1994 F.A.I.S. Aqua Heat AR-820 Boiler still in service in 2025

austinado16 · December 13

Hello All!

New guy here. I'm located on the CA "Central Coast" and the owner of a still operational F.A.I.S. Aqua Heat AR-820 Boiler. It powers the baseboard and floor heat, as well as domestic hot water, in my 1,200sqft, 1903 Victorian home. I relocated the home in Dec. 1993, and during the restoration, had a local company install the hydronic heating system.

It's always been a somewhat problematic system, both due to the extremely poor installation of everything (I knew nothing about this sort of thing at the time), and of course, the boiler unit. The hard water here does no favors, as well. When Solar Ponics was still willing to work on it, they finally installed a Taco controller, which greatly improved function. The pressure gauge on the dual gauge(temp and pressure) repeatedly failed on the pressure side, and eventually they/we just stopped replacing it. A rodent got into it from the open back side and created a massive short in the circuit board which burned up the board. I fixed that myself by resoldering the board and moving some pin locations to re-create the original layout, and it's been functional like that for probably 20-something years.

In Dec. 2017, there was a major failure of the boiler, and after the original installation company charged $450 for a service call to condemn it, I decided to take on the project, learn about boilers, learn how to sweat pipe, and rebuild it. I replaced the heavily corroded water pump, all of the pressure reliefs, and bypassed the pancake pressure tank and installed a modern tank external to the boiler, along with an adjustable water pressure regulator, external temp gauges in 2 locations, and a new top assembly for the air bubbler. To my amazement, the system refilled, bled itself, and worked better than it had since installation in 1994.

Recently the boiler has started to whine and howl about 30 seconds or so before the burner flame is shut off. I took the boiler apart enough to remove the blower fan housing, the vent located up in that top right corner, and get to the silicone hoses, as well as visually inspect the boiler matrix to see if it was cracked (it was fine). The vent seemed to be clogged/not working, so I cleaned that and confirmed function. One of the silicone hoses was kinked flat on the back side of the boiler, and I was able to resolve that by just repositioning the hose. Blower spun fine and was quiet still (amazing). I checked and pumped up the pressure in the pressure tank. No real change in the whine/howl even with changes to the system pressure using the pressure regulator located on the fill side.

I think I have a failing temperature controller on the front of the boiler. It seems to have lost sensitivity below the temp point of where it's been sitting all these years. So if I move the dial towards a cooler boiler temp, even a "smidge" of a movement, the boiler will not work. If I move it back towards hotter, just a "smidge" it will work, but then I get the howling/whining. I've noticed that the howling/whining doesn't occur as frequently when the system is heating the house, but when it's heating the water in the adjacent 40gal water tank, it howls/whines every time it cycles on and off, during that water heating for the tank. So literally about every couple of minutes until the water tank water is back up to temp and the system shuts down.

I popped the front off of the boiler yesterday and that temp controller is made by "Prodigy" in Italy, and is just a simple 2 prong unit with a probe up into the water pipe housing near the water pump. I found an identical until online: COSMOGAS 62101044 and it's somewhere in Europe on a website. I also found a ton of generic ones. I've ordered a cheap generic one just as a tester for my theory that I have a dead contact area in the existing controller.

I see in a thread here from 2021, a few of you were installers of these. It'd be great to get your thoughts, as you have waaaaaaaay more experience in these then I every will.

Thanks for reading my loooong story!

Here's the heart of the system(front panel removed for photo):

Here's a video I made in 2017 after my big repair:

https://www.youtube.com/watch?v=7vy8GuhZvRs

HeatingHelp.com · December 13

Welcome to Heating Help, @austinado16! I've removed you duplicate post to prevent confusion. Thanks.

austinado16 · December 13

Perfect, thank you!

hot_rod · December 13

Amazing that you kept it going all these years!

Howls or whining sounds are often related to scale formation inside the boiler. The minerals in the water cook out and coat the inside of the HX. As the flame hits the metal the scale forms an insulation layer, so boiling occurs on the metal surface and can make all sorts of unusual noise higher temperature increase the noise.

Old tea kettles can make similar sounds as well as water heater tanks

There are cleaners you can inject to dissolve the scale and flush it out. The cleaners help descale all the components and heat exchangers metals.

I suspect the minerals laden water is what took out air vents, air purger and relief valve. The white meringue is what we call the scale formation on the components

You are risking getting pin holes in the boiler if you use aggressive cleaners however

Maybe you have been saving up since 2017 for a replacement

Its not a matter of “if” but when it finally fails🫣

austinado16 · December 14

Thanks for all that info Bob! Coincidentally, Caleffi components are on this system!

The water here is very hard, so that could certainly be the issue, and having zero experience and knowledge with these systems, I had no idea. That said, the reasoning that made/makes me think it's the temperature control, (the knob on the lower panel with the white ramp painted on the dial, in the photo above) is that the sensor in the controller is literally dead at even the tiniest rotation "cooler" than where you see it in the photo.

