Trooper's Circulator Post Purge "Mod"

**Rockledge** · 12-21-11, 04:33 AM

Originally Posted by NJ Trooper

If your boiler is within the heated envelope of the home, keep in mind that the heat which remains in the boiler isn't really 'lost'. It will radiate into, and contribute to, heating the home.

My boiler is in an unheated (relatively) 'utility room' which is between the house and the garage, thus I NEEDED to get the heat into the house proper else lose it into the garage.
.....

How I did my post-purge

A 'strap-on' aquastat on the supply pipe out of the boiler measures the temp of the supply water. The 'make on temp rise' contacts on the aquastat are wired 'across' the circulator relay in my 8148A aquastat. I use about 15° of 'differential' on the strap on a'stat. The setpoint is currently at 110°.

When the water gets to 110°, the strap-on a'stat switches. Since this a'stat is across the circulator relay in the boiler a'stat, when the heat call ends, the circulator will continue to run until the boiler cools to 95°.

Troop, this sounds like an excellent idea.

The fact that it's based on water temps. instead of a timer makes it all the better. I'm thinking that a post purge circ. function like this would be well-suited to a One-Pipe/Diverter T/Single Zone system like the one I have at my home, would you agree?

I have a spare Honeywell L4006A that used to be mounted on that Everhot tank which was swapped out a few years ago with a newer model (w/better temp. range). I'm thinking that I might somehow rig up a way to mount the L4006A to the supply pipe (1 1/4" black iron) coming out of my home boiler...

**Rockledge** · 12-21-11, 06:24 AM

I've been reading through the L4006A manual and I don't think it's a suitable post-purge circ. control. It only has one switch function, which is break on temp. rise. But what is needed is a make on temp. rise-type switch. So it looks like it won't be a freebie for me on this one.

But in looking over some inexpensive temperature controls, I came across THIS which looks like it would fit the bill nicely.

**TBurr** · 12-21-11, 06:34 AM

Might work....

Would there be a way to set this up on a system that has two zones and two pumps?

I'm thinking perhaps with a relay that would be n/c providing power to the aquastat contact. So when the circulator is off, the relay provides power to the aquastat contact, which it could then power the circulator with until the aquastat reaches it's limit.

Is it hard to change the microswitch in the aquastat?

Might be a beneficial junkbox parts project.

**PeterNH** · 12-21-11, 07:42 AM

Originally Posted by Rockledge

But in looking over some inexpensive temperature controls, I came across THIS which looks like it would fit the bill nicely.

Ranco makes reliable stuff.

Peter

**Rockledge** · 12-21-11, 09:04 AM

Originally Posted by PeterNH

Ranco makes reliable stuff.

Peter

That's good to hear. The Ranco control I linked to looks to be quite versatile for a reasonable price. It's only 10 bucks more than companies like Taco charge for their post-purge "cards" and much more adaptable to other uses, if necessary. And of course by utilizing it as a post-purge circ. control ala NJ Trooper, you get the added benefit of controlling the purge by way of water temperature, as opposed to time. Seems like a "win win" situation.

**NJ Trooper** · 12-21-11, 04:30 PM

what is needed is a make on temp

Yeah... I believe that would be the ' B ' model... or one of the 6006's which would give you either (DPST).

That Ranco looks like the 'ticket'. No capillary tube to kink, nice long wire... you would need to set it to the 'cooling' mode so that it makes on temp rise.

Would there be a way to set this up on a system that has two zones and two pumps?

I've been thinking about a way to set up a system for zone valves, which has turned out to be much more difficult than expected. The couple ideas I've had are both 'fails'. I had a few other ideas that would be far too costly to ever pay back.

I think that it might be easier to do with a pump zoned system... let me think about that for a bit.

How are the pumps being controlled now? If relays, what model, etc?

I have to say again that unless the boiler is located outside the heated envelope of the building, the addition of an automatic vent damper would probably be a better choice.

**Furd** · 12-21-11, 07:50 PM

Originally Posted by TBurr

Is it hard to change the microswitch in the aquastat?

