Replacing a humidistat with a thermostat

[UniversallyChallenged]

Hi folks,

With gas prices going through the roof I've been looking to maximise the efficiency of our heating. We've got a Potterton combi boiler which is regularly serviced and has generally worked well for the 4 years we've been here.

What has always confused me is the 'thermostat', which is marked with an H%, the dial going from 30 to 100. I finally got around to looking into it and it turns out we have this:

Room humidistat HSC 120 ► SAUTER Controls

HSC 120 | How energy efficiency is improvedEnables humidity control devices to be switched on according to needs

www.sauter-controls.com

For the life of me I don't know why - various other things suggest to me that the guy who renovated the house in 2012 was a right bodger.

I know of no other thermostat in the house other than on the radiators. The heating does seem to kick in more readily when the dial is turned up on the humidistat, but in hindsight I suppose that could be me just assuming that's what's happening.

My question is, is there an easy way to investigate what's going on? And if the humidistat is in fact connected to the boiler, would it be a simple matter to just swap it out for a thermostat?

TIA

 

[Deleted member 120897]

You could try turning it up and down, and see if that brings heating on and turns it off. You may be able to check the wiring if you clarify which model of potterton Combi (some boilers case seals form part of the combustion circuit).

 

[UniversallyChallenged]

You could try turning it up and down, and see if that brings heating on and turns it off. You may be able to check the wiring if you clarify which model of potterton Combi (some boilers case seals form part of the combustion circuit).

It does seem to kick in when we turn it up. Usually our standard setting is 65%, but I don't think the house is usually at 65% humidity. We have a hygrometer on the clock in the kitchen and that's usually between 50-60.

The boiler is a PROMAX SYSTEM 24HE P.

 

[Chuck]

Are you sure it's not a thermostat that has had the cover replaced by the wrong part? A photo of the innards might be enough to confirm / deny this (unlikely) possibility.

A humidistat measures relative humidity (as a percentage) and should be connected to plant that controls humidity (air conditioning, ventillation, dehumidifiers, etc.) Domestic boilers must be controlled by a thermostat so if all you have is a humidistat then it needs replacing.

Of course, there are unusual sophisticated systems that use the external temperature and a computer model for the building to control the heating but a 'right bodger' is not going to have installed anything like this.

 

[Deleted member 120897]

If it’s coming on and off when requeste, then i‘d say it’s connected to the thermostat terminals at the boiler, you can swap this out if you wanted and as Chuck states, maybe the wrong cover has been fitted (unlikely).

 

[UniversallyChallenged]

I'll take the front off and see what's going on inside. I take it swapping it out for something like this:

https://www.NoLinkingToThis/p/drayton-rts8-room-thermostat/46637

Would be a relatively straightforward job of screwing wires into terminals?

 

[Deleted member 120897]

Would be a relatively straightforward job of screwing wires into terminals?

Yes it would be 👍🏻

 

[Basher]

If it is actually the humidistat inside, I see the data sheet for it says "At temperatures other than the compensation temperature, the change-over point is shifted systemat- ically (effect of temperature)."
So it might be sort of working as a crude thermostat!

 

[Murdoch]

That’s a very odd thing to use if it is a humidistat !

 

[Ben-gee]

I’m guessing as a bodger he ‘Had it in the shed’ and used it as basic switch.

 

[UniversallyChallenged]

I’m guessing as a bodger he ‘Had it in the shed’ and used it as basic switch.

That's my thought too.

 

[king of pipes]

You would be better to get a EPH wireless thermostat , all the wiring is carried out at the boiler this would it you added time and tempreture control over your heating and the opportunity to move the stat to variety of positions but be aware that where the final position for the thermostat is selected the radiator should have no thermostatic head fitted, Your programmer time switch is left on 24 hrs for the heating and still used to time the hot water settings consult a electrician for details. Kop