russell armstrong

Registered with
Monday 2nd June 2014

Latest Comments

Total Number of Property118 Comments: 6

russell armstrong

15:06 PM, 5th June 2014, About 8 years ago

Heating cost control in HMO's

Reply to the comment left by "Harlequin Garden" at "05/06/2014 - 14:20":


Air change rate is the single biggest killer of heat retention. If its old Edwardian there is a high chance of fire places as well, is that correct?

If it a solid (non cavity) double skin structure then I would first look to start sealing the building. The ventilated floor will also be a big killer, to slow this air change rate down you could try a very good quality rubber (as opposed to foam which lets air through) thick underlay. Maybe laying a polythene sheet (taped and sealed joints and edges) first.

Of course the more you seal the more condensation becomes a problem (due to a thing call dew point and humidity levels) Condensation at a given relative humidity forms as soon as it hits its dew point temp, the greater the RH the more easily it will form as condensation on cold surfaces.

On the matter of air change rate, if you had a hermetically sealed building your heat loss due to infiltration (except when windows and doors are left open!) would be 0.

This is why plate heat exchanger vent systems work so well as they introduce tempered "fresh air" into the building by reclaiming the heat energy from the exhausted warm moist outgoing air. That's called controlled ventilation vs casual ventilation (which is not controlled).

All these systems the guys are discussing are all good and its just a matter of cost verses effectiveness and control. If you are fortunate enough to be able to completely start again and re-pipe the entire heating system I would always choose weather compensated controls.

As I said before they load match the outside air temp and the thermal performance of the building so much better than any other method.

Russ... Read More

russell armstrong

14:04 PM, 5th June 2014, About 8 years ago

Heating cost control in HMO's

Reply to the comment left by "Harlequin Garden" at "05/06/2014 - 13:41":

Hi Harlequin

What is the structure of your property, how old is it and how well is the structure sealed against infiltration (trickle vents, vents for gas appliances etc)?... Read More

russell armstrong

16:04 PM, 3rd June 2014, About 8 years ago

Heating cost control in HMO's

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... Read More

russell armstrong

15:03 PM, 3rd June 2014, About 8 years ago

Heating cost control in HMO's

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.


Russ... Read More

russell armstrong

14:49 PM, 3rd June 2014, About 8 years ago

Heating cost control in HMO's

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.


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