Motorized valves near the header

ross swazy

I manage an apartment building with a two-pipe steam heating system which operates under vacuum generated by a Dunham & Busch vacuum pump.
The system has three zones and each zone has a motorized valve on the main.
Dan Holohan's A Pocketful of Steam Problems recommands the installation of a vacuum breaker on the boiler or the near boiler piping to avoid the formation of a deep vacuum in the boiler if a motorized valve closes while the boiler is steaming.
Can someone tell me whether the installation of the vacuum breaker would not cause problem with the operation of the vacuum pump? In other words, would the vacuum breaker not prevent the vacuum pump from drawing a vacuum?

Unknown

you are correct

It would compete with the vacuum pump. What pressure are you running on the steam side? I presume that you have a boiler feed pump. Do you have motorized valves on the pump lines to the boiler? If not, the vacuum will be broken when the boiler sucks water from the tank through the pump, only if the zone valves are all shut when the steam shuts down.

The important thing to keep track of is the water temperature of the condensate coming into the vacuum pump. If failed traps blow steam into the return, and it gets hot, your pump seals will fail.

Noel

ross swazy

Motorix=zed valves near the header

Noel,
Thanks for your answer.
The system I am dealing with does not have a boiler feed pump at present. It uses a vacuum/condensate pump that discharges directly into the boiler's Hartford loop when it feels the urge to do so.
The system serves two apartment buildings which are next to each other. One building is 5 storey high with ten to eleven apartments per floor and the other is 4 storey high with four apartments per floor starting from the second floor. In total 64 apartments.
The buildings were built in the early 50's. The original boiler was a big chested Victor from Montreal that lasted until five years ago when it gave up the ghost and was replaced by a Weil-McLain 14-88 (i.e. much smaller chest and possible water problems with consequent need to install a feed pump! I will find out that pretty soon when the heating season starts).
The system has been running at around 5 lb of pressure since the replacement of the boiler and the vacuum pump was not generating a vacuum for some time. During the past summer I have had the header rebuilt to correct evident piping problems, I have added a trap testing station for both radiator traps and F&T, I have checked ALL the traps and replaced a whole bunch of disks, I have opened the condensate return lines and flushed them out, I have cleaned all the strainers and installed a new motor plus impeller and volute to the vacuum pump. Unfortunately I have not been able to obtain from Dunham & Busch original parts to rebuild the vacuum pump (I was told that this pump was produced in Toronto, Canada and D&B does not have parts or records of the work done by the local plant?????).
In any case the pump, with the inlet and outlet valves closed, is now drawimg 27 inches of vacuum, so I am hoping for the best until I possibly locate a correctly sized rebuilt pump that does not require me taking out a new mortgage on the building!
I have adjusted the boiler operating pressure down (Dan will love to hear this!) to the lowest level I could. It apeears to be between 2 and 3 lbs. I mentioned to the contractor who has been doing some of the work on the boiler that we probably need a vaporstat but from the look I got I concluded that he probably thinks that I am on drugs! If you can suggest a quality model to be used I will be grateful.
My next step is going to be to find out if I need a feed pump and, if so, the appropriate size of the receiver.
I have installed a water meter on the automatic water feeder line and I will keep an eye on the water usage upon start up of the system and watch to see if the boiler floods when the condensate gets back. By the way, do you have any idea of the operating range of a 14-88 Weil-McLain boiler? My prelimimary calculations point to a usage of approx. 7 gallons of water a minute and, unless I am way wrong with those calculations, I do not think that the boiler will give me more than a few minutes to get the condensate back.
In your response you made a very important comment about the importance of keeping good track of the temperature of the returning condensate. I am aware of the importance of staying within a max of 160F. but I have no idea on how to read the temperature of the condensate.
If you look on The Wall, you will find a question I posted on 9/17 under the heading "The condensate is too hot for the pump" where I am trying to find out whether thermometers could be installed on the condensate return lines to read the temperatures. Have you ever done that and, if so, how did it work out?
Noel, I think I asked a lot of questions in this message and I do not want to abuse of your patience, so I will shut up now and wait for your comments.
Thanks in advance for your patience,
Ross