For example; yesterday I reset the dial literally "barely any rotational movement" cooler than where the boiler was running at. I then lowered the thermostat in the house to 69*F, and let the house cool overnight to see if when the thermostat called for heat, would the boiler kick on. The weather has been summer-like here, so the house will sit at 72-74 all day, and still be 70 in the morning. At about 8am, I heard the digital thermostat "click" on and call for heat. I confirmed on the thermostat that the house was 69, and then went under the house (I can stand up in the crawl space) to watch what the boiler did. The boiler did not turn on. I waited for a moment, and still nothing. I touched the temp knob on the boiler and just wiggled it a little, and "click" the temperature control turned on, the boiler came alive, first powering the blower and turning on the water pump, and then the ignitor fired, the gas lit, and I was back to normal boiler function. I set the thermostat in the house to 72, just to let the system run for a long time, which meant cycling on and off quite a few times, as well as heating the domestic water, and everything worked fine… except for the howling that occurs just before the flame shuts off on each cycle. Pressure stays pretty constant, but looking at the 2 temp gauges that clamp onto 2 different areas of the system, the temp is up to 150*F. The system probably doesn't need to be that hot, am I correct? If I manually operate the temperature control, while the system is functioning, and shut the flame off when water temps are in the 140 range, I don't get the howling.

kcopp · December 14

Many years ago a supplier here in NH brought those in. They were a heat / dhw package an neat space. Indirect WH were a 26 gallon tank w/ a huge coil inside that had tremendous recovery.

The price point was very good hence my employer used them.

I am told the boiler was marketed in the UK under the name of Ravenheat.

It is similar to the Embassy BMS which is a Cosmogas boiler. Not 100% the same though.

I agree w/ hot rod about flushing it out. Unless you are ready to deal w/ the consequences dont use a descaler on it. Maybe a late spring project?

That way you could temporarily install an electric WH to get you through till you get a replacement.

austinado16 · December 14

I really appreciate the information and feedback on this! Thank you!

I grew up with oil fired hydronic baseboard heating in Alaska, which was fantastic. It's like having a fireplace that heats everything in the home. In my teens I lived in a cheap "track home" in coastal NorCal (Arcata) that had forced air. It was horrible. So when I "built" a house I was dead set on having a hydronic system. In 1994, quotes for a forced air system were only $1,500, installed. This system, with floor heat for the kitchen and master bath, and around the master bed, plus baseboards throughout the house, was $5,000. Have never regretted the decision, except for the repeated issues with the F.A.I.S boiler, even under warranty, and then of course after. It's also an extremely bad, poorly done, poorly laid out system, to the point of being embarrassing, and that has done it no favors either.

Mine is coupled to a 40 gallon stainless (I believe Italian made) boiler, part of which can be seen in the photo and video. Unlimited hot water, even when we were raising the family, and of course the heat in the home is fantastic. I let it run from 69*F in the house to 72*F this morning, just to see what it would do on an extended run. It howled a few times during the initial cycles, and was silent after that, other then the clicking of the baseboards.

A cheapie "replica" thermostat controller is on it's way, and when it arrives, I'll pop it in and see if the boiler temp can then be controlled as it used to be, and with it set to a lower temp, if the howling is cured. I went with a cheapie, because I couldn't find a quality replacement that appeared to be identical, and the COSMOGAS version is in Europe. I hate using cheap replica parts (I'm a mechanic), so this will just be for diagnostics.

If anyone has a used boiler or parts that they'd like to sell, I'd be interested in buying. This has never been difficult to repair, and even the big "redo" in 2017 where I was fully up against the learning curve, wasn't bad. Everything came from SupplyHouse, and I was able to replace the guts of the water pump IIRC.

bburd · December 14

Keep in mind that the European version of that controller probably runs on 240 V as used in Europe, not the 120 V used here. Some newer electronics are universal voltage, others are not.

austinado16 · December 14

Good call! Thank you! Since this a just a 2-wire version, is it taking 120v from one wire, and passing it to the other wire, which takes that voltage to the circuit board, which in turn, causes the burner to be activated… and then run until this unit breaks contact between the 2 wires. If so, does it care if it's fed 120v (which is what my boiler runs on) or 240?

Here's the actual OE unit. This is the one currently available in the UK, for $78US, labeled COSMOGAS. The replica I've purchased is identical, including the probe size, but a different color, and $22.

bburd · December 14

If it is basically a switch with dry contacts either voltage should work, depending on the ratings of the contacts; half the voltage means twice the amperage for the same load. You'd have to check the specifications.

austinado16 · December 15

Ok. Thanks. The original "Prodigy" one is rated 20A at 120v and 16A at 240v.

Alan (California Radiant) Forbes · December 15

We installed a couple of these back in the 90's and, of course, they are all gone now. Hydronic Specialties Co. (HSC) in Oakland sold them along with Infloor manifolds and polybutylene tubing. We've learned a lot since then.

austinado16 · December 15

Thanks Alan! "Solar Ponics" were the installers of my system, and at the time, it was probably one of their first/earliest installs. We offered our home to be a model to other customers, should SP want to show people an installed system and see how it worked.

I learned the hard way that the system was very poorly installed, and many of the initial issues in the first couple of years, were due to that. It would function "ok" for a while after they'd come out and repair it, and then return to having issues, which I/we just lived with because by then it was out of warranty, service call fees and the work/parts were expensive….etc. It was very frustrating and disappointing. When I'd go visit my brother in Illinois and see the system he'd built himself, all laid out on a large section of plywood, mounted to the wall, all organized, and easily diagnosed and repair, I'd be even more disappointed in what had been done with my system, and how difficult it made it to work on, and poorly it operated.

Not until the big failure in 2017, and my doing the work to it, has it ever run so good, and been totally silent (until the current boiler howling). The floors never worked well, and since 2017, the work fantastic, as do all the baseboard units. Again this morning, I left the system set to 69*F overnight, and then bumped it to 72*F just to let it run for an extended period. I heard the bowler howl, but not very loudly, a couple times, and after that, the system was silent other the clicking from baseboards. So even as-is, it's still functioning very normally, and so much better than in those early years.

1994 F.A.I.S. Aqua Heat AR-820 Boiler still in service in 2025

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