Radiant floor heat - water heater discharging

[Toddjb]

All, I just installed the radiant system in my shop.

All is working as intended, except when the system cycles off a cup or so worth water comes out the water heater discharge pipe.

Any ideas why this is happening? And how to fix it?

This is a completely closed loop system. I have the water heater set to 120 degrees.

 

[Plumber69]

All, I just installed the radiant system in my shop.

View attachment 77478

All is working as intended, except when the system cycles off a cup or so worth water comes out the water heater discharge pipe.

Any ideas why this is happening? And how to fix it?

This is a completely closed loop system. I have the water heater set to 120 degrees.

First you need an expansion tank. What pressure are you running it? What's the relief valve in hot water tank set for (psi)

 

[Sponsor]

 

[Toddjb]

First you need an expansion tank. What pressure are you running it? What's the relief valve in hot water tank set for (psi)

I was under the impression expansion tanks were not need for closed systems because you were not introducing cold water. If that is not the case, where in this system should it be, or does it matter?

No additional pressure has been added. I flushed the system, then refilled and the system and then tested it.

Pressure relief is 150psi/210 degrees

 

[John Gayewski]

The only time you need an expansion tank is in a closed system. Anything that gets hot expands. Where will it go? Your system pressure is getting over 150 psi because there is no where for the water to expand.

 

[John Gayewski]

Your system is not set up correctly. The pump needs to pump away from the heat source. That water heater will be toast in less than 5 years.

 

[Toddjb]

Your system is not set up correctly. The pump needs to pump away from the heat source. That water heater will be toast in less than 5 years.

John, that's good info, I've never heard that before. I was instructed to put the pump pushing the "cold" water into the water heater, because having the pump pull the water out of the tank would ruin the pump faster due to the extra heat of the out going water. And forgive my misunderstanding, but how is the pump pushing water into the water heater different than a water main pushing water into a water heater?

How would you propose it be set up (placement of the pump and the expansion tank)?

 

[Toddjb]

https://diy.stackexchange.com/quest...ed-on-the-supply-or-return-of-a-forced-hot-wa

https://inspectapedia.com/heat/Circulator_Pump_Installation.php

These are links that directed me to put it on the return side - for reference. But they both indicate a "boiler" and not specifically a water heater.

 

[Sylvan]

I like placing the circulator on the return line

1- The water is slightly cooler

2 Colder water is more dense so it helps in natural circulation

On a boiler Dan wrote articles " pumping away" but for over 5 decades I installed circulators on the return and never had a problem

Also when I used a water heater for heating I installed a 30 PSI relief valve with an expansion tank

There is no reason to have such high pressure in a closed heating system and check the temperature as it maybe the cause of seeping prior to fully discharging

 

[Plumber69]

You want the pump pulling away from the expansion tank. But what is the pressure in your system? You only need 12 psi. I don't know if you can run heating at 50-70 psi. That's going determine what expansion tank you need cause your system pressure should match expansion tank pressure. You have no gauge to monitor your pressure

 

[John Gayewski]

I like placing the circulator on the return line

1- The water is slightly cooler

2 Colder water is more dense so it helps in natural circulation

On a boiler Dan wrote articles " pumping away" but for over 5 decades I installed circulators on the return and never had a problem

Also when I used a water heater for heating I installed a 30 PSI relief valve with an expansion tank

There is no reason to have such high pressure in a closed heating system and check the temperature as it maybe the cause of seeping prior to fully discharging

The problems occur when you don't pump away mainly in a larger building. If you read the book it's explained very well and in great detail with science. But there are more reasons other than cavitation on a large building. You want to catch the air at the expansion tank becuse that's where the water is hottest and you pump away from the expansion tank. If you've ever put hot water into a clear jug it looks cloudy. That's the air coming out of solution and turning back into air.

 

[John Gayewski]

John, that's good info, I've never heard that before. I was instructed to put the pump pushing the "cold" water into the water heater, because having the pump pull the water out of the tank would ruin the pump faster due to the extra heat of the out going water. And forgive my misunderstanding, but how is the pump pushing water into the water heater different than a water main pushing water into a water heater?

