Temperature Cycle / Multi Zone

SeanF

Hi:



We are entering our fist winter in a new house (New to us, built in 1940) and the house has steam heating system with a fairly new boiler. I've never had a house with steam heat before and I have a couple questions:



The Boiler is a Burnham V8 Series, KV89, Low Pressure Boiler, which was new about 10 years ago, 2000. I have a programmable thermostat (Honeywell RTH2410) which is set to 65 when we're in the house and 58 overnight and during the day.



The house is about 3,000 sq.ft, is well built and seems pretty tight. When it's 30 degrees outside and the heat comes on at 6:00 PM to bring the house back to 65 degrees, the heat doesn't need to run again until 6:00 AM and in that time, the temperature has only dropped to maybe 60.



1. With Steam heat, what's the most efficient temperature cycle? Is it better to have the difference greater so that the heat comes on fewer times but needs to bring the temperature up from a greater deficit? Or is it better to have the difference smaller so that the heat runs more frequently but for shorter periods?



2. The House has only one zone of heat and the thermostat is in the front hall, near a large living room. The bedrooms, upstairs, get much warmer and are heated at times when they are not used that much. The only way to regulate the heat is by adjusting the valves at the radiators themselves and this is far from an exact science. Does it make sense to divide the heating into multiple zones? Is there a limit as to how many zones are advised?



Thanks

nicholas bonham-carter

how much setback?

if you do a search here for "setback", you will find varying opinions as to the amount of setback which will actually save money on fuel cost. sometimes, the energy used in recovering the higher temperature, is equalled by the amount save during the low temperature period. obviously, if you will be away for a week, there is the potential to save fuel for that length of time, but for shorter periods of less than 1 day, it may be better to choose a constant 64 deg or so, and leave it at that.

is the thermostat near the front door, influenced by drafts? it could be moved to the upstairs bedroom to maintain a constant temperature. has it been set for steam, at 1 CPH?

is your system 1-pipe or 2-pipe? on 1-pipe systems the inlet valves should never be closed except for service work, and cannot be used for temperature control. where bedrooms are unused for long periods of time, TRV's can be installed to control the output of individual radiators.--nbc

BobC

Hot upstairs

Sean,



Steam heat does not like large temperature setbacks, anything over 5 degrees is not desirable and many hold the temperature should remain pretty much constant. The thermostat should be set to 1 or perhaps 2 cycles per hour, and if a temperature differential is offered it should be set low (2-3 degrees).



Is this single pipe steam? With single pipe steam you have one pipe going to each radiator and there is a air vent about half way up the other side that allows air to escape but snaps shut when it senses steam. IN SINGLE PIPE STEAM THE INPUT VALVE HAS TO BE FULLY OPEN. The overheated bedrooms can be a venting issue, the air vent on the end of the radiator should be slow (lower venting rate) so that radiator heats more slowly. Another method is to use a thermostatic valve on the air vent so it shuts down the flow of steam to the radiator when a preset temperature is reached.



If this is two pipe steam with a pipe coming out of both ends controlling the steam with the input valve helps but it's more effective to use a themostatic control valve at the input to shut the steam down when the room reaches a preset temperature.



In either case the location of the thermostat could be an issue if that thermostat is below an open stairwell. That location works well in some houses and not so well in others. Heat rises and you might want to sense the heat someplace that is a little less open so you don't flood the second floor with rising heat from the first floor.



If your new to steam heat you should consider buying some of the books offered under the SHOP heading. A sad fact is there are not a lot of qualified steam contractors out there. It's important that you understand your heating system so you can tell the contractors what is wrong and then judge their level of knowledge by the response you get. This package deal will give you all the information you need to get started - http://www.heatinghelp.com/products/Super-Deals/14/129/A-Steamy-Deal



Bob

SeanF

One Pipe AND Two Pipe temperature control

Thanks for your comments. Seems the more you know, the more you realize you don't know.



Our system seems to be both two pipe and one pipe. The radiators in the second floor bedrooms and bathrooms are all one pipe. The radiators in the first floor bedrooms are one pipe, but the radiators in the dining room and living room are two pipe... Is that unusual?



I have reset the programmable thermostat to high/low of 65/61 and Have rest the cycles to 2/hr. (that's as low as it will go)



So, if I need to open the one pipe valves all the way, the bedrooms are going to get really hot. Moving the thermostat upstairs might help but then the living room will be too cold. Regardless, there will be a big temperature difference. Or... could it be that by opening the valves, the system will be more efficient and "even itself out"?



Question: What happens if I don't open the valves all the way? Will that hurt the system? What if I want to shut off the heat in rooms that aren't used for weeks at a time? (The kids are in college)



Finally, most of the bedrooms has two radiators, so if I install "thermostatic valve on the air vents" to regulate the heat, how would that work? I would need two thermostats in each room or one thermostat to control two radiators? Sounds expensive.



OH, also, just another tidbit of information.... The house has tankless hot water so the boiler fires on occasionally to heat the water, not sure if that's significant.



Thanks again

jpf321

valves and TRVs and Hoffman 1As

For your 1-pipe rads .. the floor rads should be either fully open or fully closed .. and even when they are fully closed, they are suspect. This is because the water and steam share the same pipe/valve in 1-pipe operation .. if you restrict the space for them to share, they unpleasant things could happen .. but you won't necessarily break anything, but it really shouldn't be done.



In terms of TRVs .. thermostatic radiator valves .. for 1-pipe systems, go on the vent side of the radiator .. and they restrict the release of air from the rad, and therefore the inflow of steam. The restrict this flow based on the ambient  temp of the room .. it takes a few days of trial and error to dial them in .. however, once dialed in, the rooms, in theory should not overheat. For 2-pipe systems, they perform the same task, except they are installed in place of the radiator inlet valve (in 2-pipe you are allowed to adjust the since there is no sharing of space and you are only restricting inbound steam, not outbound water) .. again once dialed-in the 2-pipe TRV closes the valve to inbound steam when the ambient temp hits desired temp.



Another way to "cool down" rooms that seem to be overheating on the 1-pipe rads is to install vents that decrease the flow of outbound air. Adjustable vents exist and cost less than TRVs .. for example a Hoffman 1A vent will allow adjustment: http://www.simplyplumbing.com/hoffmanspecial-1a.html .. SLOW means let steam come in slower, hence heat slower.



For rooms that are going to go unused for significant lengths of time, the preferred way to shut down a 1-pipe rad is to turn the vent upside down. this SHOULD, assuming it is a working vent, close the vent and not allow steam entry, or at least just a little, to the rad.



Leave those floor valves wide open in 1-pipe rads.