Boiler short cycling?

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Old 01-13-15, 06:44 PM
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Boiler short cycling?

Hi,
My boiler frequently runs for just a few seconds and I wonder if it's bad for it? Is this what you call short cycling? I sat with it for a 1/2 hour and recorded what it was doing...
I have a Taco 6 Zone Valve Control that tells me when a thermostat calls for heat (CFH) and when the zone valve opens and when the zone is satisfied (SAT). And it's hard to tell if the circulator pump is running when the burner fires, but I think it was running.
Now I should also say that it does a fine job of keeping my home nice and warm. But if this is inefficient or bad for it, please tell me what I can do to improve on my system. I'm open to any suggestions.

7:04 Z4 CFH boiler temp 155 F
7:04 Z4 SAT valve never opened
7:05 Z3 CFH boiler temp 155 F
7:07 Z3 valve opens, burner fires, I think circ pump starts, runs 7 seconds
7:07 Z3 SAT everything shuts off
7:09 Z1 CFH boiler temp 155 F
7:09 Z4 CFH boiler temp 155 F
7:11 Z1 valve opens, burner fires, I think circ pump starts, runs 5 seconds
7:11 Z1 SAT everything shuts off
7:11 Z4 SAT valve never opened
7:15 Z3 CFH boiler temp 155 F
7:15 Z4 CFH boiler temp 155 F
7:16 Z3 valve opens, burner fires, I think circ pump starts, runs 10 seconds
7:16 Z3 SAT everything shuts off
7:16 Z4 SAT valve never opened
7:17 Z1 CFH boiler temp 155 F
7:18 Z1 valve opens, burner fires, I think circ pump starts, runs 5 seconds
7:18 Z1 SAT everything shuts off
7:22 Z4 CFH boiler temp 155 F
7:23 Z4 SAT valve never opened
7:25 Z3 CFH boiler temp 155 F
7:25 Z1 CFH boiler temp 155 F
7:26 Z3 valve opens, burner fires, I think circ pump starts, runs 7 seconds
7:26 Z3 SAT everything shuts off
7:27 Z1 valve opens, burner fires, I think circ pump starts, runs 5 seconds
7:27 Z1 SAT everything shuts off
7:28 Z4 CFH boiler temp 155 F
7:30 Z4 SAT valve never opened
7:31 Z2 CFH boiler temp 155 F
7:31 Z2 SAT valve never opened
7:33 Z3 CFH boiler temp 155 F
7:33 Z1 CFH boiler temp 155 F
7:34 Z4 CFH boiler temp 155 F
7:35 Z3 valve opens, burner fires, I think circ pump starts, runs 15 seconds
7:35 Z3 SAT everything shuts off,10 seconds later
7:35 Z1 valve opens, burner fires, I think circ pump starts, runs 5 seconds
7:35 Z1 SAT everything shuts off
7:36 Z4 SAT valve never opened.

It does run longer than this at times. But during this particular 1/2 hour, this was all it did. I live in upstate NY, it was 3 - 4 degrees F outside. My house was between 67 - 68 degrees F inside.


Roughly 1500 sqft house with cathedral ceilings, partly renovated 10 yrs ago with some updated insulation, windows, and doors (haven't done the heat loss calc. yet)
1977 The New Yorker boiler AP-790 154,000 BTUH
Beckett oil burner AC-046132 running a .80 nozzle
Honeywell TAR L8124A hi 160, lo 130, diff 20
Taco 6 Zone Valve Control Module with Priority ZVC406-4
1-Taco circ pump 0011-F4
5-Taco zone valves 571-2
4-Honeywell thermostats T87F temp set to 69 F anticipator set to .6
30lb. pressure relief valve
12-15 lb automatic feed
3 zones of a radiant heating system, copper in slab, mostly circa 1947
1 zone a small pathetic 1968 addition having slant fin radiators and an uninsulated floor
1 zone indirect 40 gal HWH on priority

Please let me know what you think,
Thank you,
red rocket
P.S. I also wanted to say thanks for the advice you gave me when I was plumbing in my indirect this summer. You guys are great!
 
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Old 01-13-15, 07:00 PM
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No way Rocket man... something wrong there...

Can't answer in depth at this time, but will look later, possibly tomorrow.

