Energy Kinetics System 2000 EK-2 configuration question

wvriem

Hi,

Newbie here, so I hope I post this in the right forum. Please forgive & correct me if I didn't.

I've recently bought a house (New England) with a EK-2 boiler feeding two zones - air handlers (First Co.) doing heating (and cooling). The heating coils in the air handlers are rated around 91k BTU (basement and first floor, 4 zones via dampers an ducts) and a smaller one in the loft for the second floor (around 50k BTU, two zones via dampers and ducts), at 140ºF. EK2 can do in the range of 147 to 200k BTU approx depending on setup.

The air handlers are older than the EK2, though they seem to be matched in capacity. I do not know what kind of boiler was in place before.

When both air handlers are working, they can distribute the boiler's heat well enough; after running say 45 minutes I see the return temp at the EK2 at 140-150 and feed at around 175. That seems to stay stable as long as both air handlers are working. I don't have the tools but based on the led indicators and temperature/pressure sensor I estimate about 30-35 ºF difference between feed and return when running steady.

With so many zones in the house both zones concurrently is hardly ever the case. I've scheduled the thermostats to all switch on together in the morning to maximize the time both zones are working together, as this seems to be the optimal situation.

But what happens when the EK2 is only feeding ONE of the air handlers? Obviously this is not going to be able to shift all the heat the EK2 generates, and water temperature will keep rising. The EK2 says it is controlled by the RETURN temperature, and the controller should switch the burners off when return exceeds 170ºF.

By the way, the heating coils are rated at 180ºF max.

In my current setup the High limit aqua-stat is set at 180ºF (I guess to limit the outgoing water temperature to 180ºF) and stop the burners, but keep pump going, when the water gets too hot.

So my question is:

Is using the high limit aqua-stat (which I thought was a safety measure to be set at 215ºF) to limit water temperature to 180ºF in order not to overheat the coils the correct way to go? It feels like this is not what the designers of the EK2 had in mind, when they control the burner with the temperature sensor on the RETURN.

Return water temperature reaches just 160ºF before the feed temperature exceeds 190ºF and over.

Is there another problem (Insufficient flow? Bypass settings?) or is this problem inherent to any oil burner that services multiple zones and are rated for the max of all zones added together?

This is my first encounter with an oil based forced air heating system, (I had a modulating gas fired hydronic with radiators previously) so please forgive me any stupid questions!

Hope somebody can shed some light on this setup.

Thanks.

STEVEusaPA

Much like saying 'Beetlejuice' 3 times, someone from EK will most likely pop on shortly.
For starters, did the installer leave a sticker on the boiler?
You're going to need a service tech, who knows EK's (preferably the one who installed it) to perform annual maintenance anyway, so better to find them before you need them.
I don't seem to think you have a problem, but I wouldn't change the high limit settings just yet (or at all unless instructed by someone from EK).
The main advantage (there are many) to that boiler and it's programming is after all zones are satisfied, the Manager will pump out all the boilers residual heat to a designated zone or indirect tank, so there are no wasted btu's.
You may need to adjust the bypass.
But hang on until you get qualified help.

Erin Holohan Haskell

@wvriem, welcome to Heating Help. You're in the right spot. Here are some more tips on using this forum: https://heatinghelp.com/forum-user-manual

Help is on the way regarding your Energy Kinetics questions.

Roger

Thank you for your question @wvriem .

The safety high limit should be set for 215°. The energy manager is the operating control, and that will allow the burner to fire appropriately.  As the boiler water gets hotter, your air handler will also output somewhat more heat as well.  My initial thought is that 180° "rating" mentioned is for output purposes and not a maximum hydronic temperature. If for some reason it is a maximum supply temperature for safety purposes, please let us know.

Regarding the boiler operation, the burner will simply cycle to match the output required for your handler. When the zone is finished calling, if the air handler‘s are wired properly, the remaining heat in the system will be purged to that air handler. Because the boiler only takes about two minutes to come up to temperature, there’s only about two minutes of heat left remaining in the boiler so it will not cause overheating in that zone.  Combining heat and hot water with this low mass and thermal purge design allows the system to achieve higher annual efficiently than modulating condensing boilers as demonstrated in a Department of Energy study.

If there is some symptom like over or under heating that you are concerned about, please post a reply explaining what it is.

Thank you,

Roger

wvriem

Hi @Roger,

Thank you for the quick reply. Seeing your callsign you're the guy to talk to!

The air handler is an 60mbxr-4hw, I'm just going by the sticker on it that says 180ºF max. Not sure if that's a hard max (as in leaking) or a soft max (as in end of optimal efficiency range).

So I assumed that is some sort of safety limit. And this made me assume the boiler should not be outputting hotter water than that, which made me assume that somehow on normal operations, the EK2 should normally be outputting close to 180ºF and for some reason (this is where I was thinking of limited flow or bypass issues) this was not working as it should and somebody adjusted the high limit as a workaround.

As you see, a lot of assumptions on my part.

If I increase the high temp limit the output water temperature will increase accordingly. I experimented and dared not go further than 200ºF, at which point the return temp is still below 170º to make the controller switch the boiler off.

If it is perfectly normal to run 205ºF water through heating coils in air handlers, then everything would fit - when I increase the high stat (I did this bit by bit) I can see both feed and return increase. Possibly the coils are very old fashioned (they are older than the EK2) and maybe coils nowadays can handle hotter water, I don't know.

I have not yet dared to put the high stat so high that the return temp reached 170ºF and the burners would be interrupted based on return water temp as opposed to high limit. Feed water would be close to 205ºF in that case. (using approx. 35º delta I observed).

