I'm in the midst of installing a Ritetemp 6030 programmable thermostat to replace an ancient Honeywell Chronotherm. The wiring was simple enough(R and W) but I am wondering if there is a way to derive 24V(C) from the Honeywell Aquastat(model L8148E). I found there is a separate transformer on another wire pair that is(now was) used to power the clock in the Chronotherm but being separate, I have no C.

Any ideas? I have to do this install again on the other side of a duplex and would hate to have the tenant's heat fail because the batteries in the thermostat died... not to mention on the owner's(my GF) side...

 

The obselete H-W L8148E has a built in transformer and will supply 24v from its T & TV terminals to your thermostat.
You don't need the seperate transformer. Here are some wiring diagrams for what I assume is your model of Chronotherm:
Product
This leads to a page from HW. Go to the bottom of the page, choose T8095 to get a .pdf. The last page on the pdf has the schematics you want.
Tom Beer 4U2

 

This is the RiteTemp wiring:The RiteTemp Support Site - Label and Remove Wires
Between the 2 diagrams, It should be easy to figure out the wiring.
Tom Beer 4U2

p.s. In this it states "The batteries will last longer with the transformer hook-up." The batteries only come into play during a power outage, and then, only to keep the clock at the correct time...so you don't have to reset it when the power comes back on.

 

You should have the two wires from the thermostat connected to the T and TV terminals in the 8148E, is that correct?

If so, you can pick up the 'other' side of the transformer on either the W or the Z terminals, which should be linked together with a jumper.

If you do this, be certain that the RH terminal on the t'stat is wired to the TV terminal on the aquastat, and the W terminal on the t'stat goes to the T terminal on the aquastat.

In other words:

thermostat / wire / aquastat
RH ---/---RED---/---TV
W----/--WHITE-/---T
C----/--OTHER-/---W or Z

Refer to:

8148 install PDF

While this doesn't show the use of that terminal, it does show the internal transformer connected to those terminals.

You do not need the other transformer...

Those batteries should last a good long time though if you choose not to wire the power.

(Tom, you type fast! Beer 4U2 )

 

Hey Trooper, I would have replied quicker if I didn't have to look up 2 obsolete parts and a big box brand T-stat... Haven't seen a Chronotherm in a while.
Tom Beer 4U2

 

Guys,

Thanks for the info, was surprised with the response time what with "the game" yesterday.

T and TV connections are as Trooper asked. The W/Z terminal is unused and I will tap that for the C. I will probably run some new wire as the existing is 2-conductor lovely cloth insulated type which is spliced halfway along the run to newer wire. An added benefit is being able to remove the extra transformer which is a little noisy.

Sometimes it can be scary to unearth things while doing projects like these... this part will be easy compared to what I have to repair as far as where the t'stat mounts(old crumbling plaster lath)

 

One thing to beware of when remounting the thermostat... make sure you plug up the hole where the wires come through, you don't want the cooler air from inside the wall flooding the inside of the t'stat and 'tricking' it into thinking the room is colder than it is.

I was bored with that game... yawnnnnnnnnnnn.

 

That's going to be the fun part... it's a BIG hole that was covered by the Chronotherm's subbase. I have the t'stat temporarily installed(read: hanging by the R and W wires) and I suspect that phenomenon prompted a call from the GF today about the way the system is running. I'm sure it has something to do with why the old thermostat never got turned up past 65.

Between fixing the wall and running a new wire for the C/W/H I'm gonna be into it a few days... isn't this the way it always happens!

I guess I can look at it as R&D for when I do it on the other side...(such an appropriate smiley)