Large apt building - random overheat/underheat

steamislife

Howdy,
Somewhat stumped by this issue.
We have a 53 unit high-end co-op building with 2-pipe, vacuum steam system.
They are having issues with over-heating and underheating. I believe many issues are stemming from bad traps (need to check them) and bad controls (heat timer needs calibrating).
What is odd is that there is one apartment that is way over-heating - max recorded temp is 87 in his apartment.
It's a six-floor building that's about 200' long. This apartment is on the 4th floor, at the far end of the building from the boiler room.
Other apartments are too cold, getting down to 64 degs. Some are close to boiler, some far - top floors, 1st floor... no apparent rhyme or reason for it

Some apartments have danfoss valves (the hot one does not).
Someone did install a 'main trap' in the boiler room on the main condensate.

Trying to think of what causes overheating...
Poor controls, but that would cause general over-heating.
Too much radiation - but other identical problems would have the same issue (they don't)
Renovations that improve the envelope (didn't happen)

Any other ideas??

Thanks in advance for your help

Paul48

Poor system maintenance, and repair. If it is because of cheapness, shame on management. If maintenance has been paid for and this is what you have....fire the outfit doing the maintenance.

steamislife

Ha, yes clearly... But I need to figure out what the specific issue is.
Clearly they need to inspect/replace traps.
Need to remove main trap.
Need to recalibrate heat timer.

But what specifically would cause one apartment to way over heat??

Thanks!

Paul48

That has to be your apartment, because any rational person would be more concerned with many cold apartments rather than one hot .

Paul48

Here's a WAG..........That apartment was owned by an engineer, and he repaired his traps, rather than wait for building management to never do it, like they were doing to the rest of the building.

Abracadabra

Paul48 said:

Here's a WAG..........That apartment was owned by an engineer, and he repaired his traps, rather than wait for building management to never do it, like they were doing to the rest of the building.

lol... that's xactly what i was thinking..

Pumpguy

Can you provide more information like building steam supply pressure, returning condensate temperature, and return line vacuum?

A common cause of uneven heating is operating with too high steam pressure.

vaporvac

Is this a naturally induce vacuum system, or does it use a pump?

nicholas bonham-carter

My guess is that this apartment gets steam sooner than the others, and is not throttled down by TRV's.
Can you close the inlet valves on the radiators to reduce the heat?--NBC

steamislife

Paul48 said:

That has to be your apartment, because any rational person would be more concerned with many cold apartments rather than one hot .

Nope - but solving underheating is a lot easier if there isn't also overheating... Plus, the guy in the overheated apt is on the board and complains more than those in underheated apartments. And refuses to install Danfoss valves. We're probably going to make him install them, but I still want to figure out why his apartment is so significantly hotter than any others...

Paul48 said:

Here's a WAG..........That apartment was owned by an engineer, and he repaired his traps, rather than wait for building management to never do it, like they were doing to the rest of the building.

The whole wing of the building he is in had the traps replaced 2 years ago - and the guy in that apartment is definitely not an engineer

Hatterasguy said:

Yeah, the super constantly changes the System Set Point Temperature - which should not have to be changed

Pumpguy said:

Can you provide more information like building steam supply pressure, returning condensate temperature, and return line vacuum?

A common cause of uneven heating is operating with too high steam pressure.

Steam pressure is currently set at 2.2 psi during the day and 1.7 at night. This is controlled by a Heat Timer Multi Mod.
A Heat Timer MPC Platinum does the cycling etc.

There are two vacuum pumps. One is at far end of building from boiler room on grade - set @5.5"HG
The other is in boiler room - 10" HG

The system set point uses a sensor on the dry condensate at the furthest point on ground floor. Last I checked the Heat Timer was set for 160 with a 25deg system setpoint differential

vaporvac said:

Is this a naturally induce vacuum system, or does it use a pump?

Has vacuum pumps

nicholas bonham-carter said:

My guess is that this apartment gets steam sooner than the others, and is not throttled down by TRV's.
Can you close the inlet valves on the radiators to reduce the heat?--NBC

Oddly, this apartment is on the opposite side of the building from the boiler room ~200' away and then up on the 4th floor (6 floor bldg)

I'm not sure about closing the valves - seems like the obvious solution, not sure if they tried that or not.

Regardless - I could solve this by doing that, or installing valves if necessary, or installing danfoss valves, or removing radiators....

