VAPOR STAT

Tom51

Morning Folks,
What are the vapor stat options besides honeywell L408J1009?
Missing the old merc style that seemed to last forever.
These mechanical models.... well lets just say we need a different type.
Thanks for your input

JohnNY

This is an odd post, but I have to say I agree. I wish there were other options for the fine control of something running at very low pressure. The sliding scale indicator alone is so out of date.

Jamie Hall

The old mercury models did indeed pretty much last forever, and were very precise. The change to microswitches was not an improvement, mostly because the microswitch tripping force isn't always exactly the same. This degraded the precision. Neither one, however, was or is necessarily accurate as it comes out of the box, and for that reason it is a very good idea to calibrate them against a known good pressure gauge. The mercury switch type is can be calibrated, but is usually only necessary to ensure that it is actually level and stays that way. The microswitch type has several different ways in which it may be calibrated.

If you don't take the time to calibrate them, then problems will occur -- but don't blame the device.

EBEBRATT-Ed

Mercoid probably has something. Would cost $$$$ though. I had thought someone had posted on here about Johnson Controls (Penn) but maybe it was not a vapor stat

mattmia2

Dwyer probably has something that could be used as the operating control with a vaporstat for a safety backup.

109A_5

If you want a Honeywell Mercury Vaporstat check out eBay there is a bunch there now, 5/13/2022.

Dwyer has a few Mercury type pressure switches, Series AP, Series DA, Series PG. As a safety switch they may work fine. As a method to tame an oversized boiler, maybe not so good. These Dwyer switches have a very limited and narrow (in some cases non-adjustable) Deadband, Differential or Hysteresis (what ever term you prefer). Honeywell, to me has a niche market, Dwyer is maybe more general industrial. With the addition of a delay timer the Dwyer switches above may work OK, but that is more stuff to fail.

If I had an oversized Boiler I would probably go with a Dwyer Photohelic switch and leave the Honeywell micro-switch stuff for Safety only. Again more stuff to fail, but I like gauges, and gauges with easily settable limit switches is all the better (for me).

Mercury use is maybe political, enough said.

Jamie Hall

Part of the question is that lovely tradeoff between accuracy, precision, reliability -- and cost. If you are building a rocket to send a man to the moon and get him home, you need the best of the first three -- and cost was no object.

But controlling a residential steam boiler? You do need reliability, yes. Microswitches are pretty reliable. But you don't need either precision or accuracy to the milliounce. If you can control the boiler to within an ounce or so, you're fine. You can spend a lot more for greater precision and accuracy, if you like -- the sensors and controls are certainly available, and are used for some purposes. But why?

Perhaps we all got spoiled by the mercury switches? They combined all three desirable characteristics at very low cost. But we can't have them any more, and that's that. Did we need that level of precision and accuracy? I'd argue we didn't for most applications, and that cost and reliability should be what we are looking for.

ChrisJ

If I wanted, or needed precision I'd go for a Dwyer Photohelic A3000 series. But you may need to incorporate a delay timer with one.

But I'm betting no one will want to pay $582 for one.

But they're accurate and repeatable and reliable.

mattmia2

Doesn't dwyer have electronic systems too where it is all adjustable? Or maybe just a pressure transducer that works well in that range an a plc.

ChrisJ

mattmia2 said:

Doesn't dwyer have electronic systems too where it is all adjustable? Or maybe just a pressure transducer that works well in that range an a plc.

Probably, but I honestly don't know.

All of it is too expensive for the typical heating system though and honestly really not needed.

BobC

I got a NOS mercury based vaporstat on ebay over a decade ago and switched it over to my new boiler when the Burnham v75 puked. Mine is more then accurate enough but what endears me to it is it's reliability and repeatability. As long as it's level when hot your good to go.

Bob

mattmia2

ChrisJ said:

mattmia2 said:

Doesn't dwyer have electronic systems too where it is all adjustable? Or maybe just a pressure transducer that works well in that range an a plc.

Probably, but I honestly don't know.

All of it is too expensive for the typical heating system though and honestly really not needed.

You could do it with a transducer and raspberry pi for under $100 or a used plc and transducer or even an fpga. Upper limit safety is easy. Lower limit is harder since you dont want no heat if your unlisted control fails.