ross swazy

Motorix=zed valves near the header

Noel,
Thanks for your answer.
The system I am dealing with does not have a boiler feed pump at present. It uses a vacuum/condensate pump that discharges directly into the boiler's Hartford loop when it feels the urge to do so.
The system serves two apartment buildings which are next to each other. One building is 5 storey high with ten to eleven apartments per floor and the other is 4 storey high with four apartments per floor starting from the second floor. In total 64 apartments.
The buildings were built in the early 50's. The original boiler was a big chested Victor from Montreal that lasted until five years ago when it gave up the ghost and was replaced by a Weil-McLain 14-88 (i.e. much smaller chest and possible water problems with consequent need to install a feed pump! I will find out that pretty soon when the heating season starts).
The system has been running at around 5 lb of pressure since the replacement of the boiler and the vacuum pump was not generating a vacuum for some time. During the past summer I have had the header rebuilt to correct evident piping problems, I have added a trap testing station for both radiator traps and F&T, I have checked ALL the traps and replaced a whole bunch of disks, I have opened the condensate return lines and flushed them out, I have cleaned all the strainers and installed a new motor plus impeller and volute to the vacuum pump. Unfortunately I have not been able to obtain from Dunham & Busch original parts to rebuild the vacuum pump (I was told that this pump was produced in Toronto, Canada and D&B does not have parts or records of the work done by the local plant?????).
In any case the pump, with the inlet and outlet valves closed, is now drawimg 27 inches of vacuum, so I am hoping for the best until I possibly locate a correctly sized rebuilt pump that does not require me taking out a new mortgage on the building!
I have adjusted the boiler operating pressure down (Dan will love to hear this!) to the lowest level I could. It apeears to be between 2 and 3 lbs. I mentioned to the contractor who has been doing some of the work on the boiler that we probably need a vaporstat but from the look I got I concluded that he probably thinks that I am on drugs! If you can suggest a quality model to be used I will be grateful.
My next step is going to be to find out if I need a feed pump and, if so, the appropriate size of the receiver.
I have installed a water meter on the automatic water feeder line and I will keep an eye on the water usage upon start up of the system and watch to see if the boiler floods when the condensate gets back. By the way, do you have any idea of the operating range of a 14-88 Weil-McLain boiler? My prelimimary calculations point to a usage of approx. 7 gallons of water a minute and, unless I am way wrong with those calculations, I do not think that the boiler will give me more than a few minutes to get the condensate back.
In your response you made a very important comment about the importance of keeping good track of the temperature of the returning condensate. I am aware of the importance of staying within a max of 160F. but I have no idea on how to read the temperature of the condensate.
If you look on The Wall, you will find a question I posted on 9/17 under the heading "The condensate is too hot for the pump" where I am trying to find out whether thermometers could be installed on the condensate return lines to read the temperatures. Have you ever done that and, if so, how did it work out?
Noel, I think I asked a lot of questions in this message and I do not want to abuse of your patience, so I will shut up now and wait for your comments.
Thanks in advance for your patience,
Ross

Unknown

vapor

Where to start.....There are two good models of vaporstat, by Honeywell, for steam boilers. On small systems, I like a L408A1132, (breaks on pressure rise, 0-1 PSI) because it is very sensetive below a pound of pressure.

I like a L408A1157, (breaks on pressure rise, 0-4 PSI) on a bigger system, because sometimes 1 PSI isn't enough pressure to heat all of the radiators. I bet this one is right for you.

I like to think that there is a "sweet spot" on each system that is the pressure that 1)heats to the last radiator on the system, and all others, and 2) produces nice long run cycles. It is fun to find that setpoint.