But again, why would one apartment be so hot??
Remember, we're talking 87* when other apts are 68-75

Thanks guys

nicholas bonham-carter

If this is a vacuum system, then why is there any pressure in it at all?
This might need some wireless data loggers to find out where the temperatures rise to and when, as he seems to get steam quicker than the others. If this is a down-feed system, with the steam going to the attic first, and coming back down, then he is closer to the supply, than those under him. How are the temps in the apartment above this one?
You mention the west wing traps having been changed. Are there any (working) crossover traps?
All in all, a good mystery!--NBC

steamislife

nicholas bonham-carter said:

If this is a vacuum system, then why is there any pressure in it at all?
This might need some wireless data loggers to find out where the temperatures rise to and when, as he seems to get steam quicker than the others. If this is a down-feed system, with the steam going to the attic first, and coming back down, then he is closer to the supply, than those under him. How are the temps in the apartment above this one?
You mention the west wing traps having been changed. Are there any (working) crossover traps?
All in all, a good mystery!--NBC

Excellent question... They could probably heat the place with 0-1 lbs... Although, 2.2 lbs is not that high - so not sure if that would cause too much of an issue - maybe so though?
It's an upfeed system.
I have readings from the 2nd floor and the 6th floor (below/above this apt) - cold in both. Again, the hot apartment is on the 4th floor.

There are crossover traps (F&T)- they look new, I don't know if they are working properly. That will have to be checked

Speaking of wireless data loggers - any recommendations on specific brand/model?

thanks

nicholas bonham-carter

This thread has some recommendations:
http://forum.heatinghelp.com/discussion/comment/1418513#Comment_1418513

Jamie Hall

First, a warning: I'm not particularly familiar with the idiosyncrasies of systems with vacuum pumps. So take what I say with a lot of caution...

That said, in most two pipe systems the most obvious suspect when one has one radiator or set of radiators which is wildly hot and the rest of them cold or inadequate is a bad trap -- stuck open -- on the hot radiator, allowing steam or pressure to rise in the returns and blocking steam flow to the other radiators...

I know, though, that you say that that apartment was overhauled recently... correctly?

gennady

There few reasons to have 2 pipe steam system off balance.
1. defective traps
2. improperly set inlet valves or improperly installed danfoss valves.
3. missing orifices
4. missing vacuum breakers on radiator with danfoss valves. It is the reason of premature failure of the traps.


In this case, the fellow with overheated apartment probably has traps failed open, effectively closing traps nearby and causing other problems.

Just my 2 cents.

nicholas bonham-carter

I hope they do not have the one-pipe system, air-vent type of Danfoss valve installed on these radiators, as it is two-pipe.
I think some neighboring failed traps could certainly be to blame, even though they were said to have been changed!--NBC

steamislife

gennady said:

There few reasons to have 2 pipe steam system off balance.
1. defective traps
2. improperly set inlet valves or improperly installed danfoss valves.
3. missing orifices
4. missing vacuum breakers on radiator with danfoss valves. It is the reason of premature failure of the traps.


In this case, the fellow with overheated apartment probably has traps failed open, effectively closing traps nearby and causing other problems.

Just my 2 cents.

Don't you not want vacuum breakers on a vacuum system??

Pumpguy

My thoughts exactly. You wouldn't want vacuum breakers on a vacuum return system.

nicholas bonham-carter

He must have been thinking of TRV's on a one pipe system.--NBC

gennady

yes, no vacuum breakers on vacuum system.

aircooled81

when do we get to see some pictures of these radiators and their control valves?

steamislife

aircooled81 said:

when do we get to see some pictures of these radiators and their control valves?

Here ya go - Yes they are convectors, not radiators...

gennady

Returned to this topic again.
Even thou you clearly have a balancing problem, after re-reading your posts I'm confused. You are writing that there different pressure settings for day and night, and different vacuum settings on 2 vacuum pumps. It does not make sense at all. Vacuum system should work on outdoor reset, where steam pressure depends on outdoor temperature, while vacuum pumps are keeping constant vacuum.
Or you might just have vacuum return line system, where vacuum pump just assisting condensate return maintaining low level vacuum.
Multi-mod has a build in outdoor reset for hot water boilers, but for steam system it needs MPC panel.
Do you have a motorized steam valve on the boiler steam outlet?
Also, where TRV sensor is located?

steamislife

gennady said:

Returned to this topic again.
Even thou you clearly have a balancing problem, after re-reading your posts I'm confused. You are writing that there different pressure settings for day and night, and different vacuum settings on 2 vacuum pumps. It does not make sense at all. Vacuum system should work on outdoor reset, where steam pressure depends on outdoor temperature, while vacuum pumps are keeping constant vacuum.
Or you might just have vacuum return line system, where vacuum pump just assisting condensate return maintaining low level vacuum.
Multi-mod has a build in outdoor reset for hot water boilers, but for steam system it needs MPC panel.
Do you have a motorized steam valve on the boiler steam outlet?
Also, where TRV sensor is located?

