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  #1   Report Post  
Old December 11th 03, 06:37 PM
David Hearn
 
Posts: n/a
Default Another heating problem question!

I added TRVs this weekend and the week before replaced the boiler
thermostat. Since doing this I've noticed that the downstairs is not as hot
as it used to be - even with the TRV heads off. I've also noticed a lot of
boiler cycling (old Baxi WM 531 RS boiler).

Previously the living room (large room with 2 radiators) used to get quite
hot with the heating on - now it gets warm, but not warm enough really.
I've tried rebalancing (which previously got the downstairs nice and toasty)
but that doesn't appear to make a significant difference. I did struggle to
get much of a temperature drop on some radiators - some only had as little
as a 3 degree drop with just a 1/8's of a turn on with the lockshield. The
highest drop appeared to be on the largest (and furthest radiator which
isn't getting quite as hot) which was 20. The majority of the rest were
about 5-8 degree drop.

The pump (UPS 15-50) is running on its slowest speed and always has done.
Anything more than this and there's a noticeable noise from the
pump/pipework. I did a test last night and increasing the pump speed
altered the boiler cycling times only slightly (5 seconds different) and
failed to make any difference to the temperature of the pipes to the largest
downstairs radiator.

Specifically, with the boiler thermostat set to 3 (with 5 being highest) the
boiler would heat the water for

Boiler thermostat setting Pump setting Time boiler on
Time boiler off Pipe therm 1 Pipe therm 2
3 1
1 min 35 secs 1 min 45 secs 50
30
5 1
2 min 25 secs 1 min 20 secs 50
30
3 3
1 min 40 secs 1 min 45 secs 50
30

The pipe thermometer readings were from the large (9') radiator which was
the one which got cold when it wasn't balanced properly.

As you can see, the boiler is cycling about every 2 minutes and changing the
pump speed made little difference.

The radiators closest to the boiler do get hot and the downstairs radiators
don't get as hot, but are hot.

I've got a thermometer (built into a small travel clock) and I've yet to
make the temperature in the living room more than 20.5 even though I've set
the wall stat in the hall to anything up to 25. Note, I did these checks
with the TRV heads off - so they're not restricting the flow and I got the
same reading with both TRV's set to 5 (the highest on the Pegler Terrier
II).

I'm sure the cycling times dropped when I changed the boiler thermostat, but
I'm confused that increasing the pump speed makes little difference.

What sort of noise would you expect from my pump on speed 3? The pump is
very quiet on speed 1 but becomes quite noisy on speed 3 (and its about 3"
away from a bed in a spare room - so I don't want to it be too noisy). I've
checked that the system has been bled properly including the pump.

I'm going to continue tweaking the balancing of the radiators - but I'm
puzzled that it used to get uncomfortably hot but now it doesn't even when
the TRV's are off and that the pump speed makes little difference to the
temperature and boiler cycling.

Any ideas?

Thanks

David

--
To send email to me - remove references to NoSpam, and Spammer from my email
address.



  #2   Report Post  
Old December 11th 03, 06:43 PM
Tony
 
Posts: n/a
Default Another heating problem question!

Don't know what kind of TRVs you've got, but on my old house if we wanted a
radiator to get super-hot, we had to unscrew the top unit of the TRV a few
turns. Even though they were fully opened, it seemed that the valve was
partially closed and only the unscrewing made them fully open.

Tony

"David Hearn" wrote in message
...
I added TRVs this weekend and the week before replaced the boiler
thermostat. Since doing this I've noticed that the downstairs is not as

hot
as it used to be - even with the TRV heads off. I've also noticed a lot

of
boiler cycling (old Baxi WM 531 RS boiler).

Previously the living room (large room with 2 radiators) used to get quite
hot with the heating on - now it gets warm, but not warm enough really.
I've tried rebalancing (which previously got the downstairs nice and

toasty)
but that doesn't appear to make a significant difference. I did struggle

to
get much of a temperature drop on some radiators - some only had as little
as a 3 degree drop with just a 1/8's of a turn on with the lockshield.

The
highest drop appeared to be on the largest (and furthest radiator which
isn't getting quite as hot) which was 20. The majority of the rest were
about 5-8 degree drop.

The pump (UPS 15-50) is running on its slowest speed and always has done.
Anything more than this and there's a noticeable noise from the
pump/pipework. I did a test last night and increasing the pump speed
altered the boiler cycling times only slightly (5 seconds different) and
failed to make any difference to the temperature of the pipes to the

largest
downstairs radiator.

