Thermostat Question

SLC

I have steam heat and radiators and with the help of the good folks here regarding balancing, I ordered Gorton #2's for my mains to help with balancing. In the meantime I decided to replace my Honeywell Magic Stat thermostat since it's 10-14 yrs old, so I bought a Honeywell RTH6350. I installed it and programmed it for steam heat (as it says it will work on steam heat) according to directions. Fired it up and heat kicked on quickly. I then went downstairs and looked at the boiler and the pressure gauge it was up over 5, I have never seen the gauge budge past .5. So I shut it down. I looked up my old thermostat and it says not compatible with steam heat. Also it was hooked up Red to RC and White to W....So I'm confused now if my heat never worked properly for the last 12 yrs because of this old thermostat, or is the new thermostat bad.....Any help would be appreciated.

nicholas bonham-carter

over pressure

try setting your pressurtrol down to produce a cutout of 1.5, and a cutin of .5. it looks to be set too high now.

the new thermostat would have no control over the pressure, as it fires the boiler when the temperature drops, and turns off when the temperature is reached.--nbc 

Jamie Hall

Nothing like a little curiousity...

As NBC says, the thermostat has nothing to do with the pressure.  And that pressuretrol is set way too high.



What he didn't mention is that those 0 - 30 gauges are there to humour the code enforcement and insurance people, and are  next to useless in finding out how your system is running.  I would look at what the gauge says when the system is off and cold, and then fire it up, after adjusting the pressuretrol.  It should shut off when the gauge rises from wherever it was cold to about a pound and a half or two pounds higher, and then shut off.



Let us know.

SLC

Thanks

I'll give it a shot....Lower the pressurtrol to .5 PSI on the scale?

SLC

Worked Great

That worked but the thermostat I purchased must not be for my system, The boiler continuously runs. Will check with Honeywell tomorrow........Thanks for the help

nicholas bonham-carter

Continuous running

Does the thermostat maintain the set temperature, or will it keep on going?

Remeber that the colored wires may not be wired right in the old thermostat, and therefore when you put in the new one, it may not work properly.--NBC

SLC

same temp

It maintains the same temp, but the boiler keeps running and doesn't shut down like before. The old thermostat I labeled, R and W and was connected to the old one in that manner. Should I try to reverse them?

nicholas bonham-carter

Cycling boiler

Probably your boiler is not oversized, and will not build too much pressure (good). The old thermostat may have had its anticipator set incorrectly, and that caused the wasteful cycling.--NBC

Jamie Hall

Probably too obvious for words...

but... what happens if you turn the thermostat down?  If you turn the thermostat below the space temperature, in a minute or two the boiler should shut off.  If it does, the thermostat is working...



That thermostat should work just fine for steam, and it doesn't really matter which wire is connected to which terminal, although it's always nice to keep them straight.

SLC

Yes

Yes, if I turn down temp setting on New Thermostat it shuts off. It appears the new thermostat has a bad room reading -5 deg off..because I would set the operating temp at 69 and the room reading was 65 .so it would run and run.and it felt like 75 degs in the room and the radiators where hissing like crazy.... So I put a digital temperature gauge along side it and it read room temp @ 69 deg, at cold start.while the new Thermostat read 65. So I'm taking it back and trying a new one. will keep you posted.......Thanks for the input

Burnerboy2

interesting post

Yes, please keep us posted, this post was interesting to me. As I have had the same question from time to time...

Thank you

Ronnie