Help please with spec for central heating for 1 bed flat

kbdiy · 10 Sep 2014

berg222 said:
D_Hailsham said:

I have had 2 quotes & been advised that the installation needs to ensure water continues to circulate for as long as boiler is above its safe internal temperature. This to be achieved by having 1 radiator (hall usually chosen) not having a TRV but to be always open & on.

Click to expand...

Put a TRV, set low, on the hall rad, but not on the one in the living room; and install the thermostat in the living room.

If there is a TRV in the same room as the thermostat, the TRV must be set to max.

Click to expand...

If we had non-TRV rad in living room means this room would always be heated when heating is on. Tenant would not have option of turning off the living room heating. But this room often only required to be heated in evenings. In day time it would usually be kitchen that heated. Tenants will not want to heat empty rooms. I am trying to find out if we can have all rads with TRVs with heat dumping provided by ABV and without the fixed thermostat and its associated non-TRV radiator. I would not want a TRV radiator in same room as thermostat as TRV could get turned off with stat calling for heat for hours.

For me, the issue with having a stat in the living room is that when this room is occupied, the temp rises, cuts the stat and the rest of the flat will drop cold, so bedroom cold when they go to bed. Hence the normal recommendation is for a stat in the hallway to keep an overall ambient temp and use TRV's in occupied rooms to control the individual temps.

To be honest I think you're trying too hard to out-guess your potential tenants. Keep it simple and they will figure it out for themselves. They will soon learn to adjust their usage when they get their first bill.

Let's face it, a 1 bed flat isn't going to cost a lot whatever you install.

D_Hailsham · 10 Sep 2014

berg222 said:
D_Hailsham said:

berg222 said:

I always use TRVs as on/off switches - is there another way for tenants to easily turn rads on/off in rooms you don'nt want to heat.

Click to expand...

In that case you are wasting money on TRVs; just install standard wheel head valves.

Click to expand...

Did not realise that was an option.

Strictly speaking, it's not, but I was reacting to your statement that you just use it as an on/off control. If you are using it for its true purpose of maintaining a constant room temperature, then they are not a waste of money.

Benefit of TRVs is they maintain the temperature of a room within a narrow range - assuming they accurately measure and respond to room temperature. But in practice do they do this reliably?

Yes; if the system is correctly balanced. Beware if the installer tells you that you don't need to balance a system with TRVs as they are self-balancing. B*ll*cks.

Incidentally I found out recently the reasons why TRVs just have numbers and not temperatures:

1. They can be used for both Celsiuis and Fahrenheit.
2. Users will set them according to how comfortable they feel and not get fixated by the actual temperature.

vulcancontinental · 10 Sep 2014

berg222 said:
D_Hailsham said:

berg222 said:

I always use TRVs as on/off switches - is there another way for tenants to easily turn rads on/off in rooms you don'nt want to heat.

Click to expand...

In that case you are wasting money on TRVs; just install standard wheel head valves.

Click to expand...

Did not realise that was an option. The council housing dept & building control all pushing TRVs. To comply with Part L to make the installation as efficient & controllable as possible. To enable tenants to keep down heating bills. No local RGIs mentioned wheel head valves. But also need capability to adjust each rad individually from v low background warmth to 21 degrees. So need on/off/adjustable rads. Can wheelheads but turned to any position to control heat output ? Benefit of TRVs is they maintain the temperature of a room within a narrow range - assuming they accurately measure and respond to room temperature. But in practice do they do this reliably.

Doubt there would be any cost saving on minor changes to spec. Would expect the same cost whatever arrangement of wheel head valves & TRVs we specify. If we went for a cheaper boiler or fewer rads would expect cost adjustment. Contractors good negotiators – they hold their quotes well – not easy to shift.

But in practice do they do this reliably?

No, due to the reasons given in earlier posts. They are fine, they work but they must be positioned correctly and have free passage of air from the room so that they can respond to changes. They are primarily a user comfort control not a system efficiency control.

I think for a landlord with a flat interested in efficiency I'd fit a simple Danfoss Open Therm room stat after finding a boiler with which it will work, unfortunately not one of ours if it's a combi. That will depend on the software in the boiler. Possibly an Intergas will.

None will offer 10:1 turndown and that's too bad because of the probable minimal heat load of a flat.

Weather comp is fine if you can locate the sensor in a suitable position.

