Constant circulation with a coal boiler and CI radiators

Steve Thompson (Taco)

Hot Rod - I am curious about your "go to sleep mode". Unless you are referring to night setback I am not aware of any ECM circ that "go into sleep mode when not needed". Please enlighten us.

hot_rod

"sleep" is maybe not the best term. Would "no-flow requirement" be a better description?

When there is no flow requirement, the pump goes to a 5W consumption mode.

With a fixed speed, non ECM in constant circulation with a PAB, that the OP is considering, the power consumption would be much higher, was the point I was trying to make.

Trying to get more folks to consider ECM pumping options

jrv8984

Should the ecm circs be wired to the tekmar 260 or just plug them in since I want constant circulation?

hot_rod

plug 'er in. In fact the Grundfos Alpha is available with a power cord and plug, ready to go.

jrv8984

thanks, i just received two viridian 1816's in the mail for an amazing sale price

jrv8984

What other products can I use for boiler protection / differential pressure bypass other than the thermobloc (it's a little pricy)

hot_rod

Any high flow (high Cv) thermostatic mix valve will provide return temperature protection. It is a temperature regulating device, it doesn't function as a pressure bypass.

There are fixed temperature, non adjustable thermostatic valves for that applications, available from several manufacturers.

Here is one we offer, from Caleffi.

http://www.hydronicspecialtysupply.com/uploads/1/0/1/5/10157904/caleffi_280_thermomix_tech_specs.pdf

jrv8984

as far as the boiler protection valve goes. My supply is 1-1/2" to the dump zone (which will eventually be the entire 38'x62' garage, and then down to 1-1/4" which tee's to 1" to parallel circulators, and then back together to 1-1/4" into the house.

I'm concerned that a 1-1/4" boiler protection valve wont allow enough flow back to the boiler once the garage radiation is installed, I would be forcing 2 1-1/4" returns through an 1-1/4" boiler protection valve?
Are my concerns valid?

jrv8984

I want to pull the thermostat off of the indirect hot water heater, I want some kind of thermostatic valve with a remote bulb to stick into the well of the old thermostat.
So I guess I am basically looking for a remote bulb TRV that is made for HIGH temps, can somebody point me in the right direction?
Thanks

hot_rod

jrv8984 said:

thanks,
Should my return manifold be upside down to create a heat trap, if so how long far down should the piping extend before going horizontal? how long should the horizontal pipe be before it turns up or could I just use copper return bends?

also as far as the boiler protection valve goes. My supply is 1-1/2" to the dump zone (which will eventually be the entire 38'x62' garage, and then down to 1-1/4" which tee's to 1" to parallel circulators, and then back together to 1-1/4" into the house.

I'm concerned that a 1-1/4" boiler protection valve wont allow enough flow back to the boiler once the garage radiation is installed, I would be forcing 2 1-1/4" returns through an 1-1/4" boiler protection valve?
Are my concerns valid?

Here is how you size a valve, any valve.

The Cv number indicates how many gpm will flow thru the valve with a 1 psi pressure drop.

The chart show how the pressure drop increases as you push more flow thru the valve.

Here is the chart for the caleffi valve mentioned above.

Across the bottom axis find the flow rate you will be needing. Run vertical to the valve performance slope, cross to the right axis to read pressure drop.

So the 1-1/4 valve Cv 14, flowing 22 gpm would have a pressure drop around 2.5 psi, acceptable.

jrv8984

I want to pull the thermostat off of the indirect hot water heater, I want some kind of thermostatic valve with a remote bulb to stick into the well of the old thermostat.
So I guess I am basically looking for a remote bulb TRV that is made for HIGH temps, can somebody point me in the right direction?
Thanks

jrv8984

Thanks hot rod

jrv8984

Solid fuel man
With your simple system design, Since I am using the pre made copper manifolds, should I be creating heat traps on the return manifold, or is this not necessary when running constant circulation, I am imagining that with the TRV's closed, I am going to be sending heat up my returns to my radiators

Solid_Fuel_Man

Your using home run 1/2 pex correct? I haven't had any problems with heat migration much further than a few feet. Now if you had 1" copper or iron vertically to rads then some type of trap would be necessary.

Solid_Fuel_Man

Regarding your indirect TRV idea, a simple on/off zone valve controlled by the aquastat is all you'd need. You could even use a 120volt version and avoid having a transformer.

jrv8984

Home run 3/4 pap, since I am running constant circulation I figured I could do the TRV idea for the indirect and not have to run power for it in the basement.

Solid_Fuel_Man

If each radiator is a home run, I see no reason to heat trap. You'll only get 5 feet or so of hot PAP, unless it's a straight vertical run directly off the manifold.

jrv8984

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jrv8984

So I am going to have 2 circulators in parallel through 1" iron pipe, when I recombine them can I use a 1-1/4" flow check, have the one circulator flow straight through, and the other would flow through the bottom. Or is this a bad idea?

Also, how close or far away from the boiler should the low water cutoff be placed, same goes for the supply temp sensor well?