radiant heat

Constantin

... on the boiler, system, etc. among other things. Some boilers like the Viessmann Vitola and the Buderus G215 have no issues with very cold return water temperatures and thus do not need mixing valves when all they heat is a all-radiant heating system. However, the minute you add IDWH, need multiple water temperatures, or use a non-condensing boiler that does not incorporate some form of flue gas condensation protection, mixing valves or injection systems become necessary.

The system diagrams I have seen place the circulator "downstream" from the mixing valve. Usually, radiant systems require very little "injection" from the primary loop compared to the water being moved within each zone. Having the circulator within the zone loop ensures proper circulation speeds no matter how open or closed the mixing valve is.

[Deleted User]

circulator placement

I am about to start a radiant job ,and I am trying to figure out the best way to do it.I have been told by many people in the industry to use mixing valves to temper the water.It seems like an ok way to go but, my question is does the circulator come before or after the mixing valve for each zone Thanks for your input.

Rodney Summers

Mixing valves are

a good way to control flow rates and water temps. The advent of more sophisticated circulators capable of variable speed and the controls that can respond more precisely - as well as more economically, should command your attention. Primary/Secondary being a real solid design.

Dan's night school(s), and the seminal book he wrote on the subject of radiant heat would answer any question you may have. Take a look at this: http://www.heatinghelp.com/shopcart/product.cfm?category=2-2

Good stuff.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Andrew Hagen (ALH)

Mixing Valves

Pump away from the mixing valve toward the system. Are you using a thermostatic or a motorized mixing valve? Is it 3-way of 4-way? What kind of boiler are you using? What's the heat emitter? What valve you use, what size it is, and what circulator you use are all important choices.

-Andrew

hydronicsmike

Mixing details

Please read through the attached Essay. It explains the available Mixing options and how they should be piped.

A mentioned above, it depends on the type of boiler, as some require proper flow through its heat exhanger where others may not need it as much.

If you read through the Essay, have a closer look at Figure 12 on Page 3. This is how I prefer to pipe a 4-Way Mixing Valve and Figure 8 is how I prefer to pipe a 3-Way Valve. Both show a Pump on either, the boielr AND system side. Although Figure 8 references a 3-Way Thermostatic rather than Floating Action type Mixing Valve, the piping would be the same in either szenario.

Both of those piping methods ensure proper flow through a boilers heat exchanger and both also can ensure boiler protection to prevent thermal shock (if cast iron boilers) or flue gas condensation. Don't skip the Variable Speed Injection option, as it is (in my opinion) a more superior and cheaper option to get mixing done.

If you have any questions, please never hesitate to call me at 250-545-7749, Ext. 214.

Best Regards,

Mike

heatboy

Correction...............

While the Buderus is a fine boiler, let's not confuse it with the Vitola. The Buderus can tolerate cold returns, but it can not run sustained low water temperatures without damage. The Vitola, on the other hand, can run at 100° all day with no added boiler protection.

Ron Schroeder_3

except that

variable speed injection requires three circulators and a mixing valve only one with a high mass cast iron boiler and two with a low mass boiler. That equates to either 66 or 33 percent less circulators, the electricity to power them, the service to keep them alive and the ultimate replacement costs when they pack it in. Just a thought...

Constantin

Agreed...

No question, the Vitola has a leg up on its competition WRT its internal water temperature capabilities. However, I thought the thread parent was concerned about the external piping to the boiler, not the boiler temperatures themselves. After all, the pump logic built into the Logomatic controls for the G215 seems to work effectively to protect the boiler from flue gas condensation even if it requires the internal tank temperature to be 120°F or higher.

That the Vitola can run a low-temp emitter system more efficiently than a comparable high-temp boiler is pretty certain due to its lower standby losses, all other things being equal. Similarly, a Vitola kept at 140°F will have higher standby losses than one kept at 90°F. However, the low-boiler temp feature only becomes truely relevant for those users who benefit from emitters that work at very low temperatures (above floor RFH, large radiators, etc.), right?

Rodney Summers

That's true, but...

I've never seen a three or four-way mixing valve that didn't leak or blow up the operator in the first year or two.

Add to that the price of the valve and operator vs. the alternative(s)...



To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

heatboy

Since I have not used Buderus.....

I can't speak to the Logomatic control. I do know that to maintain boiler temps above condensing limits, circulation must be stopped or a shunt pump must be utilized. Both of which will cost more to operate.

As far as the Vitola's use is concerned, I have a few that run standard fin tube baseboard and will modulate down to room set point, if needed. Granted, there aren't very many BTUs available at 110°F, but when it's 50°F outside, how many do you really need? Gets back to that over-used and misunderstood phrase "constant circulation", which is at best, just an idea.

hb

Constantin

Ditto..