That 011 pump is probably wrong, but doubtful it has anything to do with the frequent short calls.
 
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Old 01-13-15, 07:15 PM
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With only the information provided I think that you are trying to micro-zone the house, have the thermostats differential set to 0.5 degrees and your boiler is at least fifty percent oversize for the real load.
 
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Old 01-13-15, 09:22 PM
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Running Taco zone valves. Tstat anticipater setting at .9. Taco very specific about that. Taco takes the most power to open among zone valves in the industry.
Wrong anticipater setting will cause short cycling due to the improper voltage going to the zone valves they constantly try to open and close. Eventually will burn out.
It's like putting 60 volts to a 110 v light bulb. Brown out.
Set your stats to .9
You may have other problems but that at least will save your zone valves.
 
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Old 01-14-15, 03:31 AM
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Spott, does that also hold true when there is a Taco zone control board between the thermostats and the zone valves?
 
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Old 01-14-15, 08:11 AM
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New Yorker boiler AP-790 154,000 BTUH
Beckett oil burner AC-046132 running a .80 nozzle
Unless the oil pump pressure has been jacked up over 100 PSI, that boiler is firing at 112K BTUH.

Taco circ pump 0011-F4
As mentioned previously, that pump is likely a bad choice... UNLESS the tubing in the slab is a small diameter and has very high 'head'. The 11 pump is for high head systems. MOST residential systems don't need that. BUT, not the cause of this problem.

Why does the boiler temp never move off 155F ? Are you sure the temp gauge is not stuck?

Let's start with the very first two entries in your log:

7:04 Z4 CFH boiler temp 155 F
7:04 Z4 SAT valve never opened
Z4 CFH and then SAT in under a minute? WTH? How can that even happen at all?

Then the next entries:

7:05 Z3 CFH boiler temp 155 F
7:07 Z3 valve opens, burner fires, I think circ pump starts, runs 7 seconds
7:07 Z3 SAT everything shuts off
There is no way that Z3 t'stat satisified in seven seconds.

Not going to repeat this for the rest of the log, because all the results are similar.

T'stats calling and hanging up in seconds, and boiler temp never changing.


1 zone a small pathetic 1968 addition having slant fin radiators and an uninsulated floor
Which zone number is this?
 
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Old 01-14-15, 11:24 AM
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Furd,
Yes it does. The control board just basically takes the place of the 24v transformer and makes for a neater job but the tstat still has to open the zone valve and that takes .9 amps to do that.
I've seen them actually melted from the heat of trying to open up on inproper settings.
 
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Old 01-14-15, 12:06 PM
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I've seen them actually melted
Seen what melted? Thermostat? Zone valve? Zone panel?
 
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Old 01-14-15, 12:21 PM
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The zone valve head. It generated so much heat from the wrong amperage it acted as if it was going through a brownout. Without the proper amps the weakest component will eventually fail and it is the zone valve in this case.
All other control will run at .4 or .5 or whatever with no problems. It just lengthens or shortens the tstat call time.
Taco is the only valve I know that requires a specific amp. value to operate correctly.
They started making a new valve that would operate on .2 but I haven't seen many around. Possibly because the heads aren't compatible with the original bodies. You must change the whole valve.
 
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Old 01-14-15, 01:02 PM
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It generated so much heat from the wrong amperage
But the anticipator doesn't do anything at all to change the amperage in the circuit.

If you had a melted zone valve head somewhere, it was from another cause.

It just lengthens or shortens the tstat call time.
Right... by changing the amount of heat that the little heater inside the thermostat puts out.

When you set it to shorter cycles, that little heater in the t'stat puts out more heat and 'tricks' the thermostat into thinking the room is up to temperature.

That's ALL it does. It can not and does not change the current in the wires.

BUT, that said, I do agree that the anticipators on those thermostats should be increased to 0.9 for the Taco zone valves.

I'm not sure it's going to make a difference though. Those thermostat call times are WAY TOO SHORT ... there's something else going on there that we don't know yet.
 
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Old 01-14-15, 01:51 PM
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Those stats are not actually controlling the zone valve directly that's going through the controller.
Geo
 
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Old 01-14-15, 01:55 PM
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Ahh, but they are.

