baseboard loop design help

PDB2

I'm replacing the boiler in my home and trying to decide whether to make any changes in the circulator/zone plumbing. Replacement boiler is non condensing 70k in, 59k out. The original design is a simple radiant baseboard, 2 zone, 2 circulator, series loops which seems to work just fine, but maybe a primary/secondary or one circulator with zone valves would be an improvement ? It's seems to be hard to find info on the advantages and disadvantages that match my situation.

 This is a small 1400 sq.ft. two level (700 up and 700 dn) home. The zones are divided in that way also. My heat load calculations show don't show a lot of difference in heat loss in the 2 zones. Any thoughts on how best to plumb this ? Would a multispeed circulator with series loops and zone valves be any better as there is some difference in head between zones ?

STEVEusaPA

few questions

First, are you adding domestic hot water to this with an indirect?  That would help with design options.  What type of boiler are you going with, and is it gas or oil? Can you say why you didnt go with a mod con boiler (if gas)?  You may want to leave the rest of the piping as is if:

a) It has worked fine-no velocity noise, water fall sounds, heated up fine, never air bound, etc.

b) You're new boiler doesnt have a high head loss requiring a circulator, or a bigger circulator to get the water thru the boiler.

Also decribe (post pics) of all the piping.  Are the circuits 3/4", total length of the run, and total length of baseboard per circuit.

If you are well insulated, are you sure about that 59k btu's....sounds kinda high especially if theres no DHW.

Greg Maxwell

Boiler Replacement

If it is a tankless coil boiler that you are putting in, the first thing is make sure the boiler is sized appropriatly for your existing load. I wouldnt change a thing about the piping, just try to gure if you may be overloaded with baseboard in your house, and if you are, run your high / low limit down to give you better efficienct.

If it is a cold start boiler, with an indirect water heater, I would still check the heating load by doing a heat loss, and I would recommend the use of an outdoor reset control such as the new Honeywell AQ251, with the AQ1000 thermostats. You will get a whole lot more efficiency with that type of system, and you dont have to repipe there either. You will be able to take advantage of modulated water temps that will heat your home very comfortably, and will see a difference in your fuel bills.

Good Luck

PDB2

more info...

I'm not adding indirect now but would plumb a connection for future. The boiler is a atmospheric vented NG (wiel-mclaine cga3) spark ignition. I debated long and hard about a mod-con, even went to triangle tube 2 day installer school. I guess the deciding factor other than at least twice the money and payback period, was being able to condense a good share of the time with the higher temps required for a comfortable radiant baseboard system that is in place. If it was a radiant floor system I would have done the mod-con for sure. Anyway, it's a done deal as the boiler is ordered.

 I wouldn't say the old didn't have it's problems with some noise and holding pressure...it was 50 yrs. old and had the old style no badder expansion tank and no air separator of any kind. Even with that I probably would have continued to nurse it along had it not developed a CO leak at the masonry vent/tubes junction.

 The old one is already torn out so can't help with pictures. It was pretty simply tho....just two bell gossett (100 series) pumps in series from the boiler , each one feeding a separate zone via separate thermostats. One zone for upstairs and one for down.

Upstairs zone is 142' 3/4 copper with 36' total finned emitters. Downstairs zone 134' total 3/4 copper with 21' emitters. I'm going to add about 4' emitter to this level while I'm at it.

The home has a lot of glass area for its sq. footage and a large masonary fireplace that we don't use anymore (sealed off the firebox) so used the higher heat loss figures of the ones I calculated....... the next step down in boiler size seemed a little risky with it not modulating.

So you guy's are thinking other than the high/low settings, just plumb the zones as they have always been with a pump on each zone ? The old piping had balance valves on each return but were never set anywhere but wide open. I guess I would use some temp gauges this time try balancing zones a little. And an autofill setup with a good air seperator. Other than that no fancy multi-speeds or zone valves ?