Size of supply pipes for radiators

Size of supply pipes for radiators

PostBy: tjzmc On: Fri Oct 30, 2009 10:12 pm

I have an EFM S-20 stoker in a three story house. There are two big rads on the first floor plus about a total of 30 feet of cast iron baseboards. The second floor has one large and four medium size radiators plus a large rad on the third floor. Everything is currently on one zone. There is two inch iron pipe supply and returns in the basement that have 3/4 inch supply and returns branching off to each radiator. The problem is that when it calls for heat the circulator runs for about maybe a minute and it sucks all of that cold water into the boiler and then shuts off. The boiler has to run for awhile to heat the water up and then the proccess starts over again until it gets caught up. My plan is to split the system into two or possibly three zones. With one being the cast baseboards in the kitchen and back of the house, the second being the other two rads on the first floor and the third being the second and third floors combined.
My question is what size of copper tubing to use for the supply line? I am going to replace the iron with copper right up to the radiators and baseboard on the first floor. The second and third floors I'm going to tap into the 3/4 " iron in the basement going to the radiators. Thanks.
tjzmc
 
Stove/Furnace Make: EFM S20
Stove/Furnace Model: Tri Burner

Re: Size of supply pipes for radiators

PostBy: Sting On: Fri Oct 30, 2009 10:23 pm

You can flow/transfer 10,000 btu/HR per gal per minute in a wet system. 1/2 inch copper or iron pipe will move/flow about 1.5 gpm and 3/4 .... about 4GPM - and 1 inch pipe will move 8gpm or 80,000 BTU/Hr --- that's a trouble free rate.

Your system splits will have to be quite a load to surpass this amount of energy.

Perhaps you could balance the system you have now -- some old dead plumbers designed - built it - and proved it worked in the past.

My suggested reading list and system balance sermons may be all that's needed as it sounds like the appliance is working just fine.

Kind Regards
Sting
Sting
 
Other Heating: BurnHAM=NG-gas

Re: Size of supply pipes for radiators

PostBy: franco b On: Fri Oct 30, 2009 11:10 pm

Unless you are unhappy with the balance of the system I would agree with Sting to leave it alone. In the colder weather the water in the pipes and radiators will be a lot warmer with a lot less cycling of the circulator.

I assume it is 2 pipe hot water with a loop for feed and a loop for return. One inch copper mains should be plenty big enough should you decide to zone.

Richard
franco b
 
Hand Fed Coal Stove: V ermont Castings 2310, Franco Belge 262
Baseburners & Antiques: Glenwood Modern Oak 114
Coal Size/Type: nut and pea


Re: Size of supply pipes for radiators

PostBy: tjzmc On: Sat Oct 31, 2009 12:28 pm

franco b wrote:Unless you are unhappy with the balance of the system I would agree with Sting to leave it alone. In the colder weather the water in the pipes and radiators will be a lot warmer with a lot less cycling of the circulator.

I assume it is 2 pipe hot water with a loop for feed and a loop for return. One inch copper mains should be plenty big enough should you decide to zone.

Richard

Thanks to both of you. The syatem is balanced well. You are correct the colder it get the more efficient it is because the returns stay warm. It just seems like such a waste of coal to heat all of that cold water up and let it get cold again two or three times a day unless it is really cold and windy outside.
The system isn't really plumbed correctly anyway. The efm manual states that you should use both returns in the boiler and an 1 1/4 in bypass line as to not shock the boiler with cold water. There is only one return being used and a 2" bypass which stay very hot all of the time so it isn't letting any return water bypass.
tjzmc
 
Stove/Furnace Make: EFM S20
Stove/Furnace Model: Tri Burner

Re: Size of supply pipes for radiators

PostBy: Sting On: Sat Oct 31, 2009 1:28 pm

When I speak of system balance -- the one primary point is Supply and Return water in any one radiator - zone - or loop has a Delta T of 12% + or - 2% all season.

If, as you describe the boiler is hi firing for long periods in this weather, struggling with large amounts of cold liquid, and heating the load three times a day -- Sorry to say your wrong, but the system is not balanced.

And it may not be possible to balance it if its not piped correctly. On another board this week, we debunked an installation where a so called professional installed a biomass boiler via an energy isolation loop - into the return side of the existing system -- and didn't even put a pump on it :?
Sting
 
Other Heating: BurnHAM=NG-gas

Re: Size of supply pipes for radiators

PostBy: franco b On: Sat Oct 31, 2009 2:52 pm

By balance I meant how even the heat is room to room and floor to floor.

