pressure for 7 storey bldg

john_58

I just started the daily management of a seven storey building. They have the pressure for the heat (water) set to 38 lbs cold, and up to 45-50 lbs hot(210F). There are 4 AOSmith 680btu heaters with relief valves set at 75psi. I thought it was a high setting, but they claim its been like this for the past 20 years. Any input would help.

Steve Paul

A pressure of 38 PSI will raise the water to a height of 87.78 feet. If you figure 12 feet per story the actual height is 84 feet. So the 38PSI setting is workable, perhaps a little on the conservative side. 40 PSI would make me feel more comfortable.

oil-2-4-6-gas

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i think i would be more concerned with the temperature than the pressure --210 is too high -the gage might be off but it should be calibrated and verified accurate -if this reading is correct that might be the reason for the high pressure ---or you have expansion tank sizing issues//// you need a service tech to check your expansion size ,, location--and calibrate the temperature gage set it below 210*

john_58

Thanks for all the input. Ceiling heights are 8 ft with about 1 foot solid concrete floors in between. So I guess they are pretty close. The reason for 210F (max) is that they are having a hard time keeping it warm. The boilers themselves are set to cut out at 220F but apparently the outlet temp about 10 feet down from all 4 heaters will hit 210F max. There are 6 thermometers located in and on the plumbing, all are reading within 5F. The expansion tank is huge and located on the top floor, the glass on reads about 2/3rds full of water.

oil-2-4-6-gas

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you should look into tightening up the building,insulating pipes take care of drafts ,,replace the windows --its time for some new equipment--if its not keeping up in this weather -its gonna be a long winter // did this system ever work,,how was it last season?

john_58

Well.... within the last three years all the windows have been replaced the AOSmith heaters and tekmar controler are new (2002), and the roof was replaced in October with an additional R20 from nothing at all before. The baseboard style rads are cleaned frequently as well. Would insulating the pipes in the boiler room (only access is here) help? The main pipe is about 8 inch dia. and totally uninsulated. There is about 20 feet exposed here.
And no, the heat has never been sufficient, at some point, extra rads have been added to existing to help colder apartments, probably at the detrament to apartment downstream. When its cold it is hard to keep the apartments at the legal level (70F). They have been subsidising for decades with electric heat. They are obviously trying to fix this, but they would like to shy away from siding. The building is 1964/5, concrete/brick veneer with MAYBE 1 in syrofoam insulation. Thanks again.

oil-2-4-6-gas

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you need more BTU's ----you cant add more radiators if you don't have the output----- if it's been a problem since the first season sounds like you are undersized --unless you are operating a 3-way valve and you have other issues ---i would have the meter clocked and see what you are actually burning if they want to fix the problem --find out what the actual input BTU's you have, not the rating of the units, get them tuned and running efficiently as possible ---if they are running where they should be ---well problem solved--just add more units

john_58

Thank you very much! Seems simple enough and cost effective. Each existing unit is rated at 590 input btu, i think, and there are four of them for this 61 suite apartment building. The return water is coming back at 170F (at the max) though. Would adding size to the rads in the problematic suites do the trick, or is this causing other problems. PS This board rocks!

oil-2-4-6-gas

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i'm talking about more boiler not radiators you need a pro-to check it out --check the controls do a heat-loss calc and see if you have enough boiler and baseboard ////check and size pumps correctly

john_58

Will do, thanks again.

jerry scharf_2

If I read it right...

You have a 40 degree delta T (210 out, 170 back.) That sounds like a bit of a flow problem. If you get the delta T down, you may find you hey more heat output on the radiators (higher mean temperature.) I think it would be hard to figure out the flow without spending some time on site with the pipes.

just a though,

jerry

Mark Eatherton1

I second Jerry post...

There are only a few things that will muck up a heating system, and in my experience it is RARELY an undersized boiler. More than likely it is a poorly configured system, or a system that has never been balanced, or pumps that have been changed to a lesser capacity,or a lack of swing checks on parallel pumps. Raising the operating temperature is generally the worst thing that could have been done, but is generally the FIRST thing to BE done. It's called the "turn it up" syndrome. It usually pushes the problem a little further up the hill, but never really fuly addresses the issue.

Water, by its nature, is generally wet, lazy and stupid. Just like my ex-son-in law :-) You have to show it where YOU want it to go. Given the opportunity to make up its own mind, it will always follow the path of least resistance back to the pump for another ride. In your case, with the delta T being so wide, I suspect a grossly undersized pump. The only way you'll figure it out is to re-engineer the system, from scratch. Loss calcs, flow requiremens and pressure drops.

What kind of heat emmitters are we talking about here?

You may have to hire an expert to come out and take a good long hard look at your physical plant, but it should pay for itself in increase comfort and lower utility bills. Running the system at 210 degs. F is only masking the real problem, and could create a dangerous situation because the water could flash to steam at the top of the system if the pressure drops too low. I'd keep the pressure at around 50 PSI.

ME

bb

find a pro

John, it seems to me like a good idea to have a pro come out to your building and check the system out. There are a lot of things to consider as you have noticed from the other posts.

click on the "Find A Pro" link and enter your zip code.

bb

john_58

Thanks everyone for your input. A pro is a must, I just need a little knowledge to convince the owners that this system can work. It really is just borderline now - real close to what it needs to be. Unforunatley the local pump/heater guys have not helped too much. We are in Toronto, Ontario. I think I have found someone who is quite good though. Will assess after a real diagnosis. Sincere thanks to all.

Jeff_38

Toronto Heating Technicians

John
if you are still looking

Jeff_38

Toronto Heating Technicians

John
If you are still looking for a quality heating technician in the Toronto area to help out let me know. I can give you a few names to contact.

john_58

Thanks Jeff! I do have someone right now, but I wouldn't mind having a back-up. I run a few small buildings and a good heating guy/gal is worth knowing. Thanks again.