Condensation Tank Nightmares'

adnrahin

I’m a new homeowner and still learning how my steam heating system works. I recently started running into some issues with my steam boiler, and I wanted to explain the problem step by step to get advice and feedback.

How my system is supposed to work

My home has a steam boiler with a condensate return system. When the boiler runs, it produces steam that travels through the pipes to heat the radiators. As the steam gives off heat, it turns back into water (condensate). This condensate flows into a condensate tank.

Inside the condensate tank there is a float switch. When the water level in the tank rises to a certain point (I’m not exactly sure what level), the float switch turns on the condensate pump. The pump then pushes the collected water back into the boiler so it can be reused.

What actually happens during a heating cycle

When the boiler starts and the heating cycle is running, steam leaves the boiler and the water level inside the boiler naturally drops. This seems normal at first because some of the water is out in the system as steam and condensate.

However, before the condensate has time to fully return to the tank and get pumped back, the boiler water level drops too low. At that point, the Low Water Cut Off (LWCO) detects a low-water condition.

Once the LWCO senses low water, it shuts off the boiler for safety. The boiler stays off for a few minutes while it waits for water to return. During this waiting period, the thermostat is still calling for heat, but the boiler cannot run because the LWCO has stopped it.

If the condensate return is delayed, the LWCO then signals the automatic water feeder to add fresh water to the boiler. This happens even though condensate is still on its way back from the system.

As a result, the boiler ends up with too much water. This causes water to be carried into the steam piping, leading to loud water hammer noises and water spitting from radiator air vents.

Turning off the auto feeder

To stop the hammering and vent spitting, I turned off the automatic water feeder. Doing this immediately reduced the water hammer and improved system noise, which confirmed that overfilling was a major part of the problem.

New problem: long boiler shutdowns and lack of heat

However, with the auto feeder turned off, a new issue appeared. When the LWCO detects low water, it shuts the boiler down and keeps it off until enough condensate returns naturally. In some cases, I’ve observed the boiler staying shut off for a very long time sometimes more than an hour even though the thermostat is still calling for heat.

During these long shutdowns, the system does not produce enough steam, and the house does not heat properly.

The main problem seems to be timing and coordination. The condensate pump, LWCO, and auto feeder are all working individually, but they are not coordinated properly. Condensate takes time to return, but the LWCO and auto feeder react faster, which leads to overfilling and water hammer.

I’m trying to understand whether this is a control issue, a design issue, or something that can be corrected with better settings or updated components.

4GenPlumber

It sounds like the condensate is having trouble getting back to the pump. Have you checked the wye-strainer on the inlet side of the pump housing?

Captain Who

Is there any sight glass on that condensate tank to verify that it is full to nearly the point where the float switch should activate the pump? At that point even the slightest amount of condensate from the radiators should trip it.

What happens when you jumper out the float switch? Does the condensate pump get power and pump condensate into the boiler? How much does it add in height on the boiler sight glass before shutting off?

Jamie Hall

Condensate receiver tanks are OK, I guess, if your system really needs them. However condensate return pump arrangements are, in my humble opinion, a contrivance of the devil.

Is there any way , as @Captain Who asked, to check the level of the condensate in that tank when the condensate pump turns on? It should be at least two thirds full, maybe more.

Second, is there a check valve on the outlet from the condensate return pump and is it working?

Third, is the float switch in the condensate tank working reliably? The float is free?

The fundamental problem is, most likely, slow returns — if they can be flushed out in some way it may help. However, the real problem is the whole condensate return pump thing. It's just wrong — though common.

Fortunately, if you have a good technician, there is a work around, and it may even be "no parts required". What needs to happen is to rewire the system so that when the low water cutoff asks for water(which it should do at a slightly higher level than shutting off the boiler) it turns on the condensate return pump, not the automatic water feeder. Then rewire the float (you may need a relay here) in the condensate receiver to the automatic water feeder so that it turns on the water feeder when the water in the receiver is low. Now reroute the pipe from the water feeder so it goes into the condensate receiver, not the boiler.

This simple modification will eliminate the problem of overfilling the boiler.

Fundamentally this rewiring is rather simple, but needs to be done carefully and thoughtfully. Depending on the voltages of the LWCO and the feeder, you may need a relay in there. A good technician will know.

Now however… with the slow return problem, it will probably overfill the condensate receiver. You will need to provide an overflow from the receiver to a floor drain. This overflow must be below the boiler water line elevation!

Fixing the slow return problem should eliminate the overflow problem, but in the meantime the boiler will operate as it should and give you the heat you need.

JUGHNE

I would check that wye strainer and the gate valve for the inlet to the pump tank.

Also it looks like there is a drain down valve on the return line before the strainer.

That should be checked for free flow.

ethicalpaul

Is it possible that the issue is the boiler is carrying over/vomiting its water into the main resulting in a water level drop that no condensate tank would be able to recover from fast enough?

Out of curiosity, how large is this home? Is the condensate tank even necessary?

JUGHNE

The cond pump may have been added to try to correct the problem of slow cond water return.

The return looks high enough to be gravity return without a pump.

The pump tank makes more water available for the system but the return is still too slow for even that.

A boiler feeder pump would have been a better choice. It is controlled by the LWCO in the boiler and the water fill connection is at the pump/tank.

adnrahin

@4GenPlumber Yes I checked wye strainer and it's working fine. Water comes back to tank fine.

adnrahin

@Captain Who there is no sight glass on the tank. But when pump pushes water once it's full It goes all the way up.

Typically in that level lwco shut off the boiler,which is strange. In most boiler I see this is enough water to operate.

And when pump pushes the water often its above blue cycle in the below picture

adnrahin

@JUGHNE I checked wye strainer and did some cleaning. Also checked both red and yellow velve. Red velve is just for draining out the water that's my understanding.

adnrahin

@ethicalpaul what do you mean by carrying over/vomiting its water into the main?