How would you propose it be set up (placement of the pump and the expansion tank)?

We push cold water into a water heater in a recirculation system for domestic hot water. Space heating is a closed system and the pump uses differential pressure at low static pressure. Different than domestic.

 

[John Gayewski]

 

[Jadnashua]

The water will be constantly getting warmer and cooler as it is pumped around, and as the WH heat source is cycling on/off...this will cause the volume of water in your system to be constantly changing. You absolutely need an expansion tank to take some of that pressure cycling off of the system...water does not compress, so heating it, while expanded, immediately causes the pressure to spike...the less air in the system, the more immediate that pressure spike is.

Ideally, the ET would be installed on the inlet of the pump, so when the pump turns on, it can add any volume back to help prevent cavitation.

As noted, the pressure only needs to be high enough to prevent boiling and to overcome any issues with elevation changes that could cause a vacuum to be generated...12-psi is a common one used with boilers, and is more than enough on a single story heating system plus, 30-psi T&P valves are readily available.

The higher pressure will tend to weaken the tank faster, leading to earlier failure, especially if you don't add an ET!

A T&P or even a pressure relief valve generally should be replaced if it has regularly been exercised...generally, they're designed as an emergency device, and not to be regularly operated.

 

[Sylvan]

The problems occur when you don't pump away mainly in a larger building. If you read the book it's explained very well and in great detail with science. But there are more reasons other than cavitation on a large building. You want to catch the air at the expansion tank becuse that's where the water is hottest and you pump away from the expansion tank. If you've ever put hot water into a clear jug it looks cloudy. That's the air coming out of solution and turning back into air.

WOW

Thank you.

I guess I need to go back to 600 third ave and reinstall the circulators I installed in 1970 and do what you and Dan suggested.

Thankfully the warrantee is expired so I am off the hook and I cannot imagine how the circulators managed to work and was never on the check list

https://42floors.com/us/ny/new-york/600-3rd-ave

 

[John Gayewski]

WOW

Thank you.

I guess I need to go back to 600 third ave and reinstall the circulators I installed in 1970 and do what you and Dan suggested.

Thankfully the warrantee is expired so I am off the hook and I cannot imagine how the circulators managed to work and was never on the check list

https://42floors.com/us/ny/new-york/600-3rd-ave

Explain your stance. How does the water being cooler do anything? Why do you think the full pressure of the circulator shouldn't be on the system piping but shot into the boiler and lost to the expansion tank? How does this help natural circulation (which isn't a factor in a forced system)? The pump being on the return just makes air difficult to bleed and wastes the opportunity to efficiently start a system.

 

[Sylvan]

Explain your stance. How does the water being cooler do anything?.

Ok class is in secession

There is a new phenomena recently discovered called " heat rises" and cold water is heavier (denser) then hot water.

Because of this recent discovery old heating systems that relied on this principle, the heating lines were over sized before circulators came into play and it took lots of energy (coal ,wood) to heat the water required for the old cast Iron radiators.

This was a waste of fuel and it took lots of time for the heated water to rise and then cool off and start to circulate naturally and once this newly discovered heating was in place there was no way to stop the natural flow as long as fuel was being used to heat the water.

Also in the attic or highest point there was an open tank that prevented over pressure and guaranteed the system was always full of water

As an added benefit it was also discovered "Bubbles" in water rise to the highest point so being air bound was rare and each radiator did have a bleeder valve installed at the highest point .

To control the return water and balance out the system valves was installed on the RETURN with a thermometer placed just above the balancing valve that resembled a gas cock.

As the return cooler water was recorded the dead men at that time adjusted the flow by decreasing the return and by looking at the temperature the system was now set.

As circulators came into play that assisted circulation the systems became extremely hot and there was a need to prevent unwanted "stratification" of the hot water molecules rising so a device was needed called a "FLOW CONTROL" which added enough resistance to stop the natural "heat rises problem" until the thermostat called for heat, circulator came on and had just enough force to over come the weight inside the flow control valve.

