Ok, a hot water pressure washer works on the same principle as a tankless hot water heater, this unit has a beckett burner that is placed under a large coil. It is natura gas, with water pressure of 3000 PSI at a volume of 5 gallon a minute.

There re two units within the same room, they are the same brand and were installed the same day

The one unit works fine and has for almost 2 years. The other has had a issue from the beginning and we repaced the coil for the heater last month.

The only differnence is the one unit sits about 1 1/2 foot from a wall on back and one side, the other unit just has a wall in the back.

Ok, the one unit has water that develops on the coil when the heater is on. ( not when the heater is off) it builds up and drops to the bottom of the burner it got so bad it would even put the burner out. There is no leaks, it merely condisates on the pipe of the burner.
Then when it goes to the bottom of the burner, the heat inside turns it to steam and it goes back up and adds to more water vapor. A never ending cycle where water just runs from this unit

In 10 years of working on these I have never seen it, The factory that makes it, says it should not happen and do not know why.

We have taken heat readings of the outside and inside of coils, they are they same, they both use the same water line coming into the building. And share the same gas line. There is enough gas pressure and water volume to run the units.

I am about to recommend they move the unit out of the corner toward the midde of the room, that is the only difference we can come up with.

*** these are large units so it is not a cheap issue


So any ideas, we have access to almost any test equipment and may have already done a few things.

We replaced the coil because the vapor had rusted it to such a point it was bad. A coil shoud last 5 to 10 years at least, this one lasted less than 2 years.

At this point I'm thinking the start ambient temperature in that corner is just cold enough to cause the difference and produce the condensation.

Before you move the unit I would try a small quartz fan heater and warm up that corner/ area for some time and see if that makes a difference for condensation situation when the heater fires up. If it does make the diff Then moving it out of the cold corner is a given.

See what others have to say can come up with.

Yes I will note this is in a concrete room ( think bunker) both units are vented out the roof ( straight up no bends)

The room as a over head garage type door. I have ran it door up, door down, The room is heated, and have done it heater on, heater off.
Same result.

I have not tried the heater in the corner.

I am afraid I can't be much help on this one, this is probably the only tool/machine I don't own. It seems to me that this much water can't be just condensation. I know you replaced the coil but I am wondering if you tried this failed unit with the Ng shut off. I'm think that maybe there is another small leak aside from the coil.

No, there is no leaks, pressured tested to 4000 PSI, and runs with no water without heater burner going ( the water still runs though coils ** there is a off /on swtch for the heater.

I ran it for 30 min today with no heat, not a bit of water, within 5 min of heat on, starts to drip, within 10 min you can see visible water vapor in unit

Example, just the heating coil of this unit is over $ 3000 dollars. This unit is a 20 plus thousand dollar unit in a commercial setting

I'm along with bal1 as as far as not knowing the unit. Is it possible the unit was not insulated properly or is there some kind of passage for the warm heat "residual venting" that's clogged or not venting in the unit itself aside from the chimney?

A port plug at top of unit not taken out after shipping, a removal thing that was missed?

A very radical approach would to power vent it for a test.?

What does the unit look like?

Just taking a stab at it with simple science.

No, took off vent pipes , you can see the flame ( not a bright thing to do) though the top of the unit

This is "simular" the actual unit is a specia production unit and no photos are allowed inside ( company secrets to manufactoring) but this is a stock unit that would be sort of similar. Again it is not this brand this photo ony first similar one I found

Whoa Fr_Chuck, you are out of my league with this unit. I am mostly residenial when it comes to tools, equipment and repairs. Let us know if you figure this out.

I keep coming up with the defect being the inside units chimney chamber is restricting air flow to join the main chimney right before the unit.

Or something as simple as a manf, Mon morning insulating worker installed insulation around that side chamber to cause this.

Chuck. This would drive me nuts in curiosity to try and remove the outside metal jacket and get into it. Its already not working well.

The way insul works if it gets 5% of humidity in it its lost 95% or its insul properties.

So its fine on pressure but when the heat is turned on it acts like a summer picture of Ice ater on a 100 degree day. So on that principal I go for insul checks first and then the air flow residuals.

Sorry Im giving it my best here and still feel Im not helping much if at all. I think on it some more.

What's the BTUs here or the stack size?

I don't see any choice but to smoke test the vent. Operating if possible. Use something like: Smoke Generator Candles, Single Wick - Superior Signal - Mfg# 2B

And have someone inside and on the roof.

You may have interacting stacks.

So, that's one possibility.

Condensation is usually caused by a cold surface and humid air. Measure the relative humidity and temperature of the air and any nearby cold surfaces. The burner's may not be adjusted right because a higher gas flow would cool the burners. So, if someone has a combustion anayzer, that might help too.

TPI Combustion Flue Gas Analyzer, TPI, Combustion Gas Analyzer - Mfg# 712

Those are my ideas You want to be looking at draft and excess air and compare.

Chuck Most all boilers big or small has an insulated jacket outside of the heat chamber. Newer ones are foiled heat reflected with the insul. Is it possible to take some hex head screws out and take the outside metal jacket to inspect it. The top jacket is one of my suspicion. Even a domestic gas fired water heater on a complete cold start drips a ton of water and you think the flame might drown.

Its just a very expensive boiler/pressure washer.

I remove jacket and attack it before I would move it.

