Heating Help

Low pressure gauge

@ February 20, 2012 8:35 AM in Vaporstat vs pressuretrol

Before you go to the trouble and expense of installing the vaporstat, I would first set up a low pressure gauge to see at what pressure the system actually operates at. If  your system pressure never rises above a few ounces before the thermostat is satisfied, the vaporstat limit will never be reached either and you will gain nothing.

Does your system pressure ever rise high enough to shut down on pressure with your current pressuretrol? If the boiler and firing rate are well matched to the radiation, the vaporstat may be unnecessary.

Setback and efficiency

@ February 20, 2012 8:10 AM in Understanding Setback. This is a long question, not a lesson.

First of all let me say I completely agree with you as to the idea that it will never take more net energy to bring the house back up to temperature after setback than to maintain constant temperature. However, it is possible that may take more fuel in the recovery situation.

In the forced hot air case with a non condensing furnace, there probably would be very little difference and setback makes a lot of sense.

But in your situation with a modcon the results may be different. Remember the graph I posted a while back showing the reduction in boiler efficiency as firing rate increased? If you are just maintaining constant temperature, you are probably at low fire and fully condensing with efficiency in the 95-97% range. But if you are recovering from a deep setback, the boiler may go to full fire and the efficiency can easily drop below 90%.

So in this situation it is possible to burn more fuel with setback than just maintaining constant temperature.

Bearing assembly lubrication

@ February 18, 2012 7:40 AM in Oil furnace water ciculating pump making noise

If the bearing assembly hasn't been oiled for years and you only added 3 or 4 drops to location "C", you still may not have enough oil. A completely dry bearing may take a couple of tablespoons of oil to fill the reservior. There is wool wicking inside to absorb the oil and it should be saturated to keep the bearings lubricated.

I would continue to add oil to location "C" and see if it reduces or eliminates the noise. If you overfill it will run out the overflow underneath so you might want to put a rag there in case.

If the bearing assembly seal is not leaking water, I wold not consider replacing it until I tried oiling it further.

Yes

@ February 16, 2012 3:30 PM in Calculating cost of running electric motor?

Yes, 1.73 (square root of 3) is first used to convert line to neutral to line to line and then again in the power calculation.  120V x 1.73 = 208 (line to line)

When using line to neutral directly and simplifying the two equations, 1.73 x 1.73 = 3 so the power equation simply becomes 3 times (line to neutral) voltage times the current.

As an example, a B&G PD-37  3/4 HP 3 phase motor draws 2.4 Amps per phase.
120V x 2.4A = 288 Watts per phase. Each phase draws the same current, so the total power is 288 W x 3 phases = 864 W.  (120V x 2.4A x 3)

You get the same result by using 208V x 2.4A x 1.73 = 864 W.

Confusion

@ February 16, 2012 2:29 PM in Calculating cost of running electric motor?

Zman, as Larry says the line to line voltage times the measured current times the square root of 3 will give the total apparent power.

But in your example, you're using the line to neutral voltage instead. So in your example 120V x 1.73 = 208v line to line.  Then 208V x 1.73 x 10 = 3600 Watts.

If you use the line to neutral voltage 120V,  the apparent power is just 3 x 120V x 10A = 3600 Watts. The total power is just the sum of the individual phase power's if the phase loads are identical and balanced as it would be with a motor.

Motors and Watts

@ February 16, 2012 9:01 AM in Calculating cost of running electric motor?

Mark, I think some of the varied answers may be due to Tim's given 12 RLA spec. This might be the locked rotor current rating, not the actual operating current.

I work with a lot of large B&G motors. A single phase 3/4 HP motor at 208V draws about 3.5 to 4 Amps at full load. This current would give answers consistent with the watts per HP method.

Here is a good article which goes into detail about calculating motor wattage loads:

http://www.motorsanddrives.com/cowern/motorterms16.html

Best Guess

@ February 16, 2012 12:23 AM in Calculating cost of running electric motor?

I would say you would be pretty close at between $1.50 and $2.00 per day. Just because you have a 3/4 HP motor installed does not mean that its running at full load. If it is not, it will draw less current and use fewer watts.

 Without knowing the actual efficiency of the motor, all these calculations are approximate anyway, and without knowing the power factor of the motor, V x A will not give a really accurate answer.

So to be safe, just call it less than $2.00 a day?

Phases dont matter

@ February 15, 2012 11:53 PM in Calculating cost of running electric motor?

No the phases don't matter in the wattage calculation when using the conversion factor from mechanical energy to electrical energy.

 For example, a single phase 3/4 HP motor might draw 4 Amps at 208 across two phases, but an equivalent 3 phase motor only draws 2.4 Amps per phase. In the end they consume the same number of Watts if the load and efficiency is the same

Phases etc.

@ February 15, 2012 11:45 PM in Calculating cost of running electric motor?

The type of motor or the number of phases doesn't matter in the wattage calculation. A multiphase motor just draws less current per phase for the same HP output as would as single phase motor.

If you are operating 208V across two phases of a 3 phase circuit, the motor is only acting as a single phase as that's what it sees

What really counts is the wattage consumed, which is what you pay for, which can be calculated from the 746 Watts per horsepower, divided by the efficiency.

V x A

@ February 15, 2012 11:37 PM in Calculating cost of running electric motor?

Mark, how did you come up with that number?

With an inductive load like a motor, you cant just multiply volts times amps without taking the power factor into account.

If you assume an efficiency of 40 % then take 560 watts divided by .4 = 1400 W

That gives 14 cents per hour or $3.36 per day, or about $100 per month

Energy conversion

@ February 15, 2012 11:15 PM in Calculating cost of running electric motor?

One horsepower is equivalent to 746 Watts, assuming 100% efficiency. 3/4 horsepower would convert to .75 x 746 = 560 Watts at 100% efficiency.

A real 3/4 HP motor might be 80% efficient, so then actual wattage consumption would be 560 W /.80 = 700 W.

Assuming $.10 per KWh x .700 KW = $.07 per hour.

So actual cost of operating the motor might be about 7 cents per hour or $1.68 per day.

Electric Intensity

@ February 11, 2012 10:21 AM in What does the I in ohms law literally represent?

Electric current was originally referred to as "electric intensity",  which is where the abbreviation "I" came from.

http://en.wikipedia.org/wiki/Electric_current
 

Control range

@ February 10, 2012 6:35 PM in Modulating Pressuretrol - how should it work and be optimized

Yes, if the modulating pressuretrol is set correctly, then it will reduce or eliminate the constant cycling of the cutout limit pressuretrol.

That's the benefit of the modulating system. The burner always fires at only the minimum necessary to meet the steam demand at that time.

Setting the modulating pressuretrol diff setting as low as possible will result in the minimum firing rate for the given steam demand. For example, if the main is set at 2 PSI and the diff at A (1.8 PSI) then the firing rate will begin to reduce from 100% beginning at 2 PSI, but not reach the minimum 20% rate until the pressure reaches 3.8 PSI.

On the other hand, if the main is set a 2 PSI and diff is 0.5 PSI, then minimum fire will be reached at 2.5 PSI and the burner will be at relatively lower firing rates for more of the time, resulting in  tighter control of the steam pressure. Only when the demand is so low that even at minimum fire of 20%, more steam is still being generated than can be condensed, will the pressure rise to the 4 PSI cutout and the burner shut down completely.

So with the lower diff, the boiler will spend more time closer to 2 PSI than to 4 PSI, which is the result of the firing rate being reduced to a greater extent by the tighter control range.

Differential range

@ February 9, 2012 6:30 PM in Modulating Pressuretrol - how should it work and be optimized

I am not sure I understand your question. Reducing the differential setting does not decrease the time the firing rate is lowered. Instead it may actually reduce the firing even more, so that the pressure will never even reach 3 PSI.

It appears that your Powerflame burner has a 5 to 1 turndown ratio. This means that the lowest firing rate is only 20% of full fire. Because it is a modulating burner, the modulating pressuretrol can set the firing rate anywhere from 20% to 100% of full fire, depending on steam demand.

For example, if the zone valves are all off, the pressure may quickly rise to 2 PSI, at which time the pressuretrol will rapidly reduce the firing, perhaps all the way down to 20% to prevent it from rising further. If a zone valve now opens, the pressure may momentarily drop below 2 PSI, now the pressuretrol will increase the firing just enough to maintain 2 PSI. The whole purpose of the modulating system is to maintain a constant steam pressure, regardless of the load or demand for steam.

The differential setting detemines how close to the main setting the pressure is regulated. So if the main is set at 2 PSI, and the diff at 0.5 PSI, then the pressure should never rise above 2.5 PSI unless the demand for steam was so low that even at 20% firing rate, the pressure continued to rise. Then the firing would remain at minimum until the pressure rose to 4 PSI at which time the cutout pressuretrol would shut down the burner entirely.