Condensing boilers work most efficiently running cooler TRV's cannot help in this, WC or OT can, or simply use a Vokera with the automatic temperature adjustment program (SARA) built in and a standard room thermostat, wired or RF..

berg222 · 10 Sep 2014

vulcancontinental said:
Thank you for mentioning the Linea One Dean but it's 38KW for DHW and 15.6l/m which is is only useful if the flat has a cold supply that good.

If the flat has a lower supply pressure and flow rate the Unica i also has a 10:1 turn down ration and is 28, 32 or 36 KW so obviously the 28 can give 2.8KW to the heating and 11.8 l/m of DHW.

We have 19 Litre/min on incoming cold water supply at 2.5 bar static pressure and bit over 1.5 bar dynamic. Also plan to fit a shower with water heated by combi. So want suitable hot water flow rate for a shower. DHW usage would be 1 person normally so not having other demands while shower on.
Thanks for telling me about the Vokera brand – new to me – offering 10:1 modulation – will check the specs – do they need specialist installer. I'm starting to realise being able to modulate down to a few KW for heating the rad water is v important consideration. We will be requiring the boiler to operate at low % of its max power output much of time. If lowest burn rate is 7 KW then there will be plenty of times when this too high resulting in multiple wasteful off/restart cycles in boiler.

berg222 · 10 Sep 2014

vulcancontinental said:
TRV's in a house, never mind a one bed flat, are often a waste because of lack of space as furniture, curtains, in fact anything that restrict the air flow across them means the blessed thing has to be left wide open to get the thing to open anyway.

Rads will all be installed in empty spaces on walls. The TRVs will be oil filled & mounted low & vertical with air flow unobstructed.

berg222 · 10 Sep 2014

Justin Passing said:
Mr Landlord, be careful
If you encourage your tenant to keep rooms cold, you risk condensation in them. The tenant complains, stops paying rent, and YOU have to deal with the problem and the mouldy walls, his mouldy clothes, etc.
Making the system efficient for him is of little direct benefit to you. If you get just one callout because he doesn't understand it, or it isn't working the way he thought it would, or he's forgotten, YOU pay. Weather compensated systems tend to be like that.

Building Regs (I believe, you can check) demand TRVs only in the bedrooms. If you do use them in all rooms (Other than the living room where the thermostat can go) you can set some types with pins inside the head to stop the tenant turning them right off. That stops the rooms getting too cold (condensation) relative to the others.

Don't overestimate the sophistication of your tenant. Digital 7-day timers are beyond the "can't be ar*ed" limit for many of them. A typical Australian (or warmer country) tenant will ask "What's a thermostat?". They may have never seen one before.

Wireless thermostats have batteries in the sensing end. Tenants are likely to see them as something you should change, and you get a callout because it's "not working".

Portable thermostats are carried about, dropped and then also "not working". Timers are for turning the heating on before the occupier gets out of bed.

Make sure you explicity forbid them to dry any clothes on the radiators, too

Yes, I'll go for uncomplicated to use. I'm trying to put in a system that affordable for a tenant to turn on. Which is why been talking about heating 1 room only. Monthly heating bills getting unaffordable. Timer to be 24 hour – maybe mechanical. Will have better idea on TRVs & thermostats by end of this thread. I dry clothes on the rads & I'm the landlord so I should'nt complain if tenants do it. Thanks for the points you made.

vulcancontinental · 10 Sep 2014

You must know before I explain the brand that I work for them.

If you go Vokera then Open Therm would be best but it's too complicated for a tenant to use, sad but true. Even if the first tenant loved it and didn't play with it the second or third would and trouble you with it all the time.

Go WC with a simple timer and room stat or just simple timer and room stat and use SARA which is incorporated in our boilers (and patented).

Not quite as good as WC but free and simple (runs the boiler cool in condensing mode but increases the boiler temperature during periods of prolonged demand automatically, user knows nothing about it).

The Linea One 15.6l/m or the Unica i 32 or 36 13 or 14.6l/m respectively would do the job. Check space and prices as they are big boilers and different outlets have different offers. The Unica i is my favourite but the Linea has some fancy features.

They'll need an annual service as all boilers do. The Vokera's have a service reminder dependent on how many hours the boiler has spent in condensing mode (2500 hours, approx 5 years). That one is the main one and it will need it done thoroughly because these condensing boilers really do condense.

You can ring the office for approved installers in your area, there are some good ones as I've done training up there but I see so many I never remember their names.

berg222 · 10 Sep 2014

vulcancontinental said:
You must know before I explain the brand that I work for them.

