Discuss No power to Manifold in the Water Underfloor Heating Advice area at Plumbers Forums

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Hi folks, hoping someone can help with a problem that's been perplexing me since just before Christmas..... I have a wet underfloor heating system installed in 2003 and manufactured by Underfloor Direct in NI - Now out of business. It's one of their triple tube systems and hasn't given me much bother since installation. It has 2 manifolds - 5 zones downstairs, 4 zones upstairs controlled by 4 wire thermal actuators (the additional 2 wires switching the pump via a microswitch in the actuator). There's also a thermostatic cutoff by the manifold that trips the power to the manifold and pump if the temperature gets above 60deg. I've changed a number of the actuators over the years but as I said, not many issues.
Just before Christmas, we woke up to a cold house. On checking the manifold it was clear the pump wasn't running. Trying the reset on the thermostat cutoff had no effect as it hadn't tripped and it was clear after checking with a meter that there was no power to either manifold and no power to the thermostatic cutoff either. I then wired the pump directly to the mains with a timer synchronised to the boiler, disconnected the actuator heads and felt like a hero for getting heat back into the house. Now that it's summer though I'd really like to see if I can find the issue.
There might be a timer somewhere. Whenever I've reset in the past, it takes about 10minutes for the pump to activate. However, there is none visible on any of the wiring visible around the manifolds. I've checked at the consumer unit and it's giving 240V no issues. There's also a general CH power switch under the stairs at the main manifold which is not showing any power. I've replaced an actuator to guarantee that there is at least one microswitch functional on the offchance that was the issue (the microswitches fail fairly often)
I'm thinking there must be a timer circuit somewhere that has failed after 20 years. However, It's not visible on any of the wiring. Is there a chance the original installer hid a timer circuit in the wall? If so would there be a favourite location for this? I've checked within the power switch under the stairs, but haven't looked behind yet.....
Or is there another, more obvious reason why there is no power getting to my manifolds?

Any help greatly appreciated!

Thanks

Graham
 
There should be a time control somewhere for your heating.

In order check

Supply to the CH system. This will be typically from the ring main with a fused spur but do check your consumer unit that they've not put in a seperate circuit for your CH. The fused spur or plug could be at the boiler or an old airing cupboard. Check you have a 240v on the supply going into the fused spur/socket and then 240v on the load on the way out (aka checking the fuse)

Once you've established the circuit is live the next thing will be the timer which you need to find. Again typically in an airing cupboard or by the boiler. It also might be built into the boiler. Once you have found this you need to check 240v into it and then 240v out. Do this by turning the demand for everything off and then one by one turning it on and checking the terminals for voltage. The timers might be the room thermostats.

Do the same again for the room thermostats. checking voltage is present and then voltage is going to the underfloor heating manifold when there is a demand

After that the power goes to the manifold. There should be a wiring center there that picks up all the thermostat cables and then connects to the actuators. The actuators will likely connect to the boiler in here

Check the thermal cut off as well. It will be a normally closed switch meaning it creates a circuit unless tripped. This is easily testable by checking continuity on the 2 terminals


A photo of your power switch under the stairs might be helpful for us to help diagnose
 
Any pictures of the manifold / wiring and the boiler
 
There should be a time control somewhere for your heating.

In order check

Supply to the CH system. This will be typically from the ring main with a fused spur but do check your consumer unit that they've not put in a seperate circuit for your CH. The fused spur or plug could be at the boiler or an old airing cupboard. Check you have a 240v on the supply going into the fused spur/socket and then 240v on the load on the way out (aka checking the fuse)

Once you've established the circuit is live the next thing will be the timer which you need to find. Again typically in an airing cupboard or by the boiler. It also might be built into the boiler. Once you have found this you need to check 240v into it and then 240v out. Do this by turning the demand for everything off and then one by one turning it on and checking the terminals for voltage. The timers might be the room thermostats.

Do the same again for the room thermostats. checking voltage is present and then voltage is going to the underfloor heating manifold when there is a demand

After that the power goes to the manifold. There should be a wiring center there that picks up all the thermostat cables and then connects to the actuators. The actuators will likely connect to the boiler in here

Check the thermal cut off as well. It will be a normally closed switch meaning it creates a circuit unless tripped. This is easily testable by checking continuity on the 2 terminals


A photo of your power switch under the stairs might be helpful for us to help diagnose
Thanks for the prompt reply, and reassurance that I'm on the right track! I'll get a photo on the power switch under the stairs after work today. In terms of the rest of your reply and some further information:

1. The CH is on its own circuit from the consumer unit and I've checked that 240V is going out from there.

2. The boiler was installed as a 'hot running' configuration with it always supplying a hot source to the manifold. It's on a seperate circuit joined by a heat exchanger (as the UFH pipes have no oxygen barrier). Around 10 years ago I moved the original oil boiler (Warmflow 70/90) to the garage as a backup and installed a wood bellet boiler (MCZ Compact 24) to the garage also as the main heating. Removed the 'hot running' configuration to save money and now only have it come on at timed intervals. The room thermostats are setup to take advantage of then the heat will be available. I don't think there's any timer on the boiler side as they work independently.

3. Room Thermostats are Danfoss TP5's which are battery powered but appear to switch 240V connections from the manifold (which in my case has no power). One thought I did have was whether these may have been slowly failing over the last 20 years and the last one gave up in Dec. However, I'm not seeing 240V supply getting to these so I think they are not the issue.

