Quick Question re: TRVs

Mark Eatherton

Comfort and conservation. If you don't need it (heat) then you aren't firing the boiler as often.

It will keep people from using their double hung thermostats (a.k.a. windows) and THAT HAS to lead to energy conservation...

ME

FJL

Do Their Use Affect Gas Consumption?

Reviewing the gas consumption for the winter season and was thinking about next season. Would use of TRVs in one or more apt reduce the amound of gas consumption by the system, all other things being equal? Or does the use of TRV simply affect comfort?

nicholas bonham-carter

TRV's and cost of operation

i will take a stab at this by saying that they primarily affect comfort, in that they will not necessarily reduce the run-time of the burner, and therefore its use of fuel.

of course i have stated before that they are only to be installed after the rest of the system is in tip-top shape: VENTING + LOW PRESSURE + THERMOSTAT FUNCTION + BURNER HEALTH. i will certainly be interested to hear other views on this!--nbc

nicholas bonham-carter

good point!

good point about the infamous double hung thermostat. now DHT will join the ranks of TRV et al.--nbc

FJL

Affecting Both . . .

Residents opening the window is not a problem for us. The t-stat is in one apt, where the residents keep the window closed during the heating season. I am thinking more of TRVs in the other apts, which tend to overheat because those apts lose heat slower than the apt with the t-stat. I would think that if the TRVs close off the rad during a cycle, the steam would "skip" the apts with TRVs and travel to apts that still need heat, causing those apts to heat faster than they otherwise would, leading to a shorter cyle run. Not sure how much this would actually save in practice, but that is my thinking.

Mark Eatherton

10 to 15% Reduction has been my experience...

And yes, you are correct, it thermal dynamically balances out the system.

A worthwhile investment in every case I've seen them applied. Will probably end up being mandatory ow that our current administration has recognized the fact that there appears to be an environmental crisis at hand...

Get ready. The fun is just beginning...

http://www.breitbart.com/article.php?id=D97ECHLG1&show_article=1

ME

McKern_2

We have a similar setup, i.e., the t-stat is in a unit where the residents are conscientious about doors and storm windows.

We've been told that turning off radiators in unused rooms can save heating costs, which makes sense on the surface, but I don't see exactly how this works, given that the heating cycle begins and ends based on the temp in the unit with the t-stat.

Similarly, how would the use of TRVs in units without the t-stat shorten the heating cycle?

What am I missing?

J.C.A._3

It depends !

Before you go chasing rainbows.... what is the piping lay out?

It could be the deciding factor.
JMHO? Chris

FJL

Piping Layout

What do you mean? How does piping layout affect what we're talking about?

J.C.A._3

Oh My!

So much to learn!

Ask away. I do know why...but I ain't selling the shop for it.

Do you think I'm that stupid?
Use the Find a Pro at the top of the site.

If you're smart...it will be less expensive in the long run. (time IS money) Chris

Mark Eatherton

thermostat Location, Location, Location...

The t-stat is typically in the central core of te building. When using NETRV's, it should be located in the worse case scenario position, i.e. Northwest corner, top floor apartment.

As for shortening cycles, if rooms are not calling for heat (internal or external gains, including solar, lights, people etc) then the boilers on cycle will be short because it will hit the hi limit pressure setting quicker.

I have some apartments with NETRV's that don't have a thermostat inside the building, but has a sensors outside monitoring the outdoor air temp, as well as indoor temp feedback and it will will cycle the boiler based on the temps. The original complaint on this building was high fuel bills and dis-satisfied (too hot or too cold) tenants. Post retrofit, no more complains, and a 30% reduction in fuel consumption.

ME

nicholas bonham-carter

TRV's saving fuel?

if you have 2 one-pipe radiators sharing a common riser side-by-side, they will each have steam arriving at the same time. each one will heat up at the same rate. if one of them has it's vent closed, then will the open one heat up more quickly? if that is the case, then that radiator needs less run-time of the boiler to be hot [as long as the control system is aware].

as far as turning off radiators, to save money, i would suggest using the air vent to do this, by turning it upside down, as the steam valves frequently allow enough steam in when closed to fill the radiator with condensate, starving the boiler. this a type of TRV with the room occupant as the actuating mechanism.

i do agree that anything which reduces open windows in winter, other than for fresh air [or allowing a trapped bat to fly out the window!!] is a big plus.--nbc

nicholas bonham-carter

uneven heat

by other apartments overheating, are you talking about more than 5 degrees of difference?

as far as piping layout goes, i think a counter-flow system may be harder to put a TRV on, as many of these rely more on oversized rad vents, than in the case of the parallel-flow system. reducing the venting on 1 rad would affect them all.--nbc

FJL

I Don't Think You're Stupid . . .

I answered your question by asking a question, which is very common on this board, at least in my experience. Also, there have been numerous postings about TRVs here and I've never seen any of them discuss piping layout as a factor. So that is why I asked my question.