Two screws. The calibration might be a bit off after the change but it isn't all that critical anyway. You might be able to drill/tap out the unused connection on the existing Microswitch (Honeywell trademark) or maybe just solder a wire where the screw terminal would go.

**Rockledge** · 12-28-11, 07:15 PM

Well, the Ranco ETC temp. controller arrived yesterday and I installed it this afternoon. Works great as a post-purge circulator control! I was able to mount it on a wall next to the boiler and run the 8' sensor cord over to the boiler supply pipe. Very easy to use and adjust. Like Trooper mentioned, the control needs to be set to "cooling mode" in order to get the make on temp. rise switching that's needed. Right now I have the Ranco initially set at 130* and will play with it from there.

**TBurr** · 12-31-11, 05:34 AM

I'm tempted to try this on a recent install...

On a large mass system it's a no brainer, but what about for a cast iron one that holds 3 gallons? Will it be worthwhile to do?

**rbeck** · 12-31-11, 06:00 AM

Rockledge why stop at 130f? Why not run it down to 110f or 100f?

**Rockledge** · 12-31-11, 06:01 AM

On a large mass system it's a no brainer, but what about for a cast iron one that holds 3 gallons? Will it be worthwhile to do?

I would say yes, why not? My Utica MGB holds only 4 gallons of water, but there are many more gallons of water in the One-pipe/Diverter-T system that the boiler is hooked up to. So I think another way to look at is: how many gallons of hot water are left sitting in the entire system when the pump shuts down normally? Do you want that hot water to continue to flow through your emitters and provide heat to the living areas?

Remember too that, post-purging the boiler and piping of residual heat is another way to help extend boiler ON/OFF times.

**PeterNH** · 12-31-11, 06:08 AM

lHello TBurr
Maybe.
How much does it weigh?
Is it oversized?
Any sort of outdoor reset?
What's the temp in the boiler room?
Any sort of stack damper?
Hows the draft?

There's about 25 lbs of water
Say maybe 250 bs of iron???
equal to about 30 lbs of water
55 lbs total
If its holding 50 degress,
then maybe 2700 btus could be recovered, Not exactly nothing...
But then it will take more fire on the the next call to re-heat
unless the calls are far apart and it would cool off anyway.

Close call

Peter

**Rockledge** · 12-31-11, 06:18 AM

Rockledge why stop at 130f? Why not run it down to 110f or 100f?

I suppose I just wanted to start out somewhat conservatively. But I am indeed going to go lower on the temps. and fiddle around some more with the differential.

**PeterNH** · 12-31-11, 06:41 AM

Hello Rockledge,
I you have an Alpha or Stratos, you are golden,
Otherwise, from what i read, a typical 007 uses about 60-80 watts.
Say about 245 btu's.So at some point it doesn't pay to pump, if you are not gaining much heat.
Although some of the wattage ends up in the water or all of somewhere in the house/cellar.

Peterr

**Rockledge** · 12-31-11, 08:43 PM

Hi Peter. Happy New Year!

The pump is a Grundfos 15-42, mounted on the supply side after the expansion tank.

Thanks for your feedback.

Joe

**J3ffrey** · 01-01-12, 05:30 AM

Is there an easier way to do this manually?

I would just like to be able to hit a button somewhere that will run the circulator pump until it's cool and then shut off the boiler for the day.

I guess the automatic thing would be cool, but I think if my boiler got down to 110, even if there was no known demand (therm not calling for heat) it would still turn on... right?

**TBurr** · 01-01-12, 06:38 AM

Originally Posted by PeterNH

lHello TBurr
Maybe.
How much does it weigh?
Is it oversized?
Any sort of outdoor reset?
What's the temp in the boiler room?
Any sort of stack damper?
Hows the draft?
Peter

The non-modulating cast iron boiler weighs about 300 pounds and holds 3 gallons of water, is oversized and cycles frequently, there is an OEM outdoor reset, it's about 50 in the basement and it's power vented through the foundation.

