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Valiant Ecotec Plus 637 radiators not heating up fully

Discussion in 'Plumbing and Central Heating' started by Marc118, 12 Oct 2019.

  1. lightning

    lightning

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    What size is your pipe work it should be 28 mm off boiler
     
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  3. Marc118

    Marc118

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    It looks more like 22mm off the brass fitting from the boiler.
     
  4. Marc118

    Marc118

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    The heatings been on for 3 hours, downstairs only and the return has increased to 59’C. the radiator temps At the top are from 40’C to 52’C so not great considering I have a flow of 75’C
     
  5. Gasguru

    Gasguru

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    Post a pic of the boiler data plate underneath.

    A bungalow with a 637...was the boiler thrown in by a builder? That's a very powerful boiler for the property unless it's huge. The larger Vaillants nearly always have problems with heat dissipation.
    I would try and estimate the Kw rating of the radiators/building heat loss; although the boilers heating output is set to automatic it may be beneficial to adjust it to a more appropriate Kw output in the settings (with a sensible allowance for the cylinder).

    Have a look at the status codes with the heating on....anything like S53 codes etc indicates an issue with dumping the heat.
    Ensure the cylinder zone valve pipework is cold and check it doesn't excessively heat when operating the radiator circuits...to rule out let-by on the zone valve.
    You should have a valve on the cylinder pipework to limit the flow to the cylinder when both circuits are operating...otherwise the heating performance can suffer until the cylinder is up to temperature.

    Your return temp shown on the boiler might be higher than you think either due to the internal bypass valve or you are using an infra red thermometer without emissivity adjustment (these thermometers are notoriously inaccurate)..

    The 637 has significant head loss (or friction) across it's heat exchanger and the internal pump has little reserve capacity for the radiator/cylinder system.
    The default pump setting is automatic however the boiler software doesn't know the radiator system (ie. how much friction there is) and to set the performance it makes assumptions based on the temperatures across the heat exchanger and burner output. It may be beneficial to change that setting to a fixed speed setting in D014 say 85 or 100% to see if performance improves. The electrical energy cost increase is insignificant but there might be an associated noise issue.

    The internal bypass valve can be turned down but that involves removal of the front casing (which forms part of the safety system) and therefore is beyond diy.
    In addition turning the bypass down too much (especially without and external bypass) could damage the heat exchanger/pump.
     
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  6. Marc118

    Marc118

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    Image attached of the data plate.
    The Bungalow was converted by the previous owners and no expense has been spared on the rest of the house so I wouldn't have expected the boiler installation to be a crap job.
    It's a converted bungalow and is a decent size, the living/kitchen room alone is 12m x 9m. In there alone we have 4 of the fancy black radiators but I'm unsure how to work out the duty of each rad. There's nothing stamped on them to indicate.

    There's no fault codes at all on the system and there hasn't been any since we moved in more that 11 months ago.

    There is a zone valve for the hot water along with a gate valve on the primary return outlet pipework coming out of the tank but that is it. When testing the radiator circuits, I've made sure that the hot water is disabled on the stat so the zone valve stays closed.

    I'm using 2 calibrated pipe clamp sensors that I use at work for measuring superheat/subcooling so I know they're accurate and both are reading exactly the same. I've confirmed that by closing the gate valve on the 'bypass' the heat back to the return drops, which it does, along with checking that each of the zone valves aren't passing, which they are not.

    The internal pump always seems to be at setting 1 and I did change it to No2, which is 60% I think but it didn't make much difference. I didn't put any higher because I thought the issue with the bypass line was more pressing at the time.

    At the same time as putting the pump of the speed up I looked at the internal bypass valve and did go to adjust it as per the engineers instructions but unfortunately the brass bit of the screw snapped as I tried to turn it (yes I was using the correct sized flat head). It seemed unusually tight and there was the green lock paste on the thread.

    I do have a feeling that this boiler just hasn't been set up correctly for the size of the house and would benefit from an adjustment on the heating output.

    As a test on this, could I work out the size of each room and use a figure of 90w/sqm or is this too much ( I know this is dependant on heat losses) and then set this in the boiler?
     

