Embassy Onex suddenly won't heat past 67-70F

cjalbert

Hello all - I recently purchased a new home with an Embassy Industries Onex 160C combi unit for domestic and heat. I've already found useful information on this forum so decided to make an account and post a request for help. I honestly don't know much about heating so have been reading and learning quite a bit but still have limited knowledge. I tried to provide a decent description but let me know if you'd like more info or pictures.

Background:
The unit was installed in 2011 and appears to have been serviced, by the installers, yearly. I am waiting on copies of the previous records. It's a ~1500sqft house with two zones, controlled by taco zone valves, and baseboards for heat. We have a hydronic heater in the garage that is on an open loop, with the fan controlled by a thermostat. The unit is piped for natural gas. There is an external expansion tank and some sort of condensate neutralizer built into the system. When we first moved in, the temps dropped to -30F and the heater seemed to hit whatever temp we set it to.

Work done:
Soon after the cold snap, we had a "FILL" error, which turned out to be a bad/ dirty fill sensor. We had a technician come out and replace the sensor, he also noticed a loud noise on startup and replaced the combustion fan. He left and the next day our house was up to 80F. We realized the downstairs zone valve was left open. After closing the valve the temp dropped to thermostat temp (68F-70F).

Issue:
The next day we left on vacation (~3 weeks) and when we came back the house would not heat past 67F. Turning the thermostat resulted in the boiler running constantly (LCD panel displayed "c.#.#.#.#) but didn't increase the interior temps. Also, we noticed an increase in the gas bill so I assume it was running frequently while we were away. The tech came back and said everything is functioning mechanically but tried turning the unit to "high-temp" mode by flipping one of the switches, as described in the manual. He bled a tiny bit of air from the lines, but said it wasn't very much. It was in the teens but now it's getting into the high 30s during the day. The combination of high-temp mode, no air in lines, and increased outside temps allow the house to heat to 70F. Also, weather records indicate similar lows but higher high temps now then when the house hit 80F.

What I've done:
Turned up the thermostats to high 70s. Left the zone valve on 'open' overnight. Tested temps of downstairs registers, which I think are okay (~170-180 as checked with my muti-meter probe?). Increased the pressure from ~16PSI to 20-21PSI. Tried a new thermostat. Checked voltage (~27V) and operation of both zone valves when thermostats call for heat. Checked to make sure that the auto-vent on the Onex was open.

Finally, we didn't use the original installers for this work because we were given a home warranty and this new company is only option under the warranty.

Questions:
Should I be able to heat my house to more than 70?
Why did the house get hot (80s) with an open zone valve but now it only reaches 70 with an open valve?
Could the described repairs have anything to do with this?
Should I take apart and clean the unit as mentioned in the yearly maintenance section of the manual?
Is it worth reaching out to someone outside of the home warranty network (i.e., original installers)?
Is there anything else I should be asking / looking at - again this is all new to me so feel free to inform me of very simple things I should have looked at prior to posting...

Thanks for any help and sorry for such a long post!
Chase

kcopp

Is the outdoor temperature sensor wired into the unit? What temperature is running out to the system?
You need to get someone there who knows how to go through the control and look at the parameters/ settings of the control.

SuperTech

You shouldn't have raised the pressure, the boiler pressure and the settings of the fill valve and expansion tank are all set in accordance to each other. Leave the thermostat set to a comfortable temperature and leave it alone. Don't force the zone valve open, let the thermostat control the zone valve.
It sounds more like something is screwed up with the boiler settings or outdoor reset control, which it should be using. I'd see about getting someone else in there that is familiar with that make and model.

cjalbert

kcopp said:

Is the outdoor temperature sensor wired into the unit? What temperature is running out to the system? ...

The outdoor temperature sensor is wired to terminals "OS" inside the unit. I haven't checked the probe end yet. The display shows 186F and the heating supply pipe measures ~176F, just under the unit.

SuperTech said:

You shouldn't have raised the pressure, the boiler pressure and the settings of the fill valve and expansion tank are all set in accordance to each other. Leave the thermostat set to a comfortable temperature and leave it alone. Don't force the zone valve open, let the thermostat control the zone valve. ...

Should I be concerned about the pressure increase or reset the pressure to what it was? The manual mentions bringing the pressure up to 20 if it was below that, so I just assumed! Also, I quit messing with thermostat and zone valves and they've been on 'normal' for a few days (68F and auto).

Thanks for the help - It looks like both of you recommend having someone more familiar with the system check it out so I'll see if the installers can make it out.

SuperTech

Let us know what the diagnosis of the problem is, and what they are recommending.
A competent technician will drain the boiler and remove the expansion tank from the boiler piping or empty the boiler and check the pressure of the air bladder, he should make sure the fill valve is set in accordance to the pressure of the tank.

Unless it's extremely cold where you are or your boiler is making DHW the outdoor reset isn't working. But I don't understand how you are having a problem heating with the boiler at max temperature.

Time to start feeling pipes and seeing if you are circulating hot water properly. I would like to see pictures

kcopp

Boiler temp is at 186? That is plenty hot. Air locked? How is it piped? Got pix?

cjalbert

Well the home warranty folks wanted to install a zone valve in my garage loop thinking that it was returning hot water too quickly and shutting down the unit. The quote was $, so I held off.

However, the original installers came out and found: 1) air in the buffer tank and 2) said the P-parameter was likely set high. It was at 100 so he turned it down a bit. My understanding was this could have caused it to heat too quickly and shutdown (short-cycle?).

Last night, we turned the thermostats up and the home heated like it used to! I think the issue was solved but I added a few pics of the install.

Thanks again for the recommendations.

kcopp

Ideally should have been piped pri/ secondary. The install manual shows it should at least have a bypass w/ a throttling valve. Glad its working for you...