Snubbers, time delay relays, and pig tails

DomesticEngineer

Is there another name for 'snubbers'?  I know they are recommended but I've been looking for some parts for our steam boiler gauges and when I'm on those websites, I search for snubber and no parts match that description.



Anyone have a good source for a time delay relay (up to 20 mins) that would work well to keep the boiler from short cycling?



And our pig tail is connected to the boiler by a 90 degree elbow ( we believe without it there was no clearance to thread in the pig tail).  Unfortunately due to this, we only have 2" clearance from the gauge to the boiler manifold. 

We've had problems finding a pigtail that will suit our needs, do we have to make our own pigtail or can we just add a 3" extension between our vaporstat and the pigtail?

nicholas bonham-carter

short-cycling problems

what are your pressure settings, and when does this short-cycling occur? if it is at the beginning of a cycle, during venting then you probably need more main [not rad] vents. with generous venting, my system of 55 rads vents at 2 ounces back-pressure, as a result of having a total of 17 gorton#2's on 6 dry returns, and naturally there is no short-cycling. a delay timer, in this case would be of no benefit. a good low pressure gauge would be useful for diagnosis.

another cause of short-cycling could be the wrong anticipation setting on the thermostat, or its bad location. the honeywell visionpro is a good steam-rated model, and can have a remote sensor.

without a picture of your pigtail, it's hard to visualise what is there, or what would be best. there are 2 different shapes of pigtail-1. for a vertical port, and 2. for a horizontal port. you can always add more piping to raise it above the boiler, and unions to make cleaning easier, without the un-wiring of the pressure control.--nbc

Rod

Snubbers Etc.

Hi - For Gauge Snubbers try  at  http://www.valvestore.com/products.asp?dept=1122

 (They are a dept of the Gauge Store)

Ray Gauge Snubbers

Porous for Steam - Part # 32627  - 1/4 “  NPT Stainless

                           - Part # 32618  - 1/4 “ NPT Brass

Pigtails - Mc Master Carr   www.mcmaster.com/      has good assortment of these in several types of material. Red Brass (Bronze) is best for steam. As NBC mentioned you could possibly can just extend the old one.

Timers-  For a timer, try Allied Electronics  http://www.alliedelec.com/

- Rod

Jamie Hall

Snubbers

Have a very specific use, and it is important to make sure that they are appropriate to the problem(s) you are encountering.



Which is not to say that they will hurt anything -- they won't -- but they aren't free, and if you don't need one...



That said, what a snubber will do is cure difficulties arising from short term fluctuations in steam pressure -- they will act to effectively average out the pressure being sensed over a period of time, usually on the order of several tens of seconds (depending a lot on the specific piping configuration they are used on).  Therefore, particularly if you are running very low steam pressure settings where short term variations in pressure are similar in magnitude to the set pressure, they will work wonders.



What they will not do is cure or reduce short cycling caused by a mismatch of boiler capacity to EDR (condensing capacity) -- which occurs late in the cycle -- or inadequate venting -- which occurs early in the cycle -- or misadjusted thermostats.



Therefore, you need to analyse which of the possible causes of short cycling you have (could you describe it further?), and then address that.



There are any number of time delay relays, many adjustable, available.  If you decide to try one -- which is most assuredly a bandaid approach where a splint is needed.

DomesticEngineer

clarifications

A busy life has stepping the way of replacing our old pressure regulator.  Since we'll be putting a noticeable amount of money into it, we don't want to put the new one on our old 'set up' knowing that the position of the new vaporstat to the water level from the pigtail will start to damage it right away.  (hence the extension for the pigtail.)



The short cycling is a preventative measure as we are running much higher pressures than we currently need.  I've also heard that a snubber is also a good idea for a vaporstat (we'll be buying the honeywell L408J1009 (0-16oz).  (we'll also put a T in to add a 0-3 or 0-5psi gauge so that we have a new/accurate idea of pressures it's actually running at.



I'm not quite sure about the relative 'correctness' of our thermostat.  The thermostat will continue to tell the boiler that it needs heat, the vaporstat determines if it will actively try to produce that steam.  We often kick the heat down to 55 degrees when we are sleeping or gone for the day, so there is generally quite a bit of run time when we want the house warmed back up.



I'm not sure what the difference between main versus radiator vents are so I'll have to do some looking into that.  The main floor of the house has 6 radiators, we have no qualms with the heat distribution of the house. (we currently don't use the upstairs dormer and have the vents turned off up there.)



By the other comedy of errors that we've seen with how the boiler is set up, there may very well be a problem with the boiler capacity to the EDR.  As I really know nothing about this currently, I couldn't really say.  I just know that I don't want to put on the new vaporstat and have to take it off before we can keep it from short cycling.... if that happens.  By ordering online and doing this ourselves, it essentially pays for itself.



I don't have the camera download cable available so I can't attach pictures tonight.

nicholas bonham-carter

timed delay

it would be better to try to cure/identify  the problem causing the short cycling, rather than by putting on a band-aid [time delay].

the problem of an over-fired or over-sized boiler is of course very difficult to cure so you may have no other choice.

at least by installing a known good thermostat, you could be certain that device is not the problem. if your present thermostat is more suitable for forced air only, then it will "anticipate" and will turn off the boiler early to prevent temperature "over-shoot", adding to the short-cycling problem. the tekmar thermostat can i think lengthen the heating cycle so as to function a bit like a delay timer.

the low pressure gauge should tell you if the venting is adequate, by showing you the back-pressure during venting. --nbc 

DomesticEngineer

Snubbers, time delay relays, and pig tails

Ok.  More on the application.  See below photos.



There is one overall of the manifold, pressurestat, and pigtail.  There are two detail photos that show the pressurestat to side of the boiler clearance (approx. 2") and the height above the boiler for the pressurestat (approx 2.0").

sreja

re: Snubbers, time delay relays, and pig tails

The question about pigtails brings up an issue that has always really perplexed me.



Pigtails are talked about as if they are some magical device -- but really wouldn't basically any piping arrangement that held a trap of water work just fine?  As long as you have a piping arrangement that dips down and then back up, so that some water is kept at that bottom of the loop to prevent steam from hitting the gauge, you are doing what a pigtail does, right?

Jamie Hall

yup

but pigtails are so simple...

Rod

Pigtails are better

You can use pipe fittings to accomplish the same purpose as a pigtail (see attached drawing) though as Jamie mentioned a pigtail is a lot simpler and  I think much less likely to collect crud especially if it is positioned so that water drains away from it.

- Rod

Rod

Raise the Controls

Hi- Ideally the Gauges/controls should be located well above the waterline. As you mentioned, where your controls are located now, the clearances are pretty tight. With a pipe nipple and a few fittings you could extend your piping so the controls would be located  in  higher.and a more convenient location.  Check the Mc Master Carr link I gave you as they have all types of pigtail configurations. They may have one that would work better than what you presently have. Get a pigtail in bronze ("Red brass") as they are less likely to corrode.

- Rod

Charlie from wmass

Pig tails offer

Less joints to leak and if you are paying a professional to install an item two threads to seal and tighten cost less than 10 joints, 4 fittings and 5 pieces of pipe. And thats if you do not install the recommended tees with plugs at the low spots.