Boiler sequence and temps

jayrtiger

Hello,
I have read many blogs on the forum and find them very useful, but this is my first entry. I have an Oil fired Weil McLein WGO, with a super store, and a Taco ZVC406, using 4 zones with a priority for the domestic hot water.
The boiler will fire, heat water to the set high temperature (195 F) and shut down.
A zone will call for heat and the T-stat call indicator light will come on. The valve open indicator light will come on and the boiler will fire even though the water temp is approximately 195F. The zone gets satisfied or the high temp is reached again and the boiler shuts off. If another zone calls for heat, with the boiler water at the higher end of the set high temperature (approx. 195F) the same events occur. Basically what happens, whenever a zone calls for heat the boiler fires. even though the boiler water temperature is at the higher end of the the set temperature.
Is this the correct sequence of operation ?

2 - Honeywell Digital Tstats set for hot water boiler
2- Robert Shaw Digital Tstats set for hot water boiler.

Any comments or advice is welcome.

Thanks
Jay

RJMCTAFO

Is there a wire going from the XX terminal on the zone panel to the TT terminal on the boiler aquastat? I am assuming the Indirect is also using a zone valve and not a separate pump? I would check that first and take a few pics so we can see what your system actually is.

Next check would be high and low limit settings on the aquastat. Let us know what they are set at.

I have seen a half dozen boilers or so with TT jumped on the aquastat bouncing off high limit.

jayrtiger

Thanks
I will check that
Appreciate it
Jay

jayrtiger

Thanks for the reply,

The indirect has a separate pump. The high limit is set at 195F and the low at 140F. In the attached pictures you can see wires from the T and X terminals at the zone control going to the T and X terminals at the aqua stat. I think that is what you mean. I didn't see any TT or XX terminals.

Thanks Again
Jay

Steamhead

I think what you're looking for is a way to have the boiler water temperature change according to the outdoor air temperature, except when your indirect tank calls- correct?

What model aquastat relay is on the boiler?

jayrtiger

I appreciate the reply.

I dont , know what model the aquastat relay is but, will get it.

I am trying to figure out why when a zone calls for heat the boiler fires even though the boiler water temperature is between the limit settings. Actually it fires even if the temperature is towards the the high limit.

Thanks,
Jay

Steamhead

The "low limit" is probably set up to stop the circulators below a certain temperature. We'll know more when you can get home and tell us what control it is.

Also, where are you located?

Paul48

I'm trying to make heads-or-tails out of what you have there. On your dry contacts at the ZVC, the wires are not the same as the ones at T-T on the aquastat. On the aquastat , you have 1 wire on C1 and 1 on B1. That zone valve control can only provide priority to a zone valve, not a circ. What am I missing? Anyone? Back-feeding 2 separate circuits?

jayrtiger

Steam H,

I am located in the greater Area and I will get the Aqua stat relay model

jayrtiger

Paul,
Thanks for the reply, I spoke to Taco and they said the ZVC406 can operate up to 3 circulators if configured right.

Regarding the wires at TT and the dry contacts they are different. The Aqua stat TT wires appear to be control wires and the dry contacts at the ZVC look to be larger gage like line voltage.

Do you guys agree the operation sequence is not correct...
The boiler fires to often...

Jay

Paul48

If I read you correctly, and you are saying the boilers stand-by temperature is hi-limit, that is not correct.

jayrtiger

I think that is it. I boiler installed by a licensed contractor that I know and all went well. I explained to him what was going on and he thats the why it runs. It does not seam right to fire the boiler when it is at its high limit temp. I have seen boilers circulate water until the boiler low water temp was reached.

I will get some more info for you.

Thanks
Jay

Glenn H

in your ZVC control the top left wire on the XX terminals go to the TT terminals on your Aquastat -- that is correct

in the ZVC control at the bottom left you have 4 wires , the 2 on the right (purple and black) are for the indirect circulator-- that is correct

the 2 wires on the left (2 black) are on a pump contact --uncertain what that is for?, possibly a secondary circulator

The C1 terminal on the aquastat is for the boiler circulator -that is correct

On a call for heat your boiler should run to the high limit and cycle between that and the differential setting.

You are correct that your boiler should not refire unless it falls below the differential setting.

Your low limit setting at 140 indicates that your boiler maintains that temperature year round. If your aquastat allows it I would make the boiler a "cold start". Some might disagree, but with an indirect I don't see any reason for maintaining heat in the boiler.

Glenn

Steamhead

jayrtiger said:

Steam H,

I am located in the greater Area and I will get the Aqua stat relay model

Which "greater Area"?

Paul48

It appears to be a Hydrolevel hydrostat, similar to this.

http://hydrolevel.com/wp-content/uploads/2015/12/HydroStat-3250-Plus-Inst.-final.pdf

Steamhead

Paul48 said:

It appears to be a Hydrolevel hydrostat, similar to this.

http://hydrolevel.com/wp-content/uploads/2015/12/HydroStat-3250-Plus-Inst.-final.pdf

If so, getting the boiler to run in Thermal Targeting or Outdoor Reset mode should be as easy as falling off the proverbial log.

4Johnpipe

It looks like the "economy" dial is set to off. If so try turning it up to 4 or 5

Paul48

It doesn't work when set for "indirect". The way I read it. In fact, unless the boiler has a tankless coil, they say the lo-limit should be off.

jayrtiger

Thanks for the replies and I apologize for the typos I was working from my phone.
Steam H. I am in the greater Boston area and you are correct the Hydrostat is the Fuel Smart 3250.
I checked the boiler again last night and it never dropped below 177F with out firing. That can not be right. Glenn H I am going to confirm that wiring also thanks.

Jay

Steamhead

There are several good contractors in and around Boston who can help you with this. Go to Main Site, then Find a Contractor and search.

jayrtiger

Thanks
I am researching the aquadstat settings I think that is the issue.

jayrtiger

Hello,
I researched the Fuel Smart HydroStat aquastat 3250 Plus, this is what I found out. The boiler will fire until the high limit is reached (195F). If there is not a call from a zone the boiler temp will drop to the low limit setting (140F). If there is a call from a zone and the boiler temp is at the high limit the boiler will fire when the boiler temp drops 10 degrees and will continue doing this until the calls are satisfied. I have four zones so the boiler was firing a lot.
I shut the T-stats off and the boiler temp dropped to the low limit temp. I raised the indirect Super Stor temp as a test and the the boiler fired. All seems good.

There is a setting on the aquastat called Thermal Pre-Purge. "This will supply latent heat that may remain in the boiler from a previous run cycle to the heating zone that is now calling. The control monitors how quickly the boiler temperature is declining and activates the burner only when it determines that the latent heat is not sufficient to satisfy the call."

I am going to try this, its sound better than firing every time the temp drops from the high limit. I am also thinking of going to cold start in the non heating months.

Jay