Heating cost control in HMO’s

Reply to the comment left by "Steve Masters" at "03/06/2014 - 14:03":

Steve,

You could make the Vaillant VRC470 WCO tamper proof by putting inside of a well ventilated locked box. However it is designed for an open plan house where the entire house gets about the same heat loss. I don't think it will work well in a HMO.

I looked at the Vaillant controls for “room by room” temperature control and they were out of the question on cost including needing a pump and motorised mixer value for each room.

Do you have the DHW tank controlled by a Vaillant temperature probe with a VR 65/66 consoler, if so at least you can turn down the temperature of the flow to the radiators when it is not very cold.

I believe that Ideal has a nice simple weather compensator for their boilers, but you need a high end boiler so that the flow to the DHW is control separately, as otherwise you can't get the DHW tank up to 60c.

Industry Observer said

"Russell the issue here isn’t how to do it, it is whether it is legal to do it, or if it is how far you can go."

Mark Alexander said

"I disagree IO, please read Mark Hartel’s post which started this thread (top of page). The issues of law are thread drift, not the “how to” and sharing of best practice as that was the basis of the original question"

&

"Hi Russell and welcome to Property118.

Please feel free to continue to educate us. If it turns into a sales pitch I will be referring you to our sponsors rules....."

First in response to Mark, thank you for your welcome. I pride myself in being professional enough to avoid the "sales pitch" and besides which I don't sell WCO
controls and I am a wet plumber not gas plumber so I don't tend to get involved with fitting controls, however I do know about controls.

Cutting across everybody's posts about the "legality" of controlling the tenants temperature regime I have two observations about that.

Tenant one of five hates heat and turns the controls down for his/own benefit
Tenant five loves heat and turns them up again, constant yo yoing.

WCO has the major benefit of only providing the energy required to suit the BUILDINGS needs.

The output flow temperature is regulated AUTOMATICALLY in line with the temperature of the DIFFERENCE between the outside temperature and the current inside temperature.

The greater the difference the more energy is put in and as the temp stabilises the flow temp backs off back to (if possible) maximum condensing (and therefore max efficiency) temp.

The whole system is enabled 24/7 it just sets itself to provide enough energy to keep the thermostat satisfied at whatever temp is specified (say 19degC ground floor hallway)

There is no need to control it after that, you will be complying with any requirements (because you have enabled it to make sure hallway is at 19degC and almost by definition each room outside that hallway can reach a comfortable 21-23degC.

For instance depths of winter coldest day, the building looses max heat and heating need to keep running to stabilise max heat loss (the total energy input into the envelope must equal the total loss from the building in order to keep steady state) The energy input required is whatever it is 10-20-30kw, if you want to keep energy CONSUMPTION down at this point insulate & close windows, if you want to keep costs down do the first two and the hunt for better prices of fuel). The system may have to run at full flow temp (80degC) at max pump speed just to keep everything in check at 19-21degC, you have no choice its just the way it is. At 80degC you will be getting less efficiency than at 50-55degC because your system will not be running in condensing mode.

Now lets consider a part load condition say mid Autumn, cold enough to want to have some heating on but not at full blast.

WCO controls know that its a bit cold so will run the flow temp lower and still make sure it is satisfying the hall temp stat at 19degC. If that's in condensing mode the boiler will be running more efficiently so that's good but even if tenant in room has his TRV set at max the rad will only give up the difference between its mean and the room temp i.e. its output will be lower because it has a lower temp SAVING ENERGY

The beauty is that this temp alteration happens automatically and variably as it also detects the rate of change (that's all to do with PID controls Proportional, integral and derivative - too complex for me that is!) so if the temp of the room sensor rises or falls quickly the flow temperature adjust accordingly quickly.

In short the WCO system allows a more efficient building to be run by LOAD MATCHING the building heat loss against the outside temperature whilst keeping within parameters of the temperature sensor set point (19degC or whatever it is set at)

So can existing boilers be fitted with WCO controls, find out what your boiler is and go ask your boiler manufacturer, the older the boiler the less likely the chances.

For example WCO controls to be supplied to be fitted to a Worcester boiler for as little as £120 (fitting extra) but there nay have to be alterations to the pipework in the boiler depending on your system.

Also the domestic WCO controls are not as fancy as the one I have described above as I do not believe they use self learning algorithms but are pre-determined based upon a curve. That is not to say they are no good, far from it they are still the bees knees but they do not control as closely as an all singing all dancing very expensive BMS system.

I hope this helps and would be willing to answer any questions about it as and when I can, here on this thread or via PM.

Russ

PS the chances of anyone living in Derby reading this forum wanting my minor works services would be very remote.........(punt lol)

Reply to the comment left by "Ian Ringrose" at "03/06/2014 - 14:40":

Ian is correct

For max controllability each tenant zone would have to be operable via its own sensor modulating pump and valve. Uber expensive for domestic situations.