Specifically, with the boiler thermostat set to 3 (with 5 being highest)

the
boiler would heat the water for

Boiler thermostat setting Pump setting Time boiler on
Time boiler off Pipe therm 1 Pipe therm 2
3 1
1 min 35 secs 1 min 45 secs 50
30
5 1
2 min 25 secs 1 min 20 secs 50
30
3 3
1 min 40 secs 1 min 45 secs 50
30

The pipe thermometer readings were from the large (9') radiator which was
the one which got cold when it wasn't balanced properly.

As you can see, the boiler is cycling about every 2 minutes and changing

the
pump speed made little difference.

The radiators closest to the boiler do get hot and the downstairs

radiators
don't get as hot, but are hot.

I've got a thermometer (built into a small travel clock) and I've yet to
make the temperature in the living room more than 20.5 even though I've

set
the wall stat in the hall to anything up to 25. Note, I did these checks
with the TRV heads off - so they're not restricting the flow and I got the
same reading with both TRV's set to 5 (the highest on the Pegler Terrier
II).

I'm sure the cycling times dropped when I changed the boiler thermostat,

but
I'm confused that increasing the pump speed makes little difference.

What sort of noise would you expect from my pump on speed 3? The pump is
very quiet on speed 1 but becomes quite noisy on speed 3 (and its about 3"
away from a bed in a spare room - so I don't want to it be too noisy).

I've
checked that the system has been bled properly including the pump.

I'm going to continue tweaking the balancing of the radiators - but I'm
puzzled that it used to get uncomfortably hot but now it doesn't even when
the TRV's are off and that the pump speed makes little difference to the
temperature and boiler cycling.

Any ideas?

Thanks

David

--
To send email to me - remove references to NoSpam, and Spammer from my

email
address.




  #3   Report Post  
Old December 11th 03, 07:32 PM
Ed Sirett
 
Posts: n/a
Default Another heating problem question!

On Thu, 11 Dec 2003 18:43:55 +0000, Tony wrote:

Don't know what kind of TRVs you've got, but on my old house if we wanted a
radiator to get super-hot, we had to unscrew the top unit of the TRV a few
turns. Even though they were fully opened, it seemed that the valve was
partially closed and only the unscrewing made them fully open.

Tony

"David Hearn" wrote in message
...
I added TRVs this weekend and the week before replaced the boiler
thermostat. Since doing this I've noticed that the downstairs is not as

hot
as it used to be - even with the TRV heads off. I've also noticed a lot

of
boiler cycling (old Baxi WM 531 RS boiler).

Previously the living room (large room with 2 radiators) used to get quite
hot with the heating on - now it gets warm, but not warm enough really.
I've tried rebalancing (which previously got the downstairs nice and

toasty)
but that doesn't appear to make a significant difference. I did struggle

to
get much of a temperature drop on some radiators - some only had as little
as a 3 degree drop with just a 1/8's of a turn on with the lockshield.

The
highest drop appeared to be on the largest (and furthest radiator which
isn't getting quite as hot) which was 20. The majority of the rest were
about 5-8 degree drop.

The pump (UPS 15-50) is running on its slowest speed and always has done.
Anything more than this and there's a noticeable noise from the
pump/pipework. I did a test last night and increasing the pump speed
altered the boiler cycling times only slightly (5 seconds different) and
failed to make any difference to the temperature of the pipes to the

largest
downstairs radiator.

Specifically, with the boiler thermostat set to 3 (with 5 being highest)

the
boiler would heat the water for

Boiler thermostat setting Pump setting Time boiler on
Time boiler off Pipe therm 1 Pipe therm 2
3 1
1 min 35 secs 1 min 45 secs 50
30
5 1
2 min 25 secs 1 min 20 secs 50
30
3 3
1 min 40 secs 1 min 45 secs 50
30

The pipe thermometer readings were from the large (9') radiator which was
the one which got cold when it wasn't balanced properly.

As you can see, the boiler is cycling about every 2 minutes and changing

the
pump speed made little difference.

The radiators closest to the boiler do get hot and the downstairs

radiators
don't get as hot, but are hot.

I've got a thermometer (built into a small travel clock) and I've yet to
make the temperature in the living room more than 20.5 even though I've

set
the wall stat in the hall to anything up to 25. Note, I did these checks
with the TRV heads off - so they're not restricting the flow and I got the
same reading with both TRV's set to 5 (the highest on the Pegler Terrier
II).

I'm sure the cycling times dropped when I changed the boiler thermostat,

but
I'm confused that increasing the pump speed makes little difference.

