Honeywell Y Plan plumbing question

[westmoorfarm]

Our central heating uses the Honeywell Y plan and I am trying work out the purpose of a piece of pipework and a stop valve.

On the main circuit downstream from the circulation pump and upstream from the mid position valve there is a 15mm pipe tee'd off from the 22mm main pipe. This pipe has a hand operated stop valve on it and is then tee'd into the outlet (cool side) of the hot water tank heating circuit.

What is the purpose of the circuit and should the valve be open or closed normally?

Thanks

P.S. The system was probably installed in the early 1990's and has an oil fired Worcester Danesmoor boiler if that makes any difference.

 

[keego]

This is a bypass, the valve should be open about half a turn. It's main purpose is to provide some circulation for the boiler if all the TRV's shut down, some people say it's not strictly necessary on a Y plan,although it's good practice to provide one.

 

[westmoorfarm]

Thanks for the quick answer. It's closed at the moment, but given that most of our TRV's are on 6 most of the time this shouldn't cause an issue. I'll open it half a turn next time in there.

Cheers

 

[D_Hailsham]

most of our TRV's are on 6 most of the time

Why on 6? Do you like your rooms heated to 28°C or more? Or is that the only way your rooms can get up about 21°C?

If so, then your radiators and/or boiler may be undersized; or you system is not properly balanced.

 

[tonybhoy]

most of our TRV's are on 6 most of the time

Why on 6? Do you like your rooms heated to 28°C or more? Or is that the only way your rooms can get up about 21°C?

If so, then your radiators and/or boiler may be undersized; or you system is not properly balanced.

Most of the country's TRVs are on six including mine. People simply don't use them. End off

 

[D_Hailsham]

Most of the country's TRVs are on six including mine. People simply don't use them. End off

More likely people don't understand how they work and how to use them. They feel the radiator and it's cold (room up to temperature so TRV has shut off). Something is wrong, they think, the radiator should be hot. So they open the TRV a bit. And so it goes on until the TRV is set to Max and the rad stays hot all day long. It's working properly now, they think.

 

[westmoorfarm]

It's probably the latter, some of the rooms will just about make it to 21 with the TRV's full on. It's a fairly old house so our insulation possibilities are fairly limited, so it could be heat loss. It's also fairly open plan downstairs, with a large glass area at the back which doesn't help. Most of the upstairs rooms are OK, in fact the TRV's in the bedrooms are set at around 3 which gives a temperature of about 19.

The boiler may well be under specified (and about 17 years old) although we usually leave it's front panel temperature (i.e. temperature of circulating water) at about mid position, perhaps this should be set higher.

I may have a go at balancing the radiators as there are some temperature variations when full on; I think there was guide on here somewhere - I'll take a look.

Thanks

 

[tonybhoy]

More likely people don't understand how they work and how to use them. They feel the radiator and it's cold (room up to temperature so TRV has shut off). Something is wrong, they think, the radiator should be hot. So they open the TRV a bit. And so it goes on until the TRV is set to Max and the rad stays hot all day long. It's working properly now, they think.

Agree entirely however IMO they are only good for turning the rad on and off . The old el-cheapo-rad valves leak when used and TRVs don't so from that point of view they are fine and for controlling room temps you don't use much (ie turning the rad off in those rooms) but for yer 'actual' temp control they are way too mystical for your average customer.

Try selling some of them on roomstats as opposed to TRVs

 

[D_Hailsham]

Most of the upstairs rooms are OK, in fact the TRV's in the bedrooms are set at around 3 which gives a temperature of about 19.

That's good; bedrooms should not be hot.

The boiler may well be under specified (and about 17 years old) although we usually leave it's front panel temperature (i.e. temperature of circulating water) at about mid position, perhaps this should be set higher.

You have a Y Plan, so you must have room and cylinder thermostats. These control when the boiler is alight. Turn your boiler thermostat to maximum and let the other thermostats do their job.

I may have a go at balancing the radiators as there are some temperature variations when full on; I think there was guide on here somewhere - I'll take a look.

I recently wrote a treatise on balancing; see Balancing Procedure

 

[westmoorfarm]

I'd not considered turning the boiler to full (it's oil fired if that makes any difference), presumably things would come up to temperature more quickly at which point the thermostat's would do their thing, and the system would shut down, so in theory we shouldn't use much more fuel that way

Thanks for the balancing link .

 

[tonybhoy]

I'd not considered turning the boiler to full (it's oil fired if that makes any difference), presumably things would come up to temperature more quickly at which point the thermostat's would do their thing, and the system would shut down, so in theory we shouldn't use much more fuel that way

Depends on whether you have room stat if you don't your boiler will cycle (hunt) and you will use more fuel. That is the downside to TRVs.

 

[westmoorfarm]

Yes, we do have a room stat (as of last week), never had one before...

 

[tonybhoy]

Yes, we do have a room stat (as of last week), never had one before...

Sadly not that unusual in general but with a Y plan I think that is criminal.

Both Y Plan and S plan fully pumped systems of heating control are the most efficient ways to use a heating system but without one of the main components they are almost useless. Almost as bad as a combi boiler system with only TRvs to control the space heating temps.