LGB-8 - converting condensate pump to feed pump, possible, worth it?

bkc

Hi everyone. I am a trustee of a small church, tasked with 'maintaining the boiler'.

We have a 2-pipe system with a Weil-Mclain LGB-8 (22 HP) boiler that was installed in 2019, replacing an existing boiler that likely never had a periodic blow-down.

There are (3) 8000 EDR condensate pumps feeding a single Serlco 45 gallon steel simplex condensate tank/pump in the boiler room. I don't have a complete history of this church, but I do know at one point they had single-pipe radiators and a coal-fired boiler. After they added rooms to the basement level, they switched to using condensate pumps for all returns except two small radiators that wet return into the boiler room condensate tank.

The boiler has an MD 150SHD LWCO that activates an automatic water feeder to fill through the boiler intake (lower part of the loop). It also has a secondary MD 2M cutoff.

The condensate pump dumps when it wants into the boiler.

Based on date codes, I think the condensate pump motor was made in 2008, though the tank looks much older. The system must have been working ok with a condensate pump, but I don't know the type and size of the boiler that was previously installed. The LGB-8 recommends a feed pump configuration.

For the past 2 years a lot of make-up water has been going into the boiler as I've been slowly battling leaks, failed steam traps, broken 'remote' condensate pumps, etc.

In the past 3 months I found the pump on the boiler room condensate tank has been sucking air and randomly losing its prime. This ultimately results in a flooded boiler due to more make-up water. Fortunately our church has been closed, so I've been able to run the boiler only one or two days a week for the past 3 months.

About 2 weeks ago I got a seal kit for the pump. Unfortunately I was not able to remove the rotor, so I took it to a motor/pump repair business that has a pretty good reputation.

I heard from them on Friday that the pump is probably not salvageable. They also had trouble getting the rotor off (now its bent), they think the motor shaft is also bent too (hmm ?).

Ultimately the biggest issue is that the pump housing is cracked. We can rebuild from lots of little parts or replace the entire pump. I expect to get an estimate back from them tomorrow for either of these options.

Online prices for a replacement pump run between $800 to $1200.

Interestingly I see that an entirely new 45 gallon boiler feed pump (steel tank) can be had for $1800 to $2400. I wonder, is now a good time to change to a feed pump?

Another crazy idea.. can we convert our existing condensate tank into a feed pump configuration by reversing the 9037HG2 pressure switch to 'activate low' (for make-up water), re-wiring and re-plumbing?

The current condensate tank doesn't have a site glass, which seems like it would be handy to have to tune the switch settings.

I'm also concerned about those 2 radiators that wet return into the tank. After converting to a feed tank I expect the average water level to be higher than in the condensate tank configuration. I don't have elevation figures off-hand but it's possible the steam trap outputs could be 12 inches or more below the 'new' top water level in the tank.

There's also problems with near boiler piping, copper joint leaks, no throttling valve, etc. Seems like a good summer job.

I am interested in opinions I can take back to the other trustees.

We do not have a lot of money to spend, we'll likely do the work ourselves since we have some volunteers that have experience and tools to do piping and electrical work.

1. Replace the pump as-is or switch to feed pump configuration?

2. If moving to feed pump, retrofit our existing tank or replace?

For example this 'new' 4100 series appears to have the same tank we currently have, except for the site glass

https://www.sterlcosteam.com/wp-content/uploads/2019/01/TS-Sterlco-4100-Series-Boiler-Feed-Pumps-Rev11.14.2019.pdf

With "Solenoid operated make-up water valve with reverse acting float switch"



Here's our current configuration (and leaks)



and



I think 45 gallons should be large enough. Unfortunately I haven't 'timed the condensate return' before the pump failed, but based on this WM chart 45 gallons should be good enough for 20 minutes.

I see WM shows plumbing into the loop (which is what we have now), rather than to the boiier return per Dan's suggestion. Should that be changed?

Thanks,
-Brad

Jamie Hall

First comment -- not only can you convert a condensate tank and pump into a condensate tank and boiler feed pump, but it would be a very good thing to do.

That said, just how complicated you want to get is the question. If your church is anything like my parish, you don't have a whole lot of extra cash...

The simplest thing to do would be to go with the new boiler feed pump arrangement, as you mention that the existing condensate tank pump is probably toast. That gets you a nice new tank and pump all meant to go together in one go -- which has some serious advantages. Honestly, it's what I'd try to persuade my vestry to do if I were faced with the problem. The other possibility, though, is to purchase a new feed pump and match it to the existing condensate tank. Can be done, but will require a bit more ingenuity -- and if the condensate tank is doubtful, may not be worth the efort.

The second difference is in control. The boiler feed pump is controlled by a low water sensor on the boiler. What do you have on there for a low water cutoff now? Some LWCOs have a boiler feed contact built in. If so, it's just a matter of wiring that to control you new boiler feed pump (probably through a relay/contactor). It would turn on the boiler feed pump when the boiler water was low.

The third difference is control of makeup water and where it is added. Which a boiler feed pump, the makeup water is added to the condensate tank, not the boiler, and there is a control on the condensate/feed tank which senses low water in that tank -- not the boiler -- and adds water as needed. So some repiping there, but nothing major.