Right now, I'd venture to say it's running at 150 and cooling to 70 between calls from the thermostat.

What would you suggest?

I like your chain of analysis, Peter. Thanks.

**TBurr** · 01-01-12, 06:43 AM

Originally Posted by J3ffrey

Is there an easier way to do this manually?

I would just like to be able to hit a button somewhere that will run the circulator pump until it's cool and then shut off the boiler for the day.

If that's all you want to do, you can buy a mechanical timer switch - just turn the dial to the number of minutes you want. It will fit into the same box an electrical switch does.

Like this, many places sell this stuff:
Amazon.com: Jasco Products Company 15084 Wall Switch Timer 15 Amp: Home Improvement

**PeterNH** · 01-01-12, 07:25 AM

Hello TBurr,
At first i was thinking with the ODR it would be a waste of effort.
Being that it keeps th e boiler as cool as possible, instead of running it up to 180+.
On second thought 50 is kinda cold and it is oversized so..
Id' give it a try.
Maybe run it until the temp goes down to 80 or so
Might give up some heatand lengthen the cyles a bit.

Peter

**PeterNH** · 01-01-12, 07:30 AM

Hey TBurr,
Doesn't your boiler have the IQ control?
If it does there is an optional post purge card you can get for it.
Easy.

Peter

**TBurr** · 01-01-12, 08:15 AM

Hello Peter,

The post purge is supposed to be a functioning part of the ODR, but that feature is incompatible when a Taco multi zone control box is used.

There is a yellow wire in the terminal box which connects to a circulator and would easily handle the pump over run. With the multi zone setup, the yellow wire is capped in the box and the circulator power comes from the relay box.

I've thought of ways to utilize the yellow wire as a post purge, but it would require a mess of gizmos not to cross the two zones. Ideas welcome.

Are you referring to the Taco pump over run card that goes in the zone box? It controls only one zone and utilizes the priority zone, I believe, and we'd like to reserve that for a hot water heater. I don't know of a post purge card that's made for the boiler... is there one?

Thanks for the thought, and encouragement to post purge.

**PeterNH** · 01-01-12, 08:29 AM

I believe there is one for the boiler.
What is the exact model of the boiler.
However, even if there is one, the zone valve control will present the same problem.

See this thread if you want to get confused

Post Purge with Zone Valves

Peter

**NJ Trooper** · 01-01-12, 08:48 AM

Would something like this work?

Run the relay from the yellow wire.

Choose the zone you wish to purge to... wire pump...

You might even be able to do this with a single pole, but I would be leary about not providing full isolation of both the N and the H ... don't wanna accidentally cross stuff up on the AC !

**TBurr** · 01-02-12, 07:53 AM

I think that would work fine for one zone, but it wouldn't necessarily feed the zone that was calling for heat and that would be a distinct advantage.

What would happen if there were a series of relays, one for each zone, set up with the yellow wire going to a NO contact on each relay and wired to the coil in such a way it would hold the relay on when the yellow wire received power; NO to coil hot. Then, the zone control could power the respective zone calling for heat, and when the thermostat was satisfied the yellow wire would hold the circuit on for whatever time it was set to as power is fed to the circulator through another set of relay contacts. How do you do those neat schematics that make what sounds clear as mud so easy to visualize?

Alternatively, this sounds like a very simple and inexpensive way to do it. Can a Klixon switch, set to close at 100F, be secured to the copper return on each zone, the lead run to the zone box and wired in such a way that the zone box would control it's relay as always, the Klixon would turn on when the cycle ran (ie when it gets hot) and keep the circulator for that zone on until the pipe cooled to 100F? I don't know how the Klixon's flat face would connect to the return pipe and I'm probably dating myself because I believe Klixon is now carrying another brand name.

**TBurr** · 01-07-12, 06:20 AM

Would this work or blow something out? Each zone would need it's own relay.

Added: This may not work, is there crossover between zones if one ends if one zone's call for heat ends and and other is still demanding heat?