For controllability purposes I would ALWAYS recommend a boiler to be fitted with two set points irrespective of WCO controls. (BTW if you have WCO controls on a system boiler it will automatically have the ability to operate the flow temp to the DHW tank at a different temp than the heating.)

If you have a condensing boiler with one temp set point you ARE WASTING MONEY get a boiler with one for DHW and the other for heating.

In todays market fitting WCO controls is the best way to provide some way of not overheating the space because the tenants don't care.

Regards

Russ

Reply to the comment left by "russell armstrong" at "03/06/2014 - 14:49":

If the WCO does not have input of the actual and required temperature in each room, I would not trust it to work unless it is of the simple type that just set the boiler flow temperature based on a preset curve using the outside temperature.

They have been lots of complains about the Valliant (and other German) systems not working well in the UK as they assume that they can work out the heat demand from the temperature of ONE room of the house. (From my background in computer programmer, I know that such systems just don’t have the information they need to work well in a HMO.)

Hence I am considering the Ideal WC system in a property I am about to convert to a HMO, however it is a shame it will not heat a DHW tank with as much condensing and control as the Valliant system. I will also size the radiators larger than normal, so for most of the year the flow to the radiators is below 50c.

(There is also the issue with WCO that on a sunny morning after a cold night the outside sensor can be warmer then the inside of the building, so the WCO sets the flow temperature so low that the building can never heat up. However that is as much a problem with our on/off mindset for heating control in the UK.)

Reply to the comment left by "Ian Ringrose" at "03/06/2014 - 15:30":

Ian, you have a good understanding of these systems (are you a closet heating design engineer?)

On a more intricate level, if you design the whole building to run WCO (that means the mean rad temps will generally be lower then they still have to be large enough for the worst "design day" Thus inevitably they will be sized slightly larger than normal.

The Worcester WCO have several "curves" to choose from how these are designated as "appropriate" for each scenario is an unknown to me and you are right that one curve will dictate a different controls logic than the next and how even I would choose which one to use would see me phoning up the manu and asking the technical guys.

The Worcester system boiler has different set points and controllable primary flow temps, day set backs, night set backs for both hot water and heating, so its quite comprehensive but still in one simple box. The one I specified for my squash club is house in a lockable box with ventilation holes, the rad in the same space as the sensor has locked valves and is set to run at max volume (i.e. fully open)

The outside sensor should always be located in a shaded area not subject to any direct sunlight so would avoid your scenario, however it may need a shroud or ventilated cover to protect it

With regard to your system I cannot comment without seeing the layout of the house, however in order to answer the OP fitting is the BEST option (IMO) when considering the most viable ways of heating cost control in an HMO.

Actual precise comfort for the tenants then becomes a secondary factor and will always be a compromise for an HMO unless you fit individual room controlled zones!

What I am saying is that if the heating flow temperature is adjusted automatically to as low a temp as possible then even if the tenant keeps his TRV on full and windows open then less energy is used as it is not there in the first place.

Russ

Just spoke to Vaillant who said that to get WCO and separate C/H & DHW working one needs intelligent controls that talk temperature to one another, not just normal on/off call for heat controls. In other words replace all my third party controls with Vaillant ones. As my boilers are in locked boiler cupboards I will stick with manually turning the flow temp up and down in autumn and spring for now.

In addition, they suggested when designing a new system in a multi floor house to put each floor on it's own zone, each with it's own zone valve and room stat. (Something I suggested in an earlier post). I'll consider this for my next conversion.

I'm going to speak to my heating engineer who suggested I should look at Viessmann boilers.

Just spoke to my EHO who confirmed that as far as they are concerned, setting a max whole house temperature and allowing the tenants to adjust via the TRV up to that max satisfies the "Control" aspect of their HMO standards (so long as the landlord limited max is at least 19-21C).

Also spoke to the Danfoss rep who recommended their "Living Eco" range of TRV valves that offer digital temperature control, tamper proof lock and limit AND are retro fittable without the need to drain down the system. These might be a better solution than the Peglar lock and limit TRV's that I have used and mentioned in an earlier post.

Reply to the comment left by "Steve Masters" at "03/06/2014 - 17:51":

So does this mean that the heating/water is one 24/7 and you rely on the tenant/s to turn it down?

Reply to the comment left by "Steve Masters" at "03/06/2014 - 17:51":

Oh Yes, and the Danfoss Living Eco TRV's are smart in respect that they have built in open window detection via monitoring the temp curve for a sudden drop.

I'm going to get some to trial.

Reply to the comment left by "Harlequin Garden" at "03/06/2014 - 17:59":

Harlequin wrote: So does this mean that the heating/water is one 24/7 and you rely on the tenant/s to turn it down?

Yes and no.

Hot water is on 24/7/365, it is a lot easier to properly insulate a hot water cylinder than a whole house.

Central heating would be on 24/7/365 but limited by a tamper proof limiting thermostats. Tenants can turn down and up again to the LL set max but not beyond. That's the theory anyway. Seems to be working for me in the summer, I wait to see what happens in the Winter :-0