Help! Can't dial thermotrol down below 3psi

Jean-David Beyer

I have two of these, and they do have anticipators, but they are in the electronics, not a little heater. I have both a Honeywell CT3600 and a PRO TH4110D.

Where you look is in the manual or the Installation Guide (depends on what thermostat you get). There will be an adjustment called "Heating cycle rate." The number seems to be the number of heating cycles per hour (CPH). They come set to 6, that they say is appropriate for Gas or oil forced air heating systems. You can set it to 1 for radiant floor heat or gravity steam system. 3 for how water system or high efficiency furnace, or 9 for electric heat system. These numbers come with the CT3600.

The TH4110D are a little different.

1 for steam or gravity systems
3 for how water systems & furnaces with over 90% efficiency
5 for gas or oil furnaces with less than 90% efficiency
9 for electric furnaces.
It also has settings for 2,4,5,6,8,10,11, and 12 CPH.

Doug_46

Help! Can't dial thermotrol down below 3psi

I have a 2 family home with separate gas-fed one-pipe steam systems. I was having trouble getting heat to both apartments then I bought Dan's book - We got steam heat. I realized main vents needed to be replaced and thermotrol needed to be dialed down. Set 1st floor thermotrol to .5psi and replaced main&radiator vents and now system is working properly. Changed main & radiator vents for 2nd floor but cannot dial thermotrol below 3psi. Apartment heats but radiators not as warm as should be. Any ideas? Do I need to replace thermotrol? Thanks in advance.

Unknown

Bad pressure gauge? Pigtail might be blocked up with crud?
I'd clean the pigtail and temporarily swap gauges and check that it isn't just a gauge problem.

Doug_46

Rod, Thanks for quick response. I thought it might be a faulty gauge, but if you raise psi on pressuretrol to 4 or 5 psi, the gauge accurately reflects pressure. I haven't yet tried to clean pigtail. It is currently dialed all the way down to .5psi with cut out all the way down and pressure gauge still reads 3. I have the Honeywell PA404 pressuretrol.

nicholas bonham-carter

bad pressurtrol

if you replace the pressuretrol, why not get a vaporstat,[ and a good low pressure gauge] for really accurate control? the 0-16 oz. model is best.this will protect your investment in new main and rad vents--nbc

Unknown

Doug-

The pressuretrol may in fact be bad. My thought was just that it is relatively easy to swap gauges with the "good" boiler and observe how the "bad" gauge reacts there and also how the known "good" gauge reacts on the "problem" boiler. Just a primary check before condemning the pressuretrol.

Pressuretrols can go "weird" on low settings as can gauges. As NBC mentioned if you are doing a replacement you might want to look at a vaporstat.

Patriot Supply has reasonable prices for both pressuretrols and vaporstats. Prices vary a lot on these items so yu might want to check around and locally.

http://www.patriot-supply.com/


You'll probably need a low pressure gauge (leave the original gauge in place as it is required by code) For a low pressure gauge try the Gauge Store

http://www.gaugestore.com/

They have a 0-35 oz. PSI (Model 33013), 0-3 PSI (Model 33020) and a 0-5 PSI (Model 33021) - good to a max of 140 deg. so you'll need a pigtail to protect it from steam. I get my pigtails from McMaster Carr

http://www.mcmaster.com/

Catalog page 578 . I use the red brass pigtails as they don't corrode.

- Rod

Doug_46

Help! Can't dial thermotrol down below 3psi

Rod et al,

I wanted to wait and reply after I had a chance to look at system today. Upon inspection, the gauge was reading 9 psi!!!. I drained water and waited for pressure to drop back to zero. The pressuretrol was set at .5 cut-in with a differential of 1, but it is not controlling pressure. I assumed pressuretrol was bad, so I replaced it. I also switched gauges off of the other apartment's boiler (to determine if a malfunction). I filled tank above min water level and turned thermostat up. Boiler fired up and began producing steam when I noticed the psi climbing back up to 9-10 psi. Obviously, no steam found it's ways to any radiators on 2nd floor. Main vents have been replaced along with radiator vents. Why cant I control pressure???
Thanks in advance.

nicholas bonham-carter

bad presuretrol

did you replace, or clean the pigtail under the pressuretrol at the same time? if it is blocked with debris, it will not allow the pressure to be felt.

pressure that high will do bad things to your vents.--nbc

Doug_46

nbc,

thanks for the response. I did not remove and clean the pigtail. Is it as easy to remove as it looks? Will doing so keep pressure from climbing when boiler on? I will try to clean and/or replace and see if I can keep psi set per pressuretrol settings.

Doug_46

Cleaned Pigtail to no effect

Cleaned pigtail on boiler today but it had no effect in regulating psi. Doublechecked pressuretrol cutin at .5 with a differential of 1. Boiler psi continues to climb up to 10psi. If air is being trapped and compressed going up to 2nd floor radiators, one would think rad vents weren't working. All radiator vents in 2nd fl. apt. were replaced with Gortons C&Ds 2 weeks ago to no effect. I removed and checked by blowing into vents-working fine. Tomorrow, I will remove radiators and see if steam coming through valve stems. If so, must be a problem with radiators (doubtful) or vents (probable). If no steam through valve stem from risers, then I must have a blockage somewhere in the main. Do you agree with this reasoning or am I overlooking something? Thanks.

Unknown

Doug- No, If the pigtail is clear, you have either a bad pressuretrol or a bad pressure gauge. Blockage of any kind (in the exterior piping) does NOT cause excessive pressure buildup as even if the boiler was completely sealed off the outside piping, a good pressuretrol would cut out at the set pressure which should be 1 1/2 PSI according to your settings.

Since I'm assuming higher steam pressure would be self evident at the blow off or at the vents, in which case you probably have a bad pressuretrol. You might also want to check the wiring to the pressuretrol just to make sure that isn't source of the problem.

Unknown

Doug- You might want to look at the post "Buying a Vaporstat" on this page.

Doug_46

We have heat!!!

Guys,

Believe it or not, the pressure gauge was faulty. After cleaning pigtail, I purchased another gauge and installed on problem boiler. It showed a more reasonable 1.5-2psi with boiler on. I did however notice that the boiler was short cycling (cutting off after 2 mins.) I hadn't noticed it short cycling before since I was working on system with boiler off. I went to the thermostat (non-digital round Honeywell) and pulled off cover. The sliding scale on the anticipator was set at .8 After speaking with an elderly local plumber familiar with steam, I learned that steam boilers require the anticipator to be set at 1.2. (I had replaced this thermostat back over the summer and didn't touch anticipator - didn't even know what it was for) This little scale adjusts the boiler duty cycle but doesn't come out the box set for steam. After adjusting anticipator and raising temp on thermostat, the boiler fired up immediately and stayed on for a good 10 minutes. By the end of the cycle, heat was coming through every radiator in the apartment. The heat has been working properly all day. It only took 3 weeks to figure out something that someone answered for me in 5 mins. but I now have a better understanding of my heating system. Thanks to all for your feedback.

jOhn_225

I hear often that people with short cycling always talking about the anticipator setting from thermostat being the fix.
Are there any heat anticipator setting on Honeywell Digital thermostats?
I dont think so, then what is the work around?

Thanks