SHORT Cycle vapor steam MYSTERY (17 second)

RonWHC

RA117A may be out of step. Remove the cover. Dead center @ the top of the relay is a series of contacts. There is a small lever above them. Pull it forward & let it go. Do this w/ the burner off.

If you want to check it first. Do a voltage check from term 1 (hot) to term 2 (neutral) If there is 120 volts on those terminals, while the burner is jumping on & off, the relay, or stat, are the prime suspects. Is your Chronatherm a Series 10, 3 wire stat? If so, time for a new one.

adayton_2

Vapor steam short cycles every 17 seconds

with the following controls:

Trane two pipe steam system with Weil Mclain 572 boiler.

Honeywell RA117A Stack Relay

*** Honeywell PA404A Pressuretrol ***

Honeywell T8085A Chromotherm thermostat (24 volt)

Becket burner package.

one Gorton No.2 vent at end of each of two 55 foot mains

one Hoffman 75 vent at end of combined return.

This ensemble functioned fine except the pressuretrol was developing 3 PSI.

In order to lower the operating PSI the pressuretrol was replaced with Honeywell vaporstat PA404A. This was installed and squared up perpendicular to the axis of the planet per manufacturer instructions :-)... This now produces the following cycle pattern on cold start up:

(thermostat set at max for this test so it would NEVER interrupt call for heat)

(thermostat "anticipation" is set to 1.2 the setting recommended for steam operation)

cycle 1: 45 minutes burner on. (10 oz.) main pressure reached.. burner off for 58 seconds. (5 oz.) differential reached

cycle 2: 2 minutes burner on. (10 oz.) main pressure
reached.. burner off for 58 seconds. (5 oz.) differential reached

cycle 3: 17 seconds burner on. 17 seconds off

cycle n: ~~~~~cycle No. 3 repeats FOREVER, continuously "short cycle"

While this short cycling continues BOTH the thermostat and the vaporstat mercury are ENGAGED to the right in the "ON" position all the while the burner is cycling on and off.

The BIG HUGE mystery is where in this standard boiler control circuitry is something BREAKING and MAKING the circuit so as to create a continuous short cycle burner on/burner off at 17 second interval?????? (and remember that BOTH mercury switches are not moving from their ON states). Thanks for your help. Alfred/Jim

attached *.jpegs of system/controls

attached *.pdfs are control specs.

Steamhead (in transit)

Have you checked

the low-water cutoff?

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adayton_2

water cut off NOT likely

the problem. In fact I had completely forgotten that as part of the "control" circuit...oops.. lol

It is however a brand new M&M automatic water level feeder same model replacement for the original one that had worn out and was letting the water rise to top of sight glass.

Water level is now at half way mark and boiler shuts down with a one inch drop in water level. (see picture)

Is it possible that turbulence that we see in the sight glass is triggering the M&M? Why would it stay off for 17 seconds? Thanks for pointing out the feeder. What else could be causing such a uniformly repetitious continous short cycle? Alfred/Jim

Steamhead (in transit)

Turbulence could do it

but it's unlikely with the 47-2 feeder you have. Are you sure you don't have a bad connection somewhere?

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adayton_2

Loose connection

> but it's unlikely with the 47-2 feeder you have.

> Are you sure you don't have a bad connection

> somewhere?

>

> _A

> HREF="http://www.heatinghelp.com/getListed.cfm?id=

> 367&Step=30"_To Learn More About This

> Professional, Click Here to Visit Their Ad in

> "Find A Professional"_/A_

adayton_2

Loose connection

or partial break in thermostat anticipator variable resister is a strong possibility I have been considering. Each control object is accounted for as follows:

1. Thermostat: Honeywell chromotherm T8085A 10 to 15 years old, anticipator set all way to bottom which I believe is the 1.2 setting. repairing the day/night setback spring could have concieveably partialy damaged the anticipator.This only holds true if the resistor is in series with the load (relay) I have not confirmed this.

2. stack relay: Honeywell RA117A only about 2 years old

3. burner: Becket Burner

4. DHW: tankless coil with Honeywell Aquastat set to 140*F
aquastat function on/off ok

5. pressure control: was: Honeywell PA404A pressuretrol
system working fine at 1 to 3 PSI operating range

REPLACED with: Honeywell Vaporstat L408A set to 10OZ. mains and 5 OZ. differential. system runs a couple cycles then goes into continuous 17 second on/17 second off cycle.
During these continuous cycling BOTH the thermostat and the vaporstat mercury are fully engaged in the ON position (therefor they are BOTH calling for heat)

water feed: M&M 47-2 automatic water feed and low water cut off. Brand new. While there is a SMALL amount of fluctuation (turbulence)noted in the sight glass it is not sufficient to cause this mad extremely regular cycling. also the boiler although it needs a thorough bottom sludge cleanout (has not been realy cleaned in 25 years but HAS been religiously blown down every week during heating season) Also this SAME minor turbulence existed with the operation using the pressuretrol.

Pressure gage: new 3 pound range gage.

On a new note it has been observed that the mad cycling "condition" goes away after a 3 minute wait (after dropping thermostat down to effectively interrupt the cycling) and watching the pressure fall from 10 OZ. THROUGH the -0- PSI mark. Then if you restore the thermostat to call for heat a couple normal cycles occur then the mad cycling comences once again. The 3 minute "DELAY" time is fully reproduseable as is the 17 second mad cycle time.

This brings up the possible conclusion that whatever this intermittent problem IS, previously existed because when using the pressuretrol it would take 3 minutes to drop from 3 PSI to 1 PSI thereby MASKING the problem.
Perplexed, Alfred/Jim

rob brown

cycling

pretty simple deal to figure out problem. each control(lwco, pressure switch, or t-stat)all open circuit to burner.simply use a jumper wire to by-pass the wireing in each control, one at a time, until you come upon the one that elimenates the short cycling. you found your problem. if it is the lwco, then look at replacing your wet returns, as they are probobly clogged, causing slowed return of condensate from the system. rob