McKern_2

nbc & ME

I can see how turning off enough rads (closing the vents) or the use of TRVs could cause the system to cut-out on pressure, but if the t-stat is not satisfied, wouldn't this just lead to a round of short cycling until the t-stat temp is reached?

Could it be that while these options (TRVs and closing rads) eliminate overheating, they don't necessarily lead to fuel savings in systems that use a t-stat with a single temp sensor (i.e., the heating cycle isn't going to end until that sensor is satisfied)?

(Forgive me if this is a stupid question--it seems that the more I learn, the more questions I have. I own a condo in a small building (6 identical units, 1 garden unit) with a neglected one pipe system and I'm gathering info for the board. The Lost Art of Steam Heat and the Wall have been invaluable.)

Mark Eatherton

The boiler is oversized for 98% of the time...

It will short cycle until you are at design condition, and then it will STILL short cycle.

You NEVER want to put a TRV in the same room as the radiator that is "seeing" the thermostat. This is what is known as the "reference" radiator on a thermostat controlled system. When using an indoor/outdoor reset, you STILL don't want a TRV on the radiator in the vicinity of the room sensor.

If the rooms don't need heat, then why heat them? Remember, EVERYTHING in the system was sized for "design conditions", and the boiler only knows one speed, ON fully.

If you're not wasting energy, you're conserving energy.

ME

McKern_2

"the boiler only knows one speed, ON fully"

This is the part I'm having trouble reconciling, i.e., if the boiler is going to be fully on until the t-stat is satisfied, how can TRVs (in other rooms/units) result in fuel savings? The boiler will continue to make steam at the same rate.

I can see that with enough TRVs the system will cut off on pressure sooner, but won't the additional short cycling until the t-stat is satisfied eat the fuel savings?

Thank you for your patience.

nicholas bonham-carter

TRV's and run-time

if we have the same 2 rads on a riser as above, they will both heat up at the same rate [the surface temperature of the rad being equal]. if one of them is in a room with an open window, the heat load is increased for the riser, and they will both reach rad surface temperature a little slower, even though one is perfectly insulated and the other not, both are effected by the heat loss in the "cold" room. if the thermostat is in the "warm" room, it will therefore have to run the boiler a little longer to reach the setpoint. just as in this exagerated example, the TRV's make more heat available to the uncontrolled rads by reducing the steam going into the controlled rads. as a result, the rad where the thermostat is reaches its temp more quickly, and the boiler runs less.

just as important in achieving an even temperature is getting the air out as the steam is rising. with good venting on the mains, the steam fills the mains along their length first, before even going up the riser closest to the boiler. if because of bad venting, the steam goes up the first riser before the others, then you have a hot-spot where people may have to open the windows. the cost of one TRV is the same as three gorton #2's, and could have more benefit.

it should be possible to measure the surface temperature of the radiators in different parts of the SAME FLOOR of the building, and check to make sure steam arrives AT THE SAME TIME on each. assuming the venting to be perfect, any final adjustment can be done with the TRV's.

as far as thermostat location goes, Mark Eatherton's northwest top floor location is pretty simple to remember. just make sure that location's weather-proofing is representative of the rest of the building. some taylor wireless indoor/outdoor thermometers will allow you to monitor the temperatures in 4 locations without disturbing the occupants. then you can find out how "too hot" some are. i would never have a thermostat in an appartment, instead i would put a sensor there with the control in a secure area, as "playing" with the stat uses a lot of fuel.--nbc

Mark Eatherton

Have you hugged your boiler today??

Ms. McKern, You need to spend some quality time with your steam boiler... Put that really good book down, put on your coveralls, and go down to the boiler room on a marginal heat call day. Take a note book, a stop watch and a comfortable lawn chair.

Your steam boiler does not run constantly. Unless there is a LARGE hole in the system someplace (air vent stuck open), it CAN'T run continuously. If it is, you need to get an expert in there to take a look at the "system" as a whole, and not just the boiler. As Dan has said a million times, the problem is not usually in the same room as the symptom.

On a marginal call heat day (say around 35 degrees F) make note of the ON time of the burner versus the OFF time of the boiler for a given hour. This will give you an idea of the duty cycle the boiler goes through. You will also need to figure out the normal hourly input of the boiler (in GPH for oil or CCF for gas) and that information comes in handy when resizing the boiler.

Also, make notes of the conditions around the boiler. Is there a need for additional insulation on the boiler system piping? Insulation is a GOOD thing...

We're talking btuH transfer here. Just because the boiler is connected to all the radiators does not necessarily mean that the radiation is operating at maximum capacity. If all the windows were open all the time, you MIGHT be able to fire the boiler and keep it running. You hit a point of equalibrium, with these systems. When the demand is less than the capacity of the boiler, the boiler, if properly controlled, will cycle on and off. Theoretically, when you are at design condition, and everything has been properly sized, the boiler will turn on and STAY on, because demand matches supply. THeoretically being the key word here...

