Rethinking Delta-T & Delta-P Circulator in Zone Valve System

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lsayre
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Post by lsayre » Sun. Feb. 15, 2015 10:27 am

After monitoring the supply and return temperatures of my system (which due to its inclusion of a DPBV performs quite closely overall to a Delta-P circulator equipped system) for one month, I have completely abandoned any desire for a Delta-T circulator, and I'm inclined to leave well enough alone, and also to reconsider any immediate (or long term) need for a Delta-P circulator (sans to save on electricity).

As to Delta-T circulators in conjunction with a single circulator and zone valves, I can see where daily there would be multiple instances which would drive the logic circuitry of this type of circulator to derision. Among them:

1) It generally takes my system up to 5-6 minutes to settle down and stabilize at a consistent Delta-T after a T-Stat call opens a zone valve and turns on the circulator. Delta-T pumps try to compensate for this by cranking at full rated speed (for a given head) for 3 minutes before switching to Delta-T mode. For 3 minutes every time the circulator turns on I would potentially experience velocity noise and excessive wear and tear on my pipes. Yet my system requires up to 6 minutes here, and when it switches modes at only 3 minutes, it will be lost as to a proper solution to what it finds.

2) At any time a second zone valve (or a third, or even a fourth) can open, dropping the return temp noticeably and thus sending the logic circuitry of the Delta-T pump into derisions for which it will be lost as to the proper solution (since the proper solution requires merely leaving things alone and providing constant pressure delivery). Again it would speed up to maximum when this is not really necessary or desired.

3) I've even witnessed a few situations where my boiler is nearing 215 degrees and the dump zone is about to be activated, and instead a T-Stat call opens a zone valve and turns on the circulator. In this situation I've seen 215 degree water rush into the zone and 80 degree water rush toward the boiler, and at about the 3 minute mark I've witnessed a temperature inversion whereby the zone (as witnessed by the return temp) becomes hotter than the boiler itself (as witnessed by the supply temp). I presume that this would once again send the Delta-T logic into derisions and it would again be at a loss as to how to properly escape from the major dilemma at hand. But my DPBV on the other hand is open and blending hot boiler water at 215 degrees into the 80 degree returning water and the boiler equipped with DPBV is therefore not (directly) seeing 80 degree return water. The DPBV is the proper solution here, and Delta-T (along with Delta-P, both of which require that the DPBV be removed) would not be providing the proper solution here.

In my opinion at present, the correct solution for all of these situations is a DPBV (which is a constant pressure achieving device) or a Delta-P circulator (which in effect is a constant pressure achieving circulator, though it would not moderate return temp, so it is less desirable). Regardless of how many zones are open at a time, or as to when they open or close, my DPBV keeps the Delta-T stable and within close proximity of the ideal 20 degrees after things (the issues I have mentioned above) settle down. The Delta-T solution in my case however appears to be the worst potential solution of the three. Delta-T would likely work much better if it was applied in a system with zone circulators (all being Delta-T regulated) instead of zone valves.

 
CapeCoaler
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Post by CapeCoaler » Sun. Feb. 15, 2015 8:47 pm

OK what is a DPBV?


 
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lsayre
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Post by lsayre » Sun. Feb. 15, 2015 8:55 pm

CapeCoaler wrote:OK what is a DPBV?
A Differential Pressure Bypass Valve. It is a spring loaded valve. When set properly (spring tension dialed in to match the maximum friction head of the system) it should be (in theory at least) pretty much wide open (or more properly, as open as it's going to get) when only one zone valve is open, and then become progressively more closed as additional zone valves open, until when all of the homes zone valves are open it is fully closed.

If you don't have a good idea as to the maximum head of your system (which is the head of the highest friction zone, with this generally, but not always, being the longest zone). the easiest way to set one is to fully tension its spring until it (the DPBV's valve stem) is closed tight, and then open up all of your zone valves, and turn on the circulator, and then slowly reduce the tension on the spring adjusting knob until the DPBV line feels flow and begins to get warm (meaning the DPBV valve is just beginning to crack open), and then tighten the spring tensioner down a wee tad to just close it again. That's it.

 
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Sting
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Post by Sting » Mon. Feb. 16, 2015 8:46 am

adding a rule to the list

The more you mess with it the more you have to mess with it
.........

Use simple pumps and controls = balance till you get a 12% change in supply and return temps on a hi demand day [cold weather]

and relax - leave it alone

101. Install gate and check valves, but remove the gates and flappers first.

102. Clean the boiler with a tree sprayer. Just pop the flue pipe and spray all that crap down into the combustion chamber. Make sure you leave it there.

103. Install a fresh flounder between the boiler and the boiler jacket. Do this only if you're reasonably sure you're not going to be paid.

104. If you're really sure you're not going to get paid, install a piece of plate glass on top of the chimney. This is for the enjoyment of those who will follow you.

105. Pop every relief valve you come across.

106. Never clean the water side of a boiler after you've installed it.

107. If a relief valve drips, plug it.

108. If the chemical manufacturer tells you to use one can of the stuff, use five.

109. Install a dehumidifier in the duct work of a scorched air system.

110. Seal leaking steam boilers with oatmeal.

111. If you're installing a new relief valve, pipe it to the outdoors where it can discharge, freeze and then blow up the building.

112. Feel free to drop safety relief valves on the concrete floor. They're tough; they can take it.

113. Put a few nickels in the copper tubing before you solder it all together. Make bets with your partner as to where they'll wind up.

114. Install a backflow preventer on every domestic hot water system, but leave out the thermal expansion tank.

115. Make sure the people you hire to answer your phone think they're doing your customers a favor by picking up within the first 25 rings.

116. The people who answer your phone should always ask the customer, "What is this in reference to?" in the most accusing manner possible.

117. If your customers don't know the correct names for the things that are either banging or smoking or leaking in their homes, the people who answer your phone should make them feel like idiots.

118. The people who answer your phone should always say, "Well, how are we supposed to help you if you don't know the proper names of the equipment. Hmmmm?"

119. Never tell your customers about water heater anode rods in water heaters. It's so much better to sell them a new water heater every four years. Screw the environment, we can always get another one.

120. Write, "Joe, whatever you do, don't install it this way!" on the installation instructions, and then leave them where the customer can find them after you're gone.

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