TRVS not regulating heat

SFbird

Hello! We installed Danfoss TRVs on all the one pipe steam radiators in our 12 unit condo building about two years ago and some neighbors are complaining now that no matter what they are set to, the heat output is not regulated. Some say the TRV is set to lowest setting (*) and the radiators are still getting hot. Our boiler timer has it firing every 15 minutes or so during the 3-4 hour time span that it operates so the TRVs can "recover". My husband thinks the pins inside some of the TRVs are stuck in wrong position, is this what happens and can we remedy them without a plumber coming out? In our condo one is working just fine now but another has been problematic. Thanks!!

hvacfreak2

I bought 4 Danfoss TRV's last year. Some family members are telling me that a couple of rooms are over heating but I have not had a chance to look at them yet. I'm using some ridicules fast vents on them so I'm thinking that's the problem with mine. What vents are you using on yours ?

JohnNY

TRVs are a wonderful thing overall but the fact is I've come to expect not-so-much of them over the years. That said, I think your 15 minutes might be an issue. I seem to have greater success using longer cycle times (more standby time) when using TRVs.

nicholas bonham-carter

TRV’s are not the complete solution you may think, as they can only reduce the steam arrival in over heating rooms.
What you need is a good steam enabled thermostat (Honeywell VisionPro, with remote sensor), which will respond to the temperature of the coldest area of the building.
This cold room must NOT have a TRV controlling its radiator.
In addition, the system must be as well balanced and vented as possible. I believe you have posted here before, and was a solution found for the system problems then?—NBC

ChrisJ

What pressure are you running?

On a single pipe system a trv can only keep a radiator from heating or slow it. It cannot stop it once it has started

Short "on" cycles are needed as well as low pressure. Something around 1 or 2 PSI tops.

Mine do very well with 2 cycles per hour or 15 minutes on at a time

DanHolohan

Yes, the pressure is critical with these. Keep it very low.

SFbird

Thanks for the replies! We have been running at .5 PSI , 15 minute intervals. I can try setting for longer but our timer might only allow going to 30 min

After all of our initial problems that I posted about a few years ago we had someone come out to add a low pressure gauge and a thermostatic control for the boiler. We don't have any indoor air temp sensors, they installed a sensor on the back of the building, outside in the shade so now the boiler only comes on when the outside temp goes below 64 degrees. He installed a new timer so we can set it to run is those shorter 15 minute intervals whereas our old set up didn't even have that option and the boiler was just coming on and running straight out for the 3-4 hour time periods we had it set for, early morning and the again in the evening ,no matter what the temperature was outdoors- yikes!!

So far our simplistic approach has been working well. The only other time we had a problem with the new TRVs is when someone inadvertently flipped the manual operating switch on the timer and the boiler just ran, overwhelming the TRVs until we figured out what had happened and switched back to the right setting. I don't know if this might have caused some of the dysfunction in a few of the TRVs. My husband did a little tinkering with the little pin mechanism inside one of ours that appeared to be stuck and he thinks making sure it is able to move is key- are we on the right track?

nicholas bonham-carter

Not without an indoor sensor.--NBC

ChrisJ

SFbird said:

Thanks for the replies! We have been running at .5 PSI , 15 minute intervals. I can try setting for longer but our timer might only allow going to 30 min

After all of our initial problems that I posted about a few years ago we had someone come out to add a low pressure gauge and a thermostatic control for the boiler. We don't have any indoor air temp sensors, they installed a sensor on the back of the building, outside in the shade so now the boiler only comes on when the outside temp goes below 64 degrees. He installed a new timer so we can set it to run is those shorter 15 minute intervals whereas our old set up didn't even have that option and the boiler was just coming on and running straight out for the 3-4 hour time periods we had it set for, early morning and the again in the evening ,no matter what the temperature was outdoors- yikes!!

So far our simplistic approach has been working well. The only other time we had a problem with the new TRVs is when someone inadvertently flipped the manual operating switch on the timer and the boiler just ran, overwhelming the TRVs until we figured out what had happened and switched back to the right setting. I don't know if this might have caused some of the dysfunction in a few of the TRVs. My husband did a little tinkering with the little pin mechanism inside one of ours that appeared to be stuck and he thinks making sure it is able to move is key- are we on the right track?

