Testing RF link, Horstmann HRFS1 programmable thermostat.

[ericmark]

This has been going on for some time. It does not seem to matter what I do, the thermostat will start to work again as it should, then every 2 weeks or so it will play up.

I have moved the links and dip switches twice, assuming interference, renewed batteries, changed position. Each time it starts to work again.

Yesterday it failed off again, set at 22°C room went to 17°C and tell tail green light still off, removed from wall, took next to receiver, altered temp down and up again, got green light, refitted to wall, then when ready for bed found green light on when set to 16°C and room at 21°C so removed from wall and altered up then back down next to receiver to get it to switch off.

Idea was this morning to try to find the problem, but working A1 again.

Instructions simply say test if working, there is no signal strength indication. It has a single brick wall between the sender and receiver and about 3 meters between them.

It is only used in the day, at night a Honeywell Y6630D wireless thermostat is used which has at least double the number of walls and twice the distance and no problems. The receivers have a time switch and consumer unit between them. The receivers are next to back door, yesterday the exit alarm for back door went off, I don't think mother opened the door, so wondering if the door reed switch and wireless unit could cause the problem, however I would assume it only works when door is opened and that only happens 3 or 4 times a day, seems odd that it would happen at exactly the same time as thermostat called for a change.

Some where I do have a wave meter, but never really had much look using it, it was more to satisfy DTi than to use. I also have a radio FT50r, but not used in years, having a problem getting it to turn on. So I am trying to think of a method to test. Any ideas?

 

[bernardgreen]

How far is the receiver from the boiler ? If the boiler is a gas boiler that can modulate its heat output then odds are it has a variable speed fan. This is a source of spurious RF energy that is probably more than enough to compromise the operation of a near by receiver. A SRBR handset on 466 MHz had poor reception when the user was close to a gas boiler.

A failed fan recovered from a gas boiler was examined. It is a 5 phase motor with a 5 phase power generator supplying the 5 stator coils. The generator was built into the motor on a PCB without any EMC screening above the PCB. The 5 pseudo sine waves for the coils were produced by pulse width modulation of the 320 Volt DC produced by rectified 230 volt AC.

It was not possible to run this fan but the replacement fan inside the boiler could be "heard" on an AM radio receiver placed 2 feet ( 600 mm ) from the front of the boiler..

An informal chat with the fan manufacturer's technical department informally revealed that when fitted in a boiler the two layers of metal between fan and free space were more than adequate screening to meet EMC regulations.

 

[ericmark]

Boiler is 2 meters from receiver other side of built in oven. Same distance as the Honeywell Y6630D which works A1. If the horstmann hrfs1 failed on turning heat off only then maybe there is a problem with fan, but it also fails to turn on.