It isn't as if the heat were wasted, Those big mains probably allow some gravity circulation within themselves even when the circulator is off. So the radiators get that heat. Also those big radiators hold a lot of water, so it isn't just from the mains that a big slug of cold water is coming from. I assume you have insulated the mains, unless you want them to heat the basement.

You might also check the thermostat differential to make sure it is no wider than 2 degrees. The heat anticipation setting also has to be set high to prevent overshooting of room temps. which leads to long off times and the condition you refer to. You want shorter more frequent run times of the circulator for more even heat. Do this in a bit colder weather though.

Richard
franco b
 
Hand Fed Coal Stove: V ermont Castings 2310, Franco Belge 262
Baseburners & Antiques: Glenwood Modern Oak 114
Coal Size/Type: nut and pea

Re: Size of supply pipes for radiators

PostBy: tjzmc On: Sat Oct 31, 2009 5:31 pm

That is what I meant by balanced also. The floors and rooms are pretty even. I had to turn down one of the radiators in the small bedroom but other than that it's pretty good.There is a flow control valve in the system and the pipe is cold after it when it isn't calling for heat and all of the rad's and baseboards are cold.
I was talking to the older gentleman that owns the plumbing supply store today and he said that two zones with one inch copper loop and 3/4 ' branches to the radiators and baseboards would work ok.
The radiator sizes are just part of it and don't need to be changed but the oversized pipes can be and it seems that it would be more efficient if they where.
If you are running just half of the system at a time with two zones and smaller pipes it should take a big load off of the boiler. Plus the fact that when I sell the house it will be better with two zones and to see nice new shiny copper pipes instead of rusty old iron pipes half covered with asbestos.
The system was installed in 1959 with coal so cheap back then they didn't really worry about making the system being efficient as far as the amount of coal being used.
Thanks
Tom
tjzmc
 
Stove/Furnace Make: EFM S20
Stove/Furnace Model: Tri Burner

Re: Size of supply pipes for radiators

PostBy: Sting On: Sat Oct 31, 2009 8:35 pm

franco b wrote: You want shorter more frequent run times of the circulator for more even heat. Do this in a bit colder weather though.

Richard


Image

No No Acccckkkk NO! You need to go back to the reading list and understand why this is wrong. You WANT a cooler boiler – Less energy in the bearing liquid – less line loss in transmission to the load – More even and comfortable living spaces – No large slugs of cold water forcing the system into boiler protection mode – more efficient operation – less fuel burnt. Room thermostat differential is should never be set wide but a narrow setting will not fix this. Oh Me!


tjzmc wrote: The system was installed in 1959 with coal so cheap back then they didn't really worry about making the system being efficient as far as the amount of coal being used.
Thanks
Tom


The simple fact that it WAS installed in 1959 says to me that a now Old Dead Plumber that knew what he was doing installed it. Leave it alone- restore it back to original design or insert modern parts that can be run in sympathy to the old format – balance the flow - Read the books.

Image
Sting
 
Other Heating: BurnHAM=NG-gas

Re: Size of supply pipes for radiators

PostBy: tjzmc On: Sun Nov 01, 2009 3:55 pm

I didn't do anything to it yet. Before I do I plan on doing it right. I started here for info There are some smart people here and will read what I can to learn what I can. I even plan on bringing in a live old plumber to consult me as to what to do. It will be an easy couple two three hours of pay for him.
Most if not all houses built from the seventies on have multi zone heating if it was't more efficient they wouldn't spent the extra money to do it.
tjzmc
 
Stove/Furnace Make: EFM S20
Stove/Furnace Model: Tri Burner

Re: Size of supply pipes for radiators

PostBy: tjzmc On: Sun Nov 01, 2009 9:26 pm

My suggested reading list and system balance sermons may be all that's needed as it sounds like the appliance is working just fine.

Kind Regards
Sting[/quote]

Where can I get your reading list?
tjzmc
 
Stove/Furnace Make: EFM S20
Stove/Furnace Model: Tri Burner

Re: Size of supply pipes for radiators

PostBy: Sting On: Sun Nov 01, 2009 11:20 pm

I like these!

Others have their favorites - but this author is down to earth. :)
Sting
 
Other Heating: BurnHAM=NG-gas

Re: Size of supply pipes for radiators

PostBy: Yanche On: Mon Nov 02, 2009 10:05 am

Taco has some on-line educational videos for products that they sell. The home page for the site is:


http://www.floproteam.com/index.html
This link is broken, either the page no longer exists or there is some other issue like a typo.


