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-   -   No delay of Blower ON for Rheem electric furnace? (http://www.diychatroom.com/f17/no-delay-blower-rheem-electric-furnace-190030/)

justplumducky 11-09-2013 01:12 PM

No delay of Blower ON for Rheem electric furnace?
 
Rheem Electric Furnace/Model# RBHA-17j15sfa (an older unit)

Is it normal for this blower to not have any ON (start-up) delay when the t-stat turns the unit on? (compared to a standing pilot gas furnace that heats the heat-exchanger up first, then turns blower on?)

yuri 11-09-2013 03:04 PM

lesson 4 U. if you get an electronic tstst and set the switch to elec instead of gas it will energize the G terminal and start the fan instantly which is the way it is supposed 2B. some elec furnaces use contactors instead of sequencers and W pulls in contactors and a fan relay with no time delay.

justplumducky 11-09-2013 03:40 PM

Thank you for the lesson. Is it because the heating element(s) would get too hot unless air is already moving when they're switched on?

yuri 11-09-2013 05:54 PM

no. it is just the way they do it w/o sequencers.

justplumducky 11-09-2013 06:47 PM

On this particular unit, 24vac Red wire leaves transformer mounted on furnace cabinet, goes to t-stat, comes back on White wire from t-stat, connects to three individual wires at furnace cabinet, two of which feed the two heat sequencers (brass quick disconnects at base of sequencers) - the third one feeds the hot side of Fan Relay coil.

The opposite side of the heat sequencers (brass q-d's at base) and the common side of Fan Relay coil all connect to common of transformer mounted on cabinet.

As I've described the wiring connections above, the Fan/Blower will energize immediately with a call for heat, but there will be a slight delay (per the timing of the heat sequencer) of the first heating element(s) turning on. Correct? This would give an initial blast of room temperature air, before the sequencer energizes the first heating element(s). Is that normal/acceptable?

yuri 11-09-2013 06:54 PM

Yes, sequencers REALLY are there for where I am and you have 30 kw furnaces with 6 elements. the power co does not want 6 of them hammering on at the same time as lights will dim etc. electric furnaces are not really designed to be very deluxe or have comfort features just do a basic job.

justplumducky 11-09-2013 07:03 PM

The depth of your answers is much appreciated. Have a good night.

justplumducky 11-09-2013 07:45 PM

Quote:

Originally Posted by justplumducky (Post 1264598)
On this particular unit, 24vac Red wire leaves transformer mounted on furnace cabinet, goes to t-stat, comes back on White wire from t-stat, connects to three individual wires at furnace cabinet, two of which feed the two heat sequencers (brass quick disconnects at base of sequencers) - the third one feeds the hot side of Fan Relay coil.

The opposite side of the heat sequencers (brass q-d's at base) and the common side of Fan Relay coil all connect to common of transformer mounted on cabinet.

When the call for heat is removed, I believe these heat sequencers de-energize the heating elements in delayed, reverse order, but the Fan/Blower will shut down instantly when call for heat is removed. This unit is a 15 KW unit/ a total of 3 individual, crescent moon-shaped "Calrode" (so I've seen them called online) heating elements. Would that be a problem for this unit?

yuri 11-09-2013 10:21 PM

Ideally it is better to have the fan shut off after all the elements but the manufacturer did not seem to care IMO plus those old school elements were tough as nails and did not seem too care either. Nowadays they hook them up to sequencers or a time delay relay on these condo units etc.


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