TRVs on all radiators?

[Michael D]

I've got a Potterton Combi 80 boiler with TRV's on all radiators (the boiler & TRV's were all installed at the same time, by the same person, about 5 years ago). I don't know if there is any kind of a bypass and there isn't a room thermostat.

I had my annual British Gas service last week & the engineer said that I shouldn't have a TRV on at least one radiators. He advised taking off the TRV valve in the bathroom, which I've done. The heating is still working OK, the only noticeable difference is that the bathroom radiator gets warm when having a bath / shower.

I've had some mixed experiences with British Gas in the past & I was hoping if someone could tell if this was sound advice?

Many thanks,

Michael

[Jonathan Pearson]

Sound (and correct) advice, if all TRV's close your pump isn't gonna last too long as the water can't circulate! Jon

[Andy Hall]

There are a couple of factors in this.

1) Many boilers do require a bypass of some sort. This is to allow heat to be moved from the heat exchanger if the burner is firing and both HW and CH thermostats become satisfied. Generally the boiler keeps the pump running and the bypass dissipates the heat to avoid the water boiling if it suddenly stopped in the heat exchanger because the pump stopped. Normally a bypass should be created by having a lenght of pipe between slow and return before the motorised valve(s) and having either a lockshield or an automatic bypass valve. This can also be done with a radiator, often a bathroom radiator, plumbed similarly. It does mean that the radiator will heat up when you have either the CH or the HW running. 2) It is normal to have a radiator without TRV where the room thermostat is located although that typically is not the bathroom of course. If you have both, then they can "fight" each other.

The ideal solution would be to have a separate heating zone for the bathroom and a proper bypass but the arrangement that you have is OK as well. If the bathroom is getting too hot as a result, you can turn down the lockshield on its radiator. Not a lot of flow is needed for a bypass.

.andy

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[stejonda_privacy]

In message , Andy Hall writes

that's useful info especially in this weather, I'll go and turn mine down a bit - thanks :)

[Michael D]

"Jonathan Pearson" wrote

Ahhhh - that might well explain why the pump went about 18 months ago.

Do you know if it's OK to remove the TRV if there is a bypass already fitted (as I don't know if there is one).

Michael

[stejonda_privacy]

In message , "dave @ stejonda" writes

Ooops - follow-up necessary - how would I know if I've constricted it too much?

Btw, that Fernox Inhibitor Testing Kit you use (Andy) is a teeny bit pricey for a single user (GBP99!!!) maybe I should just flush and re-inhibit every n years? Or, any views on the Sentinel testing kit? (GBP10)

[Andy Hall]

If there is a bypass already in place it is typically a short length of pipe with a lockshield valve connected the flow and return together after the pump but before the motorised valve(s).

Some newer boilers have them internally, but that is when they have an internal pump.

There is no problem with removing a TRV if you already have a bypass in place though.

.andy

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[Andy Hall]

The boiler would start to make kettling or in the worst case bumping noises.

That's a reasonable strategy. If you do that, then every three years is a reasonable interval.

I've never tried it as I haven't used Sentinel products, but they have a good reputation.....

.andy

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