So you're saying the boiler is only on for 15 minutes? That should work.

What vents are on the TRVs? I've also found fairly slow vents help. You need the radiators vented so they are balanced for the most part, even without the TRVs. The vents set the system up, the TRV's do the fine tuning and compensate for sun, someone running the oven etc.

For example, the one in my front bedroom is usually closed and doesn't allow any heating, except for if we have a strong wind, it'll start to heat. A rear bedroom heats all of the time, except for when the sun warms the room. Both will work without the TRVs, just not as nice.

I'm considering adding a TRV to our kitchen radiator to compensate for when the oven is going a lot.

TRV's are a great improvement to an already properly working system, but they won't fix a broken one.

You need plenty of main venting, and likely something like a Gorton #4 on the TRVs. Radiators that tend to make the room run cooler need a faster vent. Unless cooler is what the tenant wants.

SFbird

The TRVs all have Hoffman #41's on them. We added Gorton 2 vents on the mains about five years ago when we realized there were no vents at all (!) at garage level. I'm gonna have someone come out and check all of the Gortons to make sure they are functioning correctly. The Hoffmans are all only about a year old so I don't think they are the problem- unless you think we need to switch those to a different type.

nicholas bonham-carter

You will see when you have enough main venting when the air is able to escape at 2 ounces, as the boiler begins to make steam.--NBC

ChrisJ

SFbird said:

The TRVs all have Hoffman #41's on them. We added Gorton 2 vents on the mains about five years ago when we realized there were no vents at all (!) at garage level. I'm gonna have someone come out and check all of the Gortons to make sure they are functioning correctly. The Hoffmans are all only about a year old so I don't think they are the problem- unless you think we need to switch those to a different type.

nicholas bonham-carter said:

You will see when you have enough main venting when the air is able to escape at 2 ounces, as the boiler begins to make steam.--NBC

NBC, my system vents at 1/4 of an ounce even if I shut it down, wait 4 minutes and fire it back up. So lower than 2 ounces, may be possible with some systems. Probably depends on length of piping etc.

@SFbird If all radiators have the same vent, I'm betting that's part of the problem. Speed up the vents in the apartments that are cold. One's that are really cold, try something like a Gorton 6 or even a C. The ones that are so so, start with a Gorton 5. They're available in straight 1/8" which should fit your TRVs, but they're gold not silver.

This will allow the cold apartments to get steam faster than the overheating ones.

If all of the apartments are overheating, you need to change your control strategy.

KC_Jones

To add to @ChrisJ 's comments, the TRV itself adds some resistance to venting so a slow vent will be even slower. Most that are familiar with them recommend up sizing from what you would have used otherwise to compensate for this.

I would also like to suggest that going directly to all TRV's was a mistake. You should have tuned the system, balanced the venting etc. then saw were the issues are. Even if you ended up with TRV's on all the rads at least it would have given you a baseline for the balance that you needed or that you can't get.

I also think not having and indoor temperature sensor is a mistake. You could (for all you know) be firing the boiler for no reason at all wasting fuel and your money. To me it sounds like you (or your contractor) are trying to treat it like a hot water system and it isn't that.

As Chris said, you still need balance with the TRV's I don't see any way around it.

nicholas bonham-carter

Chris, my system also does not see more than a fraction of an ounce during the venting phase, but we are fortunate to have a good match between boiler output and radiators, and main venting capacity, (you especially), and I don’t think that is often the case, and most likely not in this case.
The TRV’s can only do so much, and cannot serve as a primary temperature control, especially if the system is oversized, and unbalanced.—NBC

Paul_11

TRV''s on one pipe steam are great ideas but can only do a 99% job of keeping steam out of a radiator if:
1) boiler is 1 psi or less of operating pressure.
2) System is master vented adequately
3) boiler & basement steam piping is insulated properly
4) TRV have slow vents. I would suggest you replace the Hoffman
41 which vent at .125 @ 3oz with Gorton #4 which vent at .055
@ 3oz.