System pressure problems

[overdriv]

In a older thread,here, I explained how I set the expansion tank pressure the same as the supply pressure in an effort to control system pressure. Now I wonder if that is the correct way to do it.

The problem is in my open system, the system pressure continues to creep up untill I drain off some water to lower it.

The supply pressure is 48 PSI. There is a check valve in the supply line just before it goes into the hot water line to the floor. See pictures in the other thread. I think the problem is when it doesn't run for a longer period of time, the water cools and volume shrinks and the supply adds water to maintain pressure. Then the floor calls for water and everything heats up expanding the volume of water which is larger than before so the pressure goes up. After this happens a few times, the pressure becomes higher than supply pressure by as much as 25PSI. The highest I've let it go is 72PSI.

Am I settin g the expan sion tank pressure correctly? Or is my expansion tank not large enough? Or is there another design flaw that I am missing?

 

[tdkkart]

Why do you need an active make-up line?? Shut off the supply line, problem solved.

 

[overdriv]

Why do you need an active make-up line?? Shut off the supply line, problem solved.

It is an open system. I am using hot water for a sink in the restroom, and a wash basin in the shop area.

 

[koditten]

I was wondering if we had all the issues solved when I wrote earlier in the other thread. I think as long as you are going to use this system as an open system you are going to have problems. Is there any way you can make this a closed system?

One of the things that makes it hard to diagnose this problem is that you can't run a floor system with the water temp fluctuating greatly. When you close the system you really only want 10 or so degrees difference for your in and out water. Running your open system and using the floor system water to give you hot water to the sink is going to make your system gain pressure. You are heating up that new, cold water and making it expand.

When I saw that you pressurized your bladder tank to the same pressure as your make up water I knew we went down the wrong path. I think if you look at the bladder tank there will be a decal that tells you the pressure of the bladder. IIRC it should be around 15 psi. When you pressured the tank up to 45 psi, you totally colapsed the bladder, meaning the bladder was no longer able to flex in and out. With this kind of pressure the bladder is not doing what it was designed for.

I guess what I am trying to say is you may be able to use your system to give you hot water, but you may have to regulate the incoming water to 15 psi or so. Of course you know that will also be the pressure of the hot water to the sink as well. Make sure you bleed off the pressure in the bladder tank too.

I hope I helped, I don't do these systems proffessionally, but I have trouble shot my own systems and have learned thru trial and error.

Kirk

This is about all I can tell you, my experience is with closed systems.

 

[overdriv]

I was wondering if we had all the issues solved when I wrote earlier in the other thread. I think as long as you are going to use this system as an open system you are going to have problems. Is there any way you can make this a closed system?

It has been running as a closed system since it was started. I don't have the sinks installed yet.

One of the things that makes it hard to diagnose this problem is that you can't run a floor system with the water temp fluctuating greatly. When you close the system you really only want 10 or so degrees difference for your in and out water. Running your open system and using the floor system water to give you hot water to the sink is going to make your system gain pressure. You are heating up that new, cold water and making it expand.

When I saw that you pressurized your bladder tank to the same pressure as your make up water I knew we went down the wrong path. I think if you look at the bladder tank there will be a decal that tells you the pressure of the bladder. IIRC it should be around 15 psi. When you pressured the tank up to 45 psi, you totally colapsed the bladder, meaning the bladder was no longer able to flex in and out. With this kind of pressure the bladder is not doing what it was designed for.

I have the same sized expansion tank installed in my house, City required it's installation and furnished them. I have no idea what it's precharge was. Again city water comes in at 52 PSI in the house. It shows 48 PSI in the garage, difference in gauges I suppose.

I guess what I am trying to say is you may be able to use your system to give you hot water, but you may have to regulate the incoming water to 15 psi or so. Of course you know that will also be the pressure of the hot water to the sink as well. Make sure you bleed off the pressure in the bladder tank too.

I hope I helped, I don't do these systems proffessionally, but I have trouble shot my own systems and have learned thru trial and error.

Kirk

This is about all I can tell you, my experience is with closed systems.

Thanks for the advice, but there has to be something I'm missing as there are people that use radiant heat as an open system and supply the whole house with domestic HW.

Maybe a bigger expansion tank??