Are those normal feed and return temps?

Thanks

Attached photo of 'Max temp' sticker on air handler:

Roger

You're welcome, @wvriem . There are thousands of First Company air handlers (like the one in your very helpful photo) in use with with our boilers with the safety high limit set at 215°. For reference, most hydronic air handlers like this model are brazed copper construction which has no problem operating at temperatures that can be found in hydronic systems.

Also for reference, hydronic boilers typically operate at pressure up to 30 psi, which means that you do not have to think of water "boiling" at 212°; at 30 psi the boiling point is closer to 250°. I just mention this as sometimes there is confusion outside the trade on this point.

If the air handler is wired properly, when the last thermostat call ends, the boiler circulator and the zone valve feeding that air handler should stay on purging the heat to that zone. If the zone valve closes instead of purging, let me know and we can review wiring with your heat pro to greatly improve your annual efficiency.

Best,
Roger

wvriem

Hi @Roger,


Thanks again - I've checked and circulator keeps running, valve stays open and fan keeps running (separate controller with 2 min 'purge' to open zone). So energy recovery is covered.

So basically it boils down to (excuse my pun) me being so surprised hydro-air systems run so very hot - up to 215ºF - and the high limit is not purely a safety device, but actually supposed to be controlling the max range.

I am from Europe and outgoing temperatures would be more in the range of 150, 160ºF. Mind you, this is with wall panel radiators.

Thanks again and on to the next item: checking and flushing the heat exchanger. I think I'll leave that for the service engineer scheduled in January!



Thanks

Roger

That's good news all around, @wvriem - I'm glad to help! I also appreciate your comment on your upcoming service as having a qualified technician involved is a great way to keep you happy with our equipment running well for decades to come.

wvriem

Hi


Increasing the high limit makes the outgoing water hotter, as it is running up to high limit. I noticed as I increased the high limit aquastat step by step, at a certain point (around 190,195) the pressure needle started shaking a bit. Boiler reached high limit soon after that and shaking was gone once burners were off.

Is that normal? I have taken note of Rogers comment on boiling under pressure being at higher temperatures, so what could cause these fluctuations at higher temps?

Thanks again

Roger

Thank you, @wvriem .

It sounds like you may have reduced flow through the bypass as the lower flow means that the sensor in the return is not controlling the burner so the high limit is turning the burner off instead. Assuming your wiring is correct, the next steps would be to make sure there is no issue with the boiler circulator and circulation, make sure the bypass valve is opened appropriately, and that there is no obstruction in the hydronic side of the plate heat exchanger. It is unusual to have flow issues with a heating call unless that zone is obstructed or there is a circulation problem. It is also possible that the pressure vessel has mineral deposits; this can be cleaned like a tankless coil if that is the case.

As you have a heating professional appointment set up in the coming weeks, you could temporarily turn the high limit down below 190 where this occurs and our tech support team could review the symptoms and corrective actions with your tech. The high limit is working properly so this will be a safe condition and you should have heat an hot water. If you feel anything is more urgent, please contact your heating professional or us for direction and support.

Thank you,

Roger

wvriem

Yes, that sounds like the problem, I’ve turned it down to keep things going for now. Wiring seems to be correct as far as I understand, everything working as expected electrically.

Eagerly waiting for service engineer!

There’s no bypass valve as far as I can see, it seems to rely on the plate heat exchanger to work as a bypass? There is a small pipe going back in to the boiler in the back, just below the big hot out pipe, that could be a bypass but no valve.

Eager to hear if that’s a feature or installation fault...

Thanks again

Roger

The bypass valve is the yellow handled ball valve very close to the plate heat exchanger on the boiler (hydronic) side. It should normally be at about 45° (half open) for baseboard or air handler systems.

For reference, it can be set to full open for cast iron radiation (we recommend primary/secondary piping for the best comfort and most even heat distribution for cast iron radiators).

Roger

wvriem

Hi @roger,

Thanks for all the info.

I found the ball valve, it's fully open.

So either pump or plate heat exchanger or both is not working as it should. Oil co. Engineer ordered new plate heat exchanger, I guess pump is pretty standard so hope he will have that in stock if needed to be replaced.

For now keeping high limit at 180º hopefully keeps it ticking until engineer can have look.

-update-


engineer had a look, did suggested domestic hot water test (both boiler and domestic side getting very hot) and replaced heat exchanger. Now domestic hot water test results in boiler running steady and making domestic hot water of about 140. Looks like that was indeed the problem.

Needle still dancing a bit at the very end just before boiler stops burner on return temp exceeding 170 (feed around 200) when only one zone open; engineer looking to see if it may need cleaning fluids added to get rid of scale or other inside.

Q:

Now, in a cold morning startup and with both zones calling for heat, return temperature stays rather low. (2 bars on the monitor) and I noticed the controller cycles the zone valves a lot. Don’t recall that being the case with the furred up heat exchanger (=bypass).

Trying to get my head around if reducing the bypass by restricting flow through heat exchanger (by turning ball valve to DHW heat exchanger half closed it’ll restrict bypass flow) would increase return temp to keep boiler happier? On the one hand the bypass adds hot water back to the return, increasing return temp so reducing that would lower return temp? On the other hand, reducing bypass flow would push more water through the zones (I assume) and with water flowing faster through the zones they would return warmer water as it has had less chance to cool in before getting back?

what should I aim for to find the best setting for the bypass here?

Thanks again!