Looking for a valve

rt_2

I just started having an issue with my evactube system. I'm getting thermal siphoning at night. I installled a flow control valve (check valve wiih manual overide) by B & G #107035 about three years ago to stop this and it's been working great until now. I don't know if the spring inside has broken or if the seat is bad without taking it apart. I checked with the local plumbing supply house where I purchased the valve and they said B & G does not make a rebuild kit. Instead of replacing it with the same valve, I'm thinking about installing a 2 way selonoid valve. I would hook it up to my circulator and when the controller signalled it to start, the valve would open at the same time and then it would shut when the circulator stopped.

I need a 2 way valve normally shut, with 3/4" NPTF, 110 volts AC, working pressure is about 25 PSI, temperatures reaches 175 degrees and compatible with glycol. I would also like to find one with a built in manual override so that during summer months I can manually open the valve to create thermal siphoning to dump some of the stored heat at night. If they don't make them with a overide, I'll just install a bypass. Anyone have any ideas on a manufacturer for both styles of valves? Thanks. 

RT

 

icesailor

Valve:

What's the difference between what you are looking for and a common, run of the mill Zone Valve? Like a 24 volt Taco 1 1/4 zone valve. It has everything you want. You just need to wire it to do what you want? A zone valve is just a moterized flow check in my opinion.

SWEI

working temp

B&G rates the HydroTrol at 150F. The SA/SB series are rated to 250F.



If you do go the zone valve route, wire your pump in series with the end switch.

rt_2

Need a valve

I have a spec sheet in front of me right and it says that the model flow control valve I have is rated for temperatures up to 250 degrees.

As far as whether a zone vale would work, I have no idea. I was looking for something which would run off 110 volts. I'm just a every day limited handyman. I would have no idea how to wire up  a 24 volt DC valve like it was said. That's all greek to me

RT.

SWEI

temps

I must have gotten something wrong about your valve.  I was looking at these:

http://documentlibrary.xylemappliedwater.com/wp-content/blogs.dir/22/files/2012/07/A-411A.pdf

http://documentlibrary.xylemappliedwater.com/wp-content/blogs.dir/22/files/2012/07/A-422F.pdf



You can get 120V zone valves, but they are not common.  Most run on 24V AC, which will require a transformer, but eliminates some conduit and boxes.  The end switch closes once the valve has opened all the way, so you can start the pump without deadheading it.

rt_2

temps

Thanks SWEI,

The first link you sent me is the valve I am currently using and which is allowing thermal siphoning to take place. You lost me when you started talking about a end switch and deheading. I believe deheading means dropping the pressure down so the pump/circulator doen't have to overcome the pressure for starting. My system runs at about 25 PSI and when it's off, it maintains about 15 PSI.

RT

rt_2

temps

Thanks SWEI,

The first link you sent me is the valve I am currently using and which is allowing thermal siphoning to take place. You lost me when you started talking about a end switch and deheading. I believe deheading means dropping the pressure down so the pump/circulator doen't have to overcome the pressure for starting. My system runs at about 25 PSI and when it's off, it maintains about 15 PSI.

RT

SWEI

deadheading

Is pumping into a closed circuit -- a cap on the pipe or a closed valve which prevents any flow from occurring.  An end switch is a microswitch which closes at the end of a valve's travel.  Using that switch to control the zone pump will prevent deadheading the pump.

rt_2

Valve

Thanks for all your help. I think for now, I'm just going to order a replacement flow control valve. Once I get to remove the defective valve, I may find that it may only be gummed up. If that's the case, I'll  just clean up the old valve and keep it fo a spare. If I find a defective part, it may be a freak thing that it broke and maybe the new valve I install, will last forever.  Does anyone know if glycol after 4 years have the tendacy to break down?  Is there a rule of thumb as to whether you need to change out the glycol if ever?

RT

SWEI

glycol breaks down

over time.  Heat accelerates the process.  Extreme heat can fry the glycol in minutes.



Glycol should be tested annually, and after any stagnation event.

Kevin_in_Denver_2

ECV - Electronic Check Valve

ECV is kind of a dumb name for using a two way zone valve in a collector loop. But it seems to be catching on.



I have some observations and opinions about this problem, since I've been studying the problem hard for two years, and doing some tests. I've been a part time solar engineer since 1979.



In no particular order:



1. I'm very surprised by the high failure rate of spring check and swing check valves.



2. Solar systems must save energy, so we can't use an ECV that consumes a lot of electrical power.



3. Conventional Honeywell/Erie type zone valves have three strikes against them:

a. They use too much power

b. They have a rubber seat which will stick closed all too often.

c. They have a motor and return spring which fail all too often.

(I've replaced hundreds of them, and full-time boiler techs replace thousands.)



4. I like the Taco Zone Sentry. Although they are expensive, they are a motorized teflon ball valve that should have no trouble with the high temperatures, and aren't prone to sticking. http://www.pexsupply.com/Taco-Z075C2-1-3-4-Zone-Sentry-Zone-Valve-Sweat



5. The Taco Zone Sentry uses a reasonable amount of energy: less than $1.00 per year in most areas. They are 24v but you can install a $10 transformer for it. It also has a manual override.