What sort of noise would you expect from my pump on speed 3? The pump is
very quiet on speed 1 but becomes quite noisy on speed 3 (and its about 3"
away from a bed in a spare room - so I don't want to it be too noisy).

I've
checked that the system has been bled properly including the pump.

I'm going to continue tweaking the balancing of the radiators - but I'm
puzzled that it used to get uncomfortably hot but now it doesn't even when
the TRV's are off and that the pump speed makes little difference to the
temperature and boiler cycling.


It is likely that the old failing thermostat was effective set quite a
high output temperture to the boiler.

Is it possible that the water heating coil is taking all the flow away
from the heating circuit - is there any control on this?

Seems to me that there must be quite an easy path for the water to avoid
going to the big rad.

I wonder if turning off all the rads except the big one one would make any
difference? i.e. all the heating is going through the coil and/or bypass
pipework.

HTH

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html


  #4   Report Post  
Old December 11th 03, 11:04 PM
David Hearn
 
Posts: n/a
Default Another heating problem question!


"Ed Sirett" wrote in message
news
On Thu, 11 Dec 2003 18:43:55 +0000, Tony wrote:

Don't know what kind of TRVs you've got, but on my old house if we

wanted a
radiator to get super-hot, we had to unscrew the top unit of the TRV a

few
turns. Even though they were fully opened, it seemed that the valve was
partially closed and only the unscrewing made them fully open.

Tony

"David Hearn" wrote in message
...
I added TRVs this weekend and the week before replaced the boiler
thermostat. Since doing this I've noticed that the downstairs is not

as
hot
as it used to be - even with the TRV heads off. I've also noticed a

lot
of
boiler cycling (old Baxi WM 531 RS boiler).

Previously the living room (large room with 2 radiators) used to get

quite
hot with the heating on - now it gets warm, but not warm enough really.
I've tried rebalancing (which previously got the downstairs nice and

toasty)
but that doesn't appear to make a significant difference. I did

struggle
to
get much of a temperature drop on some radiators - some only had as

little
as a 3 degree drop with just a 1/8's of a turn on with the lockshield.

The
highest drop appeared to be on the largest (and furthest radiator which
isn't getting quite as hot) which was 20. The majority of the rest

were
about 5-8 degree drop.

The pump (UPS 15-50) is running on its slowest speed and always has

done.
Anything more than this and there's a noticeable noise from the
pump/pipework. I did a test last night and increasing the pump speed
altered the boiler cycling times only slightly (5 seconds different)

and
failed to make any difference to the temperature of the pipes to the

largest
downstairs radiator.

Specifically, with the boiler thermostat set to 3 (with 5 being

highest)
the
boiler would heat the water for

Boiler thermostat setting Pump setting Time boiler on
Time boiler off Pipe therm 1 Pipe therm 2
3 1
1 min 35 secs 1 min 45 secs 50
30
5 1
2 min 25 secs 1 min 20 secs 50
30
3 3
1 min 40 secs 1 min 45 secs 50
30

The pipe thermometer readings were from the large (9') radiator which

was
the one which got cold when it wasn't balanced properly.

As you can see, the boiler is cycling about every 2 minutes and

changing
the
pump speed made little difference.

The radiators closest to the boiler do get hot and the downstairs

radiators
don't get as hot, but are hot.

I've got a thermometer (built into a small travel clock) and I've yet

to
make the temperature in the living room more than 20.5 even though I've

set
the wall stat in the hall to anything up to 25. Note, I did these

checks
with the TRV heads off - so they're not restricting the flow and I got

the
same reading with both TRV's set to 5 (the highest on the Pegler

Terrier
II).

I'm sure the cycling times dropped when I changed the boiler

thermostat,
but
I'm confused that increasing the pump speed makes little difference.

What sort of noise would you expect from my pump on speed 3? The pump

is
very quiet on speed 1 but becomes quite noisy on speed 3 (and its about

3"
away from a bed in a spare room - so I don't want to it be too noisy).

I've
checked that the system has been bled properly including the pump.

I'm going to continue tweaking the balancing of the radiators - but I'm
puzzled that it used to get uncomfortably hot but now it doesn't even

when
the TRV's are off and that the pump speed makes little difference to

the
temperature and boiler cycling.


It is likely that the old failing thermostat was effective set quite a
high output temperture to the boiler.

Is it possible that the water heating coil is taking all the flow away
from the heating circuit - is there any control on this?

Seems to me that there must be quite an easy path for the water to avoid
going to the big rad.

I wonder if turning off all the rads except the big one one would make any
difference? i.e. all the heating is going through the coil and/or bypass
pipework.


