Pipe Size for New Zone on Gravity Size Pipe System

Nobby

I have a Residential Gravity System that has been converted to a modern boiler using the original piping. The system is set up with 2 zones running of a single circulator pump/zone valves. Having just come out of full immersion in Dan’s books I realize that the set-up on the boiler needs some modification including replacement of the high head/low flow circulator pump to a lower head, higher flow style pump.

Firstly what would be a good circulator to use I’m thinking maybe B&G 100 series, Taco 0010, or B&G PL 30? Is it bad to create too much flow I’e too much cold water to the boiler?

Secondly I am refitting the kitchen and all the piping for this was removed so I will be installing new. The kitchen will be set up as a separate zone and I shall be using the original large column radiators and I was intending to set them up with diverter tees in the returns only. My question is considering the lower head pressure pump that I plan to install should I go with fairly large piping say 1” main with ¾” feeds to the rads.. Or will the fairly small size of the zone 2 rads at approx 30” high by 40” long and one small one at 20” high by 12” long make this neglible so use smaller pipe? I don’t mind installing large pipe and see benefits from doing this. Or would making it a simple loop make sense?
Thank you

[Deleted User]

steamhead has a good way to size the pump

here is his link to the method

http://www.heatinghelp.com/newsletter.cfm?Id=125

Mike T., Swampeast MO

Sizing the pipes

Personally, I'd look at similar size rads on the same floor and size the new pipes the same. Use black iron or copper--not galvanized.

Unless this was a one-pipe gravity system (I guess they existed) I'm not quite sure why you want diverter tees on the return.

Unless the old takeoff fittings for the kitchen rads are now in an absurd position relative to the new location of the rads, I'd use the old takeoffs. You'll have to completely disassemble the system back to the new location of the takeoffs if you move them. Why make more work? If you're re-doing one of the main pairs, I'd try to size them similarly to what was there.

I'd avoid putting the kitchen rads in a loop unless they were originally done that way.

The rads in many old kitchens were sized with the old cooking stove in mind--they put out LOTS of heat. If you haven't already done so, I'd make certain that the rads are sized proportionally to the rest in the house. If you follow the old "Mill's Rule" in Dan's book "How Come", you'll likely find the existing radiation quite close to this and can verify the kitchen rads similarly.

Nobby

The original piping for the Kitchen zone was removed by the PO for kitchen remodeling as were the Radiators. I purchased the house with the kitchen an empty shell. The gravity main is blanked where the feed and return for the kitchen used to be hence the need to run new pipes and fittings. The radiators for the Kitchen I still have and will be returning according to my calculations they should be fine plus they match all the other rads in the house. I was going to run it as a one pipe zone being as its a new seperate system and that there is a circulator pump now.
Hence my questions regarding pipesize and set up. However I figured that 3/4" main with 1/2" risers would give enough gpm but I wondered if I should go bigger because of the low head higher flow pump.
Oh yeah pipe I plan to use is copper just figured it to be easier than black iron in a tight crawl space.
Should i stick with a 2 pipe system like the rest of the gravity system?

Nobby

Steamhead

I'd pipe them back in

to the old system, using the original pipe sizes. I'd also add non-electric Thermostatic Radiator Valves to them, which will limit the temperature to whatever you set them for. That way, if you have the stove cranking away to prepare Sunday dinner, the room will not get too warm when the thermostat in the other room calls for heat.

The same suggestion is also good for bedrooms- occupants can keep them cool if they want, regardless of how warm the main living areas are.

Gerry, thanks for the kind words regarding the circulator chart.

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Dave_4

pipe size

...no sense oversizing the piping unless the kitchen is the farthest (hydraulically) from the pump....what about running pex to the rads....less labour, you can use 5/8" if you're still concerned about capacity... the recommendation for non-electric thermostatic radiator valves previously noted is right on the money....

Nobby

Nice Advice Thankyou. A great welcome for my first site post.
I was intending to zone with its own thermostat. Right now I have the house split into 2 zones with large orifice zone valves and this is working fine. So see no issue adding one more zone valve.
I'll probably use copper(I have it it in stock) and it will be hydraulically closest to the pump. Right now after great thought I am leaning towards 2 pipe 1" main with 3/4" Risers.
The circ chart did indeed answer my other quest. thanks.