**PeterNH** · 01-07-12, 07:30 AM

TBurr,
Sorry if i missed it.
Do you have pumps or zone valves?

Why not keep things simple, so.
What's wrong with NJT's idea?
Just pick the zone that runs the most to purge to.
Naturally that zone would be most able to use any extra heat.

I'd suggest a manual set up with a remote toggle switch at first to get an idea of hw much heat you might get out the set-up.

Peter

**PeterNH** · 01-07-12, 07:41 AM

Oh Ya Folks,
Here is a link to the drawing.
Much easier to read in it's own browser window.
http://i1137.photobucket.com/albums/...5123/SCHEM.jpg

Peter

**TBurr** · 01-07-12, 08:07 AM

Only because what he posted appears to work with one zone and I'm trying to do multiple zones each with their own post purge.

I might end up with what he posted.... it's a lot better than nothin.

Thanks for fixing the link, Peter.

**J3ffrey** · 01-07-12, 08:12 AM

What's the overall goal of this mod? Just so I know what I'm getting into

l

**NJ Trooper** · 01-07-12, 11:01 AM

Just a hint: If you are running FIREFOX browser, you can 'right click' on any image in a post and then select 'view image' from the drop down box. It will open the source image full size. Then when done viewing, click the back button...

In my opinion, this mod is only really useful if your boiler is located in a space where any heat lost from the boiler during 'standby' times would be 'lost'... for example, if the boiler were located in an unheated garage, or similar.

If the boiler is located within the heated envelope of the home, there seems to me to be little point in doing this at all. Any heat coming off the boiler is radiated into the home anyway. In this case I feel that a far better improvement would be the addition of a vent damper assembly if one is not already installed. This would prevent heat loss up the chimney during standby periods.

In some cases this post purge mod could possibly be effective in alleviating some types of 'short cycling' problems. By cooling the boiler a bit between cycles by pulling the heat into the home, the next burner cycle will naturally be longer than if the boiler was already hot.

J3ff, the goal is simple... to pull any heat left 'stranded' in the boiler after a heat call into the home.

TBurr, I think that in most cases, one would not want to pull the leftover heat into the zone that just called for heat. It would be far better I think to pull that heat into the single largest zone, most likely the one with the most heat loss. Bringing it into the zone that just called is asking for a temp overshoot problem for sure.

If one wanted to get REALLY FANCY and spend LOTS OF MONEY FOR LITTLE RETURN, one could design a system with a series of temp sensors that would monitor the temps in each zone, and use a microprocessor to 'predict' which zone would call for heat next, and then route that extra heat to that zone... but this would be something only someone with lots of free 'hobby time and money' would want to undertake.

**J3ffrey** · 01-07-12, 12:44 PM

O boy.. a new thing to buy a vent damper thing..

I said earlier how much I'd love to have a button on my thermostat that would keep the pump running, but NOT fire the burner...

At the moment my "Fan" button.....if I switch that to ON it actually does turn the circulator pump on...but at whatever the low point is on the burner it will kick on.

What i've been doing is turning the fan to on...it heats the house a little more and then when i hear the click from the oil burner that it's about to ignite I just turn the fan button to "auto" ..

I guess I should start my own thread about how to change my settings for more efficiency.. right now I know that I see temps of 200 and then it stop heating.... if I keep the heat demand on, it'll drop to 180 and then back up to 200 before it turns off.

**rbeck** · 01-07-12, 01:13 PM

Hey NJT - AKA wiring God, maybe we are over thinking this whole thing. Trying to dump into the last zone or the largest zone. Since cast iron boilers don't hold much water as compared to the old ones let's just dump into the indirect with a mixing valve installed. The tanks are well insulated, or we could dump into all the heating zones. It would not drastically overheat any zones as the boiler would cool off quickly. With pumps this should be easy, zone valves could be tougher.
Thoughts anyone? I know i get whacked out thoughts sometimes but that is the father of creativity.

**PeterNH** · 01-07-12, 02:00 PM

Hello RBeck,
I like the all zones idea, that would get the heat out quick and spread it around the house.

