Running Circ Pump After T-Stat Off?

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Old 02-16-11, 06:38 PM
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Running Circ Pump After T-Stat Off?

OK,
So now I've got my Honeywell L8124A to run the boiler from cold starts. Working well so far, thanks guys!
I have been observing my boiler temp and return temp during heat calls and now wonder if it would be possible to wire the zone pump to continue running after the thermostat has been satisfied? My boiler set points are 140 / 180. Can I get the circ pump to continue to run (after the boiler has shut down) until the system temp is say 140 deg? Is it worth it?
As of now I've only got the first floor of the house's cast iron radiators hooked up and I have calculated the to be at about 32k BTU based on one of the rad sizing guides I found here (thanks again). My boiler is rated for 110,000 BTU so I'm sure I haven't yet reached a point of "efficiency".
 
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Old 02-16-11, 11:48 PM
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There is some kind of beckett heat manager. Look it up. Not sure if it works but it will keep the burner from firing on a call for heat if the boiler is above 140F or so. The circ will come on and use what heat in in the boiler until the temp drops.

Mike NJ
 
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Old 02-17-11, 05:48 AM
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There is an inexpensive device that will leave the circa running for a period of time.
Just can't remember the name of it anymore.

This additional circulation can provide some blending of warmer or cooling rooms, it tends to even the temps out. The idea behind constant circulation, this just improves it a bit by turning off the circa 20 minutes or so if there is not another heat call.

I will post a link if I can remember the name.
 
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Old 02-17-11, 06:04 AM
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The University of Illinois tested heating applications for almost 20 years. They proved that constant circulation saved about 15 - 20% fuel by just turning the burners on and off with the thermostat. The idea of a two stage thermostat also saved about the same. The difference is the type of radiation.
Post purge of the pump with a single zone and cast iron radiation. The same with pre-purge of the pump to cool the boiler down before firing.
As Toe stated earlier this balances out the heat in the home.
Kinda where the government is going Sept of 2012. Not sure if you know this but that is when standing pilot becomes history and the pump must come on before firing and boiler reset .
 
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Old 02-17-11, 12:01 PM
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Really..
Manditory outdoor reset... WOW. Should happen here as well, but I doubt it will.
TSSA has all but killed the atmospheric boiler market up here with all there regulations...
A few people die due to CO poisoning and they get fussy.

I always provided constant circ on any sizeable cast iron rad home that we did with a cast iron boiler. I learned that from either you or Ralph. The only problem was people never turned off the summer winter switch. So the money they saved on fuel was wasted in electricity in the summer.

Glad to see the end of standing pilots, would like to see them move to forced draft ( fan assist) appliances. I do think they are safer.
Just did an emergency call 2 nights ago where the co alarm was howling. The boiler was a copper fin, and you could not see thru it, it was sooted that bad.
 
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Old 02-17-11, 12:20 PM
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The product is called "The Smoother".
If you google it you should find out where to get one
 
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Old 02-17-11, 03:54 PM
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I guess I re-invented the 'Smoother' on my system then...

I attached a strap-on a'stat to the supply out of the boiler. Used the 'make on rise' contacts and wired from L1 to C1 in the 8148 a'stat.

I've got it set at 135 setpoint with about 15 diff.

When t'stat calls, system fires up normally, and when supply passes 135 auxiliary a'stat makes, and shunts (parallels) the circulator relay in the 8148. Heat call ends, burner shuts down, circulator continues until water drops to 120, circ shuts down.

Things I've noticed in the two years that I've been running this setup:

1. My Honeywell t'stat seems to have 'learned' to shut the burner down sooner (anticipator). It knows that the heat will continue to come... I was afraid that the rooms would 'overshoot'... and the first couple days they did... but not anymore...

(if anyone tries this method, do yourself a favor and invest in a quality thermostat that will learn to anticipate and adjust accordingly!)

2. Because of 1, the boiler RARELY fires over 150F, and most of the time I've observed it, usually only 140 or so.

3. On DESIGN TEMP nights, I have noticed on a few occasions that the circ will still be running, almost ready to shut off when the next heat call comes in, so there is nearly constant circulation when it's really really cold out. ( 0 with a wind )

4. Short cycling is a thing of the past. Since the boiler is cooled after each heat cycle, the burns are long enough to allow the boiler to get up to adequate temp and dry out any condensation (which is something else I worried about with this setup). I see no significant signs of increased condensation in the boiler or flue/chimney. I burn oil, I don't know how this would work for a gas fired system since gas fired flue product has a higher dew point... if this was a problem, it could probably be remediated by setting the auxiliary a'stat higher.

5. Based on limited data collection the past two years, I'm estimating that I'm about 8% ahead of the game as far as BTU per DEGREE DAY per SQUARE FEET. To be fair though, in the past two years I've also made incremental improvements in insulation and air sealing.

Bottom line: The house is very comfortable, and we don't notice the temperature swings that we used to feel. The baseboards are quieter because they are starting cool, ending cool, and not getting as hot. Some fuel savings has been gained.
 
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Old 02-17-11, 04:59 PM
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Sound like a lot of comfort improvements.
I would do it slightly different since I like cold start boilers and pumps. I do like the boiler to heat up than start the pumps and bring cold water back to a warm boiler. At least you are bringing the pump on early in the cycle which is better for the boiler.
I would wire the pump to an adjustable time delay relay. Energize the circ on a call for heat and when the call ends the pump continues to run. One advantage you have trooper is you can shut down at a given temp. But what is wrong with constant run or at least a longer run cycle. Put in a long enough time period to run that the boiler cools down enough. Maybe a little trial and error.
 
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Old 02-17-11, 05:04 PM
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I could set a wider diff and let it come down further I guess. I just kinda 'eyeballed' the temp settings... right now it shuts down at about 120 or so... you think I should drop it down to say 100 ? Easy enough... where's my screwdriver?
 
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Old 02-17-11, 05:14 PM
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rbeck, you said:

I do like the boiler to heat up than start the pumps and bring cold water back to a warm boiler.
Did you mean to say that you DON'T like the boiler to heat up then start the pumps?

I'm not doing that... pump starts at start of heat call... 8148 a'stat... aux a'stat holds pump on after run...
 
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Old 02-17-11, 08:32 PM
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question for trooper

be patient with me. everything i know about this stuff i learned on this forum. i also have been wondering about having the circulator run after the boiler stops, because it seems a waste to have the boiler temp at 190 and no circulator going. (calls for heat are met and boiler shuts off) i have a gas fired boiler, which heats a hydronic floor, domestic hot water and indoor endless pool. ( i am the one with all the questions about a solar array that shares this boiler loop last year). so here is my question. how does your idea work when all the zone valves are closed? or is an oil fired setup different? or do you overide a zone valve to use the heat? thanks for the explanation in advance!
 
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Old 02-18-11, 04:23 AM
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In my case, I currently have no zone valves. The original plumbing was a branch system and the whole house was one zone. Now my first floor rads are being heated direct-return as one zone. At least now it's in Pex and I've got manifolds with isolation valves and drains.
Baby steps.
I like Trooper's setup which dictates pump shutdown by temp rather than a time-delay.
I have yet to look into the off-the-shelf "Smoother".
 
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