Bypass valves for TRVs

[PEDANTICVINDICTIVEMAN]

If you fit decent TRVs such as Danfoss Ras D on the return with the arrow facing the correct way I find noise and whistling isn't a problem as long as you leave one rad free, of which I always fit locksheilds on both ends, and inform the customer as to why and not to switch it off.
I fit a lot of 28 cdi's which have an adjustable byepass built into the boiler, fitting TRV's on all rads except the one which has the Digistat in, and then follwing Worcesters commisioning instructions regarding temp diff over flow and returns, I have never needed an auto byepass yet.

I'm sure someone on here wont like it though.

 

[PaulAH]

Over-run sounds cool. But if the auto-bypass is the only form of heat dump it's not going to do much to stop the boiler - er - boiling from residual heat. A short circuit from pump to return won't dissipate much heat, especially if it's right up close to the boiler. Or is it more a question of just keeping the water moving to prevent hot spots in the heat exchanger?

More to the point, I haven't got pump over-run on my new CH. Boulter don't mention it in their manual (I think). Is it a Good Thing To Have? It's often struck me that a good arrangement would be pump AND motorised valve over-run, ie room stat shuts off boiler, water continues to circulate in the rads for a couple of mins, then whole lot stops. Result: waste heat in boiler is spent in the house, not up the flue. Is that cobblers?

Does anyone make a 'bolt-on' overrun device - single or multi-pole?

 

[blahblah]

Bypass not an issue in combis if inbuilt and on 'conventional' the MI's give a minimum pipe run distance before fitting so shouldn't really be a problem. As long as the water can keep moving after burner shuts off it can't take much to save over heat and hot spots. The circuit inside a combi can only be 3-4 feet but they're fine when the tap goes off, even after 38kw or so of burn.

 

[zutman]

It does not matter what valve you put in it can be an auto one or just a gate valve a gate valve 1/4 turn open and the auto well its an auto and it does not matter where you put it as long as you have a circulation building regs suggest you leave one rad short of a TRV and in the same room fit a room stat as well ££££££££ i can see their way of thinking but that will not bother you as this is for new properties ?? good luck .....

 

[PaulAH]

A part-opened gate valve would provide a return path but effective de-rate the boiler. The poor thing will be forever turning itself off, thinking it's got up to heat.

I hope your plumbing is better than your punctuation.

 

[corgiman]

It does not matter what valve you put in it can be an auto one or just a gate valve a gate valve 1/4 turn open and the auto well its an auto and it does not matter where you put it as long as you have a circulation building regs suggest you leave one rad short of a TRV and in the same room fit a room stat as well ££££££££ i can see their way of thinking but that will not bother you as this is for new properties ?? good luck .....

not really even basic of part L