6. I don't have much information on the long-term reliability of the motor used in the Zone Sentry -- Does anyone here have some experience?

Kevin_in_Denver_2

Forward Thermosyphoning is a possibility

Before you start the work, verify that the thermosiphon flow is in the forward direction.



I'm betting that your collector loop nighttime flow is in the same direction as the arrow on the Hydrotrol. (With ET collectors, forward thermosyphoning is just as likely as reverse thermosyphoning) The reason you just started seeing nighttime flow is because the recent colder temperatures provide just enough extra force to crack open the valve. Essentially, it's a misapplication of the Hydrotrol valve. Conventional check valves (like a Hydrotrol) usually work with flat plate collectors because flat plates tend to only thermosyphon in reverse. (Because there is more cold fluid on the supply side of the collector loop)



So a new Hydrotrol may not fix the problem, but a stronger spring inside the valve could do the trick. You should be able to measure the existing spring and order a stronger one online. (preferably stainless steel)



Mark Eatherton discusses the same problem in this thread:

http://www.heatinghelp.com/forum-thread/141895/Uninsulated-pipe

rt_2

Thermal siphoning

Kevin,

You're right. The water is flowing in the same direction as the arrow on the flow control valve. I found that out the other night, I went down to check out the temperatures in my storage tank and I found that it was quite low. I touched the pipe going back to the collector and it was warm and the pipe coming from the collector was cold telling me that thermal siphoning was taking place just like it did 4 years ago when I first developed the problem. At that time I was only using the check valve which came with the Grunfo circulator. Apparently the spring was not strong enouch to keep it closed during shutdown. I removed it and installed this flow control valve in line which has worked just fine for the last 4 years. What I liked about this valve is that it has the manual overide which I used in the summer when the temperatures in my storage tank got real high and I wanted the system to thermal siphon just to get rid of some of the heat at night. Nothing has changed in the last 4 years. I believe it was just as cold the last 4 years as it has been recently. I'll know more this weekend when I remove the valve and inspect it.

RT 

rt_2

Taco Valve

Kevin,

See my reply to your previous post.

 

I like the idea of installing this zone valve you talk about. I'm new at this so bare with me. The way I see it, if I use this valve, I'll need to purchase a transformer which will step down the power from 110 volts AC to 24 volts AC. It looks like there are 4 connectors on the back of the valve. Two of them are labeled W/Y & C. I believe these are for the 2 wires coming from the transformer. Is that right? I still want to hook up the transformer to my circulator so that when the controller sends power to the circulator to start, I want the zone valve to open at the same time. Does that sound right?

I also like the idea of the manual overide. I just wish there was a way that I could manually overide the valve and have it stay open let's say for a few days. I believe it will return to normal operation (normally Closed) the next time the system goes thru a cycle. Is that right?

I was just thinking. Now we're in trouble!!! If the valve does return to normal operation on the next cycle, all I would need to do I believe after I manually open the valve, I could install a electrical switch on one of the leads coming from the transformer which would allow me to  turn off the power going to the valve until I was ready to go back to normal operation then turn the switch back on. How does that sound?

RT

Kevin_in_Denver_2

Valve wiring

rt,



It sounds like you've got it figured out pretty well. If it were me, however, I'd go for the stronger spring solution. B&G engineers may even have a spring recommendation.



Most solar controls have a vacation mode, which would be a little simpler than setting up the Taco zone sentry for thermosiphoning.

rt_2

B & G

Thanks Kevin,

I just sent an E-Mail to B & G hoping they can help. I'll let you know what comes out of it.

I don't know what you mean by my controller would have a vacation mode. What would it do? Would I still need to install a zone valve?

Rene

rt_2

Found the problem

I removed the flow control valve and tried blowing air throught the checked side. Air went through it like like there wasn't any check valve at all. I found a little bit of rust sediment inside the valve. Without taking it apart, I was able to just flush hot fresh water and got it to hold pressure. I'm still going to try and take it fully apart and do a 100 percent cleaning inside. I installed the new valve and all systems are go now. Anyone know of a good recipee that I could soak the valve in to remove all the yukkee stuff without taking it apart? Thanks.

RT 

rt_2

Thermal Siphoning

Kevin,

I understand your theory about thermal siphoning when it get's real cold with evac tubes but that's not my case. I did change out the flow control valve and the system is working great right now. (Knock on wood!!!!!), I went into the basement this morning to check it out. My collector was reading 1 below 0 degrees F (Very cold this morning in New Hampshire) and the hot water in my storage tank  was 118 degrees F and it was not thermal siphoning.  I'm going to keep a close eye on it from now on. This summer, I may just change out the flow control valve with a Taco zone valve. That will be a much better positive shut-off. Thanks for your advice. 

RT 

Kevin_in_Denver_2

vacation mode

"Vacation Mode" is a standard option on most solar controllers. You can pick a maximum preferred tank temperature, and the collector pump will run at night, rejecting heat until the tank gets down to the desired setpoint.



This strategy runs the pump, which is undesirable, but thermosiphoning isn't as smart. Thermosiphoning will keep rejecting heat after the tank reaches the desired temperature.