The water heating is separaetely controlled and wasn't turned on during the
measurements.

I did twiddle a lockshield in the hall today (turned it from 1/2 turn to 1/4
turn I think) and this evening the living room felt quite a bit warmer and
the room temp appeared to reach 21.4!!! I'm thinking its probably just a
balancing thing.

Incidentally, I'm sure I can hear a bubbling noise from the boiler towards
the end of its heating period - and that's with a thermostat setting of 3.
I've turned it down to 2 now to see what happens to the room temp. It most
certainly does seem that this thermostat is working differently to the old
one. The old thermostat was marked 106 oC and this new one is marked 90oC -
but as people said before, 106oC is above boiling point, so it may not be a
reliable figure.

Anyway - thanks - I think I'll just try a little more twiddling (including
turning off all the other rads and seeing what happens).

Thanks

D


  #5   Report Post  
Old December 12th 03, 12:25 AM
Dave Plowman
 
Posts: n/a
Default Another heating problem question!

In article ,
David Hearn wrote:
I added TRVs this weekend and the week before replaced the boiler
thermostat. Since doing this I've noticed that the downstairs is not as
hot as it used to be - even with the TRV heads off.


Some TRVs have a built in pre-set sort of lockshield valve - the Drayton
ones I've just fitted have and you require a special tool to adjust it.
And they appear to come set back slightly and as I don't yet have the tool
so just opened up the other lockshield valves to compensate. Perhaps if
you're running at a very slow flow rate this factory setting is too low?

--
*A hangover is the wrath of grapes.

Dave Plowman London SW 12
RIP Acorn


  #6   Report Post  
Old December 12th 03, 01:10 PM
Phil Addison
 
Posts: n/a
Default Another heating problem question!

On Thu, 11 Dec 2003 18:37:04 -0000, "David Hearn"
wrote:

I added TRVs this weekend and the week before replaced the boiler
thermostat. Since doing this I've noticed that the downstairs is not as hot
as it used to be - even with the TRV heads off. I've also noticed a lot of
boiler cycling (old Baxi WM 531 RS boiler).


Boiler short-cycling means that the heat the boiler generates is not being
taken away fast enough by the circulating water. Symptoms are that the boiler
fires continuously at first, i.e. when the system is cold, but as the system
warms up to temperature the boiler shuts down for a short while every few
minutes.

The fundamental causes of short-cycling a

1) Inadequate pumping, i.e. pump set to too low a speed, or it is damaged.

2) Restricted flow to the heating circuit caused by (a) partially closed
radiator valves, (b) sludge or other obstruction in pipe work, or (c) pipe
bore too narrow.

3) Excessive by-pass flow.

In the case of 1) and 2), the return pipe temperature at the boiler fails to
reach full temperature or even remains quite cool, and some or all of the
radiators will have cool return connections. The return temperature should
reach within 11C of the flow.

In the case of 3), the by-pass circuit is returning too much hot flow water
back to the return, and the return at the boiler may be almost as hot as the
flow. However, the return water from the radiators, before it joins the
by-pass return, will be too cool.

Previously the living room (large room with 2 radiators) used to get quite
hot with the heating on - now it gets warm, but not warm enough really.
I've tried rebalancing (which previously got the downstairs nice and toasty)
but that doesn't appear to make a significant difference. I did struggle to
get much of a temperature drop on some radiators - some only had as little
as a 3 degree drop with just a 1/8's of a turn on with the lockshield. The
highest drop appeared to be on the largest (and furthest radiator which
isn't getting quite as hot) which was 20. The majority of the rest were
about 5-8 degree drop.


What procedure did you use to re-balance? Are you starting with all LSVs wide
open, and turning DOWN the LSVs on the HOT rads according to
http://www.diyfaq.org.uk/plumbing/rad-balance.html, rather than just trying to
open up the cool ones?

The pump (UPS 15-50) is running on its slowest speed and always has done.
Anything more than this and there's a noticeable noise from the
pump/pipework. I did a test last night and increasing the pump speed
altered the boiler cycling times only slightly (5 seconds different) and
failed to make any difference to the temperature of the pipes to the largest
downstairs radiator.

