Monthly Archives: March 2018

Plumbing & Heating

Central Heating Frost Protection

12 Comments

Updated 8 February 2023

Due to the recent cold snap and the fact that my central heating boiler is in the garage, I thought I’d install frost protection which will override the heating controls and fire up the boiler when the frost stat air temperature is  at or below +5℃, on the return pipework to the boiler is pipe stat set for +25℃ to turn the boiler off.

I have a Hive system which has a frost setting on the internal thermostat, this will bring the heating on if the temperature falls to +7℃ or below, the garage frost protection supplements this.

I spotted the Honeywell Frost Protection Kit – K42008628-001 comprising of a Frost Stat and Pipe Stat for £27.00 on eBay which is a really good price compared to Screwfix, Plumbase and Toolstation, so I bought it.

stat

For the installation, apart from the stats, I needed some heat resisting cable for the pipe stat and a double mounting box.

2 core and earth (3093Y) 0.75mm2 heat resisting white round flexible cable was bought off the internet from Under Control Instruments (www.undercontrol.co.uk)  for £4.00 which is temperature rated to 85℃.

The double gang surface box took a little bit of searching as I needed one with the flexibility to be used either vertically or horizontally with face-plates in the correct orientation, this cost £3.99 off eBay.

switch
Original installation showing the boilers isolating switch, the white flex is from the pipe stat.

First job was to wire the pipe stat and install it on the return pipe to the boiler, the stat is held in place with a spring which hook onto lugs on the base of the stat, getting the spring behind the pipe and stretching it to fit was made easier by tying a piece of string to one end of the spring and passing that behind the pipe.

Hooking the spring on the stat lug and keeping tension on the string, offer the stat to the pipe and pull the string to stretch the spring round the back of the pipe and hook it on the opposite lug, once done the string is simply cut off, this worked very easily once you got the knack.

pipe stat

With the power isolated, the existing isolator was opened and a picture taken for reference.

The Blue (Neutral (N)), Yellow (system calling for heat – switched 230v (L2)) and Red (Live (L1)) are from the junction box wiring centre, the opposing wires in the isolator are to the boiler.

isolator

Once everything was identified and proved dead, the wiring was removed and the new double gang surface box was fitted and wires pulled back in.

The two red sleeved blacks were separated, one will be connected back into L2, the other will be used by the frost protection system.

dual

The isolator was wired up and screwed into place, then the frost stat was fitted but it did not sit right as it was very slightly smaller than the back box so I needed packing to make it level, for this I used an off-cut of trunking lid, which did the trick.

packing

Once the Froststat was fixed in place and connected, the power was turned on and the frost protection tested by simulation that everything worked ok, including the operation of the Automatic Bypass Valve, once done the trigger temperature was set and the stat lid fixed in place.

I did notice a draft from behind my changeover switch on the left of the picture which was blowing across the face of the froststat, so I sealed the gap with decorators caulk to avoid inaccurate operation of the stat.

frost stat
Froststat and isolator, I bought additional lower cover screws and two were missing, the part number is Vaillant 290811 Clips.

As I have recently installed an Automatic Bypass Valve, I have not connected the frost stat to any motorised zone valves, therefore, once the air temperature is at or below +5℃,  a switched live will be applied to the boilers ‘calling for heat’ via the red sleeved black wire, the boiler will now fire and the circulation pump will operate.

As the motorised valves to either the central heating or hot water cylinder will be closed (‘S’ Plan system), the pumped water pressure will ‘lift’ the automatic bypass valve, maintaining a heated water flow to the boiler via the return pipework to which the pipe stat is affixed.

Once the return pipework is above +25℃, the pipe stat opens the series wired connection from the frost stat, this removes the switched live to the boiler, and the boiler enters ‘no heat run on mode’ before switching off.

The job took 2 hours and cost £35.00 and although we have never had a problem, the boiler and pipework in the garage should have had effective frost protection from day one.

Update

19 March 18 – The boiler came on unexpectedly and it was caused by the frost stat, closer inspection reveled that one of the bimetallic switch support pillar was snapped inside the unit, I’ve contacted the seller on eBay to see if I can get a replacement.