Captain Who

Have you played around with the adjustment of this? What is the position of the arrow when 1) the condensate pump starts pumping, and 2) when it finishes pumping

JUGHNE

Show us the LWCO device and it's location relative to the floor and sight glass.

ethicalpaul

https://forum.heatinghelp.com/discussion/comment/1889770#Comment_1889770

When the water quality is bad due to oils or other junk in the water, the boiler water gets carried over into the main resulting in a low water condition. Here is a video that shows it occurring on a small residential boiler that used to be in my basement, coincidentally:

https://youtu.be/WSRvvNQ5WLc

There is no actual loss of water, except temporarily where gallons of water get thrown into the main pipes.

Another thing to watch out for is if this is a two-pipe system, pressure in the system can push the water out the bottom of the boiler into the returns resulting in again, no actual permanent water loss, but a temporary low water condition that can trigger your LWCO.

These are just two possibilities to check for and eliminate if possible to avoid chasing ghosts

Jamie Hall

As @JUGHNE said, a boiler feed tank would have been a better choice — and as I outlined above, a boiler feed tank and a condensate receiver are almost the same, except for the control wiring, the routing of the makeup water, and an overflow on the tank.

pedmec

As stated above. Boiler feed tank.

adnrahin

@Captain Who Below is picture of when condesate pump start

And here is the picture of after condesate pump finish pushing water to the boiler

adnrahin

@JUGHNE

adnrahin

@ethicalpaul I am not sure if I understand what you said correctly but I have drained the water couple times and also drained the condestation tank. I saw nice clean water, and which makes sense what you just said. Maybe the bad water is getting pushed to main and remaining goes back to the condestation tank. But I have added fresh water multiple times and every time the results is same. It will run fine for few cycles and all the sudden will stop.

adnrahin

@Jamie Hall I did some googling and found out about the boiler feeding tank. I need some directions that adding new boiler feed tank will work. My initial suspect was Floating Pressure Switch which might not functional. I found a similar Floating Pressure Switch which might work. Before I replace with new tank and pump.

https://www.supplyhouse.com/Telemecanique-9037HG32Z20-2-1-2-NPT-Liquid-Level-Float-Switch-Close-on-Rise-575V?utm_source=google_ad&utm_medium=Shopping_Plumbing&utm_campaign=Shopping_X_Plumbing_X_SSC_Hybrid&utm_campaignid=22376844123&utm_adgroupid=176639540066&utm_targetid=pla-2435661369999&utm_product_id=9037HG32Z20&utm_matchtype=&utm_keyword=&utm_adtype=pla&utm_category=Plumbing

EBEBRATT-Ed

You need someone that knows steam to look at your system to find the problem. The fix could be a boiler feed tank

or a surge tank as shown in the Weil Mclain piping diagram.

A surge tank would be less $$ if that is the correct fix.

adnrahin

https://www.boilersupplies.com/sterling-condensate--boiler-feed/sterling-4028g-4128g-series-condensate-return/884

I found this pump not something like this will work.

Jamie Hall

Ah… with some ingenuity you don't need to replace either the tank — or the pump or the float switch you now have to activate the pump. Nor the low water cutoff which activates the automatic water feed.

That's a pretty good size pump, though, so you will need a relay — maybe two relays, depending on the voltage of your auto feeder and your low water cutoff.

Rewiring. Note: if wiring isn't your thing, find an electrician who understands controls and relays and get help!

Step 1. Take a relay with an appropriate coil voltage and connect its coil to the low water cutoff instead of the connection to the auto feeder. Connect the normally open contacts (of the correct voltage and current capacity) to the pump, disconnecting the pump from the float switch in the tank. Now when the low water cutoff calls for water it will start the pump.

Step 2. Now take the wiring from the float in the tank which you disconnected from the pump and connect it, with power, to the coil of a relay with the correct voltage. Take the normally CLOSED contacts of that relay and connect them to the auto feeder in place of the connection which used to go to the low water cutoff. Now when the tank float is low it will call for water from the feeder, just like the low water cutoff used to, and when the float rises it will turn off the auto feeder. Note that this is the reverse of what the float does now — now when the water is too high it turns on the pump. Using the normally closed relay contacts when the float rises it will turn off the auto feeder.

Now plumbing.

Step 1. Make sure there is a check valve on the output of the pump — which is now a boiler feed pump.

Step 2. Take the connection from the auto feeder to the boiler and disconnect it from the boiler and connect it to the condensate tank. This may take some ingenuity to find a good connection point!

Step 3. Add an overflow line from the tank to a handy floor drain. This also may take some ingenuity to do. This overflow must be below the water level in the boiler!

Commissioning

Step 1. Before you turn the power back on, make sure that the voltages are correct and that there are power supplies, if needed.

Step 2. Verify correct operation. When you lower the boiler water level to the low water cutoff, the pump should turn on and draw water from the tank into the boiler as needed and then turn off. When the water level in the condensate tank drops, the auto feeder should turn on and refill the tank as needed and then turn off.

If all is good at this point, you have just converted a condensate return tank into a boiler feed tank at the cost of two relays and some pipe… enjoy.

Jamie Hall

Note: I goofed in the above. I have made a correction which is in italics to the contacts to be used on the relay connected to the tank float.

ethicalpaul

is there often water on the floor under the boiler?

JUGHNE

Yes, what is the water on the floor from?

Your LWCO looks to have a probe into the boiler water.

That probe may need cleaning. Also the pigtail loop under the pressure control can plug over time.

You will benefit from the book "We have Steam Heat" from this website.

A picture showing the right hand side of the boiler…..full on full side will help.