... I haven't used Buderus either, but I am somewhat familiar with the operation of same. After all, how many heating systems does a mere homeowner experience in a lifetime? :-)

I also agree that the active boiler temp. protection systems, injection-systems, etc. will require more electricity, smarts to be run. That leaves more opportunities for things to go wrong. And, according to the ACEEE, some Viessmann equipment is very efficient from a fuel and a kWh consumption point of view when compared to other appliances that have equally efficient thermal efficiency.

However, considering the relatively inexpensive cost of energy at the present time, there is little difference between the costs of running an injection loop vs. using a mixing actuator. Hydronicsmike and I went through the math once, and it wasn't a lot of $$$ to run a pump all season long unless you lived in a cold environment with a high electricity price. Furthermore, it can get pretty silly to argue back and forth about the electrical consumption of injection-loop pumps as long as the norm to distribute BTUs in many homes is having one dedicated circulator per zone.

I love the elegance of the Vitola design and its very good efficiency for a non-condensing boiler, I just wish I could make it a sealed combustion appliance. Aside from that minor point, I am very happy with my purchase. It'll be entertaining to see if the calculated curve gradient of 0.6 will hold up next winter (thanks Mike!) and the water temps really only have to modulate from 90°F to 110°F.

Ron Schroeder_3

I have to defer to your far greater experience, Sir

but I have lived with a twelve year old Tekmar actuator on a 4-way Heatlink valve that has never been apart in my own home. I have seen seven year Viessmann mixing valves that have never been opened and are still working well. I have also seen circulators of most manufacturers that have calved (an agricultural expression that refers to mechanical equipment that figuratively gives birth to its insides) within a few weeks or even hours of being installed. Variable speed controllers are also known not to be immune to catastrophic failure.

Thanks for taking the time to respond, though, Ken. I do appreciate your insights. Cheers.

Paul Pollets

Reliability

I've seen earlier Tekmar mixing valves (c. 1988)have problems in jamming, but over the past 15 years I've installed several hundred (mostly Viessmann)with never a failure. The ESBE valves cost less and are not as long lasting, but I've not seen gross failures, unless the valve was manually operated, and there was poor water conditioning.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

hydronicsmike

Fred, I know where you are coming from...

...and it is just the same old story.

I would think that one who works on Valves and Pumps would most likely be able to tell you that a Pump requires less maintenance and repairs than any Mixing Valve. A Pump is easier to be replaced than a Valve if required and in most cases cheaper too. I could be wrong...Of course, not arguing any of the success stories from Paul and Fred about the Viessmann Valves.

What does a 007 TACO or Grundfos UP15-58 cost to operate IF ran continuously at 50% on average.

Your comment about having to use a single pump with Mixing Valves holds true with certain (yours - Viessmann included) boilers, but not with the majority of them.

To make it an honest comparisson, I would think one should compare the costs of Variable Speed Injection Mixing done with just a single TACO 007 or Grundfos UP15-58 Pump to the cost of a Mixing Valve with Actuating Motor. In my experience, a pump has always been cheaper....or better said, more cost effective. Then considering the fact that you still have to consider that moving an actuator still requires power, you would have to look at the difference in operation cost over a years time. So lets figure out what that would be.

Can you recover the extra cost for the Valve and Actuator by what you save by not having this little 0.7A Pump run at 50% speed on average throughout a heating season that may last 6-8 months? For sure not in one year. How many years, is the question?

Again, I may be wrong...but I am sure its a few...and thats if no repairs or maintenence is required on the valve during this time, or else, this again, is right out the window.

Please dont take any of this the wrong way. I certainly dont mean to argue ... but think that in the end, it may be a matter of preference or who's been brainwashed better

I am very much german and been nothing but a Viessmann or Buderus man before my move to North America now close to 10 years ago and I never knew anything else other than Mixing Valves, 3 or 4-way. But since, I have become a Variable Speed Injection guy and cannot think of a single reason why "I" should reconsider.

Just some thoughts if there is room for it.

Anyways, see you in November!!

Mike

Ron Schroeder_3

oops

Ron Schroeder_3

but would you reconsider

if I took you fishing? It seems that that would be most compelling, no? ;-)

Rookie

This poor guy

just waited a whole day to find out where to put his circulator, he doesn't care about fishing. Mike H who is doing you radiant design work and near boiler piping design if you have no one, then what radiant type of pipe are you buying?what kind of boiler? Go to the manufacture say for example Buderus, call Joe he will take care of any design questions, also Ken's advice on injection is good, call Grunfos or Taco.

hydronicsmike

Fred, I think it is worth...