20 March 18 – eBay seller responded to my mail and is sending a replacement unit out.

24 March 18 – Replacement froststat arrived in good order and installed, all working now and the original unit sent back to the seller.

15 December 2022 – Had a few really cold days of around -5oC and the garage internal temperature sensor was reading 4.25oC

I took the cover off the frost stat and I must have moved the dial when I was replacing the lid as it was set below +5oC, I have readjusted this now, so all should be good.

3 February 2023 – Timeguard TRT031N electronic frost thermostat arrived from Fastlec at a cost of £22.36.

Manual for Timeguard

I found the mechanical frost stat to be quite inaccurate, the replacement is electronic and should therefore be reliable.

Electrical & Security

BRK 86RAC Smoke Detector Replacement and Additions (UK)

11 Comments

Updated 6 January 2022

I have two BRK 86RAC Ionisation type smoke detector, one in the Hall and the other on the upstairs Landing, these were installed by the builder and in 2008 I added a heat detector (690MBX) in the garage, all three devices are mains powered with battery backup and are interlinked so that they all alert to a detection.

BRK 86RAC
BRK 86RAC Discontinued ionisation smoke detector.

Checking the batteries in the smoke detector I noticed the unit has a life of 10 years from date of manufacture which was 21 June 2002, as the date of noticing this was 4 March 2018, they are well overdue for replacement!

The BRK 86RAC is no longer produced and has been replaced by the  BRK 670MBX.

brk

Checking my local Screwfix had BRK ionisation smoke dectors (part number 81969) for £12.99 and the surface mounting kit (part number 30152) for £2.99, I thought I would add two more to my system, so bought  four of everything.

On opening the boxes, I didn’t realise that the detectors came with 9v PP3 type batteries, so wasted £6.00 buying them, and the other thing was that they are not a direct replacement, the 86RAC base is a smaller size and the plugin connector is a different style.

parts
In the box are the above plus instructions, sticker for the consumer unit and protective detector cover, no fixing screws are supplied.
Fitting –

First job was to isolate the mains supply to the existing detectors which are on their own dedicated circuit, once this was done I twisted the detectors from the base to allow me to take photographs of the wiring.

The existing wiring was Black to Neutral, Brown to Live and Orange striped is the interconnect wire, 670MBX uses Blue for Neutral, Brown to Live and Grey for the interlink, the existing detector had a ferrite bobbin through which all the detector wires passed, whereas the new model doesn’t, I decided to reuse these on the replacement units.

old

Once the cable colours were recorded, the detector was unpluged and the base completely disconnected to allow the replacement of the new base, once this was screwed into place, the connections were remade.

base

The wiring in the base looks more complicated than it should due to the change of cable colours, the existing 1mm CSA 3 core and earth used the pre EU harmonisation wire colour convention of Red, Yellow and Blue,  the cable to the new additional detectors which I have installed are in the office and IT cupboard, uses harmonised colours of  Brown, Black and Grey, as the installation has mixed wire colouring, a warning notice to this effect is fixed to the consumer unit.

While the new detector was on the desk, the battery was dated and connected, without a battery installed the detector will not engage in the base, this is a safety feature.

After making the connections, the detector base was fixed to the surface fitting by two supplied screws, the cardboard sealing gasket was then pressed into place covering the detector base fixing holes, the next step was to plug the lead into the base of the detector and lastly twist the detector into the base.

new

Within the baseplate of the detector is a small plastic extrusion  which can be removed, this is used once the detector is installed as a locking clip preventing the detector being removed from the base with the clip in place.

With all detectors connected and new ones installed, mains power was turned back on, and each detector was then checked that it showed a continuous green LED for power healthy and a flashing red LED every 60 seconds to show the detector is functioning.

The center test button on each detector was pressed and held, this caused the local unit to sound, followed a moment later by all the other interconnected heads.

I had already sealed the cables passing through the ceiling, the final job was to seal the base to the ceiling and paint the exposed part of the ceiling as a result of the base being smaller than the original one.

A point to note was that I was going to use flushed in circular dry lining boxes to make the connections in and hold the base, this would have made the smoke detector sit closer to the ceiling but would of meant a large hole being made, so I decided against it.

Job was very straightforward, adding new detectors was easy as I looped off the landing detector to the other units which were only a few meters away.