 

[koditten]

As an experiment, can you remove the check valve temporarily? If this solves your pressurizing problem then we will know a bit more about your system. Better yet how about installing one of the back flow preventer kits. If the pressure builds up it will just dump off the pressure.

Other than that you may have to buy an actuall well water pressure tank to use as an expansion tank. The well water pressure tanks are designed to operate at the pressures you are running your system at.

 

[overdriv]

As an experiment, can you remove the check valve temporarily? If this solves your pressurizing problem then we will know a bit more about your system. Better yet how about installing one of the back flow preventer kits. If the pressure builds up it will just dump off the pressure.

Other than that you may have to buy an actuall well water pressure tank to use as an expansion tank. The well water pressure tanks are designed to operate at the pressures you are running your system at.

I can't easily remove the check valve as it's soldered in. My water supply comes from my house which has check valves to prevent back flow into the city system. It is required in a cross connected system. Yes, I have a sand-point system connected. So I don't see how removing the check would solve anything.

The back flow preventer, I suppose is my next option.

 

[koditten]

Overdriv:

Just so I'm clear what is going on, you have a well with a bladder tank incorperated with your well pump, you mention sand pont,yes? You also have a bladder tank that the city requires you to have on your house domestic system, yes? This is odd to me. You mention that the bladder tank on the house system is the same unit you have on your garage floor system, yes? I don't remember in previous post, but I want to make sure I know for sure which house system you are referring to. Is your house heated with hot water or is it a forced air system?

Can I ask why the city requires you to have a bladder tank on the house system? I just want to make sure you in fact have your own water supply, not city water.

Forgive me for being nosy, I just love a good puzzle.

Kirk

 

[stingry]

I can't easily remove the check valve as it's soldered in. My water supply comes from my house which has check valves to prevent back flow into the city system. It is required in a cross connected system. Yes, I have a sand-point system connected. So I don't see how removing the check would solve anything.
The back flow preventer, I suppose is my next option.

IMHO removing the check valve should solve the pressure flucuating problem due to the fact that the floor heat system would always be at whatever pressure your house system is.

 

[stingry]

Overdriv:

Just so I'm clear what is going on, you have a well with a bladder tank incorperated with your well pump, you mention sand pont,yes? You also have a bladder tank that the city requires you to have on your house domestic system, yes? This is odd to me. You mention that the bladder tank on the house system is the same unit you have on your garage floor system, yes? I don't remember in previous post, but I want to make sure I know for sure which house system you are referring to. Is your house heated with hot water or is it a forced air system?

Can I ask why the city requires you to have a bladder tank on the house system? I just want to make sure you in fact have your own water supply, not city water.

Forgive me for being nosy, I just love a good puzzle.

Kirk

ME TOO!!! The plot thickens! OVERDRIV, I have been watching your posts closely since I am planning on using an "open" system in my shop also, so thanks for sharing.


Cheers
Steve

 

[overdriv]

Overdriv:

Just so I'm clear what is going on, you have a well with a bladder tank incorperated with your well pump, you mention sand pont,yes? You also have a bladder tank that the city requires you to have on your house domestic system, yes? This is odd to me. You mention that the bladder tank on the house system is the same unit you have on your garage floor system, yes? I don't remember in previous post, but I want to make sure I know for sure which house system you are referring to. Is your house heated with hot water or is it a forced air system?

Can I ask why the city requires you to have a bladder tank on the house system? I just want to make sure you in fact have your own water supply, not city water.

Forgive me for being nosy, I just love a good puzzle.

Kirk

I have city water and a sandpoint/pump/bladder tank cross-connected in my house. Both systems must be separated by check valves or other means. I have check valves on each system.

I also have had to install a small expansion tank in the water supply to my house domestic water heater.

House has baseboard electric heat.

From my common supply in the house I tapped off a line to the detached garage. I have floor heating in the garage. I also put a check valve in the garage system supply.

See Pictures of system in this thread.

The city requires these expansion tanks because the new meters they installed have a check valve in them. Also because I have a cross-connected system that back flow is protected by check valves, it protects against over pressure from water heater expansion.

 

[tdkkart]

I have city water and a sandpoint/pump/bladder tank cross-connected in my house. Both systems must be separated by check valves or other means. I have check valves on each system.

