Raypak whistling help

[ajw22]

Couldn't that be too hot and cause damage?

It is setup to allow sufficient flow even when the UG is closed.

If things get too hot due to low water flow the 130F and 135F safeties in the manifold will shut down the heater.

So the UG handles cold water and the safety switches handle high water temperatures to keep the water in the heater within the desired temperature.

 

[PoolStored]

It works like a car radiator thermostat.

I get that! Replaced one on my mom's 1964 Nova II wagon. Lol.

It is setup to allow sufficient flow even when the UG is closed.

So this indicates that the UG is closed until the water is hot enough, then opens. If mine didn't open (I ran it up to 150 on the stove and it didn't), then how did it heat the pool. See this:

 

[JoyfulNoise]

I need to go to the raypak tech docs and read up on how this works.

Nah. We need to get a couple of TFPers to do a YouTube channel that has content like the “unboxing videos” where they take apart pool equipment and show how it’s all built and works. I vote for @JamesW to explain how to install an AGP using only a pocket knife and bottle of aspirin … like McGyver or the A-Team …

 

[JamesW]

The flow through the heat exchanger is never totally blocked.

You have a small hole and the UG was bypassing some water, which was causing the noise.

 

[JamesW]

You also have some dips on the sides that allow some water to pass.

 

[JamesW]

The UG was probably partially opening somewhere below 212 degrees or the heater would be banging as the water boiled.

Try hotter water to see where the UG begins to open and where it is fully open.

 

[PoolStored]

Try hotter water to see where the UG begins to open and where it is fully open.

Never opened up to 212. Giddyap has gone up and went.

 

[PoolStored]

You do not want to run the heater with water in the 60's or below wiothout the UG.

So if I always run the heater with water above 60, I can leave the UG out?

 

[JamesW]

So if I always run the heater with water above 60, I can leave the UG out?

The manufacturer says that the water needs to be >100 F to prevent condensation.

I would refer you to Raypak as far as operating without any standard parts.

 

[JamesW]

Complete combustion is the complete oxidation of fuel.

When methane (CH4) mixed with the proper amount of oxygen (O2) undergoes complete combustion, it produces carbon dioxide (CO2) and water (H2O) vapor.

If the exhaust cools down too much, the water will begin to condense out and cause problems.

 

[PoolStored]

Got it!

 

[PoolStored]

You know, funny. Didn't connect the dots until just now. When I was by the heater when I first started it up, I thought "This thing puts off a lot of heat, I don't remember it being this hot." Now it makes sense.

 

[JamesW]

When not firing, I would think that you would avoid condensation if the water temperature is above the Dew Point.

When firing, the water in the heat exchanger gets hotter, but you also have added water in the air due to the water produced during combustion.

You can figure out the minimum water temperature in the heat exchanger based on the flow rate and btu/hr transferred.

The air is very hot at combustion, but about 84% of the heat is transferred to the water and the air drops to about 300 F.

You can figure out the amount of water produced during combustion from the heater btu/hr rating and then add that to the amount of air that moves through the heater in 1 hour to figure out the humidity.

You can figure out the air flow rate based on the temperature rise and btu/hr of heat left in the air.

From there, you can figure out the Dew Point of the exhaust to see if the water in the heat exchanger is above the dew point.

 

[PoolStored]

I'll put the UG back in when it come tomorrow. I'm mathed out.

Oh, and it is now running much cooler.

 

[JamesW]

332,000 x 0.82 = 272,240 btu/hr. transferred to the water.

332,000 x 0.18 = 59,760 btu/hr. transferred to the air.

300 - 80 = 220 F = Air temperature rise.

1132 pounds of air per hour = 14,045 cubic feet per hour.

Burning 332 cubic feet of methane at STP produces approximately 33.34 pounds of water.

If I have 1132 pounds of air at 80 f and 60% Relative Humidity and I add 33.34 pounds of water to the air and heat the air to 300 F, what is the new relative humidity and dew point?

New Relative Humidity: Approximately 1.1%

New Dew Point: Approximately 141 °F

Digital – Raypak

Raypak Pool & Spa, Residential and Commercial Hydronic Products -

www.raypak.com

 

[PoolStored]

I'm not sure what this tells me...

 

[JamesW]

The temperature of the outside of the heat exchanger will be higher than the water temperature in the heat exchanger.

If we use 272,240 btu/hr. transferred to the water and 40 gpm, then the water will increase in temp from inlet to outlet by about 13.61 degrees F.

If half of the water goes through the heat exchanger, then the temp rise is 27 degrees.

I would say that the minimum water temperature going into the heater to avoid condensation is about 86 degrees F .

Heat exchanger on Raypak

Hi, I’m new to this forum and I’m trying to figure out why my heat exchanger on my Raypak for both pool and spa are going out or bad after a years use having condensation run down the stacks and into the unit!!???? The heat exchanger are not chemically damaging themselves from the inside out...

www.troublefreepool.com

 

[JamesW]

I'm not sure what this tells me...

Basically, we are trying to figure out when you could leave out the UG without getting condensation.

You have two different equations.

1) Not firing based on dew point and water temp.

2) Firing accounting for the water vapor added to the air, plus heat etc.

 

[PoolStored]

Got it. Pool water is 85 degrees, I'll leave heater on and install UG tomorrow. I'm just frustrated it failed. I know know more about my heater and failure modes and what to look for. I might pull the UG each spring and put it in some hot water to make sure it is working.

 

[JamesW]