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  7. Gasguru

    Gasguru

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    The gate valve on the cylinder primary return should be throttled down such that the heating circuits still receive sufficient heat when the cylinder heating is in operation.
    No not fault codes...look in the manual and pull up the boiler S or status codes...they indicate what the boiler is actually doing at the time.
    37Kw is still a huge boiler for a bungalow even if its been extended...after all any extension heat loss will be minimal if carried out in recent years. Sometimes these boiler models work better when the maximum heat output is set to a more matched output rather than relying on them to modulate down themselves, AFAIR it's the D0 setting.
    Just because the hot water is turned off doesn't mean the zone valve is fully off. Unvented cyclinder manufacturers frequently package poor quality zone valves with their cylinders. It's common that Danfoss, Sunvic etc valves stick. Take the actuator off, mole grips on the spindle and tie it fully closed if necessary...every so often I come across let-by through the cylinder.
    The bypass needs sorting...there may be no option but to close it down somewhat.
    Try the pump at 100%.
    If you really need the full output of the boiler then do a search on the forum...you'll find some have had to resort to extra pumps, low loss headers etc.
     
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  8. Marc118

    Marc118

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    Okay I've just checked this morning and confirmed that the zone valve for the hot water isn't passing by but the gate valve on the primary water outlet is 90% open, When you say throttled down, to what value? 20%?

    I read on another post that a bypass can sometimes be installed when there is an S53 fault but looking through my boiler and the status codes, there's no sign of any S codes apart from burner on. For the minute I've completely closed this valve to see what effect it has on the system.
    I've tried searching about how to increase the output of the boiler but can only find threads to do with anti cycling and turning the boiler down, not up. What would be a good setting to start it on 20kw? and go from there.

    Finally, I looked at D40 and D41 and found that the flow was 69'C and my temp measurement was 69'C yet the Return sensed by the boiler was 58'C but I had it at 43'C a huge 15'C difference.
     
  9. Gasguru

    Gasguru

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    When the heating AND hot water are in demand you want to throttle down the hot water circuit to prevent the water taking an easier route via the cylinder and the heating performance suffering ie. balance the circuits.
    Otherwise if say a bath was filled and there was a long hot water demand the radiators may cool to the point where room temperatures would drop and occupants would be in discomfort.

    Leave the boiler showing the status codes and monitor them whilst the heating is on...sometimes with incorrect flow rates the boiler can sit there in S53 etc but by the look of it the temperature drop across the heat exchanger is too small.

    Check the d0 setting this is the Kw output, see what the setting is. Yes try it on 20 or 25Kw.

    The temperatures shown by D40 & D41 are from the sensors on the heat exchanger pipework. The 15 degree difference is due to the internal bypass being open.

    If those temperatures are when the system has been running for some time then you'll need to get the bypass fixed to enable it to be closed down more.
     
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  11. Marc118

    Marc118

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    Okay that makes sense. I'll hopefully sort the heating out and then once this is sorted, play about with the gate valve on the hot water to get this set so it doesn't pinch too much heat from the radiator circuits.

    I'll monitor the status codes today to see if any anomalies show up and report back.

    The D0 setting is on auto at the minute, i'll change this later on (i'm going out shortly) and see if this helps.

    Yes the temps are when the system has been running for a couple of hours. Why would the internal bypass be open when there is a heat requirement from the rads and all rads set to open?
     
  12. Gasguru

    Gasguru

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    Heat exchangers fabricated from thin gauge tube (as on the Vaillants) have very low thermal mass and will rapidly overheat and cause damage...in addition there is no water flow sensing on these models for added protection.
    The bypass ensures a minimum water flow at all times (especially when users put TRVs on all the rads or many TRVs close down).
    Your boiler comes out of the factory with the bypass set for a typical system but may require adjustment once installed.
     
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  13. Marc118

    Marc118

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    Just out of interest, does the position of the adjustment screw look okay to you?

    It looks to be wound out but then has the green locktite around the base of the screw.
     

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  14. Gasguru

    Gasguru

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    Looks to be around the default position...have a look on the web at brand new valves.
     
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  15. Marc118

    Marc118

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    I've just come back in and gone to fire up the boiler for 30mins before I have to leave to go out again and went back to it after ten mins to find the boiler display showing an egg timer. I've just checked the staus code and sure enough it's displaying an S53 water shortage. This is the first time that I have seen this before.
    What should I be looking at to rectify this.

    BTW - I haven't changed pump speed or capacity of the boiler just yet.
     
  16. ScottishGasMan

    ScottishGasMan

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    The pump speed should be either on Auto or 100%, that boiler firing at full rate will go into S.53 purely because the pump has been set on one or two and not flowing the required volume of water through the heat exchanger.

    Also the bypass is an automatic type, it will open when there is too much resistance on the system so the pressure of the water flow will push it open, indicating the system is'nt capable of flowing the full water flow the boiler needs,
     
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  17. Marc118

    Marc118

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    The pump is on auto and is as I found it. When I looked in the actual pump speed it showed that it was running at 15% even when in auto.
     
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