auto by-pass

Bob_36

Mike, thanks for the info. I've been on the Honeywell website that you listed. I brought up the same unit, but when I tried to contact someone, I just got the runaround. If you could name a supplier here or email me, I would appeciate it. Thanks again for the help.

Bob_36

auto by-pass valves

I want to install trvs on my ci rads. Which trv and auto by-pass valves do you reccomend? I have seen the Danfoss line on the web. They are kind of expensive. Are their other quality brands to choose from that are less costly? Thanks for any info in advance.

Brad White

TRV's

When you say "auto bypass" I take it that you mean "pressure differential bypass" such as for when most valves are closed, the water has a place to go. Is that correct? Just getting the terminology straight.

I have never found TRV's to be particularly expensive; they tend to be competitive across a given line of manufacturers. I prefer Macon Controls but also have Oventrop, Honeywell-Braukmann, Centra, Tour and Andersson in my home, installed over time. I find the Macon line pretty compact and with a nice Allen-wrench lug installation.

For bypass valves, all of the above manufacturers make decent ones. No real preference. My personal experience across several systems is that sometimes there is a room (bathroom or entry for example) where logistically you cannot readily install a TRV. So if you admit defeat, that becomes your bypass path without, to me, noticeable noise.

If you are using a 3-speed circulator you may find that the lowest speed does it and any "back-pressure" will allow the pump to ride it's curve with little if any ill effects. If your valves are THAT closed, I rationalize, you ought not be needing much if any heat, right?

My ideal setup would be variable speed maintaining a pressure differential. It is available and the price will be coming down. We are seriously over-pumped as a nation, IMHO.

ALH_4

TRV's

As usual, Brad is spot-on.

Caleffi also makes a nice pressure differential valve. Unfortunately their TRV's are not yet available in NA. I have used Honeywell, Oventrop, and Herz TRV's and all have been good and reasonably priced. Compare the price of a TRV to the price of a thermostat, zone valve, transformer, and thermostat wire. There are many different models of TRV's also. Some are quite a bit more expensive than the basic models.

Mike T., Swampeast MO

Regardless of manufacturer (well--I'd NEVER buy Chinese if such are even availble), TRV bodies are relatively simple, extremely robust devices designed for a very long service life with little maintenance. All I've seen have a moving stem surrounded by packing (rather like most traditional valves) that is the most likely trouble spot. With some the entire packing "gland" can be replaced without draining the system; with others the system must be drained for this repair. Since there's not much difference in price, I'd select one whose packing can be replaced without draining the system. Unlike most traditional valves however, TRV valves do not need to provide absolutely positive 100% shut-off so the washer inside of all? most? should last the life of the valve--think decades.

TRV operators are significantly more complex than TRV valve bodies. While highly reliable they cannot be as robust (at any reasonable price) as the valve bodies and are susceptible to impact damage. I suspect this is the major reason that every TRV I've seen consists of two distinct components--a valve body and an operator.

TRV operators [seem] to have two basic methods of operation. One works via varying viscosity (with temperature) of a wax-like fluid; the other via expansion (with temperature) of an alcohol-like fluid. While I've heard nothing bad about the basic reliability of either method, the ones using expansion of an alcohol-like fluid are said to respond faster and provide slightly more accurate room temperature control. This difference may well be immaterial--I'm not sure.

Differential pressure bypass valves (at least the residential variety) are also very simple, robust and long-lived. As long as they come from a quality company--e.g. not some crappy Chinese garbage made for export--manufacturer should be immaterial.

As Brad mentioned, it's possible to omit a TRV or two and avoid the use of a differential pressure bypass valve. Personally however, I would do anything reasonably possible to install TRVs on ALL radiators and use the bypass valve.

Bob_36

Thanks for quick response as usual. I tried looking up honywell on the web for the by-pass valve, but when I called to find a distributor in my area( Long Island), I couldn't get a response. Could you point me to either a web site or supplier in my area for both the by-pass and the trvs of any of the brands you reccomended. Thanks again for the rapid response.

Mike T., Swampeast MO

Honeywell Differential Pressure Bypass Valves:

3/4" part D146M1032

1 1/4" part D146M1040

Danfoss Pressure Regulator type AVDO part numbers:

1/2" sweat 003L602001

1/2" NPT 003L602002

3/4" sweat 003L602501

3/4" NPT 003L602502

1" NPT 003L603002

Danfoss makes other varieties of valves AVD, IDV-IVR but they are quite expensive and likely have a level of precision far greater than necessary for a residential job.

The Honeywell valves have a right angle configuration; the Danfoss have a straight configuration. I only work on gravity conversions and have always used the Honeywell as the right angle worked best for they application--they're also somewhat less expensive but I've found the built-in indicator useless for gravity conversion jobs as they never build much differential pressure--I adjust them by ear (pressing my ear against the valve).

Nobody in my area stocks TRVs or differential pressure bypass valves--I have to use a supplier in St. Louis and have always used Danfoss TRVs. FAR too many Danfoss TRV body & actuator sizes/configurations for me to list here. As long as you have at least 3 inches or so of space, the "side mount angle" valve bodies are easiest to use with cast iron rads as the operator will be horizontal. If you don't have the space, use the "angle" bodies. The operator will be vertical and you MUST use a remote sensing operator as the operator cannot sense room temperature properly when vertical. (Other TRV mfgrs may not have this limitation--I'm not sure--but be CERTAIN you check!)

Mike T., Swampeast MO

Sorry. I'm FAR from Long Island.