I'm almost convinced there is a separate timer circuit hidden somewhere and I'm hoping now that it's somewhere in the same cupboard as the consumer unit. I'll keep searching and let you know how I get on!

Thank you!
 
Thanks for the prompt reply, and reassurance that I'm on the right track! I'll get a photo on the power switch under the stairs after work today. In terms of the rest of your reply and some further information:

1. The CH is on its own circuit from the consumer unit and I've checked that 240V is going out from there.

2. The boiler was installed as a 'hot running' configuration with it always supplying a hot source to the manifold. It's on a seperate circuit joined by a heat exchanger (as the UFH pipes have no oxygen barrier). Around 10 years ago I moved the original oil boiler (Warmflow 70/90) to the garage as a backup and installed a wood bellet boiler (MCZ Compact 24) to the garage also as the main heating. Removed the 'hot running' configuration to save money and now only have it come on at timed intervals. The room thermostats are setup to take advantage of then the heat will be available. I don't think there's any timer on the boiler side as they work independently.

3. Room Thermostats are Danfoss TP5's which are battery powered but appear to switch 240V connections from the manifold (which in my case has no power). One thought I did have was whether these may have been slowly failing over the last 20 years and the last one gave up in Dec. However, I'm not seeing 240V supply getting to these so I think they are not the issue.

I'm almost convinced there is a separate timer circuit hidden somewhere and I'm hoping now that it's somewhere in the same cupboard as the consumer unit. I'll keep searching and let you know how I get on!

Thank you!
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Photos attached showing power switch under the stairs for the manifold and circuit for CH on the consumer unit. Cheers.
 
Do you have zone stats ? Eg room stats for each zone
 
Yep, Danfoss TP5's in each room

There’s your timers

So make them call and you should have power on the black and brown wires

If you don’t do you have 240v on the red in terminal 4/5 in the manifold jb
 
There’s your timers

So make them call and you should have power on the black and brown wires

If you don’t do you have 240v on the red in terminal 4/5 in the manifold jb
Thanks - When the thermostats call for heat you can hear the relays in them click, but no 240V in the brownor black wires. Similarly, no 240V in any of the red wires. There's just no power getting to the manifold for some reason?
 
Have you checked you have 240v going into and out of the room stats? They might be switching via low voltage battery or the relays aren’t working. You need to trace the electricity step by step forward or backwards in the switching order
 
Thanks for this - Yep, checked all room stats and there's no 240V either in or out at the back and not at the manifold side either. I'm still thinking that the 240V is going missing between the consumer unit and the understairs power switch - which is why I was thinking that there's a timer somewhere?
 
Has the boiler get power ? / picture of it please
 
Yes there should be else how does it know to heat up sounds like it’s not been wired right from day one
 
Yes there should be else how does it know to heat up sounds like it’s not been wired right from day one
Thanks. Like I say, I've had this setup for 20 years now with no real issues. Originally the boiler was in a 'hot running'configuration, constantly supplying heat on a primary loop to the manifold heat exchanger. The manifold is on a seperate hot water circuit and decides whether to distribute the heat or not depending on what the room stats are asking for. In this setup there is no need for the manifold to talk to the boiler. When the temperature in the primary loop drops, theboiler comes on and tops it up.
About 10 years ago, I changed to the wood pellet boiler and decided it could run cheaper, so set times on the boiler controls when to come on and off. I then set the room thermostats to only call for heat during these times. The operation and wiring is the same though, just at specified times.

It's been fine for 20 years, but the power to the manifold has gone now. I'm now wondering if its as simple as the wall monted power switch under the stairs. I'll check that tonight.

Thanks

Graham
 
Thanks. Like I say, I've had this setup for 20 years now with no real issues. Originally the boiler was in a 'hot running'configuration, constantly supplying heat on a primary loop to the manifold heat exchanger. The manifold is on a seperate hot water circuit and decides whether to distribute the heat or not depending on what the room stats are asking for. In this setup there is no need for the manifold to talk to the boiler. When the temperature in the primary loop drops, theboiler comes on and tops it up.
About 10 years ago, I changed to the wood pellet boiler and decided it could run cheaper, so set times on the boiler controls when to come on and off. I then set the room thermostats to only call for heat during these times. The operation and wiring is the same though, just at specified times.

It's been fine for 20 years, but the power to the manifold has gone now. I'm now wondering if its as simple as the wall monted power switch under the stairs. I'll check that tonight.

Thanks

Graham
OK, I think I might be getting somewhere now. I removed the switch plate from the wall power switch under the stairs. The switch had continuity, so all good. However, with the power on at the consumer unit I'm only getting 8V AC into and out of the switch.

Reckon it must be a bad circuit breaker or ground connection in the consumer unit. That's what I'm going to try next, so I'll report back on whether it's been successful or not. Cheers.
 
The boiler and pellet boiler wouldn’t work so not circuit breaker / mcb
 
Hi folks, thought I's just close this out with an update. I've now resolved the issue and everything is working fine. Seems that when the oil boiler was moved to the garage, the appliance power switch that was left in the utility room and I didn't think did anything, actually did. At some point I've switched that off as there's no boiler there and it's broken the cicuit from the consumer unit to the understairs manifold. Kicking myself that I never reailsed this earlier, but it's all good now. Thanks for all the assistance.

Cheers

Graham
 
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