Specifically, with the boiler thermostat set to 3 (with 5 being highest) the
boiler would heat the water for

Boiler thermostat setting Pump setting Time boiler on
Time boiler off Pipe therm 1 Pipe therm 2
3 1
1 min 35 secs 1 min 45 secs 50
30
5 1
2 min 25 secs 1 min 20 secs 50
30
3 3
1 min 40 secs 1 min 45 secs 50
30


[Reformatted for clarity]

Boiler Pump boiler boiler Pipe Pipe
stat on off 1 2
3 1 1m35s 1m45s 50 30
5 1 2m25s 1m20s 50 30
3 3 1m40s 1m45s 50 30


The pipe thermometer readings were from the large (9') radiator which was
the one which got cold when it wasn't balanced properly.


50C on the flow is not enough. What is the temperature at the boiler flow on
number 5? It should be over 80C. It seems you have hardly any flow to this rad
so you need to fully open its LSV and close down some of the hotter ones.

As you can see, the boiler is cycling about every 2 minutes and changing the
pump speed made little difference.

The radiators closest to the boiler do get hot and the downstairs radiators
don't get as hot, but are hot.


Then the system is not balanced. They should all get equally hot (or cool!!)
even if the boiler is short cycling. I suggest you study the above balancing
FAQ and try again. Note that all the flow ends should be at virtually the same
temperature, and within a few degrees of the boiler flow temp.

I've got a thermometer (built into a small travel clock) and I've yet to
make the temperature in the living room more than 20.5 even though I've set
the wall stat in the hall to anything up to 25.


Is that what you are using to measure the flow and return temperatures? If so,
the results are probably miles out!!

Note, I did these checks
with the TRV heads off - so they're not restricting the flow and I got the
same reading with both TRV's set to 5 (the highest on the Pegler Terrier
II).

I'm sure the cycling times dropped when I changed the boiler thermostat, but
I'm confused that increasing the pump speed makes little difference.


If the system is unbalanced to the extent that the radiator is not getting
hot, the room will not warm up much above ambient anyway.

What sort of noise would you expect from my pump on speed 3? The pump is
very quiet on speed 1 but becomes quite noisy on speed 3 (and its about 3"
away from a bed in a spare room - so I don't want to it be too noisy). I've
checked that the system has been bled properly including the pump.

I'm going to continue tweaking the balancing of the radiators - but I'm
puzzled that it used to get uncomfortably hot but now it doesn't even when
the TRV's are off and that the pump speed makes little difference to the
temperature and boiler cycling.

Any ideas?


It seems to me that (1) in changing the boiler stat you have now got the
boiler set at too low a temperature. It should be set at up to 82C flow
temperature, and (2) you must have closed the LSVs to install the TRVs.
Therefore you need to re-balance them. Did you record their original settings?

In addition, Ed's points about the by-pass and the cylinder coil need checking
out. If you have no motorized valve or TRV on the cylinder coil, it must be
balanced with a series gate valve used as a LSV, just as if it was a radiator.
You can get 'locking' gate valves for this purpose.

Since the system was working previously, sludge and inadequate pipe size can
probably be ruled out.

--
Phil Addison
The uk.d-i-y FAQ is at http://www.diyfaq.org.uk/
Remove NOSPAM from address to reply

--
Phil Addison
The uk.d-i-y FAQ is at http://www.diyfaq.org.uk/
Remove NOSPAM from address to reply
  #7   Report Post  
Old December 12th 03, 02:01 PM
David Hearn
 
Posts: n/a
Default Another heating problem question!


"Phil Addison" wrote in message
...
On Thu, 11 Dec 2003 18:37:04 -0000, "David Hearn"
wrote:

I added TRVs this weekend and the week before replaced the boiler
thermostat. Since doing this I've noticed that the downstairs is not as

hot
as it used to be - even with the TRV heads off. I've also noticed a lot

of
boiler cycling (old Baxi WM 531 RS boiler).


Boiler short-cycling means that the heat the boiler generates is not being
taken away fast enough by the circulating water. Symptoms are that the

boiler
fires continuously at first, i.e. when the system is cold, but as the

system
warms up to temperature the boiler shuts down for a short while every few
minutes.

The fundamental causes of short-cycling a

1) Inadequate pumping, i.e. pump set to too low a speed, or it is damaged.

2) Restricted flow to the heating circuit caused by (a) partially closed
radiator valves, (b) sludge or other obstruction in pipe work, or (c) pipe
bore too narrow.

3) Excessive by-pass flow.

In the case of 1) and 2), the return pipe temperature at the boiler fails

to
reach full temperature or even remains quite cool, and some or all of the
radiators will have cool return connections. The return temperature should
reach within 11C of the flow.

In the case of 3), the by-pass circuit is returning too much hot flow

water
back to the return, and the return at the boiler may be almost as hot as

the
flow. However, the return water from the radiators, before it joins the
by-pass return, will be too cool.


