Piping and/or Re-piping hot water heat lines to radiators

Reply

  #1  
Old 01-16-11, 01:03 AM
Member
Thread Starter
Join Date: Jan 2011
Location: USA
Posts: 4
Received 0 Votes on 0 Posts
Piping and/or Re-piping hot water heat lines to radiators

All,
I hope I am posting this in the right place. It is a mix between a boiler/ heating question and a plumbing question. I am looking for recommendations on changing or replacing the feed and return pipes to my radiators. I have a 1700 sq ft colonial with a 1978 oil boiler that heats both my hot water and my house. It is a 2 zone system the second zone was added well after the first. The second zone uses baseboard radiators on the first floor addition, and uses what I believe is 3/4 copper. My problem is the rest of the house. From the boiler there are either 3 or 4 inch black pipe that feeds and returns the hot water through the system (couldn't tell you the actual size as there are several layers of lead based paint over them). There are 3 radiators and one small baseboard on the second floor and 5 radiators on the first. When they installed this system they took a lot of short cuts and then added after. My feed and return pipes to the second floor go through my 1st floor and are exposed. The ceiling in the basement is over 7 ft but the 3or4 inch pipes are below 6ft (I have the bruises to prove it). What can I do with this system to put the supply and return lines in the basement into the joist cavity as well as reroute my 2nd floor lines through the walls? Oxygen PEX? I would like to keep costs down as much as possible.
Are these 3-4 inch pipes needed? I assume that it was gravity feed at one time, but they have since added a circulator on the return side of the system. I would also like to add TRV valves to help regulate each room. My upstairs is an oven and the 1st floor is cold due to layout.
Any help, suggestions, options or recommendations would be greatly appreciated.
Scott
 
Sponsored Links
  #2  
Old 01-20-11, 10:02 PM
Member
Join Date: Dec 2010
Location: USA
Posts: 2
Received 0 Votes on 0 Posts
We just looked at a job today that you are describing as your conditions. The lines being at 6' was probably done that way to get the slope for the gravity system. What we are doing is replacing an inefficient LP fired boiler with an on demand. All of the water lines that are greater than 3/4" will be replaced with PEX. Don't have a clue on your layout for the upstairs, but that can lead to developing your carpentry, drywall and flooring skills.....Good Luck
 
  #3  
Old 01-23-11, 02:08 AM
Member
Thread Starter
Join Date: Jan 2011
Location: USA
Posts: 4
Received 0 Votes on 0 Posts
I would truly love to do that. I could even get 3 Rinnai on demand heaters and use them for my ideal 3 zones, if I had gas instead of oil. I have installed these heaters in the past and love them. I am concerned with volume more than anything else. I know the cast iron radiators hold a good amount of water. Since I have a circulator pump is it just a matter of circulation like a baseboard setup? The 3 inch pipe is slightly pitched again assuming it was originally gravity fed at one time. If I changed all the piping to PEX probably 1 inch with an oxygen barrier & copper going from each radiator to below floor level the system works the same way correct? I read on another forum that there was some equation to finding the right pipe size based on heat loss and didn't want to consider this project without some input (3 or 4 inch pipe to 1 is a big difference). Thanks again.
 
  #4  
Old 01-23-11, 06:22 AM
Member
Join Date: Aug 2009
Location: USA
Posts: 4,947
Received 0 Votes on 0 Posts
Go to the tech menu on comfort-calc.net. They have that info there. 3/4" pipe will probably be more than enough for your zones.
 
  #5  
Old 01-23-11, 06:53 AM
rbeck's Avatar
Member
Join Date: Jul 2007
Location: Pennsylvania
Posts: 2,456
Received 2 Votes on 2 Posts
You need to know your heatloss and size pipes and pumps for that.
 
  #6  
Old 01-23-11, 10:25 AM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
3/4" pipe will probably be more than enough for your zones.
Interpret this statement correctly... this does not mean that you can replace the big ole pipe with 3/4...

As a general statement, with proper flow in the system, 3/4 is good for about 40 KBTU. 1" is good for like 80 K + ... I think this info is in the tables at comfort-calc.net

So, as rbeck stated, you do need to know the heatloss of the structure, and how many BTUs you need in each zone before you can size pipes and pumps.

One other 'rule of thumb' ... if you were feeding two 3/4" circuits, you would want one size up in the pipe feeding them in order to maintain the proper flow velocity in all the piping. Two 1" circuits would need 1-1/4" feeding them... etc...
 
  #7  
Old 01-23-11, 10:12 PM
Member
Thread Starter
Join Date: Jan 2011
Location: USA
Posts: 4
Received 0 Votes on 0 Posts
All,

Thank you for your responses. I will look into the website you recommended for more information. I am sure I have dramatic heat loss as the house is a 1935 colonial with no insulation on exterior walls (reason they ran pipes exposed to 2nd floor). I have slowly insulated attic spaces and 1st floor from basement. I am going to remove all exterior walls (Plaster is in horrible shape beyond my level of repair skills and TOO expensive to contract, sheetrock is not hard just time consuming) and insulate correctly. I am also replacing all the old 1950 single pane wood windows as well. This I am sure is going to affect my heat loss calculations. The circulator pump is oversized due to the large supply pipes (4inch OD cast iron) reduced to 1inch OD supply and return to each radiator. I am going to zone the 2nd floor and 1st separate since there is such a difference in temp between floors, 2nd is almost completed with windows and walls. I am sure I will have more questions after looking @ confort-calc, and hopefully if I do you could provide some more assistance. Again thanks for the help so far.
 
  #8  
Old 01-24-11, 02:10 AM
Member
Thread Starter
Join Date: Jan 2011
Location: USA
Posts: 4
Received 0 Votes on 0 Posts
Ok so I read many many articles over the past few hours since my previous post. With all this information has come some new questions. Am I correct in thinking of the large 4inch OD cast iron pipe in my basement as basically a manifold? If this is the case and I have a circulator pump it would be beneficial to replace this as it is hindering my heat loss. If I calculate the flow rate and BTU's of each radiator and run lenght I should be able to resize my pipe correctly? I can use a PEX manifold with the individual runs (feed, return) to each unit. Or am I misunderstanding things? I am also using suggestions from the comfort-calc.net website on heat loss and a free calculator I found online to do a complete heat loss of my home. Again thanks for the help and insite.
 
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: