Vibrating lines 1

[WARose]

This is a around-the-house type question.....it's driving me nuts and the HVAC tech can't figure it out.

I have a heat pump outside and the evaporator coils are inside. There are lines that run through the walls & ceiling to connect them.

Last night.....when we had a unusually cool night for this time of year: down in the low 50's/high 40's, don't know if that is playing a role or not but thought I'd mention it......these lines really started vibrating bad and noisily.

The HVAC contractor can't figure it out. He doesn't think it's a coolant issue. And it (of course) is not doing it with him here.

It doesn't do it constantly.....it sort of comes and goes (in terms of magnitude) in cycles.

Any idea as to what it could be?

 

[GT-EGR]

Need you to elaborate a lot more. Constant vibration, on/off for time intervals, vibrating only for a minute every so often. Has this happened more than once. What else was on in the house when you noticed this.

Also are you sure it was the piping, not something next to it?

Lots of questions but all part of ruling things out.

 

[berkshire]

Check your expansion valve, sometimes when system pressures are low, the expansion valve can flutter, If you have a capillary tube this does not get affected so much. The usual cause of this is insufficient gas pressure on the high side of the system. Get your tech to check the high and low side pressures.
B.E.

You are judged not by what you know, but by what you can do.

 

[WARose]

Constant vibration, on/off for time intervals, vibrating only for a minute every so often.

No the vibration level isn't constant in terms of amplitude......it probably acts up for a few seconds (for about every 10 minutes it runs).

Has this happened more than once.

Yep. Every time it runs.

Also are you sure it was the piping, not something next to it?

100% sure it isn't water piping. (Or anything else other than the heat pump) The only time this happens is when the heat pump runs. I tested it by doing everything I normally do without running the heat pump for 24 hrs. Nothing happened. Turn on the heat pump? It happens.

Check your expansion valve, sometimes when system pressures are low, the expansion valve can flutter, If you have a capillary tube this does not get affected so much. The usual cause of this is insufficient gas pressure on the high side of the system. Get your tech to check the high and low side pressures.

Thank you. Can coolant level play a role in that? (That was one of my suggestions to the HVAC tech.)

 

[EnergyProfessional]

just spit-balling here. When it is cold outside, the volume of refrigerant shrinks. This makes it harder to compress to a liquid. So the first 10 minutes it runs i assume the liquid line still has some gas and vibrates.
the refrigerant level should be checked at the correct operating temperature. i assume this heatpump also cools. so they may have adjusted it when it was warm outside.

For heatpumps that to operate when cold and warm, the manufacturer has some more complicated refrigerant charge procedures.

So I would have that checked. Make sure you get a good contractor that does proper measurement of pressures and line temperatures. This is best done with one of the digital devices that calculate sub-cooling, superheat etc.
Many just "eyeball" with measuring air temps or by using the analog instruments.

This may also be a sign of it not performing well. 40F outside temp may be the limit the heatpump is designed for.

not sure if the 10 minute cycling is correct, but the heatpump reverses into de-frost mode. so that may be when the vibration changes.

Make sure you have a good tech that actually understands it. The system has to work under all operating conditions, not just at the ones when the tech is on site. Believe it or not, many don't understand the systems they work on and hack it somehow. Hacking may work on an AC that only works at a small temperature range, but it doesn't work well with heatpumps.

 

[WARose]

So I would have that checked. Make sure you get a good contractor that does proper measurement of pressures and line temperatures. This is best done with one of the digital devices that calculate sub-cooling, superheat etc.
Many just "eyeball" with measuring air temps or by using the analog instruments.

Good point.

This may also be a sign of it not performing well. 40F outside temp may be the limit the heatpump is designed for.

I don't see how that is possible. This is just a ordinary heat pump. Unless you are designing heat pumps for Death Valley or Saudi Arabia.....how could you put a pump on the market that can't run at less than 40F? We get down in the teens here every winter. (And in the 100s every summer.)

 

[EnergyProfessional]

Only you know what the heatpump is designed for. air source heatpumps aren't really suitable for low ambient temperature. there are low ambient models, but they are less efficient. Efficiency and heat output drop significantly at low temp.
You should look up your model what it is rated for.

 

[berkshire]

WARose,
You are going to have to give us a bit more information here, Is this a heat pump with buried thermal transfer lines, or is it an air side heat pump ?
Air side heat pumps usually work until the evaporator coil freezes up, at which time the system will temporarily reverse to air conditioning or utilize a hot gas bypass valve to heat up the coil and drive the frost off, this type of system is usually good to about 0c. This type of system usually has a back up electric heater (E Heat)
Liquid burial lines if not properly installed can have problems with slugging of the refrigerant and compressor failure, But they are more efficient and will work down to lower temperatures. Tell us what you have.
B.E.

You are judged not by what you know, but by what you can do.

 

[WARose]

Is this a heat pump with buried thermal transfer lines, or is it an air side heat pump ?

I'm quite positive there are no buried lines with it. So it must be a air source pump.

 

[itsmoked]

As mentioned air ones typically crap-out at about 40F. If you have a sub 40F environment heat pumps are generally a poor choice since they're a more complicated compromise type system anyway.

One does better to have a heating system that is effective and cost effective at sub 40s and an A/C system that's simpler and more efficient at high temperatures.

Heat pump systems typically come with electric back up as Berky mentioned and the user doesn't really notice that the actual heat-pump part checked-out a while ago when the temps got down below 40F and they started getting electric heat (expensive).

Keith Cress
kcress -

http://www.flaminsystems.com

 

[LittleInch]

WARose,

You know the story here, drawings and pictures go a long way to understanding your issue.

Is this just a standalone reverse cycle A/C system?

Did you go and look at the unit?

Sometimes the thing just ices up and the fan hits the I've and it all starts to vibrate. The unit finally recognises that and the ice slowly goes away.

Pictures needed!

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[WARose]

If you have a sub 40F environment heat pumps are generally a poor choice since they're a more complicated compromise type system anyway.

If it's a poor choice.....it's a choice a lot of people are making. In talking to the HVAC tech this morning he said what I got is pretty much what every house in the upstate of South Carolina has. (Indeed, I cannot think of a single home I have been to in the last 20 years in the southeast that didn't have this.....unless we are talking a shotgun shack or something.)

Yes, we get below 40 (in fact we hit 39 this weekend).....but on average, we are typically well above that.

Is this just a standalone reverse cycle A/C system?

Yep. The same system can put out heat and cool air.

Pictures needed!

That would be tough because of the bushes around it. (I.e. a picture really won't tell you anything.) I was looking around on it for a model number, but I don't see it.

But it looks like this (you have to wait a second for the pic to pop up on the right hand side of the screen):

https://www.google.com/search?sourc...BAgFEFM&biw=1440&bih=809#imgrc=gjyBTjhhjoG0kM

 

[LittleInch]

Ok,

without more info difficult to say, but it does sound like the unit is going into a auto defrost cycle and either switching valves or sending the refrigerant in a different direction like berkshire said above.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.