intermittent heating problem in a closed hot water system


  #1  
Old 11-16-07, 03:21 PM
M
Member
Thread Starter
Join Date: Nov 2007
Posts: 6
Received 0 Votes on 0 Posts
intermittent heating problem in a closed hot water system

I need help. I have had two different boiler companies over at least three times and they have replaced the thermostat, the circulator (pump? I don't know if this is right word but it is what pushes water through the pipes) and purged the system of air three times and the problem keeps coming back.

This is a closed hot water system
All the other zones work fine.

On the problem zone, when the temperature goes low enough the thermostat turns on, the circulator goes on, the boiler heats up the water, I hear what sounds like the water going through the pipes, but the water does not get warm on the zone, so the thermostat keeps calling for heat and the zone does not warm up. This can go on for a number of hours, but sometimes after I turn thermostat down and back up again later, the system will immediately heat up, only to later have the same problem come back again. I noticed also that it is if sometimes the hot water reaches the cold water can can't push through and slowly the hot water that was there starts turning cold moving back from the pipes to the circulator. Any ideas at all.
 
  #2  
Old 11-16-07, 03:44 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 4 Votes on 3 Posts
Originally Posted by Martan View Post
I noticed also that it is if sometimes the hot water reaches the cold water can can't push through and slowly the hot water that was there starts turning cold moving back from the pipes to the circulator. Any ideas at all.
Huh? I'm sorry, but I don't understand that sentence at all!

If you've had two companies there numerous times replacing parts that probably didn't need to be replaced, and not being able to diagnose and repair the problem, and yet you paid them... well, I'd probably be screaming and yelling and jumping up and down on the bosses desk by now.

It sounds as though there is air in the system. Either they didn't get it all out when the purged/bled your system, or you've got a leak somewhere that hasn't been detected.

Is your 'problem zone' the upstairs (highest) loop by any chance ?

What is your temperature/pressure gauge on the boiler reading ?
 
  #3  
Old 11-16-07, 04:07 PM
M
Member
Thread Starter
Join Date: Nov 2007
Posts: 6
Received 0 Votes on 0 Posts
Thank you and more info and questions

I really appreciate your quick reply, makes one feel less alone in the world. So thank you.

The zone is the lowest level.

The said the felt there was no leak, because we have an automatic filler valve and they do not hear it filling. But the truth of the matter is that some of the pipes run under a wood floor, over a slab, so it is possible something is brewing down there. Is there anyway to check that out without tearing up the floors.

Let's see if I can explain that last sentence, it is confusing.
I know this is going to still be odd sounding. Heat is called for most of the time. When it doesn't work the pipe remains cold from circulator through all the pipes in zone. Sometimes especially after system worked. The pipes are hot up to a certain point in the system and then everything after that is cold. When the system calls for heat again and is not working properly slowly the hot pipes become cold and the cold slowly takes over the hot water that was in the pipes and the pipes become cold all the way back back to the circulator. Does that make sense? I wish I could draw a picture to show you what I mean.

Here's another question which I know nothing about. If the circulator pump is not powerful enough, one of the thoughts of the heating company is to get a more powerfull pump.

Is it harder for hot water to push through cold water, like is the cold water a barrier stopping the hot water to get through would a more powerful pump handle this issue. I'm probably showing my ignorance, but I am grasping at straws. I guess this is what I do rather than screaming and yelling.

What I still don't get is if there is air in the system, why does it sometimes work and other times not. Shouldn't it stop the water from going through all the time?
 
  #4  
Old 11-16-07, 04:10 PM
M
Member
Thread Starter
Join Date: Nov 2007
Posts: 6
Received 0 Votes on 0 Posts
more info

Water temperature reads anywhere from 140 to 200

The pressure gauge usually around 18 to 20
 
  #5  
Old 11-16-07, 05:15 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 4 Votes on 3 Posts
LOWEST level, eh ? hmmmm... that makes it interesting. Usually if there's an air problem, it affects the highest levels.

I seriously doubt that you would hear a fill valve adding water to a slowly leaking system. In fact, you might not even hear it adding water to a SERIOUSLY leaking system. A drip or two every few seconds would be undetectable noise-wise. That's a lame rationale...

I think the best way to check the system for leaks would be to shut it down, let it get cold (and I mean room temperature, the entire system, because even if it's at 90* the pressure will drop as it cools more). CLOSE the manual water supply line to the boiler. Make a note of the pressure gauge reading. Leave the system off for a day or two or a week(gettin' cold out, ain't it ?) and monitor the gauge. If it drops, you've got a leak. I don't think you want to do that now though...

Is there no access to the under floor area at all ? There are companies that have fibre-optic cameras that they can run under floors and such. Probably won't be cheap, but if you suspect there may be a leak under there, it would sure beat ripping up the floor!

I _think_ I understand what yer trying to say... those are symptoms of air in the pipes.

I doubt if a stronger pump is called for. What pump is on there now ? You said they replaced it, so you know it is good. No, I think it's an air problem.

You can't draw a picture... but if you have a digital, take as many pics as you can. Post them on www.photobucket.com (free) and provide a link to the album here and we'll take a look and see if we can spot something. Please include some wide shots along with some closer ones so we can view the entire system and know what's what. We may be able to suggest ways that you can purge air and fix it yourself.
 
  #6  
Old 11-16-07, 05:54 PM
B
Member
Join Date: Nov 2007
Posts: 160
Received 0 Votes on 0 Posts
not sure of your boiler or the type of control box, but some boiler controllers have a cold water circulator cut out circuit to keep the boilers from suffering from thermal shock.

If the control starts to go south it will keep the circulator from constantly running when called for. This can be intermittant at first.
 
  #7  
Old 11-16-07, 07:54 PM
M
Member
Thread Starter
Join Date: Nov 2007
Posts: 6
Received 0 Votes on 0 Posts
Circulator problem

I will check that out, thanks for info, though we have four circulators and the other three are working, so that might rule out that possibility
 
  #8  
Old 11-16-07, 07:57 PM
M
Member
Thread Starter
Join Date: Nov 2007
Posts: 6
Received 0 Votes on 0 Posts
Thanks again

Will check out that fibric optic camera. You're right I can't imagine shutting down entire system in until it becomes warm again.
 
  #9  
Old 11-16-07, 08:32 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 14,381
Received 35 Votes on 33 Posts
Lowest zone

I would bet dollars to doughnuts air is being trapped somewhere, probably where the pipes drop down to or under the floor. This kind of piping layout can be tough to rid of air. Sometimes I've had to install bleeders on these "traps". If you get someone who knows how to do it, a "power purge" might get rid of the air.
 
  #10  
Old 11-17-07, 05:28 AM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 4 Votes on 3 Posts
I'm with Grady ... before you spend money on a camera study, definitely try to get air out. Post those pictures, we may even be able to instruct you to do it yourself!
 
  #11  
Old 11-17-07, 05:28 PM
M
Member
Thread Starter
Join Date: Nov 2007
Posts: 6
Received 0 Votes on 0 Posts
Bleeding

I got some info as to how to purge system, which I will do. But I wonder why is it intermittent, if it works, why then doesn't it work later. Wouldn't the problem be consistent until I purge system.

Taking pictures is a bit to complicated for me.
 
  #12  
Old 11-17-07, 06:10 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 4 Votes on 3 Posts
Originally Posted by Martan View Post
Wouldn't the problem be consistent until I purge system.

Taking pictures is a bit to complicated for me.
Not always... water and air are funny that way sometimes!

If taking pictures is too complicated, then I don't know how we can tell you which valves to open and close...
 
 

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