If you go Vokera then Open Therm would be best but it's too complicated for a tenant to use, sad but true. Even if the first tenant loved it and didn't play with it the second or third would and trouble you with it all the time.

Go WC with a simple timer and room stat or just simple timer and room stat and use SARA which is incorporated in our boilers (and patented).

Not quite as good as WC but free and simple (runs the boiler cool in condensing mode but increases the boiler temperature during periods of prolonged demand automatically, user knows nothing about it).

The Linea One 15.6l/m or the Unica i 32 or 36 13 or 14.6l/m respectively would do the job. Check space and prices as they are big boilers and different outlets have different offers. The Unica i is my favourite but the Linea has some fancy features.

They'll need an annual service as all boilers do. The Vokera's have a service reminder dependent on how many hours the boiler has spent in condensing mode (2500 hours, approx 5 years). That one is the main one and it will need it done thoroughly because these condensing boilers really do condense.

You can ring the office for approved installers in your area, there are some good ones as I've done training up there but I see so many I never remember their names.

Thanks for all this info. The posts in this thread have made me reconsider boiler selection. Maybe I will start new thread on boiler selection. Discuss specs & warranties, let you know which I choose. Clearly being able to modulate down to a few kW is v important. First will have good look at Vokera website and get familiar with specs of the models.

vulcancontinental · 11 Sep 2014

Yes, look at all boilers, but my opinion is there are few poor boilers; choosing the man who does the work and correct maintenance is far more important to the life of the boiler.

berg222 · 11 Sep 2014

kbdiy said:
berg222 said:

D_Hailsham said:

I have had 2 quotes & been advised that the installation needs to ensure water continues to circulate for as long as boiler is above its safe internal temperature. This to be achieved by having 1 radiator (hall usually chosen) not having a TRV but to be always open & on.

Click to expand...

Put a TRV, set low, on the hall rad, but not on the one in the living room; and install the thermostat in the living room.

If there is a TRV in the same room as the thermostat, the TRV must be set to max.

Click to expand...

If we had non-TRV rad in living room means this room would always be heated when heating is on. Tenant would not have option of turning off the living room heating. But this room often only required to be heated in evenings. In day time it would usually be kitchen that heated. Tenants will not want to heat empty rooms. I am trying to find out if we can have all rads with TRVs with heat dumping provided by ABV and without the fixed thermostat and its associated non-TRV radiator. I would not want a TRV radiator in same room as thermostat as TRV could get turned off with stat calling for heat for hours.

Click to expand...

For me, the issue with having a stat in the living room is that when this room is occupied, the temp rises, cuts the stat and the rest of the flat will drop cold, so bedroom cold when they go to bed. Hence the normal recommendation is for a stat in the hallway to keep an overall ambient temp and use TRV's in occupied rooms to control the individual temps.

To be honest I think you're trying too hard to out-guess your potential tenants. Keep it simple and they will figure it out for themselves. They will soon learn to adjust their usage when they get their first bill. Let's face it, a 1 bed flat isn't going to cost a lot whatever you install.

Good advice, thanks. Have basic thermostat wall mounted in hall. Wireless easier for RGI to install. Will check if design that can be secured so not get moved around. Else wired. Then advise tenants to set temp to 21 degrees and use TRVs to control temp in each room. But still end up with rad in hall without TRV that will always be on when heating on. So tenants paying to heat the room least used. Just trying to get a system installed that affordable for tenants to use and where tenants can choose which rooms to heat.

This design just described involves the hall rad having a double function. Space heater & heat dump facility. The reason I started this thread was to find out if there is an alternative way of providing an always available circulation route for central heating water. I suggested an automatic bypass valve with a few M of pipe. This route would open up if required by rising water pressure else stays closed. If this possible then the hall rad would not need to provide the circulation route and could be used just as a space heater like all the other rads. And hall rad could have TRV fitted.

So can an ABV with suitable piping provide the required circulation route in systems where all rads have TRVs and those TRVs have closed all the rads.

D_Hailsham · 11 Sep 2014

You seem to be concerned about the prospective tenant being unable to afford the cost of heating the property. I hope you do a proper check on the tenant, e.g references from employer and bank, proof of income etc. If so, you should be able to estimate if they can afford the rent, council tax, and utilities bills.

If they can't then don't rent to them.

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Help please with spec for central heating for 1 bed flat

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