 AM
Member
Join Date: Nov 2011
Location: USA
Posts: 418
Received 2 Votes on 2 Posts
Would condensation be as much of a concern if the boiler is in the basement (~65'F temp average) as well as the oil tank? The stack goes horizontal for ~8ft in the basement before exiting the wall and going straight up.
I suppose it's better that the air for combustion and draft regulation is not cold, but the biggest factors of boiler condensation are the temperatures inside the boiler, flue pipe and chimney. When these temps get below a certain point, condensation will occur.

Also remember that, cold return water temperatures have a large effect on boiler temps. as a whole. So you'd still want to have some sort of low limit with regard to the circulator to make sure cold water doesn't circulate through the system upon a cold-start.


 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: