Aftermarket electric boiler controller

[jlv03]

After about 6 years of reliable use, my Thermolec B-6TMB-U electric boiler has lost its control board. Apparently the D22-B control board is no longer in production.

As the electric boiler is used to heat the floor in a 24' x 28' garage with primary bathroom and laundry room above it, I have temporarily powered one of the boiler's elements with a contactor to get some heat in the floor.

Thermolec makes a kit to replace the control board with a new version, but the prices I'm seeing online makes it hard to swallow - nearly $500.

So the question I pose - is there something else out there for cheaper? Or should I just scrap the boiler and install a cheap 7kW boiler for about the same price (referencing this I found on the Menards website: https://www.menards.com/main/plumbi...microboiler/sh3-07/p-1444433731813-c-8519.htm )

 

[fitter30]

Just get the menards boiler. Not worth trying to make another control work.

 

[PoorUB]

After about 6 years of reliable use, my Thermolec B-6TMB-U electric boiler has lost its control board. Apparently the D22-B control board is no longer in production.

Let me check Monday how much a TH22 kit will cost me. I used to sell Thermolec.

 

[PoorUB]

I am reluctant to say this, but if you are at all creative all you need is a aquastat, a contactor, and a high limit to make it work. It would no longer be modulating, but just on and off.

A friend just bought a house and the shop floor heat has a home made electric boiler, someone welded a 4" pipe closed, with a fitting for a 5,000 watt water heater element, a aquastat and contactor. About a $200 electric boiler!

Of course no UL listing, so I am surprised the city allowed it, or perhaps they never permitted the heat in the garage.

 

[jlv03]

There is a built in manual reset high limit that I kept in place for the backup/primary contactor, so it currently is not completely unsafe. I just have it setup with a second contactor to energize one out of the two 3kW elements whenever the thermostat calls for heat.

Would I even need an aquastat? Years ago I put in an ammeter to monitor if the outdoor reset was working correctly (it did not!) and I never saw the current change when the pump was on and the boiler was called for heat.

 

[American Locomotive]

Really the only thing you need is a flow switch, an aqua stat, and the high-temp cutout all wired in series to the contactor. The Aqua Stat is important to regulate water temperature, as the high limit reset switch is probably well above normal water temperatures.

You don't have to spend big money on an old school Honewell mechanical aquastat though. You can get a fairly inexpensive digital temperature controller and just stick the probe in a thermowell.

Something like this: https://chillxchillers.com/temperat...uastat-temperature-controllers?sku=112000-000

 

[PoorUB]

After about 6 years of reliable use, my Thermolec B-6TMB-U electric boiler has lost its control board. Apparently the D22-B control board is no longer in production.

I can buy the kit for $400.

 

[jlv03]

Like everything else on my to-do list, this one bumped down in priority.

I’ve been getting by with 3kW of floor heating. Even on days where the temps never got above zero F, I was able to maintain temp.

I guess this is what they mean when they say a properly designed system should keep temp on the coldest day of the year!

 

[jlv03]

It took long enough, but I finally broke down and picked up the replacement control board kit, from Blue Ridge Sales. Using a combination of the instructions in the kit, installation manuals from the latest Thermolec boilers, and these instructions (https://www.epsalesinc.com/wp-content/uploads/2017/11/D22-B-with-CM-to-TH22-Final-2.0.pdf ) I was able to get the new controls up and running.

I still suspect the outdoor reset wiring or sensor is bad, as it did not throttle on a warm winter day. Nonetheless both elements now function and the water temp goes up as expected.

What I was not prepared for is the slight difference in operation. The old D22-B controls would kill power to the heating elements right away when the thermostat signal went away. This worked great as an external Taco SR501-4 controller was used to turn on the pump and send the boiler TT signals. With the new controller, though, removing the thermostat TT signal does not immediately kill the heating elements. Instead the 2nd stage output drops out first (which doesn't do anything on this 6kW boiler) and then the elements shut off. With the pump shut off during this process the temp in the tank climbs about 5-10 degrees. Nothing dangerous, but a bit unsettling.

To get around this new problem, I swapped the SR501-4 controller for a Tekmar 301P (https://www.watts.com/products/hvac-hot-water-solutions/controls/zone-controls/301p). This Tekmar has two features that I wanted. The first is a pump exercise function. I had been band aiding a pump exercise in the summer by using the fan contact from my Nest thermostat as a parallel input into the "W" terminal on the SR501-4 and programming the fan to turn on for 15 minutes a day. It worked, but probably a bit overkill for pump exercising. Now I can skip that function on the thermostat and leave it to the controller.

The second feature, and what drove me to the 301P, is the pump purge. The 301P will keep the pump on for a few minutes after every call for heat. This allows for the orderly shut down that the Thermolec boiler expects and not produce that heat spike.

As a cold spell is coming through (high of 1F tomorrow in SE Iowa), I'll be putting this new setup to the test all day tomorrow.

 

[PoorUB]

It took long enough, but I finally broke down and picked up the replacement control board kit, from Blue Ridge Sales. Using a combination of the instructions in the kit, installation manuals from the latest Thermolec boilers, and these instructions (https://www.epsalesinc.com/wp-content/uploads/2017/11/D22-B-with-CM-to-TH22-Final-2.0.pdf ) I was able to get the new controls up and running.

Wow! Almost 1-1/2 years later!

How much was that TH22 kit? I'm guessing the price went up a bit?

 

[jlv03]

Price was about the same, which was my motivation to get moving (as there aren't a lot of things that are going down in price these days!).