I also have had to install a small expansion tank in the water supply to my house domestic water heater.

House has baseboard electric heat.

From my common supply in the house I tapped off a line to the detached garage. I have floor heating in the garage. I also put a check valve in the garage system supply.

See Pictures of system in this thread.

The city requires these expansion tanks because the new meters they installed have a check valve in them. Also because I have a cross-connected system that back flow is protected by check valves, it protects against over pressure from water heater expansion.

Wow, I'm amazed that any city would allow ANY kind of physical connection to an "unregulated" private water supply. Check valves and one-way valves are not absolutes and should not be trusted to absolutely prevent cross-contamination between systems. I cannot believe any municipality would allow this.

 

[overdriv]

Wow, I'm amazed that any city would allow ANY kind of physical connection to an "unregulated" private water supply. Check valves and one-way valves are not absolutes and should not be trusted to absolutely prevent cross-contamination between systems. I cannot believe any municipality would allow this.

I live in a small town in forgottonia. The city just started to install meters 2 years ago.

The check valves have always satified them in the past. But I will be doing away with my sandpoint this year as it's about plugged, hardly able to supply water for a car wash.

 

[koditten]

I got to be honest, I never knew any thing like this existed. There are too many variable for me to be any help. I guess, when you get rid of that well system and rely strictly on the city water I might be able to help. Right now I know I am in over my head for useful help.

It has been fun learning about these hybrid domestic water systems tho.

 

[overdriv]

I got to be honest, I never knew any thing like this existed. There are too many variable for me to be any help. I guess, when you get rid of that well system and rely strictly on the city water I might be able to help. Right now I know I am in over my head for useful help.

It has been fun learning about these hybrid domestic water systems tho.

Well, basically the garage is a totally separate system from the house. The sandpoint system is isolated, by valves when not needed. The city and the sandpoint are never valved in at the same time.

I don't see that having any relationship to my garage system. I'm sorry if I haven't explained it well.

 

[stingry]

Well, basically the garage is a totally separate system from the house. The sandpoint system is isolated, by valves when not needed. The city and the sandpoint are never valved in at the same time.

I don't see that having any relationship to my garage system. I'm sorry if I haven't explained it well.

I tend to agree. As I understand, your floor heat system basically begins at the check valve which sees approx. 50 psi pressure upstream, no mater the source but most likely city water. Is this correct?

Personally I think your problem lies with the check valve and either an undersized or not correctly pressurized expansion tank. Is your check valve externally serviceable? In other words, can you remove the check ball or flapper without unsoldering it from the line. If it is, I would remove the internals and see if that helps the problem. I can understand the logic of having the check valve to isolate the floor heat system from your domestic water but I believe this is trapping the increasing pressure rise and not allowing it to dissapate into the water system. Just a thought

Steve

 

[overdriv]

I tend to agree. As I understand, your floor heat system basically begins at the check valve which sees approx. 50 psi pressure upstream, no mater the source but most likely city water. Is this correct?

Yes, that is correct.

Personally I think your problem lies with the check valve and either an undersized or not correctly pressurized expansion tank. Is your check valve externally serviceable? In other words, can you remove the check ball or flapper without unsoldering it from the line. If it is, I would remove the internals and see if that helps the problem. I can understand the logic of having the check valve to isolate the floor heat system from your domestic water but I believe this is trapping the increasing pressure rise and not allowing it to dissapate into the water system. Just a thought

Steve

The check is not serviceable that I know of. I think you are correct in thinking the check prevents the system from absorbing the pressure increase. But that, I thought, is the job of the expansion tank. I guess I don't have a large enough expansion tank, maybe.

I have watched the system and see that when the pump is not running, thermostat not calling for heat, the pressure slowly decreases with the temperature and when it gets below the supply pressure, the check opens and adds water, holding it to system supply pressure. Then when the pump starts, thermostat calling for heat, the water in the system warms up and pressure increases. After about three cycles, the pressure is up to 70+ PSI.

I don't think that is a dangerously high pressure, but I think I need to control it better, and that is the gist of this discussion.

BTW, I have been reading on a couple of other web sites and the meer mention of an open system brings rath and pestulence upon the postee. So I'm sure a lot of people will not even consider participating in a discussion like this.

