Replace Channelplus H37XL with H3747 - issues

[coolaboola12]

Hi All

Replacing a H37XL with an H3747, i have oil fired heating with one wired thermostat downstairs and one upstairs, two zones (downstairs and upstairs) and hot water

So i took off the unit, left the wiring as is as it should be the same and installed the replacement unit on it

The unit gets power ok and i can pair the PDT , all that works fine but the issue is that the oil burner isnt firing

I have just selected the first zone for example and click boost and nothing happens , i have also set the PDT for zone 1 to be a target of 27 degrees (its showing as 20 now) and again nothing happen

Any ideas ?

 

[stem]

They are different devices and the wiring is different.

H37XL is a 3 channel programmer which as you can see below requires separate wired "room stats" and "cyl stat"

H3747 Is a 4 channel smart thermostat that communicates wirelessly with PTD's (Programmable Thermostat Display) There are no wired room thermostats shown on the diagram below the wiring goes directly to the zone valves.

To use the H3747 to replace the H37XL your system will need rewiring to decommission the old wired thermostats which will then be replaced with wireless PDT's. The old wired thermostats can't just be removed they need to be electrically bridged to complete the circuit.

So the question is what has happened to the old wired room thermostats and their wiring? If they have been left wired in as they originally were, you should find that turning them up to their maximum setting will allow the PTD's to control the heating. If they have been removed, then the wiring should have been modified to facilitate their removal.

 

[coolaboola12]

The thermostats are still wired, nothing bad changed on that front. I turned up the thermostat to the max and thought the boiler would fire but it didn't

I read online that you can use your original thermostats with this device

 

[stem]

If the original thermostats have been left wired in as they originally were, you should find that turning them up to their maximum setting will allow the PTD's to control the heating.

If the H37XL is faulty and you can't find a new one, as they are no longer manufactured, then another 3 channel programmer that requires wired room thermostats can be installed [i.e. not a programmable thermostat] The Sangamo Choice for example. The wiring terminals on the backplate are slightly different so some of the wires will have to be moved to different terminals, but that's all.

If you have removed the old wired thermostats they would need reinstating.

 

[coolaboola12]

Ok thanks. There was nothing changed on the wiring so all should be good there. I'll check out the sangamo , thanks for the help

 

[coolaboola12]

Can you post a link to the correct sangamo choice please ?

 

[stem]

There's a link here. Other 3 channel programmers are available

I can't give it a review I'm afraid as I've never used one, but interestingly the wiring diagrams look remarkably similar in style to the Horstmann programmers. The terminals are in a different order, so some minor wiring adjustment would be required

Sangamo Choice PR3n Programmer.

 

[coolaboola12]

Thanks so much for the help.

 

[coolaboola12]

Is the wiring as simple as moving the wires from 1,3 and 5 on the horstman to 3,4 and 6 on the sangamo ?

 

[stem]

Yep, that's it.

CH1 on H37XL 1 = PR3n 4
CH2 on H37XL 3 = PR3n 6
HW. on H37XL 5 = PR3n 3

Assuming of course that your old wired thermostats are still connected as they were originally.

 

[coolaboola12]

Yep they are, thanks a million, you have really helped a lot