Had a similar problem with some steam boilers the size of a suburban. They were twins and one sweated horrendously. Insulation problem

This has been a problem for many folks over the years usually with boilers in homes but the condensation problem can effect any water based heat style system. We all know what condensation is so that does not need to be addressed. The location of these units is ideal for a condensation problem. Concrete/block or any masonry surface contains water weather you can see it or not. The one unit you are having a problem with is just experiencing more of a problem probably since it is in the corner and has more wet surface area (walls/concrete/block) than the other unit. But the other unit could also be having the same problem it is just not as pronounced.

Try this cure. Pipe some of the hot discharge water back into the cold water intake. This should be done right at the intake and discharge valve lines. Also install a gas cock or other style valve that can be adjusted and then tightened down to prevent tampering once the ideal setting adjustment is made. What this does is elevate the incoming water temperature above the condensation range and the condensation problem goes away. I would be a rich man if I had a dollar for every one of these setups I installed or recommended.

The incoming water temp combined with the moisture in the area creates a perfect storm when heat from the burner is applied. The moisture falls out of suspension and causes the water problem. By increasing the incoming water temp the problem goes away. On a typical 150,000 boiler I have used a 1 inch copper line for the bypass and just installed two tees one in supply and one in discharge with the valve to control the issues. BUT I have no way of knowing how serious your issue is so installing a larger pipe and valve might be smart.

Once installed open the bypass and run the system and the problem should be taken care of then you can close the valve to the proper level to prevent the moisture from happening to start with without losing much output as you would if the valve was not installed at all. Any questions?

Another note for you to read.

Hydronics Piping Checks Can Be A Breeze

HVAC1000's solution will probably work. Because of the 3500 PSI problem, you may have to do it with a heat exchanger.

This will solve the problem of pulling hot water from the unit to pre heat the cold going into it since you have High pressure to deal with. Also the unit doesn't have to be disturbed in any way.

Just use some domestic hot water and set up the old fashion mixing valve except its just in reverse.

Valve on hot water side tee in to cold line that's feeds to heater. Simple adjustment there to balance the domestic hot water added to the cold for input temp to boiler

Don't know how hard it will be to recycle hot water out of the high pressure unit since its way above domestic pressure.

Check valves on the hot and cold before the mixing valve. That way there is no reverse when the reg waterlines are used elsewhere.

A domestic set up would be a snap if a hot water line is near by. If its close and you have the hot water valve open and its just not quite enough to completely stop the problem. Another valve on the cold side added to balance it even closer. But if this is done a pressure gage needs to be after the mixing valves to monitor the pressure right before the unit after the mixing. You don't want to have both valves out of balance to have pressure drop feed to boiler of what it needs to operate at its proper feed pressure.

Very good input all around. I have nothing to add at this time. Perhaps not ever. :D

One last item Fr. Chuck. The manufacture does have an engineering problem as far as I am concerned. The best principal is to heat the water before you pressurize it not after. This eliminates many problems. Five gallons a minute is not that much volume. My 30 year old instant boiler that I use to heat this house will produce 7.4 gallons per minute of 190 degree water with 55 degree entering water temperature and the unit hangs on the wall so it is very small. Now at 3000 PSI you could run a higher temp and actually have steam at the nozzle tip depending upon the usage and setup of the equipment. Now they might have to heat the water after pressurization if they are going for higher temps or otherwise it will boil in the coil.
I understand you not being able to tell us exactly what it does due to proprietary information concerns.

One other factor on what is called an open system (constantly using fresh water makeup) is the lime factor. When you are constantly running cold water through a coil heating it up the minerals have a tendensy to lime up or collect other debris. Has your system had that problem or are they treating the incoming water to prevent it? A coating of lime or other debris will definitely cause a major temperature exchange problem between the burner and the water in the boiler itself. Just thinking out of the box as usual since I have no real idea of what this device is used for but cleaning or production is my best guess.

To address some of the issues
1. lining, all insulation replaced when new coil put in. ran both units with no exhaust but just exhausting into room, still probem with on but not other.

The "toilet" effect was my thought also, just can't figure why one is doing it so pronounced.

Thus is what I look at all day, but yes just really big pressure washers and boilers.

Hi chuck. I still feel its an insulation problem and or a residual problem of hot gass not moving around the chamber properly.

The control/variable is the second unit which has no problem.

I'm not sure how the settings are on the unit for any adjustments. I would see if you can check what the gas nozzle sizes are on that unit compared to the other unit. That could drastically change the temp start up etc. If these are custom built so to speak then maybe you have wrongs size nozzles on that unit that was put in from the factory which supposed to be on a different size unit that they build

Check to see if there is a control adjustment for air flow to the burner chamber. Usually on a gas fired boiler/heater there is no such animal .

The last ditch effort would try the premix/mixer valve as I suggested before of taking it off the domestic pressure side to pre heat the water going into the unit with the domestic hot water supply instead of getting into the unit and fighting the high pressure equation.

Since you the volume demand is not a lot there. ( 5 Gal per min) I would use two garden hoses from domestic supply not from one hose and cold from other. Put a cheap hose Y connection that has the ball shutoff valves on them and this would be a quick cheap mixer valve to experiment with.

If that works then it may be the way you have to go for the unit to work better. Then you could plum it up in permanent water line

Chuck. I'm with the rest of the guys here. I've never worked on one either.
However, since this is such a expensive unit and you've tested everything twice and found zip let's think outside the box. What's the best fix for toilet tank condensation outside of a fuzzy jacket? You temper that water going into the tank to eliminate the condensation.
How about installing a tankless water heater on the cold water feed to the unit? Each time the uniut makes a draw the heater tempers the water.
Think that might work? Just a stray thought. Tom