I certainly don't want anyone getting sick from my open system, but sure seems a waste to not be able to tap that hot water source just to wash ones hands.

I'm beginning to think I ought to just go to a closed system and put another water heater in for the two sinks. A 110V point of use tankless water heater isn't looking to bad at this point.

 

[sneezer41]

Sounds like your pressure tank is full of water instead of air, or has a hole in its bladder

when system is not hot, tank should be mostly air

 

[overdriv]

Sounds like your pressure tank is full of water instead of air, or has a hole in its bladder

when system is not hot, tank should be mostly air

Yes, I agree. Is there a certain way to set up a charge in the tank?

I took the system to zero pressure and put 48PSI into the tank as a pre-charge. Is this not right? I wonder if I don't have enough pre-charge??

 

[koditten]

Just to be clear, are you using compressed air to charge the bladder tank? On the bottom of the bladder tank there is a black cap that unscrews, under that is your normal tire valve stem type filler (schrader valve). I just wanted to make sure you are charging the correct side of the bladder in the bladder tank.

I am almost sure that the bladder tank that you show in your pics is not designed to run at 50 psi long term. I don't see why you couldn't try and pressure it up to 45-50 psi and see if it works for a while. The main problem we are running into is that we can't keep the system pressure above the inlet pressure. If we can keep the system pressure above the regulator setting of 45 psi, the system won't call for make up water until you use some water for the lavatory sink.

By the way I like how you are thinking about going to a closed system. Of course we won't have a puzzle to try and solve

 

[stingry]

The check is not serviceable that I know of. I think you are correct in thinking the check prevents the system from absorbing the pressure increase. But that, I thought, is the job of the expansion tank. I guess I don't have a large enough expansion tank, maybe.

I have watched the system and see that when the pump is not running, thermostat not calling for heat, the pressure slowly decreases with the temperature and when it gets below the supply pressure, the check opens and adds water, holding it to system supply pressure. Then when the pump starts, thermostat calling for heat, the water in the system warms up and pressure increases. After about three cycles, the pressure is up to 70+ PSI.

Here's what I see happening: When the pressure increases to a certain point, you manually relieve the pressure by draining off some heated water. Then, when the system cools down, the system pressure drops below system pressure and the check valve allows makeup water to enter the system as you describe and then the cycle starts all over again. Why not let it stabilize, possibly it needs to go to 70-80 psi in order to work. These certainly are not pressure levels to be concerned about.

I don't think that is a dangerously high pressure, but I think I need to control it better, and that is the gist of this discussion.

BTW, I have been reading on a couple of other web sites and the meer mention of an open system brings rath and pestulence upon the postee. So I'm sure a lot of people will not even consider participating in a discussion like this.

I've gotten this feeling myself whenever I mention that I am considering an "open" system

I certainly don't want anyone getting sick from my open system, but sure seems a waste to not be able to tap that hot water source just to wash ones hands.

My feelings exactly!! I see no need for antifreeze in my system so I see no reason why an "open" system won't work.

I'm beginning to think I ought to just go to a closed system and put another water heater in for the two sinks. A 110V point of use tankless water heater isn't looking to bad at this point.

C'mon man, don't bail on me now!!!

Cheers
Steve

 

[koditten]

I got to thinking about this some more. What is the pressure relief on the water heater set at? You could change out the pressure relief to a lower pressure valve. These valves are not designed for constant cycling, but if you wanted to put up with tank "burping" once or twice a day, this would keep the system from over pressurizing. It is suprising how little water will get relieved from the system. You could just put a 5 gallon bucket under the relie valve discharge valve.

 

[overdriv]

Don't worry, I haven't given up yet.


The T&P relief valve on the water heater is set to 150PSI as far as I know. I think I'd rather come to a different solution than changing it out, although that may be a workable solutionin the end.

BTW, thanks for all the discussion guys. I'm as new to this as it gets and the system is new so bound to be some bugs.

Man, so far I'm loving the floor heat. With room air temps in the low 60s, it is a bit warm if you are working steadily. I'm thinking 58 might be about right.

Still trying to understand the relationship between the slab sensor and the room air sensor. I'm thinking an outside sensor would help the system better anticipate needs.