Redundant cut-off

VTsteam

I searched this topic, unable to find an answer.

We are installing a new, 650 MBH Burnham steam boiler. Impressed with how complete the kit is and how easy it assembled. The existing, old boiler has a series 67 low water cut-off, and series 101 fill value. The fill valve developed a steady leak so it was eliminated. Water was manually added as necessary. The low water cut-off had not been trouble free either. Plan was to maintain manual fill with new boiler and use a reliable, electronic, cut-off. A Hartford Loop would also be added. However, the new boiler kit has both a series 150S-MD primary cut-off/pump control, and back-up series 63M cut-off. Am confused on the best course of action. Should we use the included controls, or stick with the plan? If using the new controls is it best to mount in vertical, equalizer pipe, or use the 3/4 NPT ports on front of boiler?

Sincere thanks in advance for your consideration.

Steamhead

What model Burnham?

Does the system have a boiler-feed pump that pumps return water into the boiler?

VTsteam

Boiler is a V905A. System has a condensate return pump.

Jamie Hall

I'm a little conservative, but... even on a small residential boiler I would have two low water cutoff devices. If there is an automatic feeder or a condensate return pump (I hate those things), one of them would also control that -- turning it on slightly above the cutoff level. The other would be a manual reset device at a lower, but still safe level, so that when the automatic whizbang fails the boiler will still shut down.

The Hartford loop will protect you against draining the boiler into the wet returns or condensate feed tank, depending on how the latter is piped. It will not protect the boiler from a failure to feed.

EBEBRATT-Ed

Don't know what code VT follows but in MA 2 low water cut offs are required on a boiler that size. 1 must be a manual reset. The 150S is your primary LWCO and also operates the boiler feed pump. The 63M is manual reset back up LWCO.

2 things are critical for this to work. 1. Skimming the boiler and proper piping you have to prevent a bouncing water line at all costs it will drive the 150 nuts. There isn't much differential between the 150 low water and feed pump switches. (I sometimes prefer separate feed pump and lwco)

And I would consult with Burnham as far as control mounting heights if they are not spelled out in the manual

ch4man

so to be clear, do you now have a condensate tank, or boiler feed tank?
if a feed tank is needed for the system you NEED the MM150. there are no electronic LWCO that will last a year being used as a pump controller. around here a 650 CFH steamer requires redundant cut offs, 1 man, 1 auto

VTsteam

Thanks for the helpful feedback. The Burnham installation manual does indeed show the series 63 and 150 LWCO mounting arrangement. There is an existing condensate return pump operated by an integral float switch. Have tentative plan to trigger a city water fill solenoid using the 150's pump control contacts. Need to confirm solenoid current draw. Suggestions?

ch4man

is the condensate tank right next to the boiler, or remote.

the original system must be very well balanced to use a condo tank effectively. my concern is if the newer boiler has a smaller steam chest it will go unbalanced and a feed tank will be required. perhaps Burnham expects this and just includes the 150 & 63 because they feel most installations need a feed tank.
just me, but I have never seen an installation with just a condo tank. yours must be a very well designed system.

I'd talk with Burnham and give them all the specs on the old boiler and press the issue of remaining balanced. otherwise i see flooding on shoulder seasons

Jamie Hall

Be very very cautious with a condensate feed tank.

If at all possible, arrange the controls so that the higher level switch of the 1505 controls the pump from the tank to the boiler. This will make it a boiler feed pump, which should work OK. Do NOT, repeat NOT, control the feed from the condensate return tank to the boiler with a float in the condensate tank (the classic condensate return pump). Doing so will result in the boiler overfilling and all kinds of resulting havoc, including you getting called out at oh dark hundred in a blizzard to fix the no heat call.

Then use a float in the condensate return tank to control an automatic water feed to the system, in the event of leaks. Your idea of using the 150 contacts to trigger a city water feed will, again, guarantee an overfill.

Steamhead

There are two types of these tank/pump combinations: One is a "condensate pump" which has a small tank and a float switch in the tank to operate the pump, and the other is a "boiler-feed pump" with a larger tank, where the pump is controlled by a 150S-MD or similar unit on the boiler.

Many times a steam system can be operated on gravity return without the use of a tank and pump. One exception is when the system is divided into zones using zone valves. Another is if there are radiators below the boiler's waterline.

Tell us more about your system...................

VTsteam

ch4man said:

is the condensate tank right next to the boiler, or remote.

the original system must be very well balanced to use a condo tank effectively. my concern is if the newer boiler has a smaller steam chest it will go unbalanced and a feed tank will be required. perhaps Burnham expects this and just includes the 150 & 63 because they feel most installations need a feed tank.
just me, but I have never seen an installation with just a condo tank. yours must be a very well designed system.

I'd talk with Burnham and give them all the specs on the old boiler and press the issue of remaining balanced. otherwise i see flooding on shoulder seasons

Jamie, most sincere thanks! I appreciate your experience and will be taking your knowledgeable advise.