No 3 might be something - I've covered that below though.

Previously the living room (large room with 2 radiators) used to get

quite
hot with the heating on - now it gets warm, but not warm enough really.
I've tried rebalancing (which previously got the downstairs nice and

toasty)
but that doesn't appear to make a significant difference. I did

struggle to
get much of a temperature drop on some radiators - some only had as

little
as a 3 degree drop with just a 1/8's of a turn on with the lockshield.

The
highest drop appeared to be on the largest (and furthest radiator which
isn't getting quite as hot) which was 20. The majority of the rest were
about 5-8 degree drop.


What procedure did you use to re-balance? Are you starting with all LSVs

wide
open, and turning DOWN the LSVs on the HOT rads according to
http://www.diyfaq.org.uk/plumbing/rad-balance.html, rather than just

trying to
open up the cool ones?


Well, my procedure was to open up all the lockshields and then turn the
lockshields on the rads closest the boiler (the hottest ones) to get them as
closed as possible yet still giving an adequate temperature drop and still
hot to the touch. It wasn't a 'to the letter' following of the FAQ.

The pump (UPS 15-50) is running on its slowest speed and always has

done.
Anything more than this and there's a noticeable noise from the
pump/pipework. I did a test last night and increasing the pump speed
altered the boiler cycling times only slightly (5 seconds different) and
failed to make any difference to the temperature of the pipes to the

largest
downstairs radiator.

Specifically, with the boiler thermostat set to 3 (with 5 being highest)

the
boiler would heat the water for

Boiler thermostat setting Pump setting Time boiler on
Time boiler off Pipe therm 1 Pipe therm 2
3 1
1 min 35 secs 1 min 45 secs 50
30
5 1
2 min 25 secs 1 min 20 secs 50
30
3 3
1 min 40 secs 1 min 45 secs 50
30


[Reformatted for clarity]

Boiler Pump boiler boiler Pipe Pipe
stat on off 1 2
3 1 1m35s 1m45s 50 30
5 1 2m25s 1m20s 50 30
3 3 1m40s 1m45s 50 30


The pipe thermometer readings were from the large (9') radiator which

was
the one which got cold when it wasn't balanced properly.


50C on the flow is not enough. What is the temperature at the boiler flow

on
number 5? It should be over 80C. It seems you have hardly any flow to this

rad
so you need to fully open its LSV and close down some of the hotter ones.


I've yet to manage to get the thermometer onto the boiler pipes directly
(very tight squeze above the boiler or floorboards up directly above the
boiler). I'll try to get this done tonight and see what's actually coming
out of it.


As you can see, the boiler is cycling about every 2 minutes and changing

the
pump speed made little difference.

The radiators closest to the boiler do get hot and the downstairs

radiators
don't get as hot, but are hot.


Then the system is not balanced. They should all get equally hot (or

cool!!)
even if the boiler is short cycling. I suggest you study the above

balancing
FAQ and try again. Note that all the flow ends should be at virtually the

same
temperature, and within a few degrees of the boiler flow temp.


I'm pretty sure that most of the radiator flow ends aren't at the same
temperature - I'll work on that part by rebalancing (and following the FAQ
more accurately I guess).

I've got a thermometer (built into a small travel clock) and I've yet to
make the temperature in the living room more than 20.5 even though I've

set
the wall stat in the hall to anything up to 25.


Is that what you are using to measure the flow and return temperatures? If

so,
the results are probably miles out!!


No, I've got 2 pipe thermometers for the radiator feeds - I'm just using
that thermometer as a basic indication of room temp.

Note, I did these checks
with the TRV heads off - so they're not restricting the flow and I got

the
same reading with both TRV's set to 5 (the highest on the Pegler Terrier
II).

I'm sure the cycling times dropped when I changed the boiler thermostat,

but
I'm confused that increasing the pump speed makes little difference.


If the system is unbalanced to the extent that the radiator is not getting
hot, the room will not warm up much above ambient anyway.

What sort of noise would you expect from my pump on speed 3? The pump

is
very quiet on speed 1 but becomes quite noisy on speed 3 (and its about

3"
away from a bed in a spare room - so I don't want to it be too noisy).

I've
checked that the system has been bled properly including the pump.

I'm going to continue tweaking the balancing of the radiators - but I'm
puzzled that it used to get uncomfortably hot but now it doesn't even

when
the TRV's are off and that the pump speed makes little difference to the
temperature and boiler cycling.

Any ideas?


