Webster JB1 burner

ben_18

I recently had a Webster JB1-07 oil-gas conversion burner installed on an Eastmond FST-50 boiler. The boiler is rated at 2100 mbh. It supplies steam heating to the building and also supplies hot water through an in tank coil.
As discussed on this wall many times I would like to make sure the pressure of the boiler is right.
The building is a 17 unit apartment building. I have measured many of the radiators and the boiler seems to be about double the size that the building needs. This burner is supposed to be a low-high-low burner so I figured that would be a good way to compensate for the oversized boiler. The burner will start on low go to high and once it reaches a certain pressure (should it be 3-4 psi?) it will go low. Then once it hits a low pressure (.5-1 psi?) the boiler will then run high and so on until the end of the cycle. (It is run with a heat-timer).
My question is, is this how this burner runs? The contractor says it goes low-high-off. And then will turn on again when it goes below a certain psi. Is this really the case?
Also what are the recommended low and high psi settings for the pressuretrols that are recommended? Is it high cutoff at 2,3 or 4 psi and then goes to low until it reaches .5-1 psi?

Dave in QCA

The burner is available with several control options. They are, on/off, on/off with low fire start, Low-High-Low, modulation, etc. It is impossible to answer your question without knowing exactly what option your burner was equipped with.

Your wish to use a low-high-low operation to compensate for an oversized boiler is a very good approach. This should give you very good economy of operation. On/OFF with low fire start will not give you much advantage at all. Ignition is a little quieter, other than that, there is not much advantage over simple on/off.

For steam boilers connected to proper piped heating systems, (assuming there are no air handlers or other equipment that is specifically designed for a higher pressure) the highest pressure you should EVER have is 2 psi. This will give you a control challenge when using normal pressuretrol devices, but you should switch to vaporstats for both the HI/LO control and the normal operating control. They are much easier to get an accurate setting.

I have adjusted the controls on my 2 stage Riello burner which fires a Weil-McLain 680 as follows: Operating vaporstat cuts out at 16 oz. Hi low vaporstat cuts to low fire at 11 oz and back to hi fire ate 5 oz. (it is the narrowest that I could adjust the band to).

Hope this helps.

ben_18

Thank you for your response. I spoke to Webster and they checked the model number and said it was set up for a low-high-low sequence. Although they said that there would be another control on the outside of the boiler that would be needed to utilize the low-high-low. Do you know about that?
Also when you set your Riello to 11oz and 5 oz how frequently does it cycle? I'm afraid if the difference in pressure settings between the high and low is not big enough it will cycle high and low too frequently. There are also no main vents so I think the pressure would have to be a little higher than normal.

JStar

How tall is the building? How many stories?

ben_18

It is 5 stories tall and 3 units per floor.

Dave in QCA

Tell us a little more about your system too. Is it one pipe or two pipe. If one pipe, what kind of vents are you using. Are there Thermostatic Radiator Valves on the vents? If it is a two pipe, what type of setup, if you know. What kind of traps. Are there TRVs on the inlets? Or... is it an orificed system, or perhaps a Moline system? All of these things are important in setting the right pressure for your system.

Also, just as a double check, can you post a picture of a typical radiator showing the end, along with its height measurement. It might be good to verify your measurements.

When you did your calculations, did you add in an additional 34% for piping loss and pickup factor?

EBEBRATT-Ed

Find the wiring diagram and you will be able to find the lo-high fire pressure control. Then find the terminals in the burner panel that it is supposed to be wired to and see if they installed it. If they installed it your boiler would have 3 pressure controls.
(1) Manual reset high limit , (1) operating control, (1) lo-high fire control. The operating control and the low high fire control are usually 2 of the same controls. The manual reset control is a safety high limit with a manual reset button on top. If you have only 2 controls they probably didn't install it. It will be a challenge as Dave correctly pointed out to keep the pressure low and make this work. The trick it to fire the burner at the correct rate which is base on several factors. You have to fire enough to keep the flue gas from condensing.

JStar

How tall is the building? How many stories?

ben said:

It is 5 stories tall and 3 units per floor.

I would set the Low Fire trigger at 10oz with a 4oz differential. Then set the main Pressuretrol at 1.5psi, or as low as it will go. You shouldn't need more than 10z max to reach the furthest radiator. As for the burner, a smart technician can turn most any two-stage burner into low/high/low or low/high/off.

ben_18

EBE- I'm pretty sure it only has 2 pressuretrols and it doesn't have one of those manual reset ones.

Jstar- so your saying it's not so hard to change it.
Where can I find a wiring diagram for this boiler?

Dave- I am attaching some pictures of the radiators. There are two per apartment. My calculation for 1 apartment is
Height = 37"
Rad 1 = 8 sections
Rad 2 = 6 sections
4 edr per section
total of 56 EDR
(one of the pictures has a six section one and one has a seven section one. That was probably not from this apartment.)

