Underfloor heating in new build ... does it comply with regulations?

[ChrisHD]

Hi ... I'm a keen DIYer who has installed a few systems in the past. My parents have just moved into a new flat and are finding the heating system very difficult to use. I am wondering if the below specification is sensible or even complies with the regulations ...

It's a 2 bedroom flat (with 2 bathrooms) with underfloor heating. There are 6 wall mounted programmable thermostats (Heatmiser), 1 in each bedroom, 1 in the main living room/kitchen, 1 in the hall and 1 outside each bathroom. There are also heated towel rails in each bathroom with TRV's. The system runs from a combi boiler, and there is no central control system at all.

The first issue is that each of the 6 programmable thermostats has to be programmed individually, with no facility to link them together.

Secondly, I noticed that the boiler was running alot, even though all rooms were a few degrees above the thermostat setting. I talked with the site manager who showed me that the heated towel rails in the bathrooms are connected directly to the boiler without any control or timer (just the TRV's). Hence they are potentially on permanently unless someone turns the TRV's down (which he did).

I am bemused that a new build can have such a complicated system to set up and use ... 2 pensioners are required to program 6 separate thermostats and have to remember to turn TRV's up and down to dry towels.

I'd be grateful for any comments on the above. Many thanks in advance.

 

[SimonG]

Pictures of manifold?

 

[Sharp Point]

Hi,
Individually controlled room is actually the way forward in regards of energy saving, is it possible to just set the thermostat on the manual position ie 20 degrees and leave it at that.... for ease! It’ll keep that room at a constant temperature.
I personally would’ve put the towel rails on a zone valve and a programmer to facilitate control. If it’s a new build, you could get the onsite plumber to install one and get the sparky to wire up a programmer.

 

[doitmyself]

Secondly, I noticed that the boiler was running alot, even though all rooms were a few degrees above the thermostat setting. I talked with the site manager who showed me that the heated towel rails in the bathrooms are connected directly to the boiler without any control or timer (just the TRV's). Hence they are potentially on permanently unless someone turns the TRV's down (which he did).

That doesn't comply with the requirement to have an interlock which turns off the boiler when heat is not required. The only control is the boiler's internal thermostat, so the boiler will still run even though all TRVs are satisfied. (It may not run for very long; but it will start and stop continuously.)

 

[AWheating]

Time and temp required on towel rads on separate zone normally otherwise only on in winter when heating on.

 

[ChrisHD]

Thanks all for the responses so far ... I visited again today and took a couple of pics as suggested.

Following doitmyself's comment I can confirm that the pump and boiler are running permanently (short boiler burns).

Is that regulation L that the system is failing to comply with?

I'd also guess that this will considerably shorten the lifespan of the boiler and pump?

The boiler itself is kicking out an awful lot of heat. The two rooms adjacent to the cupboard it's installed in were up at 23 degrees this afternoon (15 outside). That's without the underfloor heating being triggered. They're actually having to open windows to keep the temperature down! (very well insulated new build).

Looking at the manifold it seems that the towel rails are connected to the system elsewhere.

Looks to be good news that there's a Heatmiser UH8 fitted as it's easy to connect a TM4 timer. Not sure if this would have any control over the towel rails and overall system, or if it would just control the underfloor heating zones?

Very appreciative of any further comments.

Many thanks.

 

[Ric2013]

I'm almost certain there should be a central programmer to switch it all on and off with, and, in any case, it is sensible to have one.

I have a feeling that some boilers (for example MAIN heat-only boilers) have a flow sensor that can switch the boiler off if there isn't much flow and provide interlock that way, but I would not consider that a sensible option. After all, surely the pump has to kick in to discover that there isn't much flow and then shut the boiler down again?

Nothing wrong with underfloor, and a thermostat in each room is great, but without a central on/off control of some sort, it sounds pants, if it doesn't have a way of switching off the towel rails then it is below what is standard in this industry. Or does the boiler itself incorporate a timer or programmer?

Programmable stats (plus a central control) were something I experimented with in my mother's old house. It was great to have independent control of each room, but in practice people couldn't seem to cope with a digital room thermostat that said 'on' when the main control was actually keeping the whole system off, and the (cheap Horstmann) stats I used were not very user-friendly. I didn't actually make much use of the programmable element of the thermostats, normally using them, in effect, as manual thermostats.

Sounds like your parents' system has the potential to be a very good system, with an Achilles heel that needs sorting. I must admit that, in my mother's system, I had the bathroom radiator on a manual valve; with the valve open, it came on with ANY other radiator. I wonder if you have the same setup?

 

[ShaunCorbs]

Any pics ?

 

[ChrisHD]

Any pics ?

Couldn't upload yesterday .. but working now .. here's some pics ... Can also confirm that there is no built in control on the boiler.

 

[SimonG]

Underfloor will be controlled room by room. The towel rails should have some form of control.

 

[ChrisHD]

Underfloor will be controlled room by room. The towel rails should have some form of control.

Thanks ... I will talk to the developer and get them to put it right.

 

[ChrisHD]

Developer now realises there is no interlock and has called the plumber back. However, the towel rails are apparently connected to the DHW side of the combi. Not sure how sensible this is, and whether it complies with regulations? (the only control on them is a TRV).

 

[SimonG]

Your developer is talking gonads.

 

[Ric2013]

Your developer is talking gonads.

For the benefit of the OP, a combi(nation) boiler combines the functions of a boiler and a water cylinder in that it provides hot water on demand.
As such, when the boiler is producing hot water for taps, the heating momentarily switches off and the boiler can heat the cold water coming in and sent it to the taps straight away.
If there were a hot water cylinder somewhere then it is possible that the radiators could be on 'the DHW side', meaning that the radiators come on whenever the boiler is heating the cylinder, but it doesn't seem likely that you will have a combi boiler heating a hot water cylinder (though not technically impossible).
Unless... you aren't confusing the terms 'combi' and 'condensing' are you? Virtually ALL modern boilers will be condensing - it's just a way of saying the boiler is very efficient.

 

[ChrisHD]

Thanks Ric2013, very helpful.

Definitely a condensing combi boiler with no hot water cylinder. There is no electrical system control at all other than the underfloor programmable room stats. The towel rail TRV's have an instant effect whenever they are turned up which I believe means that the pump is running permanently with the boiler heating a small circuit full time. This still happens when none of the room stats are calling for heat. The boiler is always warm and the heating flow/return pipes from it are permanently hot. The pump vibrates all the time. I believe this means that there is no interlock, which in turn fails to meet part L of the regs. If there was an interlock I assume that the towel rails would only work if 1 or more of the room stats were calling for heat. Grateful if anyone can confirm that my thinking is correct? Many thanks indeed.

 

[Ric2013]

Sounds like you understand correctly.

 

[S.P.S.]

This is pretty basic design and installation practices that any developer should know really. How the hell that passes NHBC is any ones guess. And why the plumber put it in like this is a joke.

Take the information you have learned and get them to rectify it! You should also ask them if the rest of the development is plumber in the same way. That way if he says no only yours. Then question why only yours? And if he says yes, then why have they passed it all!!