Many unknowing people stated getting into heating and undersized the boilers and decided to just make the water hotter as some systems went above 220 DEG F which was still considered low pressure / low temperature boilers according to the NBBI and ASME (160 PSI 250 DEG F)

Those who took Dan's book as gospel (such as steam without tears) did not think that the circulator on the supply side was in direct contact with the hottest water and placed undo stress on the seals, gaskets etc.

 

[John Gayewski]

Ok class is in secession

There is a new phenomena recently discovered called " heat rises" and cold water is heavier (denser) then hot water.

Because of this recent discovery old heating systems that relied on this principle, the heating lines were over sized before circulators came into play and it took lots of energy (coal ,wood) to heat the water required for the old cast Iron radiators.

This was a waste of fuel and it took lots of time for the heated water to rise and then cool off and start to circulate naturally and once this newly discovered heating was in place there was no way to stop the natural flow as long as fuel was being used to heat the water.

Also in the attic or highest point there was an open tank that prevented over pressure and guaranteed the system was always full of water

As an added benefit it was also discovered "Bubbles" in water rise to the highest point so being air bound was rare and each radiator did have a bleeder valve installed at the highest point .

To control the return water and balance out the system valves was installed on the RETURN with a thermometer placed just above the balancing valve that resembled a gas cock.

As the return cooler water was recorded the dead men at that time adjusted the flow by decreasing the return and by looking at the temperature the system was now set.

As circulators came into play that assisted circulation the systems became extremely hot and there was a need to prevent unwanted "stratification" of the hot water molecules rising so a device was needed called a "FLOW CONTROL" which added enough resistance to stop the natural "heat rises problem" until the thermostat called for heat, circulator came on and had just enough force to over come the weight inside the flow control valve.

Many unknowing people stated getting into heating and undersized the boilers and decided to just make the water hotter as some systems went above 220 DEG F which was still considered low pressure / low temperature boilers according to the NBBI and ASME (160 PSI 250 DEG F)

Those who took Dan's book as gospel (such as steam without tears) did not think that the circulator on the supply side was in direct contact with the hottest water and placed undo stress on the seals, gaskets etc.

I don't find this to be a coherent explanation for your theory. Natural gravity or thermosyphon systems don't have anything to do with circulator placement. The reason circulators were placed on the return lines when hot water came into fashion (vs steam) was due to gland packing inside of the circulator and packaged boilers having the circulator already placed there. Which isn't a good reason to pump toward a boiler once ceramics came into use.

The reason boilers got so hot wasn't becuse people undersized them. It was because early hot water systems were trying to compete with steam. Steam requires less pipe and made hotter temperatures which reacted faster, to make water that hot and keep them open to atmosphere Honeywell (Mr. Honeywell himself) invented a heat generator. Which was a pot of mercury. This acted as the first "circulator" it was teed off of the return and made the system run faster.

Old circulators leaked on purpose and had to be installed near a drain. You adjusted the packing to drip so many drips per minute and it was better for them to receive cooler water. Then came mechanical seals that contained remite. That also liked cooler water. This doesn't make it better for the system. Since the early sixties there has been no reason to place the circulator on the return side. Other than habit. Since ceramics made their way into the circulator it has been better to put the circulator on the supply pumping away from the boiler and keeping the air in check.

 

[Sylvan]

I don't find this to be a coherent explanation for your theory. Natural gravity or thermosyphon systems don't have anything to do with circulator placement. The reason circulators were placed on the return lines when hot water came into fashion (vs steam) was due to gland packing inside of the circulator and packaged boilers having the circulator already placed there. Which isn't a good reason to pump toward a boiler once ceramics came into use.

The reason boilers got so hot wasn't becuse people undersized them. It was because early hot water systems were trying to compete with steam. Steam requires less pipe and made hotter temperatures which reacted faster, .

