How to use a VXT water feeder as a delay timer?

AdmiralYoda

So....I've been wanting to get a delay timer to tame my 40% oversized boiler from short cycling when it's cold out.

I've also wanted to add an automatic water feeder to better keep track of make up water.

@Jamie Hall and @Gordo have been using the VXT for both.  I'm just a little confused on how to set this up.  Here is my thought process...

1.  Install the LWCO probe as close to the middle of the sight glass as possible.
2.  Fill the water so it's an inch or so above the probe.
3.  Wait for a cold day when the boiler is making pressure and likely to cycle.
4.  Let's say I don't want to develop more than 4oz of pressure.  So wait until the gauge reads 4oz....then drain water out of the boiler until the probe cuts in.

Then 10 minutes would pass....the condensate would return to the boiler, and if the thermostat is still calling for heat it will start all over again.

Am I on the right track or am I overthinking this?  My other concern is what happens when the water level drops a little over time?  Do I manually  maintain a certain water level so everything works right?

Thanks guys!

Mark N

I would think you would need to use the Hydrolevel Cyclegard LWCO intermittent level test. The VXT I think only feeds water if the LWCO detects a low water condidtion.

ethicalpaul

Yeah I can't imagine trying to put the water level just above the probe in some attempt to have the probe shut down the boiler due to low water as some kind of modulating system.

Jamie Hall

Bad practice. You would be trying to use one safety or control device to control a very different parameter -- not unlike using the brake pedal or ignition switch to control the speed of you car while keeping your foot flat to the floor on the accelerator.

If you want to use a delay timer based on pressure -- which does work -- use a delay timer based on pressure. And use a vapourstat set for the desired pressure (4 ounces is probably too low, even or a vapour system).

AdmiralYoda

I was originally going to install a delay timer like the one @PMJ uses, but that might stump a tech in the event I wasn't there to explain what it was doing.  

acwagner

I would do a delay timer over the Cyclegard. The cycle guard has fixed times depending on the model. The dwell time is only 60-90 seconds.

If you're concerned about a tech not understanding, you could label the timer and/or have documentation nearby showing the boiler operation sequence. That's not bullet proof, but I would think a decent tech would notice.

AdmiralYoda

Maybe I should describe my problem a bit more clearly..

My boiler is 40% oversized.  So when it's cold my boiler will keep running even though the radiators are hot.  The p-trol will cut in at 1.5psi....go back to 0.5psi and will turn back on until the thermostat is satisfied.  It's a waste of fuel.

In these conditions it takes about 20 minutes to make 4-6oz of pressure and the radiators are getting pretty hot.  At this point I'd like the boiler to turn off for say 10 minutes while the radiators continue to heat up the room.  If after 10 minutes the thermostat is not satisfied it will start all over again.

The Vaporstat does this....but not with a time limit.  Using a delay timer allows the radiators to be a bit regulated so they don't overheat the room and waste fuel in the process.

BTW I have a 1 pipe counterflow system.

ethicalpaul

When would a tech be there without you? Is this your home?

AdmiralYoda

@ethicalpaul, probably never.  In the event there was an urgent need for a tech and I wasn't home and my wife had to let him/her in.  A quick diagram/label would probably be enough.

acwagner

A timer is a good solution.

I have mine in series with the thermostat. It's not off my vaporstat. I have the timer set log enough that on a normal call for heat, the thermostat is normally satisfied before the burn timer ends. it only comes into play when recovering from a setback.

SteamingatMohawk

You guys are making this too hard and are too short sighted.

@Jamie Hall I generally agree with you, but not in this case. The function is built in to the device by a well known manufacturer and works well. It's not a homemade solution. So I respectfully disagree with your statement.

The intermittent level test has worked for me for 20+ years without fail.

The 10 minute time between tests and 90 second pause has allowed the pressure to go to 0 in my oversized system. There's a 20 minute time and 90 second pause option available. This is essentially the same as a time delay relay/timer. The only disadvantage is it has only one set of parameters.

It completely avoids the DIY risk and AdmiralYoda is not going to own the house forever.

If the boiler has a LWCO with a probe compatible with the Cyclegard, it's probably a simple matter of swapping out the external parts, if the probe is in good condition. If it's another brand, I don't know what would be required to change to the Cyclegard.

Installation instructions are here:

https://hydrolevel.com/wp-content/uploads/2018/12/CG400-Instructions-web.pdf

My steam system is in a 90+ year old 2 family house that was converted to 4 rental units and I have been flabbergasted by the lousy work done on the house in the past, including a really lousy replacement of my boiler by a plumber who I knew personally and trusted. In the last couple of years, once I found HH, I got tremendous help in undoing the "crimes of the past" and now have a well balanced system. You can see that in my other discussions.

I urge everyone to not advocate homemade modifications, that might invalidate insurance if there ever is a problem. Insurance companies look for any way out of paying.

ethicalpaul

My cyclegard is a 60 seconds every 15 minutes model and if my boiler were oversized, that just wouldn't be enough to have a meaningful affect. I also don't feel I'm shortsighted

I have just implemented a delay timer on my thermostat circuit just as @acwagner described and it's quite good.

SteamingatMohawk

I'm not debating the technical aspects at all. There are many ways to do it.

Maybe because I have owned some old houses in my lifetime and seen some weird stuff, plus being a landlord, that I could be considered obsessive about legal liability and have a different approach.

My comments about future ownership started when all these smart home wireless gadgets started invading life. While they are nice whiz-bang thingys, what happens when those houses are sold. How is the operating knowledge transferred to the new owner? Who ever bought a non-new construction house with all the technical information on the devices in the house? What will it be like in 10 or 20 years?

