primary secondary question

ffp20

In a previous life i was a service technician for an oil company many years ago and now i find myself replacing a boiler in one of my homes.

The home is 1300 sq ft home currently using an oil fired boiler with cast iron radiators on a single zone.

I will be replacing with a gas fired cast iron boiler and will be splitting off 2 bedrooms to its own zone and adding an indirect water heater, so, there will be a total of 3 zone run off of the new boiler.

I read Dans book, "pumping away" and found it incredibly educating. I wish i had it 25 years ago as i found explanations for issues i had back in my service days.

Anyway, is there any reason i cant use zone valves fed by a single circulator on the secondary circuit instead of circulators on each zone?

hot_rod

not sure you need primary/ secondary? Unless you want multiple temperatures or have pumping conflicts with high pressure drop heat exchanger type boiler.

I do like to see boiler return protection on high mass or large water content systems, it assures the boiler always reaches a good operating condition.

Ironman

ffp20 said:

In a previous life i was a service technician for an oil company many years ago and now i find myself replacing a boiler in one of my homes.

The home is 1300 sq ft home currently using an oil fired boiler with cast iron radiators on a single zone.

I will be replacing with a gas fired cast iron boiler and will be splitting off 2 bedrooms to its own zone and adding an indirect water heater, so, there will be a total of 3 zone run off of the new boiler.

I read Dans book, "pumping away" and found it incredibly educating. I wish i had it 25 years ago as i found explanations for issues i had back in my service days.

Anyway, is there any reason i cant use zone valves fed by a single circulator on the secondary circuit instead of circulators on each zone?

There's no reason you can't use zones valves as long as the smallest zone isn't over- pumped and all zones combined aren't under-pumped. I would use a Delta P pump like the Grundfos Alpha or Wilo Stratos if you use ZVs.

I agree with HotRod about p/s and return temp protection.

SWEI

What kind of emitters are installed? Have you done a room-by-room heat loss calculation?

ffp20

SWEI i have done the calculations. The rooms have cast iron radiators.
Hotrod i thought of using primary/secondary because of return preotection. As i said the house has cast iron radiators with a short 2" reduced to 1-1/2" mains. Would a bypass suffice then and not do primary/secondary?

SWEI

What water temp will you need on a design day to satisfy the load?

With CI rads, I would look seriously at a fire-tube mod/con boiler. By the time you add a motorized mixing valve with ODR control, a second circulator, and the additional pipe and labor the cost will be very close. The mod/con will take up less space and give you additional control capabilities.

ElvirMujahodzic

Hello gentalmen , I will be replacing a similar system , currently I have 1 zone hydronic system with 2" supply and return lines they out the basement in a 3 family home, I wanted to slightly over size the boiler to make up for the volume of water in these pipes and it has big cast iron rads,, it will be a oil to gas conversion as well. I will keep the oringnal zone, had a additional new loop zone on 1st floor and also add a super store storage tank, so a total of 3 zones, I was thinking about doing primary secondary pumping on this project , the question I have is , SHOULD I pipe in the domestic tank before the primary pump to help the tank keep up at high demand? Or pipe it out on the secondary pumping like the other 2 zones, and no the owner does not want a condensing boiler lol, thank you, bmtcorp@aim.com

Rich_49

Elvir , You may want to start a new discussion .