Unique Hot water heat air hammering problem

Reply

  #1  
Old 05-30-12, 02:15 PM
Member
Thread Starter
Join Date: May 2012
Posts: 4
Received 0 Votes on 0 Posts
Unique Hot water heat air hammering problem

I have a unique problem with my system. I have a 15 year old hotwater system to which a solar system was added later. The furnace is also connected to a sidearm for domestic hot water. When the furnace is heating the house everything runs quietly. The problem occurs when I am on solar heat. The solar heat system creates significant air hammering in the middle of the night. If I turn all the thermostats down and leave the solar heat only running the sidearm there is no banging...

The furnace has an expansion tank with a recently installed valve at the top of it. There is another expansion tank above the solar specifically for that part of the system. There is also another recently installed air valve at the highest point on the solar pipe sending water into the house system before that enters pipes for the registers.

The weird thing is that I can also stop the hammering almost instantly by pushing up the solar control panel thermostat and forcing the system to switch over to boiler heat. There is obviously air in the solar system but it only causes banging when the reigisters are getting water from the solar tanks --but that same water does not cause banging in the sidearm pipes.

My solar plumber who installed the system is stumped. Any ideas?
 
Sponsored Links
  #2  
Old 05-30-12, 04:18 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
The solar heat system creates significant air hammering in the middle of the night
I know this is gonna sound sorta wize-azz, not meant that way, but how do you run solar at night? Are you in the land of the midnight sun? no... CO ...

Is it safe to presume that you've got large storage tanks on the system?

As for the 'hammering', I don't think you really mean hammering. Air in the lines can make hammering noises as it passes through pumps and valves and such, but if you had actual HAMMERING, you would know the difference! It's just semantics we're talking here, but there is a subtle difference. An actual water hammer is VERY loud, and the pipes shake. Usually happens when a valve is closed quickly and the flow of water screeches to a halt inside the pipes.

So, what you hear is AIR GURGLING through the system?

We will probably need a much better 'visualization' of the entire system.

What type of solar installation is it? Drainback I'm guessing?

How exactly is the solar portion tied into the boiler system?
 
  #3  
Old 06-03-12, 08:41 PM
Member
Thread Starter
Join Date: May 2012
Posts: 4
Received 0 Votes on 0 Posts
Nope - don't live in the land of the midnight sun. The solar system heats two 50 gallon hot water tanks out in in the garage during the day - up to as much as 170 degrees. The garage is about 3 feet higher than the house, so the water flows down hill into pipe leading into the boiler room. The solar system is spliced into the pipes so that a valve can send water into the baseboard units and/or the sidearm from either the solar system or the furnace, depending on the temp cutoff set. I keep the control set so that when the temp in the solar tanks drops below 135 degrees the system switches back to the propane fed boiler.

I don't know if the solar system is what you would call a drainback system. There is a pump which sends the solar water into the house as well as a second pump which balances water between the two solar tanks and an outside bleed radiator which pumps out to cool water if the temp in the sytem gets to high.
The collectors on the outside of the garage are large vacumn tubes in which an ethonol solution is circulated to carry heated solution into the solar tanks. The collectors are fed by a third pump.

The noise I hear does sound like an air hammer - it is quite loud and I often hear the loud bang in one zone followed later in the night by a bang in another zone. To be honest I don't know if the pipes shake, but they may very well. If this is a gurgle it is the loudest one I've ever heard and it is sharp and fast, not drawn out like a gurgle.

One question is whether it might work to pick the baseboards in my two zones on the second floor and t-in some sort of air valve?
 
  #4  
Old 06-04-12, 03:29 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
Are there electric zone valves that direct the flow through the system? Is the hammer possibly related to the opening/closing of any valves?
 
  #5  
Old 06-04-12, 03:46 PM
Member
Thread Starter
Join Date: May 2012
Posts: 4
Received 0 Votes on 0 Posts
It does have electric valves. It is possible that it is related to opening and closing. One difference between the solar system and the boiler system is that I believe the solar pump is higher volume and perhaps higher speed. Unfortunately it has always done this in the middle of the night so by the time i get to the boiler room the zone is already running. I'll try some experiments over the next few days to see if I can replicate the banging that way. If so - suggestions on remedy?
 
  #6  
Old 06-04-12, 03:52 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
Believe it or not, the first thing to check is to be absolutely certain that the valves are installed in the correct 'direction'. If installed backward, they will slam shut from the force of the water.

If they are Honeywell valves, you __may__ be able to get some relief by removing one of the springs.

If the controls are such that a pump is still running when a valve is closing, then the water is still moving and it's the sudden STOP that you hear causing the hammer.

Stuff like this is sorta difficult to diagnose without being there.
 
  #7  
Old 06-09-12, 09:26 AM
Member
Thread Starter
Join Date: May 2012
Posts: 4
Received 0 Votes on 0 Posts
You are correct. The hammering is caused by specific valves closing. The honeywell valves are 16 years old and seem to have only one spring that pulls the valve shut. Am I just not seeing one or is it because they are older?
 
  #8  
Old 06-09-12, 05:15 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
Someone may have already removed a spring, it's a pretty common 'trick'.

When these valves close, is the pump still running? And the valves are 'diverting' from one system to the other? Is another valve opening as one is closing? If this is the case, the valve that is closing is probably closing faster than the other is opening.

It may be possible, depending on the system configuration, to install a 'differential pressure bypass' valve. This valve could theoretically be adjusted to partially open when it senses the pressure increasing as the valve closes and divert some of the flow temporarily to another return path.

Is it possible to draw up a system diagram? It would help to understand the setup.
 
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
Display Modes
 
Ask a Question
Question Title:
Description:
Your question will be posted in: