Mixing Valve For Steam Heat

MVO

I have a steam heating system with a hot water coil. The initial water gets hot enough that steam will flash from the closest faucet at the kitchen sink when making steam.. The inlet valve to the dishwasher has melted twice and the pull out for the kitchen sink will melt if not flushed with cold water after being on hot.

The cheap solder in mixing valve is not adequate for this set up and does not work.

The piping is 3/4 inch copper.

What mixing valve can handle this? I need something durable and meant for steam. If it has to be reduced from the new mixing valve to the 3/4 inch that will be fine.

Any help will be greatly appreciated.

ChrisJ

Welcome to the forum!



A few thoughts.

At 20 PSIG the boiling point of water is around 250°F. Water should never be flashing to steam in your hot water coil under normal use assuming the pressure is 20 PSIG or higher. In fact, at 4.5 PSIG the boiling point is still 225°F.


Solder in mixing valves should also have no problem with these temperatures, off of the top of my head typical solder melts at around 500°F. Depends on the blend, but they are all well above any steam heat temperatures.

That said,
I'd probably go for one of these, though I'd buy the solder in one. Here's a threaded one for you :

http://www.supplyhouse.com/Watts-0559134-3-4-LF70A-T-Lead-Free-Threaded-Tempering-Valve-120176-160176


Or,

http://www.supplyhouse.com/Honeywell-Sparco-AM101-UT-1LF-3-4-NPT-Union-Mixing-Valve-Lead-Free


Personally I like the second one more.



What exact valve is installed right now? Is it a Watts? Honeywell?


I'm sure some others will chime in with their experiences.

mgdesrochers

I agree that the 2nd option listed above is the better of the 2; we stopped using the 70A a long time ago & very rarely even repair them.
Although the mixing valve should be tempering the water down, the fact that you even have steam inside the domestic coil in concerning.
Is the coil submerged in water? What is the aquastat set for? Is this happening every time you use hot water or only when the boiler is running for heat? Pictures of the piping & controls might show something out of the ordinary if you can add them...

Bob Bona_4

A third option is the Caleffi sweat union model with a temperature gauge on the mix outlet. Nice.

ChrisJ

Bob Bona said:

A third option is the Caleffi sweat union model with a temperature gauge on the mix outlet. Nice.

This?

http://www.supplyhouse.com/Caleffi-521519A-3-4-3-Way-Adjustable-Thermostatic-Mixing-Valve

Gordy

mgdesrochers said:

I agree that the 2nd option listed above is the better of the 2; we stopped using the 70A a long time ago & very rarely even repair them.
Although the mixing valve should be tempering the water down, the fact that you even have steam inside the domestic coil in concerning.
Is the coil submerged in water? What is the aquastat set for? Is this happening every time you use hot water or only when the boiler is running for heat? Pictures of the piping & controls might show something out of the ordinary if you can add them...

Agreed I would be finding out why the water temp is so high as to cause damage to fixtures before installing a new mixing valve pronto!

Probably why the one you have has failed.

Jamie Hall

Gordy said:

mgdesrochers said:

I agree that the 2nd option listed above is the better of the 2; we stopped using the 70A a long time ago & very rarely even repair them.
Although the mixing valve should be tempering the water down, the fact that you even have steam inside the domestic coil in concerning.
Is the coil submerged in water? What is the aquastat set for? Is this happening every time you use hot water or only when the boiler is running for heat? Pictures of the piping & controls might show something out of the ordinary if you can add them...

Agreed I would be finding out why the water temp is so high as to cause damage to fixtures before installing a new mixing valve pronto!

Probably why the one you have has failed.

And I third that. The only time -- the only time -- that the water from a tankless coil in a boiler should approach 212, never mind hot enough to damage a fitting, is if the boiler is actively producing steam -- and even then, that will happen only very briefly as the water in the coil is replaced (and only if the tap in use is very close -- within feet -- to the boiler). Something else is wrong here.

HVACNUT

Yeah, sounds like the failures of the mixing valves are the result but not cause of the problem.
Water level, pressure etc.
Some pics of your system might help.

ChrisJ

It's a steam boiler. It runs at 212-215F while heating.

If you pull water from it slow, it's going to be that hot or close to it. Even my mudded up hot water coil got extremely hot if you ran the water slow while steaming.

MVO

Sorry it seems that I need to amend my post a bit. There has only been a few times that we have got a flash of air and what seemed to look like steam. It is only momentarily and just when the truly hot water first gushes out. This happens when the boiler is making steam and no hot water has been drawn for a while and the faucet is running wide open to get hot water to the fixture.

Steam coming out of the faucet is not the typical default condition. I did not intend to make that seem the case.

The kitchen sink is directly above the boiler.

Yes the coil is covered with water.

The water is extremely hot. The flexible plastic tube in the pull out faucet has fused closed twice. It does not if cold water is ran through it after the hot.
The inlet valve to the dishwasher has failed twice. It seemed like the plastic could not stand up to the heat of the water.

Our default way of using things is to open the hot water and when it begins to get warm open the cold and then blend them.

However the single lever on the Delta kitchen faucet seems to have only a quarter to and eight inch where the water is warm. It seems to be an eight to a quarter inch either way and the water is very cold or very hot.

The initial water is very hot and then it does fall back as the water flows through the heat exchanger. Obviously because there is not 100% instant heat exchange as the water flows through the piping. As we take a shower we have to adjust the cold back and edge the hot water slightly. With steady flow the temp does drop a good bit.

Some times the house temp on night set back will fall four degrees below day temp and has even dropped ten degrees. In these conditions the boiler can be producing steam for an hour or more. It is most definitely while making steam that we get the extreme hot water.

In the summer when there is no steam, the amount of heat in the initial water is no where near so drastic.

The solder in the fittings is not melting.

What is installed is a Watts regulator 70A---labeled-- not anti scald--- with a range of 160 to 120 on it. The mixing valve is right next to the boiler and the water hitting it when making steam could easily be 200 until the water flows for a bit.

Even adjusting the 70A creates a leak that tightening the packing nut does not fix. I had to add packing.

I have been around hot water coils in four story to six story apartment buildings for 30 years. Those mixing valves were not affected by the heat of making steam and were rock solid dependable. Iam hopeful that one of the recommendations above will work as well on this small scale.

I see the one i have was mentioned as one to look at but the Caleffi or the Honeywell-Sparco sound like they may be better.

Having a temp gauge on the outlet of the mixing valve would be awesome.

Thanks for the recommendations.

Jamie Hall

Seems to me that things are operating as would be expected -- given your set up. I would suggest that the night set back is a bit much for steam (or gravity hot water) systems; I at least really think that anything more than 3 F is counterproductive from the fuel use standpoint -- although I recognise that some folks like it really cool at night.

The real problem with mixing valves is that while they act rapidly, they do not do so instantly, and the problem of near boiling -- or boiling water -- is significant. And you have a worst case situation -- a faucet with a very short run from the boiler to the point of use, so there isn't even the effect of heating the pipe to help cool the water.

The suggested valves will maintain a proper mixed temperature -- although i notice that the Caleffi has a maximum hot water inlet temperature of 200 F, while the Honeywell is rated to 212. Both values are actually below what you are getting -- although they may manage it. What neither of them does do is shift essentially instantly. It is possible that an electronic valve, such as the ETV-Plus series from Heat-Timer, might provide tighter or quicker control; something you might look at.

In the meantime all I can suggest is to change your operating pattern at the kitchen sink! Delta faucets do have a smallish control range, but they're not hopeless, and perhaps if you got in the habit of turning on the cold first, and then bring in some hot... I hate to suggest that sort of fix, though -- even for myself, never mind for someone else (I at least react badly to someone telling me "you WILL do it this way!").

Bob Bona_4

I remember the honeywell sparcos came with a one time temp sensitive color strip to "set" the mix. You'd match the color change to a chart. Smh.

Caleffi rocks.

Fred

Does it make sense to add a small WH storage tank to this system so that that initial shot of water is buffered by the water in the tank?

Jamie Hall

Fred said:

Does it make sense to add a small WH storage tank to this system so that that initial shot of water is buffered by the water in the tank?

That would seem to me to be the best idea, if it could be fitted -- a sort of mini-indirect! With some thought, one could arrange the piping so that it would thermosiphon and maintain heat in the tank, without any odd controls or pumps. Still need a mixing valve, but the demands on it would be much easier to manage.

JUGHNE

What pressure relief valve would one put on it....it is a vessel that would require one????
DWH T&P........temp almost too high for the 210* opening point.
I assume it would be at city/house pressure.

Fred

JUGHNE said:

What pressure relief valve would one put on it....it is a vessel that would require one????
DWH T&P........temp almost too high for the 210* opening point.
I assume it would be at city/house pressure.

I was thinking the tank input would tap off of the output side of the boiler coil and the output side of the tank would connect to the house HW line. If so, I would think the boiler PR valve would suffice??

ChrisJ

Why is everyone re-engineering a simple hot water loop?

This isn't a new device.

Fred

ChrisJ said:

Why is everyone re-engineering a simple hot water loop?

This isn't a new device.

Mostly because he has a very short run to his kitchen and as the OP has already said, the temp of the water has melted a couple valves on the dishwasher as well as on the faucet and the temp of the water is at or near steam temp before the Mixing valve adjusts to the set point.

Gordy

Doesn't seem safe to me. I guess you can learn to live with it. Is this a draw back to a dhw coil off a steam boiler?

Bob Bona_4

Nothing magical happening here. At steam, the tankless is going to emit 212, at least initially.

Big Ed_4

There are better options then producing hot water the in the last century steam system

Jamie Hall

It's quite true that it isn't a new device. It's also true, unfortunately, that in some situations it can produce excessively hot water -- and this is one of those situations.

ratio

I'd think that running the outlet of the tankless through a 2-5 gal electric water heater would work just fine. A thermosiphon loop would probably be an easy add. The EWH doesn't even need powered, although if it is, it should rarely need to energize. Leave the factory TP valve in, it should be redundant but no need to excite the inspector.

I think I'd put the tempering valve after the EWH, to protect it as well, but IANAP, maybe someone else will offer an opinion.

ChrisJ

If anyone is going through the trouble to try and build some half baked buffer tank setup they should just install an indirect off of the coil, or a totally independent 50 gal electric heater and be done with it.

Both will solve the problem and perform far better. The 50 gallon electric tank heater is probably the cheapest solution assuming the electrical service has ample capacity.



If not, then try the better mixing valve. You can also install a manual valve to blend some cool water in with the output all of the time and just set it where it works best overall. This may help the mixing valve do it's job. Set it so it mixes enough cool water in while the boiler isn't steaming and the mixing valve is totally shut. The mixing valve can then take up the slack when the boiler is producing steam.



That's my 15 cents.

Gordy

I guess my question is this. What if an installer were called to handle this situation. What would be done to insure a safe, reliable, and long lasting fix to DHW supply to their customer upon finishing the job? Replace the mixing valve with one of a higher inlet temp rating? That is it?

Jamie Hall

Gordy said:

I guess my question is this. What if an installer were called to handle this situation. What would be done to insure a safe, reliable, and long lasting fix to DHW supply to their customer upon finishing the job? Replace the mixing valve with one of a higher inlet temp rating? That is it?

I don't know about you, @Gordy , but in this application -- with this history -- I'd really want a tempering tank in there somewhere... nothing like getting sued because someone scalded themselves to ruin your whole day.

ChrisJ

Jamie Hall said:

Gordy said:

I guess my question is this. What if an installer were called to handle this situation. What would be done to insure a safe, reliable, and long lasting fix to DHW supply to their customer upon finishing the job? Replace the mixing valve with one of a higher inlet temp rating? That is it?

I don't know about you, @Gordy , but in this application -- with this history -- I'd really want a tempering tank in there somewhere... nothing like getting sued because someone scalded themselves to ruin your whole day.

Being sued for following the manufacturer's instructions?

What happens when you don't follow them, and then get sued?



Here's what I have on hand from Burnham.

Notice, they show the output going to appliances before the mixing valve, even on a steam setup.

Gordy

That reason is probably for commercial dish washers. They are setup quite differently. They are designed to accommodate very high inlet temps. No towel drying allowed.

Gordy

The rinse cycle requires 180 degree water temps to kill bacteria, and aid in quick drying.

ChrisJ

That's from a V8 series manual that I have.
I highly doubt V8s were ever used commercially.


Anyway, I said my piece, hopefully I helped the OP.

Fred

Unfortunately that diagram does not address minimum distances to any appliances. If I had water hot enough to melt valves on a dishwasher and/or a faucet, I'd want some type of buffer tank in between the boiler coil and the appliance/faucets.
I'm a bit surprised @ your reaction to a workable solution to a real problem @ChrisJ . What could possibly be wrong with a small buffer tank that uses no additional or alternative power as opposed to a 50 gallon electric WH? And since when have you used Burnham as a reference for anything? That simply shows their "Standard" configuration.

Grallert

indirect water heater

MVO

Thanks everyone for the input.
The extremely hot water in the kitchen is because the tempering valve is basically not working at all. Initially I could make adjustments. That was short lived. Before I moved in there was no tempering valve at all. I installed it. The set up that exists most certainly was not engineered.

A small slug of very hot water should not be a problem. We can deal with it. The problem is that we are not getting any or much drop in temp from mixing in the cold water because the valve is not working.
We compensate at the kitchen sink by adjustment and if using the sprayer finish with straight up cold water. The dishwasher on the other hand is straight hot water and the mixing valve is the only thing moderating the temp.

My hope was to find a mixing valve that was rated for water close to steam temp with a proven track record. I certainly can see that exceeding the input rating can waste the valve quickly.

I respect the experience and wisdom of the people here. I do not have any way to evaluate the reliability of these mixing valves personally.

According to the altitude charts, water boils here some where between 211.5F and 212 F.

If the max for the Caleffi is 200F input then possibly it might receive a spike that it would not handle well.

The Honeywell rated for 212F seems like the best bet.

I certainly do not have a problem putting in a small tank or heater to temper the water to protect the tempering valve. If it is needed.

If the tank was not heated then I see a potential need to run cold water out in the summer. That would be a lot of water to flush through the tank. A small 5 gallon electric sounds like it would work. Just using the valve alone would be my first choice. That is if it will hold up. I assume that if it goes out there are rebuild kits to repair it.

Before I moved in here there was no dishwasher and no plastic hose on the sink. Probably they had no equipment failure and just lived with the condition for many decades.

After i figured out to flush the pull out hose to the kitchen sink faucet with cold water--I have not had the hose melt together. The rubber parts that ride on the ball do need replacement about once a year. Not a big deal. The plastic valve to the dishwasher is something different.

The bath room at the back of the house gets water hotter than ideal but we deal with it by how we operate it. There has not been damage to any thing back there.

If the tempering valve could stand the heat then things would be fine.

@Jamie Hall
"In the meantime all I can suggest is to change your operating pattern at the kitchen sink! Delta faucets do have a smallish control range, but they're not hopeless, and perhaps if you got in the habit of turning on the cold first, and then bring in some hot... I hate to suggest that sort of fix, though -- even for myself, never mind for someone else (I at least react badly to someone telling me "you WILL do it this way!")."

I certainly do not take any offense to direct suggestions.
We have pretty much already altered the operating pattern after melting two of those faucet pullout hoses- at $100 each. I should have just put in a new faucet---- when It happened the second time. The second time--I cut it apart to see what was going on and found the soft tube melted together. I do worry that the wife may have the water too hot some time and just shut it down. So far so good.

