Condensate Receiver Pump purpose… please explain

wcs5050

I have a job with a Weil McLain EG boiler dedicated to 2 stainless commercial kettles. Each kettle has its own inlet isolation valve, return steam trap, with the common return going back to a Hoffman receiver. I’ve been servicing this setup for years but would just like a better understanding of why the pump is needed… is there just too much condensate and intermittent pumping back is the best management? Thx all.

Big Ed_4

You need the pump to over come steam pressure of the system … A gravity return needs the hight of the return to the water line to push the condensate back in . Which will multiply with the increase of system running pressure .. Most likely they can't …. Either dig a hole and drop the boiler in or buy a pump

EBEBRATT-Ed

A condensate or boiler feed tank is used when the condensate can not return to the boiler by gravity…like water running down hill.

There could be many reasons for needing a pump to assist with this:

Steam pressure is higher than the condensate pressure can over come

elevation differences between the return pipe and the boiler

etc etc

Jamie Hall

Just, to confuse things a wee bit — be careful to differentiate between a condensate return pump and a boiler feed pump. They are exactly the same pump with exactly the same condensate receiver tank — but the former, the condensate return pump is controlled by a float in the condensate receiver while the boiler feed pump is controlled by the water level in the boiler.

A condensate return pump can, and likely will, flood the boiler. A boiler feed pump won't.

EdTheHeaterMan

https://forum.heatinghelp.com/discussion/comment/1848827#Comment_1848827

I can attest to this because I changed an existing condensate return pump to a boiler feed pump when I replaced the boiler in a church over 20 years ago. I was not sure that the new smaller water content boiler would accept all the returning condensate from the system and decided to operate the pump by way of the LWCO's Normally Open contacts. But I was also not sure that the receiving tank was large enough to hold the returning condensate since the boiler manufacturer specified a tank that was twice the size as the existing condensate feed pump's tank.

Since it was for the church, my prayers "oh God, I hope this works" were answered and the existing tank was large enough to handle the load. By the way, the auto water feed was wired to the tank float switch, and piped to keep the tank at least 1/2 full so the pump would not run dry. That pump is still the same one today as when I did the job 20 years ago. Those pumps are workhorses.

Pumpguy

The condensate return pump will keep the system in steam / water equilibrium.

Also helps with corrosion prevention.

If you dumped all the condensate from the kettles, you'd have to continuously add make up water which contains oxygen and other bad things that corrode iron and steel boiler parts and piping.

jumper

https://forum.heatinghelp.com/discussion/comment/1848804#Comment_1848804

I like the hole option. Gravity is more reliable than electricmotor•pump. Also don't like uncontrolled vent.

Big Ed_4

I agree , easier for service too . You could drain the boiler tight into the pit :)

Jamie Hall

Watch out. If you place the boiler lower to use gravity, you almost certainly will lower the system waterline enough to cause major trouble out in the wilderness.

I'm not a big fan of boiler feed pumps — but in this application, that's what you want to have. NOT a condensate receiver pump! If that's what you have, rewire it as @EdTheHeaterMan suggested to make it into a boiler feed pump. They work just fine…

wcs5050

Thanks guys. Boiler is in basement with kettles a 1/2 a floor up. Water line to kettle inlets is around 3-4 feet. It is indeed set up as an independent receiver and right now the float/pump seems to be misbehaving. 24v LWCO commands Hydrolevel VXT, so they are isolated from each other. The water line has been stable enough, but on the high side. Why does the receiver vent burp?? Maybe pump not functioning proper and condensate filling up and burping out the vent? If I rewire it to have LWCO command receiver as boiler feed pump, what will command VXT when water is consumed? Planning on opening up the pump/receiver to flush. They are mentioning grinding noise which doesn’t sound good.

EdTheHeaterMan

@wcs5050 said: " If I rewire it to have LWCO command receiver as boiler feed pump, what will command VXT when water is consumed? Planning on opening up the pump/receiver to flush. They are mentioning grinding noise which doesn’t sound good."

You need to get the float switch in the tank to keep the water level in the tank from going too low. If the float switch is a single pole double throw action (SPDT) switch then it is easy. when the tank float switch goes below 1/3, you set the "close on drop" contacts to addd water to the tank. (not the boiler). If you have the same switch as i din where it is a single pole single throw SPST that closes when the level reaches near full, then you need to add a relay to get the reverse action to happen. Then reposition the float to operate when it is closer to the bottom of the tank. That way you get a set of contacts to close when the tank is low and the water feeder adds water to the tank.

I can draw you a diagram if you need one. Hopefully you have the SPDT or DPDT contacts on your existing float switch, then you already have the "close on fall" contacts you need.

Jamie Hall

You could use the LWCO to activate a relay/contactor which, in turn, would activate the boiler feed pump. Reroute the outlet from the VXT to the condensate receiver, and activate the VXT with a float in the tank — assuming you want to keep the VXT.

I'd be worried about a grinding noise, too. Pumps aren't supposed to grind. And tanks should be seen and not heard…

EBEBRATT-Ed

Using the LWCO to control the pump is a band aid.

What will happen is the boiler will shut off on the LWCO at the same time the pump starts.

You need another control on the boiler. Usually a McDonnell Miller #150 is used for this. It has to be mounted at the correct level on the boiler to start and stop the pump above the Low water level.

So the mounting heights are critical. And the control on the receiver that runs the pump now is used to prevent the pump is running with water in the receiver. This may need a relay to change the switching action.

Where is the water MU to the system piped to? It should be piped to the condensate receiver and not the boiler. This creates another issue. You would be better served with a boiler feed tank and not a condensate receiver.

EBEBRATT-Ed

What steam pressure are you running? And what is the height between the boiler water level and the water level in the kettles?

pedmec

Boiler feed tank is used to collect the returning condensate before it can flood the boiler. In larger steam buildings the boiler will call for make-up water before the condensate can return from the system. The water level in the boiler is dropping due to steam leaving and needs to be replenished to maintain a normal working water level. If the condensate is allowed to return directly to the boiler when the boiler is off you risk a chance of flooding the boiler.

I have buildings that have radiators 300'-400' from the boiler. it takes a good 20 minutes to just to reach the farthest point. My boiler feed tank has already taken about 4 calls for water from the M&M 150 by the time it trips the heattimer system sensor. So imagine how much condensate has to come back. Most of the buildings I have have boiler feed tanks. It comes with the system.

We use the VXT as a back up to the boiler feed tank in case of a motor failure. It is wired into the alarm circuit of the 150 so it energizes the VXT to keep the heat going. I think this set up is actually good because you can identify underground leaks once they get big enough. The VTX counter will start adding up.