The vacuum system is not tied into the control system.
Outdoor reset is only adjusting cycle time through the MPC panel.
I don't understand why the steam is set for different pressures day/night or why the vacuum pumps are set for different pressures...

There is no motorized steam valve.
There is no TRV sensor - the system sensor is on dry condensate main in the garage (same level as boiler room)

thanks

nicholas bonham-carter

Is there any hammering on this system?
I could imagine a situation where a badly piped, dirty boiler splashes a lot of water up into the supplies, interfering with the steam going to the neighboring apartments, but not the "sauna" unit.--NBC

steamislife

nicholas bonham-carter said:

Is there any hammering on this system?
I could imagine a situation where a badly piped, dirty boiler splashes a lot of water up into the supplies, interfering with the steam going to the neighboring apartments, but not the "sauna" unit.--NBC

Some hammering, but not close to the boiler. This building is long - Boiler room is one on end, "sauna" unit is on other end. The boiler is also piped properly as far as I could tell. I don't think that's the problem here, although I spent a lot of time looking at that.

gennady

It looks like you have vacuum return line system, not a full vacuum system.
Also you have trv installed on radiator. It must have control part mounted outside of radiator enclosure, with build-in or remote sensor. Where is this part located? It looks like a dial. Follow capillary tube to find it.

steamislife

gennady said:

It looks like you have vacuum return line system, not a full vacuum system.
Also you have trv installed on radiator. It must have control part mounted outside of radiator enclosure, with build-in or remote sensor. Where is this part located? It looks like a dial. Follow capillary tube to find it.

Oh gotcha, sorry misunderstood - It's mounted on the side of the radiators.

What differentiates a vacuum return system vs. a full vacuum system?

thanks

gennady

steamislife said:

gennady said:

It looks like you have vacuum return line system, not a full vacuum system.
Also you have trv installed on radiator. It must have control part mounted outside of radiator enclosure, with build-in or remote sensor. Where is this part located? It looks like a dial. Follow capillary tube to find it.

Oh gotcha, sorry misunderstood - It's mounted on the side of the radiators.

What differentiates a vacuum return system vs. a full vacuum system?

thanks

vacuum system has a motorized valve on the boiler steam outlet and this valve controls steam pressure. Steam pressure is changed as a function of outdoor temperature. Pressure and temperature of saturated steam are rigidly linked to each other, so by changing pressure we changing steam temperature. System steam pressure changes between 2 psi and few inches of vacuum , vacuum pump keeps about 25 inches of water column vacuum. Steam is supplied to steam system continuously, non stop. It is complete analogy of hot water constant flow system on outdoor reset.

In vacuum return system vacuum is 5-10" WC and boiler works on regular steam outdoor reset.

steamislife

gennady said:

steamislife said:

gennady said:

It looks like you have vacuum return line system, not a full vacuum system.
Also you have trv installed on radiator. It must have control part mounted outside of radiator enclosure, with build-in or remote sensor. Where is this part located? It looks like a dial. Follow capillary tube to find it.

Oh gotcha, sorry misunderstood - It's mounted on the side of the radiators.

What differentiates a vacuum return system vs. a full vacuum system?

thanks

vacuum system has a motorized valve on the boiler steam outlet and this valve controls steam pressure. Steam pressure is changed as a function of outdoor temperature. Pressure and temperature of saturated steam are rigidly linked to each other, so by changing pressure we changing steam temperature. System steam pressure changes between 2 psi and few inches of vacuum , vacuum pump keeps about 25 inches of water column vacuum. Steam is supplied to steam system continuously, non stop. It is complete analogy of hot water constant flow system on outdoor reset.

In vacuum return system vacuum is 5-10" WC and boiler works on regular steam outdoor reset.

Interesting, thank you.

But the same principles apply in the sense that a vacuum return system is always a vacuum return system due to smaller pipes, correct?

gennady

yes, that is correct, system will not work without vacuum.