thermostat

Paul S_3

Hey everyone....I recently replaced a hot water boiler properly sized to the heating load for a 12 family apartment building....previous boiler was controlled via thermostat in basement where no radiation is present and there was comfort issues.....thermostat is in same place with same problem.....system is a two pipe system....I would like some recommendations on what control to use in this situation.....boiler is 245,000 btu....can I run pump continuously and wire a control to shut pump off when outdoor temp gets to a certain temp.....and use a Tekmar control....would like to not use a thermostat.....system is one zone two pipe system thanks Paul s

Zman

TRV

How is it piped?

It sounds like you cannot add zone valves. You cannot do an aggressive outdoor reset unless you address boiler condensation.

Would TRVs be possible? TRV, constant circ, outdoor reset and warm weather shoutoff would be slick.

Carl

Paul S_3

Carl

I replaced boiler also quoted to change system piping because it's a two pipe recently done in copper.....each apartment (12) has a series loop with radiators off each branch circuit so trv's are not feasible...wanted to use constant circulation with wwsd for pump..and..use a Tekmar 256....I can do piping for boiler protection...would a simple bypass with globe valve be enough.....how about 3 way valve with 741 actuating motor?....but 256 seems better on budget.....any advice thanks Paul s

Harvey Ramer

How about

a TRV zone valve. You can put one in each circuit anywhere in the circuit. Use a constant pressure circulator. You can put an Outdoor line-voltage thermostat in place to shut down the circulator when it gets warm outside. Finally, use a flow switch to turn the boiler on or off.



Harvey

Paul S_3

reset

with that setup am i using a outdoor reset control??i cant use a tstat here....paul s

Harvey Ramer

What

kind of boiler did you install?

Paul S_3

boiler

The boiler is a atmospheric 245,000 btu hot water boiler...Paul s

Harvey Ramer

Is

it a cast iron boiler or is it a fin-tube?

Paul S_3

boiler

Cast iron

SWEI

I suspect

That a fire-tube 250k mod/con would have cost less by the time you get all the controls on the CI boiler.



Use a thermostatic boiler protection valve.  Caleffi, ESBE, and LK Armatur all have options.

Harvey Ramer

With the system

I described you are probably better off not using an outdoor reset, unless you use a buffer tank and control the tank temp based on outdoor temp.



If you choose not to use an outdoor reset you will still have to provide boiler protection. Either with a 3-way diverting valve or with primary-secondary piping.

Harvey Ramer

Your flow

switch should be set to turn on the boiler at approximately 4.4 to 5 GPM. It should be located on the secondary system piping. Your primary loop should have 24 GPM. The boiler should control the primary loop circulator and not allow it to come on till you reach approximately 140º

Paul S_3

boiler protection

I've been looking at Caleffi's boiler protection valve....which I would like to use on my job....but in the valves literature it shows it piped with some sort of primary secondary piping.....hydro seperator or buffer tank.....can this valve be used with the type of system I have.....standard two pipe with out primary secondary or woulda simple boiler protection bypass line with a globe valve be more feasible....installing a buffer tank is not realistic with budget....thanks Paul s

Harvey Ramer

I don't

think the diverting valve will be necessary. Just make sure your primary loop has 24 GPM and use the triple aquastat on the boiler to turn on your primary loop circulator at 140º to 150º You should not see any damaging water temps on your return.

Harvey Ramer

Here is another

option that will give you everything you want in a nice little package.



A Tekmar 360 Floating Action Mixing Control, controlling a 2" four-way mixing valve.

Paul S_3

what

If I cannot get the extra money for a 2 inch primary loop....would I be able to just use the boiler protection valve in these two types of ways? Thanks Paul s

SWEI

Right-hand diagram will work

left-hand one will need some kind of hydraulic separation.  The choice between the two depends on flow rates.