I have yet to see ANY space heating boiler running at 100% of capacity, at design condition, and that includes systems that I designed and sized and know for a fact are properly sized and applied. The most I have ever seen is a 50% duty cycle, meaning that the boiler and the heat emitters are approximately TWICE as large as they need to be. There are a LOT of factors that we don't take in to consideration when doing a heat loss calculation that have EVERYTHING to do with the duty cycles of heating systems. Not enough time to go there...

The bottom line to your inquiry is that you and your community are concerned with excess energy consumption, and applying NETRV's will essentially match the radiators capacity to the real time loads, and that equates to energy savings and a more comfortable occupant.

Once all energy conservation efforts are in place (storm windows, insulation, caulking, NETRV's etc) it MIGHT be possible that the steam boiler can be replaced with a down sized boiler that will short cycle less, resulting in higher seasonal efficiencies.

But you're gonna have to spend some quality time with your boiler at design condition before you can make that decision. Take pictures while you are down there. THey are worth a thousand words.

ME

Henry

It is simple! We did one floor of a commercial steam heated building. The deal was to do one floor per year. The increase in comfort and the emmidiate savings (2 months of the fall heating season) had them call us and do all 10 floors. The payback according to the building operators, was 2 years.

McKern_2

The boiler is common property, so I'm not allowed to hug it.

But I've spent some quality time in the basement and I have some pictures. I know that our system is nowhere near optimal running state. The header and sections of the mains aren't insulated, it short cycles (it would be a walk-on-water-miracle if it didn't--the mains aren't properly vented and the anticipator/cycles per hour setting on the White-Rodgers thermostat is at the factory default, not steam, setting), the 3rd floor runs a couple or so degrees below the t-stat setting, and I don't believe the system's been balanced since the building was converted (~15 years ago). However, when it comes to common property in our building, condo owners can look, but touching is best left for the pros. This is a relatively DIY-adverse group of owners--something that will need to change if we are going to get the most from the heating system. Steam experts are surprisingly rare around here.

The association bylaws make it difficult to treat the system as a whole because ownership is parsed among condo owners. All parts within an individual unit--valves, radiators, vents--are private property, e.g., the association has no say regarding the condition, brand, or size of radiator vents. People have taken to using Veri-vents as sort of a dial-your-own-comfort-level valve. (Living room not warm enough for you? Open up the vent!)

I've been forwarding info about one-pipe steam heat to other residents for the past couple of winters, but I'm sorry to say that I haven't been particularly successful at changing most folk's ideas regarding basic system operation and maintenance. About 14 months ago we had the boiler cleaned for the first time in at least 5 years, but that was only one item on a long list of recommendations.

Attitudes may be changing. Last month the board met with a heating tech regarding balancing the system. Unfortunately, he said during the consultation that he was a hot water pro and that he didn't know steam heat. The board hired him anyway, albeit just to replace the 4 failing main vents--all Dole #5, at least 8 years old.
I forwarded the info from the Wall recommending Gorton #2, nonetheless, the new vents are all Dole #5. I was told that he ordered the Dole vents because he "didn't know how to measure the mains" to determine the correct vent size. Although things didn't go all that well, there is clearly an increased awareness of the work that needs to be done. I'm putting my condo on the market soon, so I may not be here next winter (can't count on anything in this housing market). Another resident is interested in taking up the cause, so I'm organizing my material.

Which brings me back to my original question. I didn't mean to give the impression that I was overly focused on TRVs and cost control while ignoring the basic issues. The intent of my question was to better understand how one pipe systems work. Something is missing in my current understanding of things because I'm not getting how turning off radiators (closing vents) or TRVs result in energy savings in a building with a t-stat/one temp sensor.

Re this from nbc: "if we have the same 2 rads on a riser...if one of them is in a room with an open window, the heat load is increased for the riser, and they will both reach rad surface temperature a little slower." I can see that the rad in the room with an open window will draw more steam (since it's condensing more steam) than the rad in the room with closed windows. However, assuming the boiler is at least slightly oversized, wouldn't it crank out enough heat to meet the demands of both rads?

(I believe this is related to a question a asked a couple of years ago. I was told that missing storm windows in units without the thermostat would not have a significant effect on heating costs (given a t-stat located in a relatively weather-tight unit, rapidly vented steam mains, a slightly oversized boiler) because the heating cycle will begin and end based on the temp in the unit with the t-stat, and the boiler is cranking out heat at the same rate whenever the burner is operating. In short, the building would be leaking heat, but there was no way to use this "lost" heat to more quickly satisfy the t-stat. I also posted the question on the Wall (http://forums.invision.net/Thread.cfm?CFApp=2&&Message_ID=301759&_#Message301759). If I'm reading Brad White correctly, colder units could affect heating costs, but not significantly so.)