old school, newboilers

frank

Extg twin-set lead/lag steam system w/both on until 3PSI, then one off, then nex off @5PSI. Both oldies have a seperate auto feeder, and condensate from system into small condensate tank w/float contollled pump going into a common return header. These boilers are to be replaced.
MY IDEA:
Add a larger receiver w/seperate pumps for each boiler controlled by a pump controller. (Naturally, check valved.) Have make up introduced into this tank via float switch.
THEREFORE:
Condensate pumped from extg tank into new tank and into whatever boiler wants water. If tank runs dry, make up into tank and pumped to where ever. A secondary LWCO below pump on will be installed.
QUESTION:
Do we want to pump condensate into a boiler that is on or off? At what level is this pump controller set?

keith

recieving tank size can be detemined

by measuring the EDR of steam radiators. Duplex pump set up works out great. The pump controller is set at the desired water line. The secondary manual reset L.W.C.O. is set 2" below that. The condensat water needs to be pumped in 2" below the water line. It doen't matter if the boiler is firing or not when you are adding make up water under normal circumstances.

Larry C

Pump controllers

Check your Mcdonald Miller catalogue.

The controllers I'm most familiar with are the 150 & 157 these are basically the same unit with the 157 having a built in water bottle. These units are dual purpose, pump controller and LWCO, 2 switchs tripping at different levels.

This is the way to go but if your using 2 controllers you'll have to isolate the common return and make each boiler feed independent. One control per pump/boiler

I set pump on 1.5-2" below normal water line on larger boilers. Be carefull if there scotch marine boilers with coils, the normal water line barely keeps coil submerged. This is a common problem in N.Y.C. where steam boilers and coils are the norm, forcing a higher water line and affecting steam quality.

In addition to your pump control/ Cutoff an additional cutoff is required and it may have to be a manual reset type MM 63m popular here.

Check with your MM Rep they'll be more help than me

Good Luck Larry

Frank_5

old school new boilers w/a wrinkle

The previous post was w/o seeing the job, just talking to the boss. Today I looked at the monsters. We're installing two-80 H.P. Eastmond steel steam boilers that are going to be lead/lag as discussed before. Installed requires 125 H.P. and the rest is for piping/pickup. I also found out it's a vacuum system (my first one) aren't I lucky! The old boilers were twined in at both the main and returns, acting as one boiler, w/one vacuum tank receiver/feedpump, but with individual auto feeders. Now we want to seperate the boilers to lead/lag.(As per engineer) I've got the method of returning the condensate back to which ever boiler wants it, (thanks steamheads) but I'm kinda puzzeled as what to do and how to pipe this vacuum equalizer I read about in BIG DANS "The Lost Art Of Steam Heating" Is the vacuum breaker set at a specific value, or just a plain ole thing? Is there one check valve for each boiler, or two? Why doesn't the water seal in the U bend get sucked out? The size of it, etc. Any help appreciated.

DanHolohan

If the vacuum pump is staying

and you're adding a boiler feed pump you'll have to discharge from the vacuum pump into the boiler feed tank. From there, you'll need two motorized valves, one to each of the two boilers. Each boiler will have a pump controller that will open the motorized valve on the feed tank. An end switch in the motorized vavle will then turn on the feed pump.

The motorized valves will keep the vacuum pump from sucking water out of the feed tank on start up. The equalizer would go from the boiler header (through a water seal and check valve) back to the vacuum return line. Its job is to break any naturally induced vacuum in the radiators (which forms when the steam condenses) that may be deeper than the vacuum formed by the pump. It's rare for that to happen and the equalizer is really a "just in case" thing.

I've got a better description in all of this in Hot Tech Topics. It's in an article called, "The 25 Steps in the Repair of a Vacuum Steam System."

Hope that helps!

Dale

You don't want to add

water too quickly, you might want to install a square head cock after the boiler feed pump outlet check valve to limit discharge pressure to max 5 pounds over boiler pressure.

chris smith

electric valves

if your going to use electric valves to start and stop the pumps you only have to run one condensate line to both boilers the valves start and stop the pumps you can add a double pole double throw switch to choose which pump is going to run or a automatic pump sequencer if its in the budget by pipng this way you can loose a condensate pump and both boiler can still opperate as normal, years ago i piped where each boiler had its own pump now i set it up so either boiler can call on either pump just a little more reliable

chris smith

Frank_5

pumps, valves, motors, traps,etc

(1) We were thinking of installing a dual pump set w/alternating switch into a common manifold that would direct condensate into the needed boiler via motorized valves (two of 'em) controlled by pump switch such as MM150.
Our MM rep can't supply us with info concerning the motorized valves. We are trying to avoid Honeywell 'cause of price and lack of support w/their product. So this question to you STEAMHEADS is what size, & mfg. These boilers are 80 HP each, lead/lag,so we definately need motorized valves to prevent back up into the feed tank. The tank mfg has supplied us w/data that the pump(s) will be putting out about 35 PSI w/the head we have on the job. Did I mention this is a vacuum system?
(2) What about spill traps with steel boilers? We are using Easmond FST. (I agree if they are C.I., then use the spill traps.) These boilers have a rather large steam area, and we're thinking that steam from the "on" boiler passing over the "off" boiler will condendate and add to the water line, but not enough to make the water line become critical.
(3) Similiar jobs we have seen to be quoted for replacement have a common return from the feed tank pump into a return manifold. Therefore lead/lag or not, the water lines of both boilers would equalize and when one needs water, both need water and both get water. I would think with one on and one off, the pressure from the on boiler would push water into the off boiler via this common connection, then the on boilers pump switch could ask for water and maybe wind up w/too much. Am I right, or missing something here? Waiting to hear from you ole Steamheads.

chris smith_2

trap

the water colum or sight glass at desired level, this makes the condensation problem go away its actually a plus keeps lag boiler warmer, as to valve pricing i eat the honeywell money, its all about reliability and options, also on a larger system stop checks are a good idea

chris smith