EdTheHeaterMan

I have done this and it is not that hard. In my case, I removed an 80-year-old boiler from a church that was equipped with a condensate return pump on a small tank (20 gallons maybe) When I configured the controls The float switch on the tank used to operate the pump. Now one of the LWCO controls has a set of NO contacts that power the pump motor. I used the existing pump and tank because they appeared to be in good condition.

The float switch in the pump now powers the feed valve solenoid. I think I needed to reverse the float switch from Closed on an increase in tank volume to Closed on decreased tank volume to power the feed valve. There was not that much to set up the water level and, like you, I did not have a sight glass. I believe it was a better design. After about 8 years in operation, the pump failed and I replaced it in 2013 It is still set up that way today.

Steamhead

@bkc , at the very least you will need to get some on-site professional advice. Doing so might also result in some fuel savings, which would reduce your operating costs. Where are you located?

EBEBRATT-Ed

I would go with the boiler feed tank. Why put money into an old tank and pump that not the right equipment for the job?

You should figure at least 20 min run time without adding MU water.

You don't need a Hartford loop with a feed tank. Sometimes pumping into a Hartford will put water up into the boiler header. You can do it either way but I would go into the boiler if i had a choice

bkc

@steamhead we are located in Potsdam, NY 13676

In our area there are 2 companies that 'do steam', A and B. I think company A was involved with the previous boiler, and now company B with the current boiler. We have a service contract with company B for 'annual cleaning, testing and burner adjustment'. They seem to be only focused on the boiler. To my knowledge they did not look at the system as a whole, make recommendations for changing anything other than the boiler, to carry out a trap inventory, to note the leaking conditions of other condensate pumps, etc. I was not a trustee at the time so I could be mistaken. I did ask them for a quote to repair a leaking F/T trap. Their response was a $$ quote to replace the entire trap. Replacing the gasket was not even offered as an option. I replaced the gasket myself.

I'm happy to pay for good advice/specifications/instructions, if I can get it. I would like to consider the option of doing some of the work ourselves, if we have members with the skills and tools to do the work competently.


@Jamie Hall Our primary LWCO MD 150SHD currently activates the automatic water feeder. We'd need a relay to run a pump because the LWCO only supports 1/3 HP (7.4 amps) but the current pump is 3/4 HP (11.5 amps)

@EBEBRATT-Ed the near boiler piping (a mixture of copper and iron) has a number of leaks. The brother of one of our members is a "boiler man" at a local university. When he looked at it he was not impressed. It would be great to change how the return condensate enters the boiler. However that configuration would not match "the picture" in the WM installation manual. Do you think that might be a problem for our insurance company?


@EdTheHeaterMan I'm interested in what you consider to be 'good condition' for a tank. You can see some of our current tank in the pictures I posted. I should probably try to get a good look at the bottom of the tank, though you can see a little bit in the right side of the photo below.

EBEBRATT-Ed

@bkc

You wouldn't have a problem pumping tinto a return connection at the boiler. You need the equalizer from the header to the boiler return but don't need to pump into it. I don't think Weil Mclain would have an issue.

But if you would rather pump into the Hartford do that. Either way is fine. Occasionally on some jobs pumping tnto the hartford causes water to go up into the header

Jamie Hall

Ah goody. One problem isn't a problem. You can use your primary LWCO to activate the boiler feed pump instead of the water feeder. And yes, a relay wouldn't be a bad idea at all -- if only to take the current load off the LWCO contacts to it will last better. Do it, and then have someone in the congregation rig a float switch on the condensate tank to control the automatic water feeder. You can do it in an afternoon.

A word of caution: you may will need an overflow (besides the vent) on the condensate feed tank -- now boiler feed tank. The water level in that tank must not get above the low water level in the boiler!

EdTheHeaterMan

By Good condition, I meant that it was not leaking and the age was more recent than the 80-year-old boiler. It appeared to be about 30 years old maybe 40, and the float and pump were operational. I'm sure there was a little rust on the tank, but not enough o cause concern. I would check operation each year and I believe there were oil ports on the motor. the float switch was also exercised thru the full to empty range and there was no problem with movement thru the complete range.

From what I can see, your tank is just fine.

Jamie Hall

I neglected to add -- the makeup water goes into the condensate tank, not the boiler!

EdTheHeaterMan

I forgot about that too. Thanks for remembering and posting that Jamie

Pumpguy

To add to what @Jamie Hall said, sizing the boiler feed pump's tank capacity is an important consideration.

First you need to know your boiler's steaming capacity, and then determine how much capacity you want the boiler feed unit to provide before re-circulation from returning condensate starts. Typically this is in the 10-20 minute range.

The industry offers receiving tanks in 3 different materials; welded carbon steel, cast iron, and stainless steel.

Welded carbon steel is typically 3/16" wall thickness and has the shortest life span. Cast iron is the traditional choice and are frequently offered with a 20 year warranty against corrosion failure. Welded stainless steel is also offered but some manufacturers caution against use with condensate that has treatment chemicals that end in IDE.