That being said, I have two remotely operated devices for my apartments, the thermostat and a camera. I don't live at the house, but can access them remotely from my phone. Those work for me.

Please don't be offended.

SteamingatMohawk

Maybe you and @acwagner could get together and market your solution.

acwagner

I don't take credit for it. I found it here on HH in an old post by @PMJ. I personally think it's a safe and straightforward solution, but I understand not everyone will be comfortable wiring it up on their system.

But, I am curious @ethicalpaul did you put the timer on just for curiosity? I assume your boiler isn't oversized since you just installed it.

PMJ

AdmiralYoda said:

@ethicalpaul, probably never.  In the event there was an urgent need for a tech and I wasn't home and my wife had to let him/her in.  A quick diagram/label would probably be enough.

Diagrams are important. I have one on my boiler that shows how to bypass my control altogether and return to standard control.

You can also wire in a bypass switch while installing the timer and label it so one flick of one switch and your timer isn't there anymore.

ethicalpaul

acwagner said:

I don't take credit for it. I found it here on HH in an old post by @PMJ. I personally think it's a safe and straightforward solution, but I understand not everyone will be comfortable wiring it up on their system.

But, I am curious @ethicalpaul did you put the timer on just for curiosity? I assume your boiler isn't oversized since you just installed it.

It's just slightly oversized. It was the smallest Peerless available so I was constrained a bit. It gets a little bit more oversized because I do shut off a radiator in a storage room, and I sometimes turn off the radiator in my bedroom to keep it a bit cooler in there.

But even with that, I have never seen it get to 1.5 psi, so the new boiler has never once cycled on pressure due to the pressuretrol. The highest I have seen it is maybe 1.25 psi on a very long recovery that I was doing as an experiment. I think it would stay there indefinitely, especially with my Cyclegard interrupting it every 15 minutes.

But I started to get annoyed even by a .5 psi pressure buildup. It only happened when all the radiators were full of steam and I couldn't stand the idea of burning all that fuel just to keep the radiators full.

Then I even got annoyed by a 5 inches of water column pressure buildup for the same reason. That's just .18 psi, but why? Why not turn off the boiler and let the radiators give off their heat for 15 minutes, then start up the boiler again if necessary?

So I put a 15 minute delay if the system hits 4.5" WC. It only happens on a recovery from setback. I'd like to see how it would work for someone with a real oversized boiler.

Jamie Hall

Actually, @PMJ and I have gone around the houses a few times on this -- not on the use of the timer, but on how much fuel -- if any -- cycling on pressure wastes in relation to turning the boiler off for a fixed period of time and then turning it back on. Unhappily, I know of no actual, real world studies which address this matter, which means I can only address my observations on Cedric -- which isn't particularly oversize, and which, therefore, may not be generally applicable.

If Cedric cycles on pressure, which he will after about 45 minutes into a recovery from a 3 degree setback, my observation is that he will run, once cycling starts, for about 3 minutes with the pressure holding at 4 ounces. Then pressure will rise to about 6 ounces, and the vapourstat shuts it off. Post purge and pre purge together take 30 seconds, by which time the pressure has dropped to about 1 ounce. The burner refires and steam production (which never quite stopped completely) starts again and the pressure goes right back to 4 ounces and holds. Rinse and repeat. There is no time when there isn't at least some steam production, and there is no fuel wasted at all. If Cedric has been off for, say 20 minutes, it will take about 3 to 5 minutes of firing before steam production begins. As has been pointed out elsewhere, that 3 to 5 minutes, while not wholly wasted heat, is not involved in useful steam production. It will take another 5 minutes before all the radiators are receiving steam.

My own feeling -- and, as I say, I have no real world hard measurements to base this on -- is that cycling on pressure during a call for heat does not waste fuel, while a forced cool down during a call for heat (which is what the timer does) does.

Note too that this is not related to the phenomenon of residual heat in the radiators causing space temperature overshoots. Cedric is blessed with a thermostat with an accurately calibrated anticipator, so neither significant overshoot -- nor on delay (undershoot) occurs. But this is a different problem in control entirely.

For what it's worth; your mileage -- or preferences -- may vary.

PMJ

For what it is worth, I have never argued that forced shutdowns to avoid pressure will result in great savings. On this I think @Jamie Hall and I agree. The only way I see to seriously increase costs is to run for long periods at elevated pressures - which with an oversized boiler is pretty hard to do without roasting everyone.

I usually find myself defending this method of operation against claims that it causes a dramatic drop in efficiency, which after years of even or dropping gas consumption I am quite comfortable saying is not the case. The gains in time to steam because the boiler has been off a shorter period of time basically equals any losses from more starts or close anyway.

So my whole reason for running this way is for comfort. Those who I have worked with on this all had comfort issues as the main complaints. They simply are aware that their radiators are boiling hot and vents making noise and they know the boiler might as well shut down and wait a while but their control doesn't. That is all.

There is no denying the heat is more even running with more evenly spaced cycles- if only from the radiant side of things experienced by those in the room because the radiators have a much smaller range of temperature change and shorter off periods so radiators never return to room temperature.

Bottom line I think a reasonably well balanced system run either with spaced cycles or longer ones pressuring out a single digit percentage of the total elapsed time will not be all that different on efficiency. If big savings of fuel is your goal I think you will be disappointed. However, large gains in comfort with oversize boilers can be had this way - and vacuum can provide significant improvement beyond that.

Jamie Hall

Agreed, @PMJ !

AdmiralYoda

I have been meaning to install a Vaporstat to complement my P-trol.  Maybe just having it cut in at 6 or ounces.  It will still cycle on pressure, but much lower pressure.

More pressure = more fuel right?  And I'm sure my 37 year old boiler would like running at a lower psi.