80 % boiler with low temperature application

Snowmelt

keep it simple, I don't want to sell a new boiler if they have a 5 year old boiler. but they are thinking of making three rooms radiant. with a standard atmospheric boiler ( going through the chimney) I want to add three zones and make 2 more so it will be a total of 5 zones. How would you do your near boiler piping and keep the flue gas high enough to avoid condensation. I would like to also add a hydronic separator to the job ( actually would love to make one myself. Boiler is a weil mclain 120,000 btu in 100,000 btu out the existing baseboard heat is warm enough to heat the house. any more info needed?

Jamie Hall

Mixing/tempering valve for the feed for the radiant loops -- allow just enough high temperature water in and out to meet the load and let the rest just recirculate.

Rich_49

4 Way I Series w/ ODR George and a circ for the radiant .

http://www.taco-hvac.com/uploads/FileLibrary/102-145.pdf

Dave H_2

I would add the Hydro-Sep, great for maintaining that high temp return to the system and then add mixing for the radiant on the load side of the sep.
If there is an indirect, pull that off before the hydrosep and then on the load of the hydrosep, first to come off is the baseboard zones and then the radiant. As Rich said, use a mix valve with outdoor reset, it will make a world of difference

Dave H

archibald tuttle

think all the above are workable although especially on a cast iron boiler, which i assume this is, i often use an indirect tank as a radiant flywheel and complete separator. i started this way because many of the jobs i did were from the days before diffusion barrier tubing -- for that matter from the days before PEX itself, can you say polybeautiful. So I had to have separation. Even with diffusion barrier tubing, i believe it reduces but doesn't eliminate the effect -- kind of in the way the 'stainless' steel is not an absolute description, so too diffusion barrier tubing doesn't give you 0 diffusion. So if i have a copper or stainless heat exchanger boiler and all diffusion barrier tubing I don't sweat it. I hate aluminum exchangers so unless somebody gave me one i wouldn't be using it anyway. But iron is way out there galvanically so i separate regardless of tubing mix. You can use a plate style heat exchanger too which is cheaper but i found I liked the flywheel and that it kept the cycle length up without tempering the boiler side water. my 2 cents.

Snowmelt

Thanks richie and dave I will hopefully get the job but I just wanted some ideas and I think it will work .

hot_rod

So a standard cast iron boiler? Some baseboard, some low temperature radiant?

If it is a standard low pressure drop boiler really no value or need for a LLH.

You do want to have return temperature protection however, and the only way to assure that is have a means to sense and respond to cold return.

Here is another option, this uses a ∆P ECM circ, so high efficiency on the distribution. The radiant is via ODR and has a boiler return sensor to assure the boiler stay out of condensing mode.

This gives you the best of todays technology, a circ that responds adjusts to changing loads, low temperature mixing, ODR, and return protection.

It could be any type of mixing device on the low temperature but a control with return protection function would be my choice.

Page 92

https://www.caleffi.com/sites/default/files/coll_attach_file/idronics_12_0.pdf

Gordy

I remember when ci boiler had bypass piping, and a mixing valve for radiant. K.I.S.S. It seems as technology comes forth one feels the need to use it. Ya know like the nest

BobC

@Gordy I learned KISS in the army and aside from FUBAR it was the most important thing I've learned in my life. Simple systems tend to work, not always the most efficient but if they stop they can usually be fixed with common parts.

God Bless steam and cast iron!

Bob