All the ZVC does is the interconnect wiring. The load of the zone valve is on the thermostat circuit.

There aren't any relays or anything between the thermostat and the zone valve terminals.
 
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Old 01-14-15, 04:48 PM
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Wow! Thanks sooo much Spott and NJ Trooper! I can't believe the difference that made. It seems like it must be too good to be true...
I have not heard it short cycle since I changed the anticipator settings to .9. And the 2 zones that tended to run a little cool, are nice and toasty.
Unbelievable! Such a simple fix! You guys are fantastic!


I do have a couple more questions though; But should I post them on a new thread?

NJ Trooper, you're a fan of cold start with an indirect, right?
How do I do that and keep the circulator from running when the temp is low? I tried one method that I found on this site months ago and my circ ran whether the boiler was hot or cold. So I switched it back.
And do you think I would benefit from a heat manager, Intellicon, or a vent damper?
To answer some of your previous questions NJ Trooper:
I don't know how to find the oil pump pressure.
As for the pump, it replaced an old B&G 15 yrs ago, to alleviate air bound zones and a Taco 4900 air separator was added later. They both seemed to do the trick.
The temp gauge is not stuck, there is another on the manifold that feeds the zones that confirms it's accuracy when the circ is running.
Zone 1 - 16 ft of slant fin radiator with approx 60 ft total 3/4 copper loop. Also the most poorly insulated room in the house.
Zone 2 - 200 ft 3/4 copper between the joists on 2nd floor mezzanine, rarely runs, and well insulated.
Zone 3 - largest zone, 3 separate loops 500+ ft 3/4 copper in slab, 200 ft 3/4 copper between joists on first floor, 300+ ft 1/2 pex in slab, and well insulated.
Zone 4 - 2 separate loops 250+ ft 3/4 copper in slab on each loop and insulated ok.

Thanks again!
What a difference!
red-rocket
 
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Old 01-14-15, 06:11 PM
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Rocket,
Glad everything worked out. As far as the cold start question it's exactly that.
Your boiler will only run on a demand for heat or hot water if you have an indirect water heater. Your warm start will maintain boiler temp if you need heat or hot water or not. So your boiler always stays hot.
Cold start is when tour tstat calls for heat the boiler and pump come on together so for a short time you are circulating cold water through the pipes. There's no getting around it. Some people want that and some like the warm start.
Personally my boiler came with warm start years ago and when I put in an indirect I never changed it. I happen to like the instant hot water through the system and don't see a great amount more fuel usage.
It's a matter of preference.
 
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Old 01-14-15, 06:41 PM
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Darn!
I was hoping there was a way to wire up the circ so it would wait for the boiler to get up to temp. When I tried it before, both the boiler and circ ran a long time under 140 F and sometimes satisfied the zone before it even got there. I've read that can be bad for the boiler and the chimney. ( acidic or something)

Do you think a heat manager or Intellicon would make it more efficient without causing problems like that?
 
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Old 01-14-15, 07:38 PM
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Rocket,
Reading your specs you have a control with a hi & lo limit so that is what your pump does now. On a call for heat your pump will come on @ the LL setting. If the boiler temp drops below that setting your pump shuts off until the temp climbs back up.
As far as your chimney goes that could become a problem with low boiler exhaust temps. Just because your boiler water temp is 140 your exhaust temp going out of the flu pipe on the boiler is most likely at least 400 which is fine and will not cause condensation in the chimney.
The short version is they are two different temps.
Getting back to your cold start you unfortunately can't have it both ways. On a cold start control you only have 1 setting, your high limit, that is because the pump comes on with the boiler so no LL is needed.
If you have a tankless heater that is, you get your hot water from a coil in the boiler you can't put a cold start on anyway. You will never get domestic hot water because your coil will be sitting in a boiler full of cold water, especially in the summer.
Sorry for the bad news.
 
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Old 01-15-15, 03:20 AM
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Thanks again Spott,
I think I understand what you're saying. I can't get what I'm hoping for with the setup that I've got. Right? I do have a 40 gal indirect HWH. And my HI is set to 160, LO is set to 130 and DIFF is set to 20. With these settings my boiler mostly stays between 140 and 180. But I'll have to watch it now to see if that's changed at all with the new anticipator settings. It behaves so differently now.

