Central Heating controller for multiple zones?

[Alan Braggins]

I'm trying to find a central heating controller for multiple zones.

I have an underfloor heating system, which leaks. (It's an old (~10 years) Nu-Heat system with Contraflo rubber hoses. They don't use that material anymore, but that doesn't stop mine rotting - so far mostly at the manifolds, but it's going to spread.)

I am planning to replace upstairs with radiators, because I can't cope with the idea of taking down every downstairs ceiling in order to fit underfloor heating (nor of taking up all the carpets, routing grooves in the T+G chipboard for new pipes, putting a hardboard floor on top of that and taking a bit off all the doors to allow for the raised floor).

(Downstairs i) isn't leaking yet and ii) is wood block floor which is easier to take up to get at the pipes, so the current plan is to keep that as underfloor, replacing with new style pipes next summer.)

I did get a plumber in to quote for doing the radiator conversion, but since he didn't pay attention and only quoted for half the job, and given the amount of time I've spent fixing other plumbers work in the past, I decided to do it myself.

At the moment upstairs has three heating zones, each with a Danfoss TP5

5/2day programable thermostat connected to the central control box, which controls the zone valves at each manifold, and switches the heating circuit pump when any zone thermostat switches, and is supposed to switch the boiler pump when the cylinder thermostats switch, but actually runs it the whole time at the moment (so the cylinder temperature is actually set by the boiler thermostat - not ideal).

(The cylinders (two, paralleled) are thermal store types:

they are a sealed circuit, not open vented).)

What I would like, or at least what I think I would like, is to leave the existing controller switching just the underfloor heating circuit pump (based on the downstairs zone thermostats), and keep the upstairs zone thermostats with two-port zone valves and a controller that will switch the boiler circuit pump if any of the zones or the cylinder thermostats are calling for heat. Explaining this to local plumbing supplies results in quite a lot of blank looks (having spent 15 minutes explaining the existing system to a plumber with both a schematic and the actual pipework in front of us before he finally got it, this didn't surprise me). The Danfoss and Honeywell brochures I have only cover simple systems.

Any suggestions? A Danfoss FH-WC looks like it might do the job, is there any reason not to use it for radiators rather than underfloor zones?

[Doctor Drivel]

will be OK ro use with UFH or rads. You are replacing the upstairs UFH with rads, so depending on who many zones upstairs you use a controller to suit.

[Roger]

The message from [e-mail] (Alan Braggins) contains these words:

You don't need another controller if you have the programmable thermostats wired up properly. IIRC the thermostat controls the zone valve and the zone valve controls the boiler just as it would if you only had one zone.

My experience is with radiators but I don't see why the basic controls for underfloor heating should be different. (I only have 2 heating zones. Downstairs controlled by a TP75 and upstairs by a cheapo from Screwfix.)

[Alan Braggins]

The existing controller won't switch the boiler/radiator pump based on the room thermostat input, only the underfloor heating circuit pump. I'm not running the radiators off the existing heating circuit because the radiators need to be hotter, and the existing underfloor heating hoses aren't compatible with steel.

[Alan Braggins]

I could replace the existing controller rather than add to it, but I don't think it's going to work with just the existing controller - the logic needs to change for the new circuit.

[Doctor Drivel]

You have the controller activate a zone valve or a relay. The end switch on the zone valve switches the pump, or the relay switches the pump. A stab can be in series to activate the relay or zone valve. Depending on how the store in configured, the boiler operates independently on the store. Some have the top switch by a DHW timeclock, and the bottom by a CH controller(s). The CH controller switches in the CH section of the store (boioer control) via time section of the controller. The CH pumps (or pumps and zones valves) by the stats.

You need to think out the logic.

Boiler control - CH zones Boiler control - DHW CH control - zones CH control - zones by stats

[Osprey]

Santoprene (rubber) was the pipes that were the triple pipe contraflow system ... originally sold & rights owned by Kee,

Nu-Heat were the UK agents for them. When Nu-Heat went their own way they continued with twin pipe variant, before swapping to Pex pipe.

Nu-Heat were advertising a 30yr warranty of Santoprene pipes, as long as it was run with a Thermal store and at the correct 'warm' rather than hot. (hence 'warm water underfloor heating') Have you contacted Nu-Heat over this, worth trying ?