It seems to me that (1) in changing the boiler stat you have now got the
boiler set at too low a temperature. It should be set at up to 82C flow
temperature,


I'll check that tonight hopefully.

and (2) you must have closed the LSVs to install the TRVs.
Therefore you need to re-balance them. Did you record their original

settings?

I recorded their original settings, but I replaced the lockshields, and I've
no idea whether the number of turns are transferrable. Initially I set them
to be what they had been on the old ones, but I soon noticed it wasn't
balanced properly - hence doing a (basic) balancing.

In addition, Ed's points about the by-pass and the cylinder coil need

checking
out. If you have no motorized valve or TRV on the cylinder coil, it must

be
balanced with a series gate valve used as a LSV, just as if it was a

radiator.
You can get 'locking' gate valves for this purpose.


The system has 2 motorized valves - one for heating and one for hot water.
When I balanced it, I did so with the water off. The water is only heated
for an hour or two morning and evening and wasn't being done when I did the
room temperature check.

I did notice a small 15mm pipe with a gate valve on it which appears to
bypass the motorized valves. After being unhappy with the balancing I did
twiddle it a little and returned it to the same place it was set to before.
Should this be open or closed - or just adjusted? I assume its a safeguard
so that when both valves are shut and the pump/boiler is on, that there is
some flow back to the boiler? If that is the case, I guess it must be open,
but not enough to cause too easy a path back to the boiler.

Since the system was working previously, sludge and inadequate pipe size

can
probably be ruled out.


Whilst I didn't use any sludge remover before installing TRVs, I did remove
each radiator and flush it through thoroughly, so any sludge etc would only
be that in the pipework (or distubed at the bottom of the header tank when
it refilled).

Thanks for the very helpful hints - I'll report back with the temperature of
the boiler output and I'll give the balancing a better go. I wasn't aware
before that the output pipe of the radiators should all be roughly the same.

Thanks

David


  #8   Report Post  
Old December 12th 03, 04:45 PM
Set Square
 
Posts: n/a
Default Another heating problem question!

In an earlier contribution to this discussion,
David Hearn wrote:


Thanks for the very helpful hints - I'll report back with the
temperature of the boiler output and I'll give the balancing a better
go. I wasn't aware before that the output pipe of the radiators
should all be roughly the same.

Thanks

David



All the radiators are (should be!) connected in parallel - so that the input
temperature is almost the same as the boiler output temperature. If there is
an appreciable difference, it indicates that you are losing a lot of heat
from the supply pipe - either because the flow is too low or because the
pipe is unlagged and passes through a very cold space, such as under a
suspended ground floor.

With all the radiator input temperatures being the same - and with the same
drop across all radiators in a balanced system - it follows that all the
ouptut temperatures should be the same.
--
Cheers,
Set Square
______
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  #9   Report Post  
Old December 12th 03, 05:25 PM
Phil Addison
 
Posts: n/a
Default Another heating problem question!



"Phil Addison" wrote in message
...
On Thu, 11 Dec 2003 18:37:04 -0000, "David Hearn"
wrote:

In the case of 3), the by-pass circuit is returning too much hot flow water
back to the return, and the return at the boiler may be almost as hot as the
flow. However, the return water from the radiators, before it joins the
by-pass return, will be too cool.


No 3 might be something - I've covered that below though.


I think not, having read the info below.

What procedure did you use to re-balance? Are you starting with all LSVs wide
open, and turning DOWN the LSVs on the HOT rads according to
http://www.diyfaq.org.uk/plumbing/rad-balance.html, rather than just trying to
open up the cool ones?


Well, my procedure was to open up all the lock shields and then turn the
lock shields on the rads closest the boiler (the hottest ones) to get them as
closed as possible yet still giving an adequate temperature drop and still
hot to the touch. It wasn't a 'to the letter' following of the FAQ.


Forget about the radiator body temperature - the key is to get the return pipe
of each radiator equally hot. It's easy to think the rad is hot to the touch
when in fact its only the top or the flow side that is hot. It's only when the
exit (return) pipe is hot, that you can be sure you have a good hot flow
through it.

If you want a 'quick' balance without the effort of the precise procedure, the
method is to locate the coolest and the hottest rad returns by hand, then
gradually close off the LSV on the hottest one. This will make that one
cooler, and divert some of its hot water into the cooler ones, which will
become hotter as a result. You just keep repeating this on various pairs until
all returns are as equal as you can tell.

50C on the flow is not enough. What is the temperature at the boiler flow on
number 5? It should be over 80C. It seems you have hardly any flow to this rad
so you need to fully open its LSV and close down some of the hotter ones.