Thanks again for the input.

ChrisJ

You're not alone with the Delta faucet.
I run our water heater at 140F and have the same problem with our Delta. It's either way too hot, or ice cold and very hard to get in between.

Frustrating when trying to quickly wash your hands.

I am glad to hear I'm not the only one with that problem and a Delta faucet. Our's is a pullout with a side mounted control.

JeffM

I have one of those Honeywell tempering valves installed on my steam boiler and it does a fine job. I find that the high temps eventually cause the guts to get sticky and it doesn't mix as well - partly calcium buildup, and partly the high temp on the hot inlet causing the seals to go bad. I rebuild the valve every 2-3 years and restore proper performance.
You may be able to replace just the cartridges (and leave the body installed) which is pretty inexpensive, but might want to have two valves around to make the swaps simpler. You can then clean up / rebuild the spare in your free time with the fresh valve in.

MVO

@ ChrisJ That faucet is the one that I have also with the side mounted control lever and pull out. Even rebuilding with a new ball did not change the hot VS cold situation. I was shocked at the $100 price tag for a new pull out hose. I am going to install a faucet with separate hot and cold at some point.

Thank you for recommending the Honeywell mixing valve initially and all your thoughts and analysis.

@ JeffM--thanks for the info. It is nice to hear your experience with the Honeywell and recommending it. Good idea about the spare. I was already leaning toward the Honeywell because of the 212F rating. Any ideas on getting the calcium dissolved once the guts are removed and changed or just get a new repair kit.

@ Grillart I agree that the best way to use a hot water loop is to set a pump on to the loop and pump the water through it from a well insulated storage tank that controls the pump from a heat sensor. I do not own this house and am limited in what I am allowed to spend. If i owned this house that would be what i would have. The pump would be an ongoing cost as it started leaking but IMO would be a good approach.

In a religious building that I took care of we installed an anti shock pump with the new boiler. The anti-schock pump adds hot boiler water directly into the return water from a hydronic system. This system heats a three building complex that is a converted steam system. That pump starts leaking every few years.

@ Jamie Hall Thank you for pointing out the Honeywell's 212F rating. The Caleffi with the gauge looked very attractive until you pointed out its 200F limit.

Thank all of you for the thoughts, analysis and spirited discussion.

I am going to order the Honeywell mixing valve. If it needs rebuilt every two to three years then I can deal with that. I may still possibly install a small back up electric heater between the tankless coil and the mixing valve if needed. The thing that i do not like is the glass lined steel tank that will rust out. i doubt that the tank will use much electric used this way.

Personally I love steam heating systems as long as they are one pipe steam. They are very trouble free in six story buildings and so are the mixing valves.

I do not like the two pipe steam because of the vulnerability of all all the exit valves on the radiators if steam gets into the returns.

I have even been to a seminar where a consultant spoke who analyzed mostly religious buildings by their utility bills and used on site examination to determine what was there. He said that in some cases new hydroinc systems with condensing gas burners and pumps cost more to operate than steam because there are no pumps consuming energy 24-7. In some other conditions heat pump installations were costing more to operate than what they replaced. Of course these results were not always the case.
Possibly not even the norm.
I would have loved to have worked with him. Sometimes peoples
visions on what to do conflict and things get blocked. He was not NYSERDA so was not to be used.

Fred

@MVO , If you do decide to add a small tank, keep in mind that it doesn't need to be connected to electric or gas or any fuel source. You don't need to heat that water, your boiler is doing that. All you want that tank to do is act like a small indirect tank to store hot water. That water will not get cold as it will be replenished every time any hot water is used in the house so it's not like you have to drain that tank at the faucet before you get hot water. Instead of the typical function of an indirect tank (which is to store hot water where a tankless may not have the capacity to meet the demand) you will be using your tank to buffer the 212 degree water from the boiler by diluting it with the water in the tank.