...a try Lets go fishing!!

coming through my way any time soon?

If not, we'll fish the frasier river or better yet, off the sunshine coast in November.

Mike

Paul Pollets

Mike...

Great pdf essay on mixing. It clearly illustrates the various strategies.

I think I'm hearing salmon flopping into the boat...

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Andrew Hagen (ALH)

Mixing Valves

Mixing valves deliver a more precise constant temperature to the system than injection can. Injection is great. It works very well. Injection is also capable of delivering incredible amounts of heat with high dT's. An HK1 with a Viessmann 4-way is not inexpensive. It depends on the customer's desire and the application. I would call the maintenance and energy consumption arguments a wash in the end. As with anything, you have to pay the price for performance.

-Andrew

Bob Sweet

hydronics mike

you're a great compliment to the Wall. Thank you.

hydronicsmike

I always believed...

Hello Andrew,

I always believed that Variable Speed Injection would naturally be able to maintain closer and more accurate target temperatures, as we can increase and decrease the speed of a circulator from 0-100% in a matter of a second or seconds, where a Mixing Valve would naturally be limited to its reaction time based on the Actuating Motors Speed. Some of the faster ones I deal with regularly (customers preference) still take 90 seconds to go from fully closed to fully open, where others, including the tekmar 011 Actuating Motor actually can take up to 160 seconds for the same stroke distance.

If you find that the supply temperature is not maintained closely, then typically an oversized Injection Pump (maybe even just the Balancing Vlave is not set properly and needs to reduce the flowrate) or a Check Valve is used in the Injection Loop.

If you like to discuss, please don't hesitate to contact me at 250-545-7749, Ext. 214.

Thank You guys for the nice comments made below. Paul, if you're ever near my area, I'd be happy to go fishing with you, or any of you guys if the opportunity arises.

Enjoy your day gents.

Mike

kb

sand vs concrete

I'm building a small round structure, 20.5 feet in diameter, 328 sq feet. I want to use radiant heating in the floor and because I want the building to be "easily" dismantled, I am considering using packed sand to cover the piping rather than the traditional concrete. I'll use closely packed 2'" garden pavers as the flooring over the sand. Does anyone have experience using sand or can anyone encourage or discourage me? I'd appreciate all constructive comments.

Thanks! KB

Ron Schroeder_3

the fishing remark was intended

as a gentle reminder to Ken of the stinging rebuke I received earlier for takng clients out on the salt. It was not intended to derail the dialog. Note it was indented under Mike's last comment that ended with him not being able to think of a single reason why he would reconsider...

But I guess if you didn't get it then an explanation won't do much good either.

Ron Schroeder_3

sand instead of Concrete

Sand is the medium we bury tubing in when snow melting under asphalt. The concern I have with packed sand in your installation is that unlike a driveway which is open to the rains, your floor will not be. You might find that the tiny airspaces that develop when your sandbed dries out actually slow the performance of your floor, but in principle this should work fine provided you do not forget to insulate beneath the sand. A very high water table would be my only other concern.

You did not say this was a residence did you?

Remember to use barriered tubing for the sake of your boiler.

Unknown

Sand is no good for a radiant transfer medium. It can work, but it's not predictable and it's not great even when it works. I would suggest waiting until the building is in a final resting place to do radiant in it. Or, perhaps an earthen floor.

Unknown

The Delta-T of a snowmelt is a bit higher than residential, which drives more heat even if you aren't using a perfect transfer medium. You hit the nail on the head with one of the problems with sand in residential heating. Packed sand is not often consistent, first of all, so you can get floor temperature variation. Air spaces is a second concern, and can result in a system that can't even transfer enough heat to meet a "normal" load.

Not trying to pick on you, but we ran into that exact problem on a job; moderate load and the floor hummed along with a six degree delta T on a 300 foot loop under close to design flow rate. It quite simply could not get enough heat out of the tube and through the sand/minimal concrete mixture to meet load. Other areas of the home, using the same method, heated just fine.

Until someone can quantify the exact methodology to *ensure* a consistent sand installation, we will never use it again in a home of any kind. If that happens, so be it... one more tool in the box.

Andrew Hagen (ALH)

Curves

Wouldn't the slower reaction time of the mixing valve be an asset rather than a detriment? It seems the circulator would "hunt" more than a valve. The pump curve is non-linear and the valve is linear.

I really haven't had any trouble with injection in any application. I just think a mixing valve has to be a bit more precise with the temperature delivery.

Have a great weekend.

-Andrew