Proper adjustment

@ February 6, 2012 8:13 AM in Modulating Pressuretrol - how should it work and be optimized

Yes, with the present settings the system will never work properly, since the cutout pressuretrol at 4 PSI will shut down the burner before the modulating range is reached.

Adjusting the modulating pressuretrol to 2 PSI or less seems reasonable as at that pressure setting the burner will begin to downfire, maintaining the pressure at probably 2 to 3 PSI and no more. Therefore you will never reach the cutout pressure of 4 PSI and the burner will run constantly without cycling until the thermostat is satisfied.

The differential adjustment is really a "gain" setting of the control servo loop, and determines how much variation in pressure is allowed above the main setting. Ideally you want to set this as low as possible without creating instability in the system. If the differential is set too low, the control loop will become unstable and the servo motor will "hunt" for the proper setting, moving constantly. If this happens, increase the differential slightly until the system stabilizes and the firing rate motor settles down.

The modulating pressuretrol will not provide low fire hold, as it calls for full fire until pressure rises to the main setting. If not already present, a temperature sensing aquastat must be added to the boiler to force low fire until it heats up to near the boiling point, say 190F or so. Then at that point, the burner will go to full fire and begin generating steam.

Control System

@ February 5, 2012 7:29 PM in Modulating Pressuretrol - how should it work and be optimized

Its not a on-off device, so using a vaporstat would defeat the modulated firing. The bellows controls a potentiometer which allows infinite variation of the firing rate. The actual burner control is done by a servo motor, which proportionally adjusts the air and gas to the burner.

Most likely, the modulation is not working because the steam pressure never reaches the proportional control range.The control could be set lower to reduce output at a pressure lower than the current  setting. It all depends on what pressure the system was actually designed to operate at.

A low fire hold would be a good idea to limit thermal stress from a cold start. An aquastat could be installed to force the burner to stay at low fire until the boiler is near boiling temperature.

Modulating

@ February 5, 2012 6:47 PM in Modulating Pressuretrol - how should it work and be optimized

The modulating pressuretrol will adjust the firing rate to maintain the steam pressure at the adjustment settings. Its hard to see, but you might have a 0-15 PSI control set approximately at 4 PSI.

If this is the case, the burner will run at full output until it reaches near 4 PSI, at which time, the firing rate will be reduced to maintain constant pressure in the range of the main setting plus the differential. The differential setting determines the range of proportional control. A low differential setting will keep the pressure close to the main setting, while a higher setting will allow more variation in steam pressure.

Here is a link to the instruction sheet on a Honeywell modulating pressuretrol:

http://customer.honeywell.com/techlit/pdf/PackedLit/60-2152.pdf

Oh well

@ February 5, 2012 10:58 AM in Copper ceiling radiant

I guess there was no guarantee that someone wouldn't mess with them over the last 60 years.

Here is a link to the Wall library 1949 B&G Handbook chapter on hydronic heating. There is a great reference to radiant of the 40's and 50' at the end of the chapter.

http://www.heatinghelp.com/files/articles/955/281.pdf

Square head cocks

@ February 5, 2012 10:08 AM in Copper ceiling radiant

The square head cocks were typically used as balancing valves for the various zones. They were recommended back then by B&G to control flow, as they were less likely to be messed with by homeowners and uninformed servicemen.

Maybe its good that they don't turn, as someone probably spent a lot of time adjusting them to get even heating throughout the house.

Vacuum?

@ February 4, 2012 6:00 PM in Failed low pressure Wika gauge

I wonder if vacuum at the end of the cycle may have damaged the gauge. The absolute pressure change when the steam collapses may be greater than the full scale rating or any steam pressure encountered during the cycle.

I messed up a low pressure gauge by applying suction once, as it was not designed to withstand any amount of vacuum.

EPC

@ February 1, 2012 7:55 AM in Heatimer EPC

The bulbs are B2A  (NE-51H) neon indicator lamps. Should be available from any good industrial supply co.

http://www.mcmaster.com/#neon-indicator-light-bulbs/=g24aj8

Info is hard to find on these. I use the data on the EPU for basic functional description.

I have rebuilt several of them, so if you need any specific info, let me know

Probe location

@ January 31, 2012 8:12 PM in gas pressure

Where are you placing the combustion analyzer probe when making the measurements? It seems you may be getting some of the dilution air mixing with the flue gas, reducing its temperature. 325F is still low for an atmospheric boiler. Usually in the 400F to 450F range is typical. The CO2 and O2 readings also seem like they may be diluted with additional air.

Are you getting the probe right down into the top of the heat exchanger area, where it will not be exposed to the dilution air from the draft hood?