Now i'll raise the pot one, in the case of zone valves.
How about opening all of the zone valves, but keep the circulator OFF.
Let the heat gravity flow around on its own. It would probably balance out naturally.

I like the idirect idea, it might never have to run on it's own call.

But would there always be cold enough water in the bottom to get the heat into? The circulator might run a long long time if the bottom of the indirect is already on the hot side.

Peter

**NJ Trooper** · 01-07-12, 02:57 PM

I know i get whacked out thoughts sometimes but that is the father of creativity.

Father Beck, if thou art whacked out, then so art I!

It had actually crossed my mind that dumping to ALL zones would be a good idea. But good garsh, think of all those relays!

Gravity flow would be a great idea... as long as there was enough height difference to make it happen!

J3ff, I think you need to find the temp control on your boiler and turn that down a few notches. I'm sure you don't need 200° water to heat your home... yes, start a new thread... and include that other post that got lost somewhere...

**rbeck** · 01-07-12, 03:54 PM

I am not sure I like the gravity idea as it will take path of least resistance and maybe not to all zones. But gravity to the largest zone may be good but a problem with this idea is what if you are in a post purge and get another call. The open valve or pump would have to close/stop or overheating will occur.
The indirect idea. I believe there is always cooler water in the bottom of the tank.

**TBurr** · 02-03-12, 05:42 AM

I have some thoughts on this, but thought I'd post here for a possible better idea than strapping it on with some heat paste and wrapping in insulation.

A thermal switch like this:
http://www.thermodisc.com/productdetail.asp?ProductID=2

attached to the return pipe would turn on from the heat of the cycle and regardless of the thermostat demand keep the circulator running until the water dropped to 120 (or whatever switch temperature is chosen). I think it only needs to be powered from the same electrical source and with the same polarity.

Suggestions for implementing this?

This is for a multi-zone system. Am anticipating using one switch on each zone return to post purge individual circulators.

**NJ Trooper** · 02-03-12, 02:31 PM

How do you plan on wiring this into the system controls?

rbeck asked in his previous post:

what if you are in a post purge and get another call?

When planning something like this one must carefully consider all the possible scenarios.

**TBurr** · 02-03-12, 03:00 PM

Geesh, you're right. There's gotta be a way to do this.

If there's another call for heat by one of the zones, then yes, the switch would hold the pump on and screw this whole concept up. And that electronic gizmo would have the same problem, wouldn't it?

I was thinking that the zone control would be wired as always, and the thermal switch would be wired with an always hot from the zone box, through the thermal switch and piggybacking a second hot wire tot he circulator. That's probably also against code, isn't it?

Sorry, it sounded good in theory at first. A timed delay off relay for each circulator is looking good.

I

**DaveC72** · 02-03-12, 08:04 PM

Trooper, would that remote control help my system out ?

If you recall, my zones and circ pumps run independently from the boiler.. the boiler's TT is just strapped and it runs hot all the time (10f diff fixed).

If I was to connect this "ETC Temperature control" to my TT control at the aquastat, and strap the sensor to my boiler outlet pipe, I'd have a new boiler range / differential ? Should make the run times a little longer .. ? The existing aquastat would serve as a safety limit control of sorts..

**NJ Trooper** · 02-04-12, 08:34 AM

It's something to think about Dave...

If you were to replace the TT jumper with this control, and set the differential wider, with the control set up to BREAK on TEMP RISE (heating mode on the setup), then yes, I believe that this would allow the new control to 'over-ride' the existing one.

One possible problem though... since the sensor will not be inside the boiler, but on an external pipe, it may not sense properly when the pumps are not circulating. The sensor would need to be as physically close to the boiler as possible and very well insulated.

You would want to set the existing HIGH limit aquastat to a few degrees above the temp on the Ranco if you did this. This way you still have the original control acting as a secondary high limit in the event the Ranco were to fail.

Yeah, it might work!

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Trooper's Circulator Post Purge "Mod"

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Unless this is against code....

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