1- It takes more fuel to produce steam and maintain it

2- I know this may should strange to you but hot water in a system holds the heat longer and the temperatures remain constant

If your in doubt it place a pot of water on a flame wait until the steam stops go back in 10 minutes and place your finger in the water


3- "Steam requires less pipe" I never knew a TWO pipe steam requires more piping then a two pipe steam system

4- A Closed water system can have the water temperature above 250 DEG F steam @ 5 PSI is around 227 DEG and most apartment buildings require around 3 PSI or less so some thing called "pressure temperature relationship comes into play"

5- Before I was master plumber I was a stationary engineer working on high pressure steam systems 125# and in the Navy as a teenager I was a boiler tender 1,500 PSI super heated steam and we had steam traps, vacuum pumps to pull the condensate back to the boiler or a place of disposal and your thoughts of "Steam requires less pipe" is neglecting how steam systems rely on fresh water which ( in case you did not know) contains oxygen which is the cause of steam piping and equipment to fail much faster then a closed water system.

Steam systems require a lot more man hours to be properly maintained

Steam stations for example which I serviced and installed and maintained used Leslie Steam Pressure Reducing Valves and the "LESS PIPING" required all piping before the valves to be welded which placed more costs on the installations costs.

If you feel PUSHING water up a pipe is easier and more efficient then pulling water that is already returning flow more efficient then more power to you

Steam piping is normally larger so even f it did require "less piping" the cost of the installation is much more

By the way I installed over 100 steam boilers over the past 50 years and for a cost effective system hydronics is more cost effective in most cases.

The ONE PIPE systems I did install were for city housing as they wanted CHEAP systems which proved to be much more dangerous then a two pipe system

 

[Sylvan]

Old circulators leaked on purpose and had to be installed near a drain. You adjusted the packing to drip so many drips per minute and it was better for them to receive cooler water".



Actually it was normally set for 8 drops or less per minute as too many drops would score the metal

Even on fire pumps we set the DPM to keep the seals cool as the drips are only used when the pumps are working

 

[John Gayewski]

1- It takes more fuel to produce steam and maintain it

2- I know this may should strange to you but hot water in a system holds the heat longer and the temperatures remain constant

If your in doubt it place a pot of water on a flame wait until the steam stops go back in 10 minutes and place your finger in the water


3- "Steam requires less pipe" I never knew a TWO pipe steam requires more piping then a two pipe steam system

4- A Closed water system can have the water temperature above 250 DEG F steam @ 5 PSI is around 227 DEG and most apartment buildings require around 3 PSI or less so some thing called "pressure temperature relationship comes into play"

5- Before I was master plumber I was a stationary engineer working on high pressure steam systems 125# and in the Navy as a teenager I was a boiler tender 1,500 PSI super heated steam and we had steam traps, vacuum pumps to pull the condensate back to the boiler or a place of disposal and your thoughts of "Steam requires less pipe" is neglecting how steam systems rely on fresh water which ( in case you did not know) contains oxygen which is the cause of steam piping and equipment to fail much faster then a closed water system.

Steam systems require a lot more man hours to be properly maintained

Steam stations for example which I serviced and installed and maintained used Leslie Steam Pressure Reducing Valves and the "LESS PIPING" required all piping before the valves to be welded which placed more costs on the installations costs.

If you feel PUSHING water up a pipe is easier and more efficient then pulling water that is already returning flow more efficient then more power to you

Steam piping is normally larger so even f it did require "less piping" the cost of the installation is much more

By the way I installed over 100 steam boilers over the past 50 years and for a cost effective system hydronics is more cost effective in most cases.

The ONE PIPE systems I did install were for city housing as they wanted CHEAP systems which proved to be much more dangerous then a two pipe system

You can trust me when I say I don't need a steam lesson. I'm telling you what happened in the past. Yes one pipe steam was the most common way to heat buildings. Yes that does require less pipe. Two pipe steam came later. Steam is very simple and has almost no moving parts. I don't really know what any of this has to do with the circulator.

You still haven't really given a reason other than habit to put it on the return. A circulator doesn't lift. There's just as much water coming down as there is going up. This being true the only other factor would be air. If you try to drag an air bubble you'll make it bigger. If you push it from behind you'll move it. It'll push itself into smaller bubbles and be encouraged to move. By putting the circulator on the return your lowering the differential pressure the circulator creates across the system. Thus creating issues you wouldn't have otherwise.