I have a 17 zone Nu-Heat system (pex) and found them a great company to deal with, with good after sales service.

Rick

[Roger]

The message from [e-mail] (Alan Braggins) contains these words:

Sorry, you have lost me. What logic? And in what way do your zone valves differ from the bog standard 2 port zone valve?

You say in reply to Dribble (who lives in my killfile) "The existing controller won't switch the boiler/radiator pump based on the room thermostat input" but on my system the controller doesn't either. The central heating is set to permanently on and the boiler controlled via the microswitch on the zone valve which is itself controlled by the programmable stat.

[Alan Braggins]

Of what gets switched when. At the moment the heating circuit runs off the thermal store, and the boiler is independent. But the radiators won't be running off the thermal store, so switching the underfloor heating pump on won't do anything to the radiators.

As it happens they are an unusual design, but I think that's irrelevent.

"the zone valve" implies you only have one. I have three zones, and want the boiler controlled by any one of them (or the cylinder thermostats). I could have a wire going all round the house with the AUX contacts of the valves in parallel, or I could have a central controller that does it all neatly. I'm hoping for the latter.

[Alan Braggins]

[...]

Yes. They offered a discount on a replacement system, and blamed Monsanto for selling them unsuitable material with false promises. I'm not the original house builder who had it installed.

(The materials cost for the replacement system is less than the cost of radiators, but the work involved in getting it under the floor would be huge. It was bad enough getting at a leak at one point under a bathroom floor where the heating hose was resting on the then-unlagged boiler pipe (luckily we wanted to take the carpet up anyway, but having now laid tiles I'd rather not have to take them up).)

has some other peoples' experience. (The Nu-Heat engineer who came to see our system also said that he'd seen the same problem in other Nu-Heat systems of similar age.)

(They have been helpful with spare parts for fixing the leaks, and advice. Last time they warned me they were running short of replacement hose material.)

[Guy King]

The message from [e-mail] (Alan Braggins) contains these words:

It's still their problem though. They may choose to take it up with Monsanto, but that's a different matter.

[Alan Braggins]

P.S. or I could if I swapped some of the valves - the originals don't have the extra contacts, but the replacements for a couple of failed ones do.

[Owain]

But the contract of sale is with the original housebuilder (and would have been a trade contract, allowing exclusions from consumer law) and not with the current householder.

Owain

[Aidan]

controllers, US (bigger houses, many zones) company. Maybe contact Tekmar in the US detailing how many zones you want & the other bells & whistles and ask them to recommend a controller. Never used them, but they're reputedly very good.

Failing that, a UK BMS (programmable controller) contractor could construct whatever you need, but BMS is aimed at comercial stuff & have commercial prices (e.g., cheapest PC interface program =A3400 ish, hardware extra) .

[Osprey]

It would be worth looking at original contract, many 'warranties' are transferable, which might assist you.

[Roger]

The message from [e-mail] (Alan Braggins) contains these words:

That depends on whether or not they have the normal functions.

No I have 2 zones (as I said in my previous post). I don't know about the TP5 but with the TP75 and normal zone valves you can wire them so the thermostat switches the zone valve and the zone valve switches the boiler. In theory you could have any number of separate zones.

[Alan Braggins]

It was a self-build, so _might_ have been a retail not trade contract. But they (allegedly, according to village gossip) left for Canada leaving a lot of debts and taking some money that wasn't strictly theirs. We bought the house from the people who bought it from them (and have had bailiffs chasing their debts too). So if Nu-Heat aren't volunteering it, my chances of finding the original contract are small.

(Given that I don't have a contract and have no evidence of a warranty, I haven't bothered asking a solicitor. Maybe I should.)

[Alan Braggins]

Most of them don't have switches, just two motor wires. But that can be changed.

That might be the answer. I'm almost certainly going to have to move some of the valves, so can't use the existing motor wiring, so can add new switch wiring that way. To the existing controller even, if I can work out why it isn't switching the boiler at the moment, just add more inputs in parallel with the existing cylinder thermostat inputs.

(I did find

which would give switching on individual radiators, but the price adds up rather.)