System 2000 EK2 Startup issues

wvriem

Hi,

I have a System 2000 EK2 servicing two air handlers, each on it’s own zone. It’s about 10 years old. It came with the house - not sure it’s been serviced really well; I’ve had the plate heat exchanger replaced because that was fouled boiler side. That helped a lot and hot water is now great. (I’ve had another discussion about that problem. Took some time to convince the Oil co to replace the PHE, but they did in the end). It’s just had a regular service/cleaning a month or two ago.

Currently it seems to work fine for both DHW and a single zone calling for heat.
Bypass (through new PHE so should be fine) is fully open.

The issue is on mild days like this spring - system has been inactive all night and then in the morning both zones call for heat at the same time. On starting up the boiler warms up before opening the zone valves. Once on temp, zone valves open and cold water comes in from the zones. Return temp drops quickly, and once below 120F the zone valves are closed to allow the boiler to warm up more. I believe that’s to avoid condensation in the boiler.

Then the process just keeps repeating itself. Open, colder, closed, warmer, open, colder... Can’t be nice for the zone valves.

Obviously by the time it takes for the boiler to warm up the air handler has cooled what little warm water it got already so the boiler never manages to break the cycle.

It keeps “limping” this way until at least one of the zones is somehow satisfied - once it’s only doing one zone it works fine. Not 100% sure but I have the impression I didn’t have this problem before the PHE was replaced. Would that have an impact on this - too much bypass maybe?

Is this open/close/open/close of the zones on startup supposed to happen, and keep going like that? Unfortunately the boiler isn’t smart enough to open the zones bit by bit or to open one at a time to avoid this problem.

I’ve tried switching to higher startup temps (150/130 as opposed to 140/120, dip switch 1) but that made little, if any, change.

Is it a design fault? - and if so, is it the boiler or the zoning/air handlers, or a sizing mismatch? (Boiler is about 170k BTU, zones about 90k and 60k BTU approx at 140F)

Any suggestions what to do?


Thanks!

@wvriem

EBEBRATT-Ed

Lets see some pictures of the bypass and how this boiler is piped

STEVEusaPA

Is there a sticker on the boiler telling you who installed/serviced it?
I suggest you either call EK, or wait for one to show up on here shortly.
You're system was installed by a factory approved contractor, in coordination with EK's sales rep. Ideally you want the original installer to come back out, but EK will find you someone very qualified in your area.

Your bypass shouldn't be fully opened. Let's see some pics like @EBEBRATT-Ed suggested.

wvriem

It’s been installed by one of the top 3 in this area - really good reputation; so I don’t expect a silly piping fault. It also looks like it is piped correctly to me (for what that’s worth).

Bypass handle was left fully open by service tech from current oil Co (when replacing PHE), not the installing one - I kept the same oil co as the previous owner, at least for the first year, to keep things simple(r)...

Don’t know if this is a new fault or has been like this or even if this is supposed to work like this.

Just know that there are probably not many people standing in the basement in their pyjama’s at 6am looking at a boiler opening valves to zones ;-).

JayMcCay

@wvriem , thank you for your post – and thank you also Steve and Ed!

We recommend connecting zone valves with end switches to control the air handler per the attached diagram. This operation will not turn the fan on until the boiler is hot enough to open the zone valves. It will also keep the fan on when the last thermostat is satisfied so thermal purge will work properly, which will save a considerable amount of energy. It looks like you have at least one zone valve with end switch wires (red wires), possibly the other end switch zone valve wires are not visible.

This upgrade will help with the cycling and improve performance. In this case, you only have air handlers connected, so the full open bypass will work to keep the return hotter to prevent cycling from cold returns. That may not be needed once the wiring change is made. It is normal to cycle a few times when recovering from setback, but it should not cycle through the entire call as it does now. If more than a few cycles on start up continues, the ball valves feeding the air handlers can be throttled back somewhat to reduce the flow and prevent repeated cycling of the zone valves (wait about 10 minutes after startup before trying to adjust so the system is not in a start up state).

We can work with your service company to make sure your air handlers are installed per these instructions, please have them call Tech Support at (800) 323-2066.



Jay

wvriem

@JayMcCay Thanks!

This definitely adds to my understanding of the system and what can be improved. Only one zone valve has red wires sticking out and even these aren’t going anywhere.

It looks like 10 years ago they upgraded the boiler but kept the air handlers (they’re much older) and didn’t hook up these red feedback wires to the air handlers. Air handler does continue (“but relatively dumb”) to fan a few (dip switch selectable) minutes after being satisfied to vent heat to all the zones (a Honeywell 4 zone controller box does that).

I am looking into replacing the 20 odd years old air handlers (at least the ground floor one) this spring so that would be something to look into.

Meanwhile I’ll see if the Honeywell zone control box (“Total Zone 4”) has something allowing for delay start of the fans. Will make sure the new air handlers can do something with this.


Thanks again

@wvriem

JayMcCay

You’re welcome, it’s still worthwhile for better operation and savings to correct sooner rather than later, and the same wiring should apply to the new air handlers. Again, if your contractor has any questions, just give our Tech Support team a call @ 800 323-2066

Regards
Jay

wvriem

Hi @JayMcCay,


I’ve had a look at the current wiring and my thermostats are connected to a Honeywell total zone 4 box, which in turn controls the fan in the air handler.

This does not have a delayed start, but it does have a delayed stop. Wiring the red switched lines back to the air handler would be complicated, as they’re not near.

Do you have any diagrams on how to wire something like this (four separate zones on one air handler, two zones on the other)? Any control systems that work well with system 2000?

Meeting installers tomorrow to talk about new ac and air handlers, so will like to include a discussion on what control tech works best with a system 2000.


thanks again

@wvriem

Alan Welch

Possible solutions. 
1.  Don't have both zones start at the same time
2.check to see if the nozzle size/ firing rate was lowered from when first installed. 
3.Install an aquastat at the air handler to shut off the blower until the water temperature is above a certain temperature,  or try running the air handler on a slower blower speed.

wvriem

@ale

Alan Welch said:

Install an aquastat at the air handler.

Thanks, that might be the easiest solution for now - and possibly for the air handler I don’t want to replace just yet!

JayMcCay

Good suggestions, @Alan Welch. Simply setting the thermostats to start 15 minutes apart could help significantly. The restricting the flow on the zone ball valves to prevent cycling with the full load if necessary.

@wvriem , we can offer wiring solutions, although we need to see the schematics of your system and the specific Taco model to be sure we’re not missing anything. Typically, there will be a common and normally open terminal on the control to pull in the fan for heating. Those wires would be connected to the end switch instead and then you would have temperature control and thermal purge. It is important to confirm those wires are not used to pull in your fan for air conditioning, and that they are dry contacts.

Jay