Better to come up from setback in one shot or 2 stages?

mrfusion

Hello, I tried reading through the forum and couldn't find a conclusive answer. I have been running our heat at 60 during the night and 64 during the day.

I noticed some of the vents were making noise in the morning coming back from the setback. They're all Hoffman 1As and most are fairly new. There are a few that seemed to be opening briefly once in a while when the radiators were getting steam. One seemed to have trouble sealing and was just making enough noise to wake us up in the morning. I swapped that one out with another new one and it had the same amount of noise. It wasn't opening like some of the others, but just making noise like it wasn't sealing perfectly.

I got up early the other day and looked at my 3psi gauge and the system was reading a consistent .26 Psi, which is about 4oz of pressure. That seems to be ok from what I understand. I also have seen discussion that creating pressure if just wasting energy. I don't see any pressure during normal daytime operation as the system maintains 64 degrees. Pressuretroll is set as per recommendations on this forum, but the pressure isn't enough to trip it anyway.

So, I thought I'd try doing a 60-62 stage and then 62-64 with a pause between the two, about an hour, so the system would run a shorter cycle and not create pressure. This morning the system seemed to be less noisy. I have not gone down to watch whether it generated any pressure yet.


I realize the problem may just be that these vents are not the quietest. The question is whether I'm using more fuel by putting a pause into the adjustment from 60-64.

Thanks!

Jamie Hall

I the system isn't cycling on pressure towards the end of coming out of the setback, I doubt that doing it in two stages instead of one is going to make much difference. Either to the noise -- or to the fuel usage.

AdmiralYoda

If I have a setback more than 2 degrees my boiler cycles on pressure.  I've found that leaving it at a single temp is easier on the boiler and doesn't make a difference in fuel cost.

Maybe I could save $10-15 per month with a setback, but my 37 year old boiler would be working it's a$$ off cycling under pressure.  The savings isn't worth the wear and tear to me.

mrfusion

Thanks for the comments.

I need to see if the system is always quieter in mornings, but this morning it seemed to be because I wasn't putting pressure on the vents during each 2 degree rise cycle.

Isn't bringing it up in stages going to keep the boiler from having to work as hard because the cycles are shorter? My boiler is also probably 37+ years old (I'm not exactly sure how old). Or is one long cycle more efficient?

I guess it could use a little more fuel in 2 stages because it has to get the water boiling again and push the air out of the system again, even if it does it fairly quickly.

I've never seen this system reach high enough pressure to trigger the pressuretroll.

ethicalpaul

I run only a small setback, so I do it at once.

But if I ran a larger setback, say more than 4 degrees, I would do it in two stages. This would be to let the radiators, probably getting nearly fully hot, radiate their heat into the living space. Then a second stage maybe an hour later.

The boiler would still be hot and the radiators would still be warm probably.

PMJ

Well balanced systems don't ever need any pressure to heat. If you simply put a limit on the maximum straight burn time the boiler is ever allowed, and also a minimum wait time between those burns, no pressure can ever develop, setback recovery or not. Just spreading things out a little solves a lot of problems.

One should not conclude that using setbacks must be abandoned because they must necessarily include noisy and pressurized recoveries. They don't.

mrfusion

Thanks, so are you concurring that my approach is good?

PMJ

mrfusion said:

Thanks, so are you concurring that my approach is good?

I am agreeing that any form of spreading things out to eliminate a pressure condition is better - like yours.

Fundamentally your fuel cost is the btu's required to replace what is lost to the outside. What is lost is directly related to the average difference of the inside and outside over time. Setbacks reduce that difference and therefore the total fuel cost, unless all the recoveries are done in a pressurized condition.

Pressure always wastes money. And from what I read from one pipe operators pressure is noisy too. Using a programmable thermostat to spread out the recovery will help some to eliminate pressure. I am talking about a more direct control of the burn cycles with a timer which would make pressure impossible no matter what you are doing. That approach requires a well balanced system to begin with though.

ethicalpaul

mrfusion said:

Thanks, so are you concurring that my approach is good?

Yes, I think it’s good. I agree with @PMJ that any pressure is wasteful.

I’ll even go so far to say that continuous firing in a properly sized system with no pressure gain can be wasteful. It takes time for radiators to give up heat to the rooms. You don’t need to be firing with fully hot radiators in a recovery situation. 

Your stepped approach will give the heat time to transfer

PMJ

ethicalpaul said:

mrfusion said:

Thanks, so are you concurring that my approach is good?

Yes, I think it’s good. I agree with @PMJ that any pressure is wasteful.

I’ll even go so far to say that continuous firing in a properly sized system with no pressure gain can be wasteful. It takes time for radiators to give up heat to the rooms. You don’t need to be firing with fully hot radiators in a recovery situation. 

Your stepped approach will give the heat time to transfer

I'm very glad to finally be reading this @ethicalpaul. You are quite correct, though I would add that you don't need to be firing into nearly full radiators in any situation. The standard control fills radiators way past what is required for the conditions on every firing even if it doesn't get to a place of pressure. This then requires a longer off period while all that heat dissipates, during which the entire delivery system fills with air and cools down. Every cycle then has a colder start. I have found this roller coaster of heat to be wasteful - definitely more so than the extra cycles required to even things out and have warmer starts a higher percentage of the time.

This is also what people seem to miss about vacuum operation. Vacuum keeps the delivery system dramatically warmer which dramatically reduces time from fire to actual steam delivery all the way to the radiators by many minutes each and every burn cycle.

ethicalpaul

I knew we’d get to the V word 😉

Id love to work with it but I just can’t find a check valve with a .25 inches of water cracking pressure!

I agree that waste can occur well before the rads are fully hot, but thought I’d start there with my heresy 😅

PMJ

ethicalpaul said:

I knew we’d get to the V word 😉

Id love to work with it but I just can’t find a check valve with a .25 inches of water cracking pressure!

I agree that waste can occur well before the rads are fully hot, but thought I’d start there with my heresy 😅

I know, and it's a shame they aren't available. I'd be doing the air lines - that's how much better I think it is. I agree with Hoffman that air is "the heat thief". See attached - you probably have already but never hurts to read again.