alternate pressurestat and vaporstat setups

matt_65

I've got a pressurestat that was orignal to the boiler, and a vaporstat that I swapped it out for to keep the pressure lower. There have been some short cycling problems with this setup, and I just replaced the flue damper as it was starting to fail intermittently.

Would there be any problem with putting the pressurestat back as it was originally setup, and moving the vaporstat circuit to the "otherside" of the damper and low water cutoff so that the only thing cycling on pressure is the burner?

This is not only to save wear/tear on the damper, but also to keep the pressure modulated between 4-10oz. In the current setup, the pressure drops so fast that by the time the damper has opened up and the low water finishes blinking the pressure has gone negative for a while and then back to 0, and the system gets filled with air again.

David Nadle

Check out the '24v delay relay' thread

A few folks have the same situation as you. We've been discussing using a delay on break relay to prevent the short cycling.

matt_65

Didn't like the relay's result

Yeah, we discussed this in an earlier thread and I had picked up a delay relay from Grainger, but after a few days I didn't really like the result. The cycles got spread out longer, but it took too long to get to temperature in some cases due to the delay each time.

David Nadle

Sorry to hear that.

Maybe you could raise the cutout pressure a little and reduce the delay.

chuckNJ

works fine

I did exactly this about 2 years ago, after inquiring here see
http://forums.invision.net/Thread.cfm?CFApp=2&Thread_ID=43472&mc=3

I have a W-M standing pilot and this hookup provides very nice binary modulation. How high you let the preasure go gives you some control over just how short the cycles are, how many times you cycle the gas valve. So you can make that trade off. But only the gas valve gets the wear and tear, the damper stays open until the stat is satisfied and thus the response is quick. I put the vaporstat on its own pigtail with my low range gauge, and wired it immediately ahead of the gas valve.

matt_65

Thanks

Just finished testing it here, and it works great. The pressure modulates nicely between about 4 oz and 12 oz no problem, and the temperature seems to come up a lot faster now that the radiators aren't sucking all the air back in between cycles like before.

Unknown

Thanks for the info. I'm now playing with a delay. Just a couple of questions:

1.How long did you set your delay time?

2.Are your mains insulated?

Just wondering because I get(not as much as I'd like) a bit of "coasting" on the pressure after shutoff. I'm wondering how the delay will affect things when it gets colder in January. Please let us know what your long range satisfaction is with your setup.

matt_65

With this setup I took out the delay relay, and just let it short cycle the burner/gas valve a few times instead. I've got fiberglass pipe insulations on the mains, but my pressure coasts for about 5 seconds before dropping like a rock.