Need Help Sizing

Chris Maderia

monoflo. Main loop out and back. Each convector is individually controlled by it's own control. Customer wants out-door reset. I plan on using a Wirsbo Promix to reset the system using primary/secondary piping. As it stands today somebody tried out-door reset but what they failed to due was change any piping. Basically the boiler resets, the pump runs 24/7, but what's happening is that the system keeps pulling all the BTU's from the boiler so the boiler continually fires to maintain low-limit. So I figure that instead of reseting the boiler I would reset
the system that way I could utilize return water and only take a few btu's from the boiler by using a 3-way motorized
mixing vlv.

Chris Maderia

Convector Sizing

I'm looking for help sizing some old hydronic convectors. There is absolutley no brand name, btu info or anything on these convectors. I need to replace an old wood/oil boiler with a Cast Iron Oil Boiler. I measured the heat exchangers in the cabinets any help would be greatly appreciated.

I have 10 that are 9" wide 24" in length. They are at a 45 degree angle in the cabinet.

I have 3 that are 7" wide and 12" in length also.

DanHolohan

What are the elements made of

and what are the cabinet dimensions?

Chris Maderia

Cabinet Dimensons

Dan,

The cabinet dimensons on the 10 would be 3' length and 42 inches high. The grills in the cabinets are on the top of each unit approx 12" in width. The 3 smaller units are 14 inches in width and 30 inches in height.

The construction of each would be copper with fin-tube no different than a kickspace heater. I've called 3 manufactuers for help on sizing these with no luck.

System piping is mono-flo with constant circulation with an ancient out-door reset control. Pump runs 24-7 and boiler keeps short cycling.

DanHolohan

and

what are the elements made of? Iron, copper, steel?

Chris Maderia

Copper

Elements are cooper fin-tubed.

DanHolohan

Here's the challenge

I'm looking in my book, E.D.R., which has just about ever covector ever made. With many of the convectors, it shows drawings of the outside of the cabinets and explains that there are no markings on the cabinets or elements and that you should match the picture of the cabinet to what's on the job. The slanted element shows up only on the Warren Webster units, but they don't list the depth of the element. Other units might have slanted elements, but there's no indication.

A question, though. Since this is a hot water job, why not just do a heat loss calculation and base the boiler size on that?

Chris Maderia

Heat Loss

I had already came to that conclusion. I wanted to make sure that my Boiler could handle the total BTU out-put load of all the convectors. A room by room heat loss in this case could possibly be irrelevant to the BTU out-put requirement for the convectors. So I am trying to size my boiler based not only on the heat loss but on the convector out-put requirement.

My other concern would be if my boiler isn't sized to the requirements of the convectors wouldn't I have a possible problem with my delta-t? Would the convectors at the end be subject to much cooler water preventing them from reaching their required BTU out-put?

DanHolohan

I think

that if you size to the heat loss and the total convector load is oversized for the building as it is today then the system will just run on a lower temperature. Are all these convectors in a series?

DanHolohan

Is the boiler

the right size for the house, based on heat loss, Chris?

(I'm away for the next few days so if you don't hear from me today that's why. Thanks.)

Chris Maderia

Current Boiler

has no btu ratings or any other markings on it. But I would say that it is oversized. I figure based on the size and construction of the house that a 4 Section Boiler is going to take care of it. I'm going to go out and due a heat loss of the house. I'm still worried about the ratings on the convectors though.

DanHolohan

Don't be concerned

about them, Chris. They can't possibly pull out more heat than the house's heat loss. Is you size the boiler to the heat loss and the radiators are oversized, they'll just to the job at a lower temperature. The reset and individual valves will help this, and the primary/secondary piping you're proposing should get rid of the problems they're having now. Go get 'em!