SCR retrofit kit

zepfan

Does anyone know if there is a field installed retrofit kit that is made to convert a three phase 15 kw, single stage electric heater to an SCR heater? And if there is an economic savings as far as energy use age to having one installed? We have a customer that has two packages AC and heat units that are straight AC with electric heat,not heat pumps.We did not install the units, and it was a bad decision to go with electric heat only over a heat pump.We are trying to get them to operate as economically as possible for this customer.Thanks to all

SWEI

Thermolec might be able to help (click on the 'Electric Components Optional' link on http://www.thermolec.com/en/components.aspx)

ratio

I've used the Viconics R820 series before to modulate a 20kW 480 volt 3 phase reheat coil, they take a 2-10V / 4-20mA control signal. (I'm not affiliated with Viconics, that's just what my favorite supply house carries). I used a Honeywell T775 to control space temp with discharge air reset. So far, it's working fine.

You might have trouble integrating analog heat with what sounds like a more-or-less standard A/C setup. I have seen interface boards that will covert staged calls into fixed analog output voltages (but have never used one), that would allow you to use a standard stat. There is a model of the T775 that has relays as well as analog output, they can be massaged into providing staged cooling with analog heating, but they don't have quite the same programmability as a programmable stat & of course look nothing like a stat to most "users".

As for the economics of it, I'm not sure there is any. The SCRs merely shorten the ON-OFF cycles from the cycles-per-hour that a stat uses to what amounts to cycles-per-minute. If you need 10 kW out of the heater to meet your heatloss, it shouldn't make a difference if that's 40 minutes ON out of every hour or 40 seconds ON out of every minute over that same hour. You may see a comfort difference, however, as that 15kW banging in and out will result in the discharge air temp going up and down -- the analog output should settle down to a fairly steady discharge temp.

zepfan

Thank you so much for such a detailed response,the more thought that I give it I don't think there would be any savings.Best option would be to replace the system with a heat pump