Coal Boiler Piping Schematic : First Draft

Please critique my first draft schematic for a zone valve install of a coal boiler as seen in the PDF file which is attached here.

You may eliminate the dump zone parts and pipes and in place use an ice cube relay to bring one or more of the existing zones on line for dump

I wouldn't' install the (ZONE) pressure bypass on the first run but rather place an isolation valve on a supply and return extra stub - it can be placed in between later if you have drama - but you won't

I would put isolation valves also on your supply outs at the new manifold

Sting, please explain an ice cube relay.

Wow looks like a P&Id from work. It seems as though you can open any or all zones as dump with the relay. Don't forget to trigger the pump for the dump. I saw someone that forgot that and had the PRV put water in the basement

I'm presently intending for the single circulator pump to run 24/7. I guess I learned it from my current oil boiler and resistance boiler system, where the circulator never shuts off unless there is a power outage.

When all zone valves are closed the DPBV opens and keeps a circulation loop going to prevent dead-heading the pump, and to prevent local hot-spots from developing within the boiler.

Actually the DPBV is progressive. The more zone valves that are closed, the more fully open the DPBV becomes. When all of the zone valves are fully closed the DPBV is (or should be) fully open. When all of the zone valves are fully open the DPBV is (or should be) fully closed. Or so the theory goes. It is set by a spring tensioning knob that is scaled in PSI. Adjust for more spring tension or less until it does what it is intended to do, and then leave it alone to do its work. Mine is a Taco 3196, and it costs just under $50.

Initial set-up of a DPBV goes like this. If you know the "head" of your system you divide the head by 2.31 to get PSI. Then you dial in that PSI plus about 0.5 PSI more for safe measure on the DPBV's PSI scale (knob). Then you test it to see if it needs to be tweaked a bit. Feeling the DPBV's downside pipe for heat during differing levels of zone valve opening and closing is the tried and true method here. A rotometer (visual liquid flow indicator with a window and a spinning star wheel) on the outlet of the DPBV would be an expensive and exotic means to calibrate it to perfection.

Lsayre, a relay is an electrical switch where low voltage (your wall thermostat) energizes a coil/magnet to make the switch for 120v line voltage ( that would run a pump). The ice cube relays look like an ice cube. Taco switching relays use them among others.

If I simply let the pump run 24/7, then would I still have some sort of need for an ice cube relay? In my current oil boiler system the circulator has ran 24/7 for nearly 10 straight years now without a hitch.

What I would do is no endorsement on what you should do

so there is my design warning

The function of the wall stats for each zone will be an open or closed signal - use these (close signals) to switch the related (low voltage operation) zone valve - each zone valve also has an end switch that will close upon activation and this can signal something as simple as an ice cube relay or a fan relay that will turn on (send a house volatage curent) to the zone pump - in turn it will send energy bearing liquid thru the open zone valve and heat that zone

- when - if another zone valve opens -the related end switch also signals the pump relay to turn on the pump but since this is a parallel voltage it is redundant until all wall stats are satisfied.

and the zone pump stops pumping because no zone calls for heat -- the boiler is allowed to rest at idle fire

in turn if the boiler drops below condensing temperature and aquastat should be in place to interrupt the pump signal and not allow pumping until non condensing temperature is again reached

now a dump zone signal is simply another call for circulation - so with relays that act as isolation from the normal circuits - any or all zones can be signaled to open the zone valves launching the pump and scrub excess energy out of the idle firing boiler.

if this is unclear

PLEASE buy the writing and circuit comic books I recommend or get an electrician with a brain to help you.

I would run a separate pump on each boiler and a pair of lift checks. That way you can set it up for auto changeover and it gives you 100% backup.

yes I agree -- but the design as drawn will work as long as the operator understands its a manual switch over

Greg has often chastised me for over complicating these installs - but what your suggesting is stepping up to primary secondary piping methods

A wonderful suggestion - but additional cost!

In my system as it exists currently there are no bypasses at all and all flow passes through both the oil boiler and the resistance boiler all the time via a single circulator. It is a straight series arrangement. The resistance boiler receives the oil boilers heated output as its input, so the resistance boiler does not generally activate since the water is already at around 180 degrees. When the oil boiler fails to warm the water, the resistance boiler does activate and heat the water to 180 degrees (as is the case for me now, since my oil boiler is down for the count). I designed my coal boiler schematic as seen at the beginning of this thread almost directly upon what I see in my present system, only I will allow for the manual switching out of the loop (bypassing) of the resistance boiler if so desired.

AA130FIREMAN wrote:Lsayre, a relay is an electrical switch where low voltage (your wall thermostat) energizes a coil/magnet to make the switch for 120v line voltage ( that would run a pump). The ice cube relays look like an ice cube. Taco switching relays use them among others.

AA130FIREMAN and Sting: I can clearly see the value of this relay in a system with individual zone circulators. Where I'm having difficulty focusing upon its value is in a system with only one circulator. Would the ice cube relay be used in a system like mine to shut off the circulator when all zone valves are closed, and turn the circulator back on when at least one zone valve is open, negating the need for the DPBV loop, and saving some electricity that is otherwise wasted in running a 24/7 circulator?

Since a coal fired boiler must always be generating heat, and since in any situation where all zones are closed (all thermostats have reached their set temperature and the house is toasty warm) the boiler is still making heat, would my DPBV loop offer some small level of continuous heat dump (would it effectively act as a small dump zone) that may actually in a small way be advantageous in preventing the boiler from overheating under the circumstance of having all zones shut down?

I run my circulator continously and that loop between the coal and oil boilers does act as a heat dump. On theother hand. coal idles nicely and I've never needed an overheat dump zone. Your installation may or may not. Yanche posted something yesterday about the proper sizing of the expansion tank may make a heat dump zone unnecessary.

coalkirk, do you have a single circulator system?