6 story Townhouse relief valve leeking

Unknown

I can't seem to remember how much head pressure is required per foot/floor when increasing water pressure to reach the highest radiators in a building?

I'm guessing I have to raise the fill water aproximately 70-80 feet high. The pressure gauge only shows I have 25psi in the system but, I don't actually know how accurate that is.

My question is, when is it acceptable to increase the pressure relief valve rating when working on hydronic systems that require elevated pressure.? The 2 CI boilers in "the pit" are about 30 years old and the owner told me that his insurance company wouldn't insure the townhouse if the relief valves were rated anything above 30PSI. (Old pipes & cast iron radiators throughout all of the building) This is a very, very old building.

I found (on the pit floor) a couple of Watts M3s rated for 50 PSI. They were replaced with 30PSI relief valves. In an attempt to stop the constant flow of water that ebs & flows from one of the two relief valves, the last guys installed TWO additional diaphram expansion tanks bringing the count to THREE expansion tanks of various sizes. Why would they do this?

The owner has expressed to me that he wishes to update the heating system with something more modern. I'm thinking that the use of a condensing heat source would make the most sense with all the mass upstairs. However, I can't imagine sleeving an 80 foot chimney in downtown Boston. No place to side wall vent as the units are attached on both sides.

What would you guys reccomend?

Gary

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install the new boilerNSTALL THR

on the upper level!

I wouldn't change the relief valve without written permission from the manufacture.

hot rod

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Kal Row

you did not gve your

ibr heat loss value so i dont know what you BTU needs are

as for the pressure you need, based on your height
6 stories + basement = 5.8 * 7 = 40.6 and the
the relief valve has to be at least 10 more
i would personally would set the pressure at 50 with the relief at 65

that pressure puts you now in the commercial world

you could try 2 slant-fin caravan units designed for up
to 100psi
http://www.slantfin.com/prod-caravan.html

with two units staging, you could go for 1.5 time your btu needs and later do other stuff, like indirect domestic hot water, snow melt (via flat plate heat-ex of course)

dont fool around with this setup, this should be done primary, secondary, mixing, differential pressure bypass, the works - gas is up 70% more lan last year, and keeps doing this every year, you want to spring for all the modern goodies like outdoor reset and whole house controls or 2 stage thermostats maybe even a large hot water holding tank

i have another crazy idea - i wonder if you could stage together, a few fully condensing boilers, like weil-mclain ultra's, near the roof (for venting), and feed the system through flat plate heat exchangers to isolate the pressures, even though you are running them hotter than, where are most efficient, (90f return / 110f supp), - your gas usage would still be less than it is now

Mike T., Swampeast MO

2.309 feet of water at 62° exerts a pressure of 1 pound per square inch at its base.

With 80 feet you have (80 / 2.309) about 34.6 pounds of pressure in the "pit". With 70 feet you have (70 / 2.309) about 30.1 pounds of pressure.

Water warmer than 62° is a bit less dense, occupies more space and will therefore exert a touch less pressure.

(See, those nit-picky things about water DO matter when you're talking hydronics.)

It sounds as if this system is on the VERY edge of being able to operate with a 30# relief.

Again, this is getting nit-picky, but your height estimate may still be a bit high--particularly if you're considering the height of the roof and the system itself "stops" at the highest radiator--i.e. no expansion tank in the attic/rooftop.

As the water in the system heats it expands, increasing the static pressure a bit. The expansion/compression tanks are there to allow this to happen without disaster, but system pressure does still rise somewhat as the system heats. Those additional tanks were probably added to try to keep this pressure rise down as much as possible as the system heats.

I'd put an ACCURATE, low-reading pressure gauge on the highest rad in the building and fill to get only ½ pound of pressure at static, cold conditions. (Two people and cell phones required.) You might want to replace the pressure gauge in "the pit" as well with one KNOWN to be accurate. If you can find an altitude gauge (really pressure but marked in elevation as well) I'd install one as it should have a sliding mark for the proper pressure/elevation. Turn any auto fill OFF for now!

Hopefully, your pressure in "the pit" will be 25 pounds or below at the cold, static condition with the system BARELY under pressure at the top--remember you don't need pressure to circulate water in the system--it's there merely to lift the water to the highest point.

Also, hopefully, the system is very tight and water does not need to be added. If they are plain steel tanks hopefully they have Air-Trol fittings--if not beg some from old stock as I believe B&G discontinued them...

On initial heatup of the system watch the pressure gauges CAREFULLY. The gauge on the highest rad will likely rise to the 2-3 pound range. Any greater rise and I'd start calculating system volume to ensure that the expansion tanks are adequate in size. Do some careful air bleeding every few days for a while to ensure you have it ALL out.

If for some reason an expansion tank is still in the attic/on the roof and the system is under forced circulation I believe you should remove it and all associated piping as it is not needed and is only adding to the static fill pressure if it has water inside and is higher than the highest radiation.

PUMP AWAY. It usually doesn't matter much in big old systems, but since you're so close to the edge....you don't want the circulator(s) adding to the pressure when it/they kick on.

Dale

Pump away

This is where you really do need to pump away. I would just put the pump(s) on the supply with the air tank connection at the pump inlet.

Kal Row

i got 5.8 out per floor

of an old book and i cant for the life of me remember were,
maybe it was "audels", i will have check at the library - who knows - maybe dan holohan would know - heating history is his baby
i think they set it for the max, maybe becaue, lots of old houses had 12ft ceilings on the bottom floor (my father's does) + 1ft thickness of the floor itself
13 / 2.309 = 5.63 - they used 5.8 per floor as a gauranteed number, maybe they use 50 degree water as the base value,
hey, they didnt have pump away, so they kept the pressure up to keep the air out, it has worked for me for 30 years - i know, such a generous round up, gets out of hand on a 6 story building

jim bannister

New Boiler

Gary,

I work in downtown Boston every day. To keep the cost minimal and the comfort level high you have a couple of choices:

1. Replace the existing boiler with one of a higher rating, I believe Slant Fin has a 50 psi model.

2. Use a standard CI boiler with a sidearm tankless and use the tankless as your pressurized loop. This would be piped with prv, relief valve, air elimination, etc.

3. Whatever method you use, install trv's on the radiators and let the apartments control their own heat. Either this or zone off each apartment with zone valves in each unit, depending on how the original piping is run.

Unknown

I've hooked a WHALE of a job

I will take into concideration all of the responses that I recieve on this job as I'm really streaching my capabilities as a one man shop on this one. I feel like I'm in the danger zone and it's keeping me up at night.

#1) Installing the new proposed hydronic heating system on the upper floor is not a possability. The people that live in the (Penthouse) just don't have the room and nobody wants to sacrafice a single SQ/FT of their precious building even for the common good.

I'm going to get really "nit picky" on this design. I just have not had the time to establish a proper heat load. It's been cold here in the N.E. and I've been swamped.

I'm seriously considering using a flatplate HX with a condensing heat source. Still not sure how I'll vent the appliance.

I'm thinking that I may be able to vent the new condensing heat sourcees out the back of the townhouse. It's about 20-25 feet horizontally (un-insulated) to the back alley. Not sure Mass code would aprove of this?

Any thoughts?

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