I bought my first Honeywell (it was called Brauckman at the time) differential pressure bypass valve at a local supply house. Had to find it myself in their books. Even when the counter man saw the page titled, "Differential Pressure Valves" he STILL asked me, "What's it called?"

Bob_36

Mike, I did the same thing. Went to the local distributor and told him what I wanted. He gave me a blank stare and asked me what it was used for and if I could get him a part number. I guess I should have steered him to this site. I'll go back to the Honeywell site and try to get a number to call. Thanks very much for all the info.

scott markle_2

variable speed pump

Consider putting the money you would spend on the differential by-pass and applying it to a smart constant head pressure circulator.

Maybe Brad could elaborate on the available offerings. From what I understand the Wilo stratos will be available in a few weeks. The smallest circ. in this series has a bit more upper end capacity than most residential apps. would require. However at it's highest output(16gpm@14ft for example)it uses no more than a 15-58 on high 85w. 10w on the low end.

One consideration is that with a well adjusted full outdoor reset curve and properly sized radiators these trv's may not be doing all that much adjusting. In this case the energy saved by variable speed pumping might not justify the expense. A more sophisticated application I can imagine for this technology might be speed regulation based on boiler firing rate (in the case of a mod-con) or speed regulation to maintain desired delta t (low return temps.)combined with min. max. head operating parameters.

Has anybody put a system like this together yet?

Mike T., Swampeast MO

One consideration is that with a well adjusted full outdoor reset curve and properly sized radiators these trv's may not be doing all that much adjusting. In this case the energy saved by variable speed pumping might not justify the expense. A more sophisticated application I can imagine for this technology might be speed regulation based on boiler firing rate (in the case of a mod-con) or speed regulation to maintain desired delta t (low return temps.)combined with min. max. head operating parameters.

Has anybody put a system like this together yet?

You're correct that with "well-adjusted full reset" the TRVs aren't [normally] doing much adjusting. Turn many (or all) down significantly however and you'll need the differential pressure bypass.

Anyone with a Vitodens 200 and TRVs on all emitters has this form of system--even if the Vitodens senses neither delta-t nor delta-p.

Since the Vitodens has no display indication for either firing rate or circulator speed it takes quite a bit of observation to get at least an idea of what's going on.

While I had originally expected that the Vitodens would vary the circulator to maintain a relatively constant delta-t, such is not the case (at least in my system). During true modulation [continuous firing for hours] of the burner delta-t is varies with the load and also with the heat authority of the heating curve.

With low heat authority (supply temperature just adequate to meet space heating needs) delta-t increases with load. With low to moderate load and low heat authority, delta-t in my system is right around 10F increasing to about 35F in the coldest weather. Circulator speed however [seems] to decrease with increasing load. (My only methods of determining circulator speed are indirect--the "feel" of the circulator and the rotation speed of the little Grundfoss "Indicator for A/C Magnetic Fields". Since the circulator is dead-quiet sound does nothing.)

With higher heat authority (reset curve significantly higher than required to meet the load), things are different. While delta-t still increases with increasing load, it does so with a much lower magnitude--even at low load, delta-t 20F - 25F or so increasing to about 40F at high load. Circulator speed increases with increasing load.

While Viessmann provides very good technical information about the Vitodens 200 (particularly in their white paper titled "Condensing Technology"), they are virtually mum with regards to the operational logic of the VS circulator. Many people (including me initially) could or cannot believe the Vitodens 200 can do what it does using only one sensor--the supply temp. I've scoured the schematics and the boiler itself and find no other sensor--and no "extra" wires anywhere--to suggest any form of temp/pressure sensor integrated into other components.

The only "explanation" for circulator operation of the Vitodens 200 in "system circuit mode" (e.g. no LLH and directly driving a system) is that it comes from a "known volume of the heat exchanger". I also know that the microprocessor is "intentionally slow". I can only assume that model-specific information is stored and that the boiler CAREFULLY watches the effect on the supply sensor when circulator speed and/or blower speed changes that it can learn to accurately estimate both delta-t and delta-p.

It would not surprise me in the least if the "self-test" it performs after approx. 24 hours of continuous fire is integral to this learning. When I first observed this on my graphs it occurred exactly at midnight. (The burner stops firing for a couple of minutes but I'm not sure about the circulator.) I first thought it was a timing error with the boiler going into reduced mode for one minute at midnight. Verified the timer--it was never supposed to go into reduced mode--and then searched the manual and found mention of the "self-test". As the winter progress, the time of that test changed, getting later and later. To my astonishment, the time of this test eventually occurred right at the time that my outside temp graphs began their sharp rise sometime after sunrise. It's almost as if the boiler was looking for that event.

scott markle_2

reverse engineering

Given that circ. speed and firing rate can only be guessed at, trying to determine how all this works is a real challenge. I have seen behavior changes in the firing patterns that suggest some "learning" to be going on. However it seems to me that there are so many variables: shading,internal heat gains,wind,weather anomalies etc. that for the boiler to adjusting it's operatiion based on learned information, the period for gathering that information would have to be sufficiently large to make that information very useful.

I think you may be attributing more "intelligence" than actually exists. However It is interesting that seasonal information is part of the programing (first day of winter ,fall etc.) what is this used for?

While viessmann provides otherwise excellent technical literature a detailed explanation of pump logic is conspicuously absent. The presence of a variable speed circ. is not enough.What exactly does this circ. do to make the vito 200 more efficient,and based on what does it make it's adjustments?

We should not be asked to reverse engineer this system in order to knowledgeably promote it.

Tom Hopkins

It's kind of funny

I find myself telling my suppliers what to stock.