50 apartments and not one with the same temperature!

Med618

We own several apartment buildings ranging from 50 to 100 units. All six story, and all but one are single pipe steam systems.



We recently installed a heat sensor system. We have thermostats in all of the top floor apartments and the length of the boiler cycle is dependent upon these thermostat readings(as opposed to before when it was just based on one outdoor sensor). Obviously the result has been shorter cycles which is after all the goal of the system.



But now the tenants are in an uproar. Some were used to 80 degrees of heat and are now only getting 73. These people I can ignore in good conscience. But others have legitimate complaints. Some apartments are downright cold and still some others have remained "window opening" hot.



It would be awesome to get to the bottom of this. Is this most likely a matter of venting? I know there's no way to tell for sure without seeing it or know more about what's going on, but has anyone had any experience with this kind of thing and maybe seen the same pattern over and over?

nicholas bonham-carter

uneven temperatures

get the main [not radiator] venting up to scratch, and monitor the pressure with a good low-pressure gauge gaugestore.com 0-3 psi]. adjust the pressure down to 1.5 psi [basic function], or 8 ounces [econom, and comfort], which will require a vaporstat.

good main venting will make sure the steam arrives at all radiators simultaneously, which is not the case now. the adequacy of the main venting can be verified by the back-pressure on the low-pressure gauge [my 55 radiators, on 3 stories vent at 2 ounces].

how are the new thermostats wired? will a call for heat from one apartment fire the boiler for the whole buiding?

for this size building it would be much better to have something like the tekmar 279 which will run the boiler based on outdoor temperature.

you could disconnect the thermostats but keep them for the tennants to play with [placebo effect]--nbc

Med618

how it's wired

It's wired so that when the majority of thermostats read lower than a pre-set temp(let's say 72 degrees) the boiler will cycle and then when the majority of the apartments are satisfied the cycle stops. It's all controlled and paid for by us. The idea is to replicate a thermostat in an individual house and to give us more pinpoint control



I like the placebo effect idea though!

nicholas bonham-carter

averaging thermostat

i assume the sensors take an average of the temperatures, and fire the boiler on that basis. even more important to get the steam arriving at the radiators at the same time.if these buildings are tall then the risers may need some venting as well. the goal is to prevent extra fuel from having to be burned in order to get the air out. even though the main vents are somewhat expensive, the cost of extra fuel is much higher over the long run.

if there were this same uneven temperatures when the building was first built, the original installer would have been barred from doing any more work in town. just return the system to its original state of operation.

another area to investigate for economy, and comfort is a hi-lo-hi burner for the boiler, and if these buildings are big, their big boilers may already have this feature.--nbc

Dave in QCA

Agree with Nicholas

I agree with all of the points that Nicholas has made, but would like to add to his comments.



5 storys is a pretty tall building and may require riser venting, so it would be helpful to know what the piping arrangement is. 

Do the mains all run around the basement area with risers going up to feed all floors?  Or, does the main go up to the top floor and down feed the floors via down feed risers? 

Are there any main vents? What type and condition are they? 

Are there any riser vents? 

Have the radiator vents been changed?  Are they all the same?  Or, is there a various assortment of types and styles?

It is possible to get this all evened out.  Running very high temps was a band-aide fix of a system that was not working right.

Med618

a real hodge podge

First thanks for the responses and the help.



I think we use a hodge podge of radiator valves. There has not to date been a coherent strategy. I know from reading Dan's book and from these message boards that there should be.



I don't know how the mains run but I am pretty sure that each riser has(or should have) an air valve on the sixth(top) floor. Should the air valves on the riser be a different valve than those on the the radiators?



I don't know about the main vents.

Dave in QCA

riser vents

The riser vents should be "main" type vents, or at least, vents that are VERY fast in the case that they are 1/8" pipe size.



Dave Bunnell's (aka "boilerpro") mantra is, "vent your mains fast and your radiators slow but completely.  In a 5 story building, your riser is essentially a vertical main, so it needs to be vented fast too.  The objective in the main venting is to get steam to the end of the mains before it begins to go into the radiators, thus the steam will arrive at every radiator at or about the same time.  Then, if the radiators are vented properly, each radiator will get its fair share of the steam and your building will be evenly heated.  There is nothing more comfortable than even heating, and nothing more efficient too.