Click the "Learn at your own pace" icon and register. It's free. Once registered you will find a tutorial on variable speed circulators. It's a multiple topic series. The topics are:

Introduction
Universal Hydronics Formula
Sample Project
Pipe Sizing
System Curves
Solving Problems
Choosing Circulators
Parting Thoughts
Review

Be aware that there are many assumptions made when designing using the formulas and methods that are explained in the videos. Many things they don't tell you about. For example, their Universal Hydronics Formula is only an approximation for cold (60 deg F) water. Pipe sizing only applies to copper piping, etc. That said you can design a system using their procedure that will work for homes. It will not be an optimized design but it will work.

For a detail engineering design of hydronic systems you need to use the John Siegenthaler book.
Yanche
 
Stoker Coal Boiler: Alternate Heating Systems S-130
Coal Size/Type: Anthracite Pea

Re: Size of supply pipes for radiators

PostBy: steamup On: Wed Nov 04, 2009 12:16 pm

tjzmc wrote: There is two inch iron pipe supply and returns in the basement that have 3/4 inch supply and returns branching off to each radiator. The problem is that when it calls for heat the circulator runs for about maybe a minute and it sucks all of that cold water into the boiler and then shuts off. The boiler has to run for awhile to heat the water up and then the proccess starts over again until it gets caught up. My plan is to split the system into two or possibly three zones.


Why split it up - to add zoning for comfort or to solve the "problem"?

What is the problem? - cold water into the boiler could be. If a steel boiler, thermal shock is not as big of a problem as cold return and condensation in the fire box. (increased corrosion). You want to maintain at least 140 deg. return water temp to a boiler unless you have a condensing type gas fire boiler.

It sounds like the system is a converted gravity system. Large supply mains with individual branches to radiators. I bet the mains and branches are precisely sloped. I have had no problem running forced circulation into gravity systems but one must understand that most old gravity systems have large mass and ample heating capacity.

I suspect that the thermostat calls for heat, the pump starts and the large mass of the gravity system overwhelms the boiler mass. The boiler then has to fire hard to catch up.

Look at your pump sizing. The gravity system will have very low head requirements. Use a small pump to supply the system. Low flow with high deta T. will move enough btu's to keep you comfortable and smooth out the boiler operation.. Maybe look at primary secondary pumping for the boiler and gravity system.
steamup
 
Stoker Coal Boiler: Axeman-Anderson AA-130, Keystoker K-6
Hand Fed Coal Boiler: HS Tarm 502 Wood/Coal/Oil
Coal Size/Type: pea, buck, rice

Re: Size of supply pipes for radiators

PostBy: Yanche On: Wed Nov 04, 2009 2:50 pm

How about a primary secondary type system using an injection type pump to modulate the temperature of water flowing in the gravity system? This would prevent a large slug of cold water from hitting the boiler when the pump first comes on. Would likely also work well with an outdoor reset control for the injection mixing. Look at some of the Taco injection pumps and controls.
Yanche
 
Stoker Coal Boiler: Alternate Heating Systems S-130
Coal Size/Type: Anthracite Pea

Re: Size of supply pipes for radiators

PostBy: Sting On: Wed Nov 04, 2009 3:57 pm

steamup wrote:
It sounds like the system is a converted gravity system. Large supply mains with individual branches to radiators. I bet the mains and branches are precisely sloped. I have had no problem running forced circulation into gravity systems but one must understand that most old gravity systems have large mass and ample heating capacity.

I suspect that the thermostat calls for heat, the pump starts and the large mass of the gravity system overwhelms the boiler mass. The boiler then has to fire hard to catch up.

Look at your pump sizing. The gravity system will have very low head requirements. Use a small pump to supply the system. Low flow with high deta T. will move enough btu's to keep you comfortable and smooth out the boiler operation.. Maybe look at primary secondary pumping for the boiler and gravity system.


I have had the -- "opportunity" to solve several of these system upgrades -- by simply walking into the basement and just about closing the isolation valve on the pressure side of the circulation pump. That serious reduction of flow, immediately brought the system back to its old gravity flow design self - pumps on replacement boilers were often over-sized for these conversions, and as long as energy was cheep -- so what - it worked.

My issue was how should I charge the customer for solving his problem in 5 minutes - with no parts - and almost no labor :oops:

System Balance!
Sting
 
Other Heating: BurnHAM=NG-gas