Are there more optimal settings for efficiency on the controller that I have?

Are there different controllers that are capable of cold start and controlling the circ on a lo setting?

Do those heat managers or outside temp reset controllers do that?

Thanks,
red-rocket
 
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Old 01-15-15, 06:47 AM
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Are there different controllers that are capable of cold start and controlling the circ on a lo setting?
Actually...

Is your aquastat the L8124 variety? I think it is.

If it was the instructions you tried that called for removing and wire nutting together the red and white wires, then you did the FULL conversion... you disabled the burner on Low limit AND also the circulator control.

It IS POSSIBLE with the 8124 series to remove ONLY the burner control and keep intact that circulator control, if that's what you want...

For this, you remove the BLUE WIRE, and place a wire nut on it (should probably tape it also... don't want that wire nut falling off inside) and tuck the wire out of the way.

After this the burner will NOT fire on Low Limit, but the circulator WILL be under control of the LOW and DIFF settings.

In other words, if the boiler temp is below the [ LOW - 10F ] , the circ will be disabled, and will not be re-enabled until the boiler temp reaches [ ( LOW - 10F ) + DIFF ]

Is this what you're looking for?
 
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Old 01-15-15, 09:11 AM
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Yes. I think that is exactly what I was looking for NJ Trooper.

What are your thoughts on running a boiler that way? Is it more efficient than a warm start, without as much of the condensation and acidic problems?

I'm hoping to cut down on fuel usage without doing damage to the system.
 
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Old 01-15-15, 03:04 PM
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What are your thoughts on running a boiler that way? Is it more efficient than a warm start, without as much of the condensation and acidic problems?
Mixed feelings...

IMHO, warm start is a waste of fuel. It simply doesn't make sense to me to 'idle' the boiler just so that there's warm water instantly available on a heat call. When it's COLD outside, the chances are the boiler isn't going to cool that much between heat calls ANYWAY. When it's warm outside, who cares if you have to wait a few minutes for the heat to come up?

Using the circulator control like that is a bit disturbing too... older massive cast iron boilers might not mind it that much, but certainly the lower mass newer boilers can be 'shocked' by cool water flowing in from the system once the pump starts.

I think you have one of those older jobs, don't you? 700 lb of cast iron?

Still, it makes me cringe a little to think about what's happening in there, cool water hitting hot cast iron... can't be a good thing.

Maybe it doesn't hurt a thing, I've been wrong b4... it's just that my gut tells me it's wrong.

As long as the boiler ultimately gets hot enough, long enough, to dry out any condensate that forms while the boiler is heating up, there's really not a problem. Acid without water is INERT.

I'm hoping to cut down on fuel usage
The best way to do that is keep the heat that you paid for inside the home. Go on a campaign to seal air leaks. Even the smallest air leaks! All those small leaks add up. Insulation is secondary to air infiltration (and EXfiltration) in retaining heat. If all those little air leaks are added up, you might be surprised to find it's equivalent to a wide open window.

Insulation and sealing foam and caulk is FUEL YOU PAY FOR ONCE!
 
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Old 01-15-15, 03:07 PM
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Doesn't NY have a program that pays for HOME ENERGY AUDITS?

A REAL energy audit, that includes what is called a 'BLOWER DOOR TEST' that measures the amount of air changes / hour in your home... not some jamoke with a clipboard walking around and checking boxes on a pre-printed form.
 
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Old 01-15-15, 04:33 PM
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Well, you talked me right out of it! Thanks NJ Trooper.

I think I get what your saying. Let me just confirm. Cold start is better when the pump and the burner run together, even when the boiler is cold.

My boiler is unfortunately steel, not cast. But it IS old. So, I guess I'll wait for a week or so, and get used to it's new behavior before I make any more changes.

Eventually I'll try the cold start again, bugging the 2 wires together and see if I get a better result now that the system isn't short cycling all the time. It might be entirely different with the anticipators set correctly.

And I will definitely work on sealing and insulation. I have been working on that quite a bit in this last year.

An energy audit is a good idea, too. Thank you. I will look into that, as well.

You have been extremely helpful!
Thank you for your time!
red-rocket
 
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