Gas Boiler Staying Hot

Does it heat domestic water also....for faucet and showers etc.?

Hi. Outdoor reset control. Uses outdoor temp sensor and indoor boiler water temperature and allows temp to adjust/reset by outoor temperature.

Different manufacturers..

Yes

Depends. You have to read install. Existing aquastat could possibly remain, it could tie into 24volt control circuit for thermostat.

It should save on your gas bills....yes, only other way to gain more efficiency is a modern replacement boiler.

@Billy NYC

Post a picture of the controls. Chances are all you have to do is disconnect the low limit you must keep the high limit

EBEBRATT-Ed said:

You don't want outdoor reset. You have to keep the flue gas temperature above 250-300 to prevent flue gas condensation which you can't do with that boiler. You have to keep the return water above 130 degrees during sustained operation.

Water below 130 is ok only on start up and for a limited amount of time

I hear this said a lot but I’d like to see data to back it up. I think these heat exchangers have too high of an approach to condense unless water remains under 100F. If you look at efficiency of these boilers on steam vs hot water and you only have a about a 0.5% change in efficiency. Maybe my boiler is just scaled up a bit and needs the flue passages cleaned but I see 300F before the draft hood and over 200 after (when its already diluted with room air). When steaming its around 350/250. Although when I’ve put a cheap combustion analyzer on it, it has excess air.

I’ve also seen high volume/mass converted gravity systems with 40 yo under fired atmospheric boilers run under 100F for 30 minutes and not a drop of condensation that I could see in the flue and no evidence of corrosion.

SO probably depends a lot on draft and how the boiler is tuned.


All that being said, outdoor reset would significantly reduce standby losses in mild weather. The downside is that with fin tube, it will likely short cycle under 160F as there is little mass.... especially once it warmed up since it’s probably already generously size with pickup losses for 180 or 190F.


Normally at minimum, end switches are used to call the boiler in a setup like this. I personally prefer to always use a zone panel as its easier to troubleshoot and cleans up the wiring, and prefer seperate pumps over zone valves.

All you need is a single-function, breaks-on-temperature-rise aquastat. If you're not piped for primary-scondary piping or are using a condensing boiler (you're not) then Outdoor Reset/Tekmar isn't going to help you.

The X1 X2 terminals usually connected to a millivolt gas valve connected thru a limit (like the L4006 mentioned) This is the minimum requirements for a safe boiler operation when the boiler was manufactured

The flame safeguard is the pilot on a Powerpile. No Flame ... No GAS. The gas valve has PP and TH/PP terminals to maintain flame safety. The TH and TH/PP terminals operate the main valve and any break in the circuit like the L4006A or whatever is connected to the X1 X2 on the back of the boiler will cut off the main valve.

Now there are probably X X terminals in the zone relays. They are connected to a set of normally open contacts. All three relays are connected parallel so that any of the calls for heat would operate the burner by way of X1, X2 on the back of the boiler.

You will want to disconnect the X1 X2 wires to see if the burner does not maintain the 190° temperature.

If the boiler temperature drops then your problem is in the zone relay boxes.

One of them is fuzed together or (more likely) one of them is not making contact anymore and a repair tech made a temporary repair by jumping the wires together with a wire nut. The temporary repair became permanent when the decision was made to leave it that way. You may have made the decision not knowing it would cost more to operate the heater. The technician may have made that decision without regard for your higher operating cost. This may have been decided many years ago.

Many of those old hydrotherm boilers especially the millivolt models, had a manual and automatic switch on the side of the triple aquastat. This would allow the boiler to fire like you are describing when the power is off so you could open the checks and Supply heat to the house by convection. Check and see if there is a small black switch, labeled manual and automatic it should be in the automatic position.

@BillyNYC Good question. If you disconnect the wires to X1 X2 on the boiler and the burner still operates the burner to maintain temperature. the wiring inside the boiler metal cover is defective. Some may incorrectly say that the wire is "shorted" but it is actually making contact to complete the circuit to the gal valve. this illustration shows that the circuit is completed at the X
where some insulation may have broken off.

We will cross that bridge once you do the test.