Hydro 3250+ jumper

dmk

My new boiler has the 3250 plus, couldnt get boiler to go over 140, so i shut off the econo and removed the jumper next to the zone/indirect switch, now goes up higher, but still having trouble with getting house above 68deg, or boiler above 170. Can someone explain the purpose of the jumper and what a good hi/low setting is? Currently at 180/160. Ive got an indirect with zone pumps. What good is the econo if you have to shut it off to get the temps up?

Jamie Hall

Theoretically the 3250 Plus should increase the boiler water temperature by itself, based on heating demand and based on the settings for the economy mode. If it isn't doing that, check your owner's manual and make sure that you have all the correct settings for your system.

Turning the Econo mode off increases the boiler temperature settings, which allows greater heat output to the radiation. In colder weather, as the heating demand increases, this is necessary. The idea is that in milder weather the boiler will run at lower temperatures, which will allow it to condense, thus improving the efficiency.

BBros

I'm assuming you have the manual, but if not: http://hydrolevel.com/wp-content/uploads/2015/12/HydroStat-3250-Plus-Inst.-final.pdf

From my understanding, the jumper only needs to be removed for modifying the low limit setting (above 140, as noted pg. 7), which really is only utilized for domestic coils (which you don't have) thus the jumper stays in place.

If the boiler isn't going above 140 with the high limit set at 180, then something else in the system is wrong. Whether it's the T-T connection or indirect wiring/sensor, I can't say, but something is not calling for heat. I've spent a lot of "time on a bucket" with the 3250 trying to sort my own issues out, and I've determined it's ultimately not a complicated unit.

I would double check the wiring for the indirect and space heating, then reset the unit to factory settings.

BBros

One more thing, if you're not careful while mucking about with the settings, because the dials/knobs are multi-purpose, the system can be left with a lower high-limit setting than intended after being in the program mode. Use the button on the top right of the unit to cycle through the settings and double check it's what you want.

dmk

I think i just realized part of my problem, I misunderstood the purpose of the low and high settings. Please correct me if I'm wrong - The low setting is what the boiler will maintain if nothing is calling - a range of 140 minus 10, plus 20deg differential (130 to 160)? Correct? The high setting is the highest the boiler will go when calling. If this is correct then i will put the jumper back in and see how it goes. My diff was at 10 but the boiler would come on every 7 minutes so I changed it to 20 to get it to not cycle so often, now its closer to 15 minutes which still seems excessive.
Without anything calling how often would you expect a boiler to fire just to maintain the low?
Do i need a low limit with an indirect?
Is there a max temp that the econo will take the boiler to?

BBros

Yes, the low limit is to maintain boiler temp with no call.

I looked at your other post and saw the photo of your system. You indeed have an indirect, and thus need not have a low-limit setting. It appears it's wired just as a zone, rather than priority to the control, but it's hard to see.

Regardless, turn the Low Limit off. The call to the boiler will trigger the firing, and it will manage the temperature needed to satisfy call.

When there is no call, the boiler should not fire... this is commonly known as "cold start" though it's really more of a "warm start" because the time between calls rarely allows the boiler to actually go to room temp.

I would try the econ mode set at 2 and see how you get on.

High limit 180 is a good start, the boiler will fire from cold (or whatever temp it fell to since last call) and target a temperature (could be 150, could be higher, depends on demand) and then maintain a 10F delta for however long the call is active.

You do not have the ability to modify the delta, it is pre-programmed. If the boiler determines the target is insufficient, it will adjust, and/or go into boost that allows the target to be the same as the high limit.

I would also enable the Purge setting, if it isn't already. It will then hold off firing the boiler if the residual heat in the system can satisfy the call. It's designed to limit short cycle... it's effectiveness can be debated.

dmk

BBros - i believe the dwh is wired to priority, but the "dip switch" on the panel is off so i dont no if its actually on or not. Any way of testing? To eliminate the possibility of a real cold start (which i believe is not good for boiler) couldnt i set the low @ say 120? My big issue is that is seems to cycle way to often, but maybe it just me..

BBros

I don't think it is set up for priority, but it probably doesn't matter because it sounds like the boiler is oversized such that it will handle both zones and dhw simultaneously.

Cold start really isn't an issue in your situation assuming it's fin-tube baseboard. There isn't enough mass in the emitters to shock the boiler, plus if it's firing every 20-30min anyway, there's no way it will cool down that much. Might run down to 120... and if you're getting burn times of 15min or more with the boiler reaching high limit each time, I would classify that as acceptable.

I still would run it with out a low-limit and just monitor it occasionally to see what it drops to and how long the cycles are.

dmk

Messing around earlier and put priority dip to on and turned dwh pump on while a zone was calling and it did shut off the zone, so it works, but is off i guess since the boiler has the capacity to run as is.
So... If the low limit is off, should the boiler fire on a call for heat? I tried and it didnt come on?

BBros

Only if the control has determined there isn't enough residual heat left to satisfy the call.

You need to take note of the boiler temperature when the call is incoming. If it's near 180 (or target) then perhaps not.

It's starting to sound like your zone control board isn't signalling across T-T and instead the boiler has been running off of low limit. That's not good, and it's why you're seeing inconsistent performance.

I don't know anything about the Grufundos control so it's hard for me to advise on that. Need to get more expertise in the conversation...

dmk

So with low limit disabled, is it ok to let boiler go down to 0 deg. if no calls come in? I just jumped out both zones, and boiler dropped to 114 and did not fire. Something must be set up wrong on the board? Need to make a grundfos post..

Thanks