Try your vacuum pump with the steam off and the pump valves open to the system. You should be able to pull the system down easily to 7-10" of vacuum, with the steam off. This leak-tests the system to a certain degree. It must be leak tight. That vacuum reaches through all of the traps and radiators all of the way back to the zone valves and the boiler. If you shut the zone valves and run the boiler, the vacuum still reaches back to the zone valves. The boiler, alone, has positive pressure in it.

With a vented system without a vacuum pump, the steam pressure alone reaches out and fills the radiators and shuts the traps. With a vacuum on the system, the pressure can be even lower. On some vacuum systems, they fed steam through the zone valve; or "king valve" only enough to bring the main to a higher pressure (which reads as a lower number on a vacuum gauge) than the vacuum in the return, but still negative. This allowed steam to be delivered at a lower temperature. They even varied the vacuum on the returns to deliver hotter steam to the colder zones and cooler steam to the warmer zones. This was around the 1930's or 40's, and is still used.

Your sweet spot will vary with the vacuum setting. It will get higher if you have bad traps, to the point that some places won't heat. Traps are the key to it all. Keep them from heating the returns and you will be OK.

Buy an infrared thermometer, a decent one, with a laser pointer. One that works twelve feet away. The cheaper ones rely on being REAL close. Using that, follow your returns out when everything is working and get used to how it runs. When traps fail, you will have a baseline to compare to.

get the book for the boiler out and see what the water level tolerences are. As you run it, the biggest load is at start-up. You don't need cold weather to time the first condensate coming back after the header gets hot with everything open (zone valves) and vacuum pump running. She either feeds new water in or it doesn't. Do it a few cycles of heating, and letting the steam go to zero. Flooding will be apparent. You can see how much range there is in the glass before the pump comes on the first time.

If you see condensate at the pump inlet above 150°F, look for bad traps.

Noel

ross swazy

vapour

Thanks Noel for your ultrafast response.
I am chewing on it right now and will get back to you soon.
Ross

ross swazy

Hi Noel!
Thanks first of all for the info on the vaporstat. I agree with you that the 0-4 PSI one is probably the most appropriate for my system.
I have tried the vacuum pump with the steam off and the pump in-let and out-let valves open to the system.
We ran the pump for about 10-12 minutes but we did not read any vacuum. The pump sucked the water from the bottom tank into the hurling chamber and discharged it into the boiler. I assume that enough water remains in the hurling chamber to prevent the pump from running dry and therefore there is no danger of damaging the pump even if there is no condensate coming back. Shall I let it run longer than I did?
By the way the vaccum pump has a D&B label attached with the following information:
size 10 - pressure 20 - capacity 10,000 - serial C62217 - CSA approval No. 361.
On the subject of the returning condensate temperature, I was looking today at some "clamp-on" thermometers made by Winters Instruments (www.winters.ca) that have a flexible steel spring fastening and are said to provide accurate temperature readings of pipes with diameters between 1/2" and 4". Their model T167 has an operating range of 30/240F.
Do you think something like that might do the trick on the condensate returns?
Noel, where is home for you?
Are you far away from Toronto? Do you ever come up here to visit?
If you do, I would like you to come and visit.
Ross

Unknown

I'm in New York

I bet you don't develop vacuum because the pump is pulling on the boiler through the piping, and the boiler is pulling water through the check valve and pump from the tank, and the vent on the tank is letting air in to the tank. With steam on the boiler and the zone valves shut, the check valve will stay closed, and the vacuum pump could pull down the pressure in the system beyond the zone valves.

Try that...

This is not a problem unless the vacuum pump is allowed to run before the steam is on. Some systems have a motorized valve after the condensate pump to prevent this.

Try this thermometer, or one like it. It's the only one you need.

http://www.raytek-northamerica.com/tools/free_form_content/view.html?phase=show&id=1013546448&tool_id=38&cat_id=4.3

Any chance you could show some pictures of the important parts of the boiler room piping?

Noel