hot water boiler pressure range

Reply

  #1  
Old 12-18-08, 12:55 PM
Member
Thread Starter
Join Date: Dec 2008
Location: colorado
Posts: 3
Received 0 Votes on 0 Posts
hot water boiler pressure range

I recently bought a house with an old montgomery wards hot water boiler. New expansion tank, pressure relief valve, pressure regulator (15 psi.) The cold fill pressure is 15 PSI. and at the high temp. (150 F) the pressure rises to around 21 PSI. I have several questions.
1 is this a normal pressure range?
2. I would like to increase the temp. to the 160 low 180 high range to increase efficiency (I'm concerned about the pressure increase.)
3. the highest baseboard is max 10' from the base of the boiler. will turning down the pressure regulator to 12 psi help?
 
Sponsored Links
  #2  
Old 12-18-08, 03:05 PM
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,493
Received 33 Votes on 25 Posts
How old is the house? What kind of heat emitters are installed, cast iron radiators or baseboard convectors? What size are the main pipes? What size is the expansion tank?

A 6 psi rise is okay, you can go to as high as 27 psi total pressure without a problem although generally I don't like to see any more than 25 psi.

Some pictures of the system would be nice. To post pictures you need to first upload the pictures to a photo hosting site such as photobucket.com or villagephotos.com. and then post the public URLs for the pictures (or album) here. More pictures are always better than fewer. Please have CLEAR pictures and have both close up pictures and ones from a far enough distance that we can see how the various parts are interconnected.
 
  #3  
Old 12-18-08, 04:48 PM
Member
Join Date: Oct 2008
Location: USA
Posts: 2,916
Received 7 Votes on 7 Posts
Originally Posted by pluggo View Post
2. I would like to increase the temp. to the 160 low 180 high range to increase efficiency.
Increasing the aquastat setting might be called for, depending on info that you didn't provide, but it will not increase boiler efficiency - it will reduce it. The flue gas temp will rise, increasing losses.
Doug
 
  #4  
Old 12-18-08, 05:01 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
You said: "160 low 180 high" ...

Does this mean that your aquastat has three dials on it? One LOW, one HIGH, and one DIFF?

Is your domestic hot water produced by this boiler? If so I would not recommend setting the LOW up at 160. Water that hot will burn/scald/injure in a couple of heartbeats. If you have a TEMPERING VALVE on the hot water supply to the home, you _could_ do that safely, but as Doug says, it will not increase your efficiency.

Yes, pics please.
 
  #5  
Old 12-18-08, 06:55 PM
rbeck's Avatar
Member
Join Date: Jul 2007
Location: Pennsylvania
Posts: 2,456
Received 2 Votes on 2 Posts
12 psi is a good place to be up to a two story home. The pressure increase should not be more than 2 - 3 psi. Was the air charge checked when the tank was installed.
Keep the boiler at 12 psi unless you want to add air to the tank, The water pressure and air charge is supposed to match.
 
  #6  
Old 12-19-08, 08:31 AM
Member
Thread Starter
Join Date: Dec 2008
Location: colorado
Posts: 3
Received 0 Votes on 0 Posts
1.1950, not original boiler. baseboard convectors. manifold 1 1/2" all the rest is 3/4" (copper). 15 extrol expansion tank.

2. Aquastat only has the high temp setting. By monitoring the temp i have determined the 20 degree diff. and low temp. The domestic hot water is not on the boiler.

3. The expansion tank was not tested prior to install. the water pressure and air charge do match. THe water feed pressure regulator are keeping the pressure cold at 15 psi. Also, expansion tank was installed upside down.

The actual high temp (using a IR thermometer) is 178 at the manifold.

Still working on the pictures.
Thanks for all the feedback!
 
  #7  
Old 12-19-08, 08:47 AM
Member
Thread Starter
Join Date: Dec 2008
Location: colorado
Posts: 3
Received 0 Votes on 0 Posts
Originally Posted by gilmorrie View Post
Increasing the aquastat setting might be called for, depending on info that you didn't provide, but it will not increase boiler efficiency - it will reduce it. The flue gas temp will rise, increasing losses.
Doug
By efficiency i mean limit short cycling and maximize the baseboard convectors. I was under the impression that 3/4 baseboard efficiency is dramatically increased as temp. goes up. With peak performance at 180 to 220 F. is this correct?
 
  #8  
Old 12-19-08, 02:57 PM
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,493
Received 33 Votes on 25 Posts
Remove the covers from your baseboard convectors and make sure they are not full of lint and dust bunnies. Make sure that you allow free airspace at the bottom and that the movable damper at the top is wide open. Do not have drapes that cover the top of the baseboard convectors. These things are more important than raising the temperature of the circulating water by ten degrees.
 
  #9  
Old 12-19-08, 05:46 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
OK, understood... that's what we needed to know...

In general, the output of a hot water boiler is set at 180 ... it can be set lower or higher ... 150 is on the low side from a standpoint of possible flue gas condensation issues ... but that depends on the temp of the return water ... and the fuel type ... Is your boiler fired with gas, or oil?

150 is as low as I would consider setting an oil boiler... and I wouldn't run a gas system lower than 160 ... and in either case keep a close watch on the return temps.

If you can run a lower temperature, while keeping the return water temps high enough so you don't condense in the boiler, and still heat the home comfortably, you will save fuel.

It's a balancing act that you have to find the right point.

baseboard efficiency is dramatically increased as temp. goes up
Ummmm, not exactly... the BTU OUTPUT goes up ... there's really no 'efficiency' to it ... in order to use the term 'efficiency' there would have to be something 'lost' in the conversion... there's nothing lost ... you pump heat in one end, heat is radiated and convected from the baseboards, and what's not used is returned to the boiler to come around again. By increasing the temperature of the water, you will get more BTUs OUT, but still, nothing is really 'lost'.

Even if the baseboards are all fouled with lint, and don't properly heat the home, there's still no efficiency lost in them. You will lose EFFECTIVENESS, but not efficiency.

Make sure they're spic and span as furd says ...

Where you lose efficiency is in the boiler itself. 15% or more of your heating dollar goes up the chimney and is 'lost'.

Don't trust IR thermometers on copper pipe. Iron and steel should be close, but unless you paint a flat black spot on copper pipe, you won't get an accurate reading.

If that 178 IS an accurate reading, then don't touch the setting.
 
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: