BDR91 vs BDR91T?

[pootle]

I bought a Value pack A, and I've just noticed I got a BDR91 and a BDR91T instead of 2 off BDR91.

The look pretty much the same inside, can I use a BDR91T as BDR91 (to control the valve on the hot water circuit).

It's a while since I bought it, initially I only wired up the heating controls, as I was waiting for some other work to be done on the hot water cylinder.

So I've only just got round to setting up the hot water sensor etc.

[Richard]

The only difference between the BDR91T and a normal BDR91 is the 'T's' ability to control heat pumps over and above its normal functions.

[mazzy89]

Despite the explanation, it is still not very clear to me the real difference.

I would like to use the BDR91A to control the hot water cylinder. can I use it? or should I necessarily use the BDR91T?

[Richard]

Despite the explanation, it is still not very clear to me the real difference.

I would like to use the BDR91A to control the hot water cylinder. can I use it? or should I necessarily use the BDR91T?

BDR91T is specifically for heat pumps, but can also be used for everything else. BDR91A won't work with heat pumps.

[peter269]

So can you explain why the BDR91A can't be used for heat pumps please? (I already have a BDR91A controlling my boiler and am thinking of getting a heat pump)

Surely both the BDR91A and BDR91T just switch the mains on and off in response to a signal from the Evohome controller. Is it a question of current carrying capacity or what?

Thanks

[cfrd]

The function of the BDR91T is to protect the heat pumps from frequent switching and therefore wear. The BDR91T function determines the time for restarting the heat pump: if the set time has not elapsed, the pump will not start. This is according to the description at https://www.bolasystems.com/wireless-re ... bdr91t1004 .

[Richard]

So can you explain why the BDR91A can't be used for heat pumps please? (I already have a BDR91A controlling my boiler and am thinking of getting a heat pump)

Surely both the BDR91A and BDR91T just switch the mains on and off in response to a signal from the Evohome controller. Is it a question of current carrying capacity or what?

Thanks

It doesn't have the appropriate firmware for heat pump control, especially when cooling is involved.