Dave in QCA

Nice pics of radiators. 4 sq ft per section is spot on. When you added up all of you rads to compare to the capacity of the boiler, did you compare to a Steam sq ft rating on the boiler, or BTU. Just questioning to make sure that you didn't make a mistake in calculations.

I totally agree with JStar's recommendations for set points and he would certainly know. He is one of the pros and knows his steam frontwards and backwards.

I will look to see if I can come up with a wiring diagram. But, on most burners, there are two points on a wiring block with a jumper on them. That jumper will cause the burner to go up into high fire. Remove the jumper, it stays in low fire. connect those terminals to a vaporstat and you got yourself a hi low control set up. Very simple. I'll see what I can find.

Dave in QCA

For wiring setup, I strongly recommend you refer to the wiring schematic that should be included with the burner. The information online covers the broad range of configuration that this burner is available in. I cannot advise from the information that I am able to find. But, it should NOT be that complicated to accomplish.

JStar

At one point, I did have some JB manuals. If you contact Webster, they will send out all of the information. Just expect a few weeks to get it.

KC_Jones

The radiator measurements you posted is that what is in each apartment? So roughly 56 EDR per apartment? If it's even in the ballpark that would come to a total of 952 EDR for the system. Your statement of the boiler being 2 times over sized would be WAY off in that case. At 952 EDR you are roughly 5 times over sized for the connected load. For the pros...if it is indeed that over sized is it even worth using high fire? I would take a guess that even on low fire the pressure is going to rise to the cutout point relatively quickly. How far can those big boilers be down fired? I just looked up the specs on that burner and even on low fire (by the numbers mentioned) the burner on the low end is double what is needed. I would guess the problem really would be if the burner can even make steam in that boiler at it's lowest firing rate? To the OP what pressure is that boiler running at now? I would have to guess it is cutting in and out like crazy. Just my observations on the subject.

nicholas bonham-carter

This would be an interesting study, to see how much more gas would be burned with such an oversized boiler. I wonder if a new, correctly sized boiler would be cost effective, and over what period of time.
With such short firing times, main venting becomes even more important to give even heat.
Why not double check the EDR ratings of all your radiators, as I cannot see why such a large boiler is in your building. Maybe at the time of installation, an adjoining building was connected as well.
Is there a rating plate on the boiler giving maximum, and minimum firing rates?--NBC

vaporvac

You mention you have no main venting.....perhaps you should look into this as well. any chance of pics of the near boiler piping?

ben_18

@Dave in QCA and @EBEBRATT-Ed mentioned that there are 3 pressuretrols needed. The operating, manual reset and hi low. How do these work? I got a hold of the wiring diagram and I am attaching it.
The high-low controller goes between 17 and 28. It seems that when those contacts are open it is low fire and high fire when the contacts are closed. So the burner would start on high fire and then when it hits the upper setting of the vaporstat (let's say 12 oz.) then the contacts will open and go to low fire. Then when it goes down to the low setting (say 4 oz. ) the contacts will close and it will go to high fire. It should keep cycling through this. Then what is the "operating" pressuretrol supposed to do? It will never hit it if it's set at 2 psi?

BTW I'm working on making a calculation of all the radiators.

Dave in QCA

If you look at the wiring diagram, it shows a HI-LO control (by others) connected via field wiring, to control cabinet terminals 17 and 28. I would bet you will find a jumper between those two terminals now.

If it is jumped now, it is going up into hi fire, and that is what would be expected without a hi-lo control. The control, (a vapor stat) if added, will cause the boiler to go down into low fire when the vaporstat contacts open. I think J-Star gave you great advice for pressure settings.

Depending on how oversized this boiler is, after you recheck your radiators, I suspect that you will be able to make it operate well. This is a fire-tube scotch marine type boiler, and it should have no issue operating at 1/3 full rated capacity, if that is necessary. It depends on whether the burner is rated for that BTU you end up firing it at and what the difference you is that you set up between hi and lo fire, and whether that burner is capable of that turndown ratio. You would be wise to have a very good burner man working on this. If you're set up for dual fuel and hi-lo, the burner tuning can be a little bit of a trick, to say the least. Follow the burner manufacturer's guide to adjusting. There is a probably a sequence that is recommended.

Dave in QCA

Ben,
Sorry, it was late last night when I posted the previous reply. I looked at the wiring diagram that you posted, but did not read your post. Duh!

The operating controller shuts down the boiler on pressure, IF the pressure climbs to its set point. You may have the boiler set up so that never happens, but there is always the "what if" situation. What if half the people in the building turn their radiators off? What is the HI LO controller fails? If pressure climbs, the controlling pressuretrol or vaporstat will shut the boiler down. The Manual Rest Pressuretrol only functions if all else fails. Since that would only happened when there are other serious problems, it is a manual reset control. If it trips, you have to actually push the button to reset it, so you'll know that you've got a problem.