I've yet to manage to get the thermometer onto the boiler pipes directly
(very tight squeze above the boiler or floorboards up directly above the
boiler). I'll try to get this done tonight and see what's actually coming
out of it.


So long as there is a good flow rate, there will not be any significant
temperature drop along the flow pipework, so you do not need to get right up
to the boiler tapping. In fact the flow connections on each rad should be
within a few degrees of the boiler output temperature.

Is that what you are using to measure the flow and return temperatures? If so,
the results are probably miles out!!


No, I've got 2 pipe thermometers for the radiator feeds - I'm just using
that thermometer as a basic indication of room temp.


Some folk swear by them but I could not get consistent readings from them, and
they take ages to stabilise. I got good results with a Maplin thermocouple
meter, but have just ordered an infra-red thermometer from CPC for 35
delivered (thanks for the tip, Moonshine, in thread "Is Grundfos ups 15-50 man
enough for 15 year old 4 bed detached 8mm Microbore CH system")

It seems to me that (1) in changing the boiler stat you have now got the
boiler set at too low a temperature. It should be set at up to 82C flow
temperature,


I'll check that tonight hopefully.

and (2) you must have closed the LSVs to install the TRVs.
Therefore you need to re-balance them. Did you record their original settings?


I recorded their original settings, but I replaced the lock shields, and I've
no idea whether the number of turns are transferrable. Initially I set them
to be what they had been on the old ones, but I soon noticed it wasn't
balanced properly - hence doing a (basic) balancing.


Fair enough. They seem to vary from several full turns to just 1/2 turn from
fully open to closed.

In addition, Ed's points about the by-pass and the cylinder coil need checking
out. If you have no motorized valve or TRV on the cylinder coil, it must be
balanced with a series gate valve used as a LSV, just as if it was a radiator.
You can get 'locking' gate valves for this purpose.


The system has 2 motorized valves - one for heating and one for hot water.
When I balanced it, I did so with the water off. The water is only heated
for an hour or two morning and evening and wasn't being done when I did the
room temperature check.


That's fine. You only need to balance the DHW coil if it is to be on
simultaneosly with the CH, but I think a better system uses only one system at
a time, then each gets the full boiler output.

I did notice a small 15mm pipe with a gate valve on it which appears to
bypass the motorized valves. After being unhappy with the balancing I did
twiddle it a little and returned it to the same place it was set to before.
Should this be open or closed - or just adjusted? I assume its a safeguard
so that when both valves are shut and the pump/boiler is on, that there is
some flow back to the boiler? If that is the case, I guess it must be open,
but not enough to cause too easy a path back to the boiler.


Thats will be it. As you suggest its setting is somewhat hit and miss.
Basically it is an unsatisfactory solution and the proper way to do it these
days is to use an automatic by-pass valve. See this link for further
discussion
http://groups.google.com/[email protected] x.com

Whilst I didn't use any sludge remover before installing TRVs, I did remove
each radiator and flush it through thoroughly, so any sludge etc would only
be that in the pipework (or distubed at the bottom of the header tank when
it refilled).


Don't forget to add inhibitor to the CH water.

Thanks for the very helpful hints - I'll report back with the temperature of
the boiler output and I'll give the balancing a better go. I wasn't aware
before that the output pipe of the radiators should all be roughly the same.


Yes, a radiator is designed to give out its rated heat when it has a certain
specified temperature drop from flow to return, typically 11C. Getting them
all the same is the whole point of balancing.

--
Phil Addison
The uk.d-i-y FAQ is at http://www.diyfaq.org.uk/
Remove NOSPAM from address to reply
  #10   Report Post  
Old December 12th 03, 08:29 PM
Set Square
 
Posts: n/a
Default Another heating problem question!

In an earlier contribution to this discussion,
Phil Addison wrote:

I . . have just ordered an infra-red
thermometer from CPC for 35 delivered (thanks for the tip,
Moonshine, in thread "Is Grundfos ups 15-50 man enough for 15 year
old 4 bed detached 8mm Microbore CH system")

Got mine after the same tip - works a treat (although I'm not supposed to
use it yet 'cos it's a Christmas present)!


That's fine. You only need to balance the DHW coil if it is to be on
simultaneosly with the CH, but I think a better system uses only one
system at a time, then each gets the full boiler output.


Not easy to achieve with most programmers which use the same on/off periods
for CH and HW. The only way I can think of to do it is to use the main
programmer for HW, setting CH to constant and actually controlling the CH at
different times with a programmable room stat. Is this the accepted way?
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is Black Hole!




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